Tag Archives: Solar and Stellar Astrophysics

Co-evolution of dust grains and protoplanetary disks [SSA]

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http://arxiv.org/abs/2303.10419


We propose a new evolutionary process of protoplanetary disks “co-evolution of dust grains and protoplanetary disks”, revealed by dust-gas two-fluid non-ideal magnetohydrodynamics simulations considering the growth of dust and associated changes in magnetic resistivity. We found that the dust growth significantly affects disk evolution by changing the coupling between the gas and magnetic field. Moreover, once the dust grains sufficiently grow, the physical quantities (e.g., density and magnetic field) of the disk are well described by nontrivial power laws, regardless of the details of the dust model. In this disk structure, the radial profile of density is steeper and the disk mass is smaller than those of the model ignoring dust growth and they are more consistent with the disk observations. We analytically derive these power laws from the basic equations of non-ideal magnetohydrodynamics. The analytical power laws are determined only by observable physical quantities, e.g., central stellar mass and mass accretion rate, and do not include difficult-to-determine parameters e.g., viscous parameter $\alpha$. Therefore, they are applicable to various stages of disk evolution. We believe that the disk structure provides a new basis for future studies on star and planet formation.

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Y. Tsukamoto, M. Machida and S. Inutsuka
Tue, 21 Mar 23
40/68

Comments: 14 pages, 8 figures, submitted to PASJ

HI line analysis of Herbig Ae/Be stars using X-Shooter spectra [SSA]

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http://arxiv.org/abs/2303.11182


Herbig Ae/Be stars are intermediate-mass pre-main sequence stars undergoing accretion through their circumstellar disk. The optical and infrared (IR) spectra of HAeBe stars show HI emission lines belonging to Balmer, Paschen and Brackett series. We use the archival X-Shooter spectra available for 109 HAeBe stars from Vioque et al. (2018) and analyse the various HI lines present in them. We segregated the stars into different classes based on the presence of higher-order lines in different HI series. We discuss the dependence of the appearance of higher-order lines on the stellar parameters. We find that most massive and younger stars show all the higher-order lines in emission. The stars showing only lower-order lines have Teff < 12000 K and an age range of 5-10 Myr. We perform a Case B line ratio analysis for a sub-sample of stars showing most of the HI lines in emission. We note that all but four stars belonging to the sub-sample show lower HI line ratios than theoretical values, owing to the emitting medium being optically thick. The HI line flux ratios do not depend on the star’s spectral type. Further, from the line ratios of lower-order lines and Paschen higher-order lines, we note that line ratios of most HAeBe stars match with electron density value in the range 10^9 – 10^11 cm^-3. The electron temperature, however, could not be ascertained with confidence using the line ratios studied in this work.

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B. Shridharan, B. Mathew, R. Arun, et. al.
Tue, 21 Mar 23
42/68

Comments: Accepted, To be published as part of the JOAA special issue on “3rd Meeting on Star Formation: Star Formation Studies in the Context of NIR Instruments on 3.6m DOT”. 12 pages, 7 figures

A young white dwarf orbiting PSR J1835-3259B in the bulge globular cluster NGC 6652 [HEAP]

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http://arxiv.org/abs/2303.11263


We report on the discovery of the companion star to the millisecond pulsar PSR J1835-3259B in the Galactic globular cluster NGC 6652. Taking advantage of deep photometric archival observations acquired through the Hubble Space Telescope in near-ultraviolet and optical bands, we identified a bright and blue object at a position compatible with that of the radio pulsar. The companion is located along the helium-core white dwarf cooling sequence and the comparison with binary evolution models provides a mass of $0.17 \pm 0.02~M_\odot$, a surface temperature of $11500\pm1900$ K and a very young cooling age of only $200\pm100$ Myr. The mass and the age of the companion are compatible with a progenitor star of about $0.87~M_{\odot}$, which started transferring mass to the primary during its evolution along the sub-giant branch and stopped during the early red giant branch phase. Combining together the pulsar mass function and the companion mass, we found that this system is observed at an almost edge-on orbit and hosts a neutron star with a mass of $1.44 \pm 0.06~M_\odot$, thus suggesting a highly non-conservative mass accretion phase. The young age of the WD companion is consistent with the scenario of a powerful, relatively young MSP indicated by the earlier detection of gamma-rays from this system.

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J. Chen, M. Cadelano, C. Pallanca, et. al.
Tue, 21 Mar 23
45/68

Comments: 11 pages, 7 figures, accepted for publication in ApJ

Modelling stellar evolution in mass-transferring binaries and gravitational-wave progenitors with METISSE [SSA]

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http://arxiv.org/abs/2303.10187


Massive binaries are vital sources of various transient processes, including gravitational-wave mergers. However, large uncertainties in the evolution of massive stars, both physical and numerical, present a major challenge to the understanding of their binary evolution. In this paper, we upgrade our interpolation-based stellar evolution code METISSE to include the effects of mass changes, such as binary mass transfer or wind-driven mass loss, not already included within the input stellar tracks. METISSE’s implementation of mass loss (applied to tracks without mass loss) shows excellent agreement with the SSE fitting formulae and with detailed MESA tracks, except in cases where the mass transfer is too rapid for the star to maintain equilibrium. We use this updated version of METISSE within the binary population synthesis code BSE to demonstrate the impact of varying stellar evolution parameters, particularly core overshooting, on the evolution of a massive (25M$\odot$ and 15M$\odot$) binary system with an orbital period of 1800 days. Depending on the input tracks, we find that the binary system can form a binary black hole or a black hole-neutron star system, with primary(secondary) remnant masses ranging between 4.47(1.36)M$\odot$ and 12.30(10.89)M$\odot$, and orbital periods ranging from 6 days to the binary becoming unbound. Extending this analysis to a population of isolated binaries uniformly distributed in mass and orbital period, we show that the input stellar models play an important role in determining which regions of the binary parameter space can produce compact binary mergers, paving the way for current and future gravitational-wave progenitor predictions.

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P. Agrawal, J. Hurley, S. Stevenson, et. al.
Tue, 21 Mar 23
46/68

Comments: 19 pages, 14 figures, submitted to MNRAS. Comments welcomed

Constraining atmospheric parameters and surface magnetic fields with $\texttt{ZeeTurbo}$: an application to SPIRou spectra [SSA]

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http://arxiv.org/abs/2303.11241


We report first results on a method aimed at simultaneously characterising atmospheric parameters and magnetic properties of M dwarfs from high-resolution nIR spectra recorded with SPIRou in the framework of the SPIRou Legacy Survey. Our analysis relies on fitting synthetic spectra computed from MARCS model atmospheres to selected spectral lines, both sensitive and insensitive to magnetic fields. We introduce a new code, $\texttt{ZeeTurbo}$, obtained by including the Zeeman effect and polarised radiative transfer capabilities to $\texttt{Turbospectrum}$. We compute a grid of synthetic spectra with $\texttt{ZeeTurbo}$ for different magnetic field strengths and develop a process to simultaneously constrain $T_{\rm eff}$, $\log{g}$, [M/H], [$\alpha$/Fe] and the average surface magnetic flux. In this paper, we present our approach and assess its performance using simulations, before applying it to six targets observed in the context of the SPIRou Legacy Survey (SLS), namely AU Mic, EV Lac, AD Leo, CN Leo, PM J18482+0741, and DS Leo. Our method allows us to retrieve atmospheric parameters in good agreement with the literature, and simultaneously yields surface magnetic fluxes in the range 2-4 kG with a typical precision of 0.05 kG, in agreement with literature estimates, and consistent with the saturated dynamo regime in which most of these stars are.

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P. Cristofari, J. Donati, C. Folsom, et. al.
Tue, 21 Mar 23
50/68

Comments: 17 pages plus supplementary material. Accepted for publication in MNRAS

Total Electron Temperature Derived from Quasi-Thermal Noise Spectroscopy In the Pristine Solar Wind: Parker Solar Probe Observations [SSA]

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http://arxiv.org/abs/2303.11035


The Quasi-thermal noise (QTN) technique is a reliable tool to yield accurate measurements of the electron parameters in the solar wind. We apply this method on Parker Solar Probe (PSP) observations to derive the total electron temperature ($T_e$) from the linear fit of the high-frequency part of the QTN spectra acquired by the RFS/FIELDS instrument, and present a combination of 12-day period of observations around each perihelion from Encounter One (E01) to Ten (E10) (with E08 not included) with the heliocentric distance varying from about 13 to 60 solar radii ($R_\odot{}$). We find that the total electron temperature decreases with the distance as $\sim$$R^{-0.66}$, which is much slower than adiabatic. The extrapolated $T_e$ based on PSP observations is consistent with the exospheric solar wind model prediction at $\sim$10 $R_\odot{}$, Helios observations at $\sim$0.3 AU and Wind observations at 1 AU. Also, $T_e$, extrapolated back to 10 $R_\odot{}$, is almost the same as the strahl electron temperature $T_s$ (measured by SPAN-E) which is considered to be closely related to or even almost equal to the coronal electron temperature. Furthermore, the radial $T_e$ profiles in the slower solar wind (or flux tube with larger mass flux) are steeper than those in the faster solar wind (or flux tube with smaller mass flux). More pronounced anticorrelated $V_p$-$T_e$ is observed when the solar wind is slower and closer to the Sun.

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M. Liu, K. Issautier, M. Moncuquet, et. al.
Tue, 21 Mar 23
51/68

Comments: 10 pages, 7 figures, and Astronomy & Astrophysics Accepted

Constraints on the Binarity of the WN3/O3 Class of Wolf-Rayet Stars [SSA]

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http://arxiv.org/abs/2303.11209


The WN3/O3 Wolf-Rayet (WR) stars were discovered as part of our survey for WRs in the Magellanic Clouds. The WN3/O3s show the emission lines of a high-excitation WN star and the absorption lines of a hot O-type star, but our prior work has shown that the absorption spectrum is intrinsic to the WR star. Their place in the evolution of massive stars remains unclear. Here we investigate the possibility that they are the products of binary evolution. Although these are not WN3+O3~V binaries, they could still harbor unseen companions. To address this possibility, we have conducted a multi-year radial velocity study of six of the nine known WN3/O3s. Our study finds no evidence of statistically significant radial velocity variations, and allows us to set stringent upper limits on the mass of any hypothetical companion star: for probable orbital inclinations, any companion with a period less than 100 days must have a mass less than 2Mo. For periods less than 10 days, any companion would have to have a mass less than 1Mo. We argue that scenarios where any such companion is a compact object are unlikely. The absorption lines indicate a normal projected rotational velocity, making it unlikely that these stars evolved with the aid of a companion star that has since merged. The modest rotation also suggests that these stars are not the result of homogenous evolution. Thus it is likely that these stars are a normal but short-lived stage in the evolution of massive stars.

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P. Massey, K. Neugent and K. Neugent
Tue, 21 Mar 23
54/68

Comments: Astrophysical Journal in press

The 17 April 2021 widespread solar energetic particle event [SSA]

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http://arxiv.org/abs/2303.10969


Context. A solar eruption on 17 April 2021 produced a widespread Solar Energetic Particle (SEP) event that was observed by five longitudinally well-separated observers in the inner heliosphere at heliocentric distances of 0.42 to 1 au: BepiColombo, Parker Solar Probe, Solar Orbiter, STEREO A, and near-Earth spacecraft. The event produced relativistic electrons and protons. It was associated with a long-lasting solar hard X-ray flare and a medium fast Coronal Mass Ejection (CME) with a speed of 880 km/s driving a shock, an EUV wave as well as long-lasting radio burst activity showing four distinct type III burst. Methods. A multi-spacecraft analysis of remote-sensing and in-situ observations is applied to attribute the SEP observations at the different locations to the various potential source regions at the Sun. An ENLIL simulation is used to characterize the interplanetary state and its role for the energetic particle transport. The magnetic connection between each spacecraft and the Sun is determined. Based on a reconstruction of the coronal shock front we determine the times when the shock establishes magnetic connections with the different observers. Radio observations are used to characterize the directivity of the four main injection episodes, which are then employed in a 2D SEP transport simulation. Results. Timing analysis of the inferred SEP solar injection suggests different source processes being important for the electron and the proton event. Comparison among the characteristics and timing of the potential particle sources, such as the CME-driven shock or the flare, suggests a stronger shock contribution for the proton event and a more likely flare-related source of the electron event. Conclusions. We find that in this event an important ingredient for the wide SEP spread was the wide longitudinal range of about 110 degrees covered by distinct SEP injections.

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N. Dresing, L. Rodríguez-García, I. Jebaraj, et. al.
Tue, 21 Mar 23
55/68

Comments: N/A

Scaling anisotropy with stationary background field in the near-Sun solar wind turbulence [CL]

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http://arxiv.org/abs/2303.10810


The scaling of magnetic fluctuations provides crucial information for the understanding of solar wind turbulence. However, the observed magnetic fluctuations contain not only turbulence but also magnetic structures, leading to the violation of the time stationarity. This violation would conceal the true scaling and influence the determination of the sampling angle with respect to the local background magnetic field. Here, to investigate the scaling anisotropy, we utilize an easy but effective criterion $\phi<10^\circ$ to ensure the time stationarity of the magnetic field, where $\phi$ is the angle between the two averaged magnetic fields after cutting the interval into two halves. We study the scaling anisotropy using higher-order statistics of structure functions under the condition of stationarity for the near-Sun solar wind turbulence for the first time based on measurements obtained from Parker Solar Probe (PSP) at 0.17 au. We find that the scaling indices $\xi$ of magnetic field show a linear dependence on the order $p$ close to $\xi(p)=p/4$. The multifractal scaling of magnetic-trace structure functions becomes monoscaling close to $\xi(p)=p/3$ with the local magnetic field perpendicular to the sampling direction and close to $\xi(p)=p/4$ with the local magnetic field parallel to the sampling direction when measured with the stationary background magnetic field. The scaling of velocity-trace structure functions has similar but less significant changes. The near-Sun solar wind turbulence displays different scaling anisotropies with the near-Earth solar wind turbulence, suggesting the evolution of the nonlinear interaction process during the solar wind expansion.

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H. Wu, J. He, S. Huang, et. al.
Tue, 21 Mar 23
56/68

Comments: 15 pages, 5 figures, accepted by ApJ

Cross Sections of the $^{83}$Rb(p,$γ)^{84}$Sr and $^{84}$Kr(p,$γ)^{85}$Rb Reactions at Energies Characteristic of the Astrophysical $γ$ Process [CL]

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http://arxiv.org/abs/2303.10282


We have measured the cross section of the $^{83}$Rb(p,$\gamma)^{84}$Sr radiative capture reaction in inverse kinematics using a radioactive beam of $^{83}$Rb at incident energies of 2.4 and $2.7 A$ MeV. Prior to the radioactive beam measurement, the $^{84}$Kr(p,$\gamma)^{85}$Rb radiative capture reaction was measured in inverse kinematics using a stable beam of $^{84}$Kr at an incident energy of $2.7 A$ MeV. The effective relative kinetic energies of these measurements lie within the relevant energy window for the $\gamma$ process in supernovae. The central values of the measured partial cross sections of both reactions were found to be $0.17-0.42$ times the predictions of statistical model calculations. Assuming the predicted cross section at other energies is reduced by the same factor leads to a slightly higher calculated abundance of the $p$ nucleus $^{84}$Sr, caused by the reduced rate of the $^{84}$Sr($\gamma$,p)$^{83}$Rb reaction derived from the present measurement.

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M. Williams, B. Davids, G. Lotay, et. al.
Tue, 21 Mar 23
61/68

Comments: 11 pages, 11 figures. arXiv admin note: text overlap with arXiv:2109.06775

Modelling Star Cluster Formation: Gas Accretion [GA]

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http://arxiv.org/abs/2303.11168


The formation of star clusters involves the growth of smaller, gas-rich subclusters through accretion of gas from the giant molecular cloud within which the subclusters are embedded. The two main accretion mechanisms responsible for this are accretion of gas from dense filaments, and from the ambient background of the cloud. We perform simulations of both of these accretion processes onto gas-rich star clusters using coupled smoothed particle hydrodynamics to model the gas, and N-body dynamics to model the stars. We find that, for both accretion processes, the accreting star cluster loses some of its original mass while gaining mass from either the ambient background or the dense filament. The amount of mass lost from both these processes is small compared to the total mass of the cluster. However, in the case of accretion from a background medium, the net effect can be a decrease in the total mass of the cluster if it is travelling fast enough through the ambient medium ($> 4$kms$^{-1}$). We find that the amount of mass lost from the cluster through filamentary accretion is independent of the density, width, or number of filaments funneling gas into the cluster and is always such that the mass of the cluster is constantly increasing with time. We compare our results to idealized prescriptions used to model star cluster formation in larger scale GMC simulations and find that such prescriptions act as an upper limit when describing the mass of the star cluster they represent.

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J. Karam and A. Sills
Tue, 21 Mar 23
63/68

Comments: Accepted for publication in MNRAS, 14 pages, 11 figures

3D hydrodynamics simulations of core convection in supermassive main-sequence stars [SSA]

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http://arxiv.org/abs/2303.10115


Supermassive stars are Population III stars with masses exceeding $10^4\,M_{\odot}$ that could be the progenitors of the first supermassive black holes. Their interiors are in a regime where radiation pressure dominates the equation of state. In this work, we use the explicit gas dynamics code PPMstar to simulate the hydrogen-burning core of a $10^4\,M_{\odot}$ supermassive main-sequence star. These are the first 3D hydrodynamics simulations of core convection in supermassive stars. We perform a series of ten simulations at different heating rates and on Cartesian grids with resolutions of $768^3$, $1152^3$ and $1728^3$. We examine different properties of the convective flow, including its large-scale morphology, its velocity spectrum and its mixing properties. We conclude that the radiation pressure-dominated nature of the interior does not noticeably affect the behaviour of convection compared to the case of core convection in a massive main-sequence star where gas pressure dominates. Our simulations also offer support for the use of mixing-length theory in 1D models of supermassive stars.

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S. Blouin, H. Mao, T. Woods, et. al.
Mon, 20 Mar 23
5/51

Comments: 9 pages, 9 figures, movies at this https URL, accepted for publication in MNRAS

Carbon-Oxygen Phase Separation in MESA White Dwarf Models [SSA]

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http://arxiv.org/abs/2303.10110


We enhance the treatment of crystallization for models of white dwarfs (WDs) in the stellar evolution software MESA by implementing carbon-oxygen (C/O) phase separation. The phase separation process during crystallization leads to transport of oxygen toward the center of WDs, resulting in a more compact structure that liberates gravitational energy as additional heating that modestly slows WD cooling timescales. We quantify this cooling delay in MESA C/O WD models over the mass range 0.5-1.0 $M_\odot$, finding delays of 0.5-0.8 Gyr for typical C/O interior profiles. MESA WD cooling timescales including this effect are generally comparable to other WD evolution models that make similar assumptions about input physics. When considering phase separation alongside $^{22}$Ne sedimentation, however, we find that some other sets of WD evolution models may overestimate the cooling delay associated with sedimentation, and this may therefore require a re-evaluation of previously proposed solutions to some WD cooling anomalies. Our implementation of C/O phase separation in the open-source stellar evolution software MESA provides an important tool for building realistic grids of WD cooling models, as well as a framework for expanding on our implementation to explore additional physical processes related to phase transitions and associated fluid motions in WD interiors.

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E. Bauer
Mon, 20 Mar 23
6/51

Comments: 14 pages, 9 figures, submitted to ApJ. Comments welcome!

Light-curve Modelling for The Initial Rising Phase of Rapidly-evolving Transients Powered by Continuous Outflow [HEAP]

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http://arxiv.org/abs/2303.09798


A wind-driven model is a new framework to model observational properties of transients that are powered by continuous outflow from a central system. While it has been applied to Fast Blue Optical Transients (FBOTs), the applicability has been limited to post-peak behaviours due to the steady-state assumptions; non-steady-state physics, e.g., expanding outflow, is important to model the initial rising phase. In this paper, we construct a time-dependent wind-driven model, which can take into account the expanding outflow and the time evolution of the outflow rate. We apply the model to a sample of well-observed FBOTs. FBOTs require high outflow rates ($\sim 30$ M${\odot}$ yr$^{-1}$) and fast velocity ($\sim 0.2-0.3c$), with the typical ejecta mass and energy budget of $\sim 0.2$ M${\odot}$ and $\sim 10^{52}$ erg, respectively. The energetic outflow supports the idea that the central engine of FBOTs may be related to a relativistic object, e.g., a black hole. The initial photospheric temperature is $10^{5-6}$ K, which suggests that FBOTs will show UV or X-ray flash similar to supernova shock breakouts. We discuss future prospects of surveys and follow-up observations of FBOTs in the UV bands. FBOTs are brighter in the UV bands than in the optical bands, and the timescale is a bit longer than in optical wavelengths. We suggest that UV telescopes with a wide field of view can play a key role in discovering FBOTs and characterizing their natures.

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K. Uno and K. Maeda
Mon, 20 Mar 23
10/51

Comments: 7 pages, 6 Figures, and 1 Table. Accepted for publication in MNRAS

Synthetic photometry for carbon-rich giants. V. Effects of grain-size-dependent dust opacities [SSA]

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http://arxiv.org/abs/2303.09984


The properties and the evolution of asymptotic giant branch (AGB) stars are strongly influenced by their mass loss through a stellar wind. This is believed to be caused by radiation pressure due to the absorption and scattering of the stellar radiation by the dust grains formed in the atmosphere. The optical properties of dust are often estimated using the small particle limit (SPL) approximation, and it has been used frequently in modelling AGB stellar winds when performing radiation-hydrodynamics (RHD) simulations. We aim to investigate the effects of replacing the SPL approximation by detailed Mie calculations of the size-dependent opacities for grains of amorphous carbon forming in C-rich AGB star atmospheres. We performed RHD simulations for a large grid of carbon star atmosphere+wind models with different effective temperatures, luminosities, stellar masses, carbon excesses, and pulsation properties. Also, a posteriori radiative transfer calculations for many radial structures (snapshots) of these models were done, resulting in spectra and filter magnitudes. We find, when giving up the SPL approximation, the wind models become more strongly variable and more dominated by gusts, although the average mass-loss rates and outflow speeds do not change significantly; the increased radiative pressure on the dust throughout its formation zone does, however, result in smaller grains and lower condensation fractions (and thus higher gas-to-dust ratios). The photometric K magnitudes are generally brighter, but at V the effects of using size-dependent dust opacities are more complex: brighter for low mass-loss rates and dimmer for massive stellar winds. Given the large effects on spectra and photometric properties, it is necessary to use the detailed dust optical data instead of the simple SPL approximation in stellar atmosphere+wind modelling where dust is formed.

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K. Eriksson, S. Höfner and B. Aringer
Mon, 20 Mar 23
25/51

Comments: 14 pages, 24 figures. Accepted for publication in Astronomy \& Astrophysics

Can we observe the ion-neutral drift velocity in prestellar cores? [GA]

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http://arxiv.org/abs/2303.09583


Given the low ionization fraction of molecular clouds, ambipolar diffusion is thought to be an integral process in star formation. However, chemical and radiative-transfer effects, observational challenges, and the fact that the ion-neutral drift velocity is inherently very small render a definite detection of ambipolar diffusion extremely non-trivial. Here, we study the ion-neutral drift velocity in a suite of chemodynamical, non-ideal magnetohydrodynamic (MHD), two-dimensional axisymmetric simulations of prestellar cores where we alter the temperature, cosmic-ray ionization rate, visual extinction, mass-to-flux ratio, and chemical evolution. Subsequently, we perform a number of non-local thermodynamic equilibrium (non-LTE) radiative-transfer calculations considering various idealized and non-idealized scenarios in order to assess which factor (chemistry, radiative transfer and/or observational difficulties) is the most challenging to overcome in our efforts to detect the ion-neutral drift velocity. We find that temperature has a significant effect in the amplitude of the drift velocity with the coldest modelled cores (T = 6 K) exhibiting drift velocities comparable to the sound speed. Against expectations, we find that in idealized scenarios (where two species are perfectly chemically co-evolving) the drift velocity “survives” radiative-transfer effects and can in principle be observed. However, we find that observational challenges and chemical effects can significantly hinder our view of the ion-neutral drift velocity. Finally, we propose that $\rm{HCN}$ and $\rm{HCNH^+}$, being chemically co-evolving, could be used in future observational studies aiming to measure the ion-neutral drift velocity.

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A. Tritsis, S. Basu and C. Federrath
Mon, 20 Mar 23
30/51

Comments: 14 pages, 11 figures. Accepted for publication in MNRAS

A catalog of nearby accelerating star candidates in Gaia DR3 [GA]

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http://arxiv.org/abs/2303.09712


We describe a new catalog of accelerating star candidates with Gaia $G\le 17.5$ mag and distances $d\le 100$ pc. Designated as Gaia Nearby Accelerating Star Catalog (GNASC), it contains 29,684 members identified using a supervised machine-learning algorithm trained on the Hipparcos-Gaia Catalog of Accelerations (HGCA), Gaia Data Release 2, and Gaia Early Data Release 3. We take advantage of the difference in observation timelines of the two Gaia catalogs and information about the quality of the astrometric modeling based on the premise that acceleration will correlate with astrometric uncertainties. Catalog membership is based on whether constant proper motion over three decades can be ruled out at high confidence (greater than 99.9%). Test data suggest that catalog members each have a 68% likelihood of true astrometric acceleration; subsets of the catalog perform even better, with the likelihood exceeding 85%. We compare the GNASC with Gaia Data Release 3 and its table of stars for which acceleration is detected at high confidence based on precise astrometric fits. Our catalog, derived without this information, captured over 96% of sources in the table that meet our selection criteria. In addition, the GNASC contains bright, nearby candidates that were not in the original Hipparcos survey, including members of known binary systems as well as stars with companions yet to be identified. It thus extends the HGCA and demonstrates the potential of the machine-learning approach to discover hidden partners of nearby stars in future astrometric surveys.

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M. Whiting, J. Hill, B. Bromley, et. al.
Mon, 20 Mar 23
31/51

Comments: AJ accepted, 14 pages, 6 figures, 3 tables. Catalog available with publication

Accreting white dwarfs [SSA]

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http://arxiv.org/abs/2303.10055


White dwarfs are the most common endpoints of stellar evolution. They are often found in close binary systems in which the white dwarf is accreting matter from a companion star, either via an accretion disc or channelled along the white dwarf magnetic field lines. The nature of this binary depends on the masses and the separation of the two stellar components, as well as other parameters such as the white dwarf magnetic field and the nature of the stars. This chapter looks at the formation of white dwarfs and intrinsic properties, before looking at the different populations of accreting white dwarf binary systems that exist. The chapter covers the characteristics of the various sub-populations and looks at how they evolve. The means to discover and study various sub-classes of accreting white dwarfs in the optical and other bands is discussed, and the role of these systems in the broader astrophysical context is considered. Future missions that will find new systems and new populations are also reviewed. Finally some of the current open questions regarding accreting white dwarfs are presented.

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N. Webb
Mon, 20 Mar 23
32/51

Comments: 48 pages, 6 figures, Invited (and accepted) chapter for the Handbook of X-ray and Gamma-ray Astrophysics, Editors: Cosimo Bambi, Andrea Santangelo

A Review of the Mixing Length Theory of Convection in 1D Stellar Modeling [SSA]

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http://arxiv.org/abs/2303.09596


We review the application of the one-dimensional Mixing Length Theory (MLT) model of convection in stellar interiors and low-mass stellar evolution. We summarize the history of MLT, present a derivation of MLT in the context of the 1D stellar structure equations, and discuss the physical regimes in which MLT is relevant. We review of attempts to improve and extend the formalism, including to higher dimensions. We discuss the interactions of MLT with other modeling physics and demonstrate the impact of introducing variations in the convective mixing length, {\alpha}MLT, on stellar tracks and isochrones. We summarize the process of performing a solar calibration of {\alpha}MLT and the state-of-the-art on calibrations to non-solar targets. We discuss the scientific implications of changing the mixing length, using recent analyses as demonstration. We review the most prominent successes of MLT and remaining challenges, and we conclude by speculating on the future of this treatment of convection.

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M. Joyce and J. Tayar
Mon, 20 Mar 23
33/51

Comments: invited review for MDPI Special Issue “The Structure and Evolution of Stars”

WIYN Open Cluster Study 89. M48 (NGC 2548) 2: Lithium Abundances in the 420 Myr Open Cluster M48 From Giants Through K Dwarfs [SSA]

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http://arxiv.org/abs/2303.09783


We consider WIYN/Hydra spectra of 329 photometric candidate members of the 420-Myr-old open cluster M48, and report Lithium detections or upper limits for 234 members and likely members. The 171 single members define a number of notable Li-mass trends, some delineated even more clearly than in Hyades/Praesepe: The giants are consistent with subgiant Li dilution and prior MS Li depletion due to rotational mixing. A dwarfs (8600-7700K) have upper limits higher than the presumed initial cluster Li abundance. Two of five late A dwarfs (7700- 7200K) are Li-rich, possibly due to diffusion, planetesimal accretion, and/or engulfment of hydrogen-poor planets. Early F dwarfs already show evidence of Li depletion seen in older clusters. The Li-Teff trends of the Li Dip (6675-6200K), Li Plateau (6200-6000K), and G and K dwarfs (6000-4000K) are very clearly delineated and are intermediate to those of the 120-Myr-old Pleiades and 650-Myr-old Hyades/Praesepe, which suggests a sequence of Li depletion with age. The cool side of the Li Dip is especially well-defined with little scatter. The Li-Teff trend is very tight in the Li Plateau and early G dwarfs, but scatter increases gradually for cooler dwarfs. These patterns support and constrain models of the universally dominant Li depletion mechanism for FGK dwarfs, namely rotational mixing due to angular momentum loss; we discuss how diffusion and gravity-wave driven mixing may also play roles. For late-G/K dwarfs, faster rotators show higher Li than slower rotators, and we discuss possible connections between angular momentum loss and Li depletion.

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Q. Sun, C. Deliyannis, A. Steinhauer, et. al.
Mon, 20 Mar 23
35/51

Comments: 29 pages, 10 figures, 5 tables, accepted for publication in the Astrophysical Journal

The effect of variations in magnetic field direction from turbulence on kinetic-scale instabilities [SSA]

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http://arxiv.org/abs/2303.09588


At kinetic scales in the solar wind, instabilities transfer energy from particles to fluctuations in the electromagnetic fields while restoring plasma conditions towards thermodynamic equilibrium. We investigate the interplay between background turbulent fluctuations at the small-scale end of the inertial range and kinetic instabilities acting to reduce proton temperature anisotropy. We analyse in-situ solar wind observations from the Solar Orbiter mission to develop a measure for variability in the magnetic field direction. We find that non-equilibrium conditions sufficient to cause micro-instabilities in the plasma coincide with elevated levels of variability. We show that our measure for the fluctuations in the magnetic field is non-ergodic in regions unstable to the growth of temperature anisotropy-driven instabilities. We conclude that the competition between the action of the turbulence and the instabilities plays a significant role in the regulation of the proton-scale energetics of the solar wind. This competition depends not only on the variability of the magnetic field but also on the spatial persistence of the plasma in non-equilibrium conditions.

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S. Opie, D. Verscharen, C. Chen, et. al.
Mon, 20 Mar 23
43/51

Comments: To be published in Astronomy & Astrophysics

Overall Binary Evolution Theory [HEAP]

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http://arxiv.org/abs/2303.08997


Accreting compact objects are crucial to understand several important astrophysical phenomena such as Type Ia supernovae, gravitational waves, or X-ray and $\gamma$-ray bursts. In addition, they are natural laboratories to infer fundamental properties of stars, to investigate high-energy phenomena and accretion processes, to test theories of stellar and binary evolution, to explore interactions between high-density plasma and very strong magnetic fields, to examine the interplay between binary evolution and dynamical interactions (in the case they belong to dense star clusters), and they can even be used as a probe for the assembling process of galaxies over cosmic time-scales. Despite the fundamental importance of accreting compact objects for astrophysics and recent progress with the comprehension of these fascinating objects, we still do not fully understand how they form and evolve. In this chapter, we will review the current theoretical status of our knowledge on these objects, and will discuss standing problems and potential solutions to them.

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D. Belloni and M. Schreiber
Fri, 17 Mar 23
7/67

Comments: Invited chapter for the Handbook of X-ray and Gamma-ray Astrophysics (Editors: Cosimo Bambi, Andrea Santangelo; Publisher: Springer Singapore)

The dusty circumstellar environment of Betelgeuse during the Great Dimming as seen by VLTI/MATISSE [SSA]

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http://arxiv.org/abs/2303.08892


The ‘Great Dimming’ of the prototypical red supergiant Betelgeuse, which occurred between December 2019 and April 2020, gives us unprecedented insight into the processes occurring on the stellar surface and in the inner wind of this type of star. In particular it may bring further understanding of their dust nucleation and mass loss processes. Here, we present and analyse VLTI/MATISSE observations in the N-band (8 – 13 $\mu$m) taken near the brightness minimum in order to assess the status of the dusty circumstellar environment. We explore the compatibility of a dust clump obscuring the star with our mid-infrared interferometric observations using continuum 3D radiative transfer modelling, and probe the effect of adding multiple clumps close to the star on the observables. We also test the viability of a large cool spot on the stellar surface without dust present in the ambient medium. Using the visibility data, we derive a uniform disk diameter of 59.02 $\pm$ 0.64 mas in the spectral range 8 to 8.75 $\mu$m. We find that both the dust clump and the cool spot models are compatible with the data. Further to this, we note that the extinction and emission of our localised dust clump in the line of sight of the star, directly compensate each other making the clump undetectable in the spectral energy distribution and visibilities. The lack of infrared brightening during the ‘Great Dimming’ therefore does not exclude extinction due to a dust clump as one of the possible mechanisms. The visibilities can be reproduced by a spherical wind with dust condensing at 13 stellar radii and a dust mass-loss rate of (2.1 – 4.9) $\times$ 10$^{-10}$ $\mathit{M}_{\odot} {\rm yr}^{-1}$, however, in order to reproduce the complexity of the observed closure phases, additional surface features or dust clumps would be needed.

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E. Cannon, M. Montargès, A. Koter, et. al.
Fri, 17 Mar 23
13/67

Comments: 13 Pages, accepted for publication in A&A

Simulations of pre-supernova feedback in spherical clouds [GA]

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http://arxiv.org/abs/2303.08827


We present a one-dimensional radiation-hydrodynamic model of a spherically symmetric cloud evolving under the influence of the self-gravity and the feedback from a star cluster forming in its centre. On one hand, the model is simple due to its 1D geometry, on the other hand, the feedback includes the ionising radiation, stellar winds and the radiation pressure acting on gas and dust. The star cluster is formed from the gas flowing into the cloud centre and the feedback parameters are determined from stellar evolution models and the cluster star forming history. The model is compared to the semi-analytic code WARPFIELD implementing similar physical processes and exploring the scenario that the young cluster R136 in the Large Magellanic Cloud was formed due to re-collapse of the shell formed by the previous generation star cluster. A good qualitative agreement is found, however, $3 – 4$ times higher stellar mass is needed to disrupt the cloud in our model, because it takes into account (contrary to WARPFIELD) self-gravity of the cloud surrounding the shell. We use the model to explore star formation in clouds with different mass, radius and density profile measuring their star formation efficiency (SFE), i.e. the fraction of the cloud mass converted to stars. We found that SFE is a function of a single parameter, $\mathrm{log(SFE)} \propto -n_{hm}^{-0.46}$, with $n_{hm}$ being the cloud mean particle density within its half-mass radius. Furthermore, we found that the feedback efficiency, i.e. a fraction of the feedback energy retained by gas, has a nearly constant value $\sim 10^{-3}$.

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M. Kourniotis, R. Wünsch, S. Martínez-González, et. al.
Fri, 17 Mar 23
15/67

Comments: 15 pages including appendix, 11 figures. Accepted for publication in MNRAS

Massive Protostellar Disks as a Hot Laboratory of Silicate Grain Evolution [EPA]

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http://arxiv.org/abs/2303.09148


Typical accretion disks around massive protostars are hot enough for water ice to sublimate. We here propose to utilize the massive protostellar disks for investigating the collisional evolution of silicate grains with no ice mantle, which is an essential process for the formation of rocky planetesimals in protoplanetary disks around lower-mass stars. We for the first time develop a model of massive protostellar disks that includes the coagulation, fragmentation, and radial drift of dust. We show that the maximum grain size in the disks is limited by collisional fragmentation rather than by radial drift. We derive analytic formulas that produce the radial distribution of the maximum grain size and dust surface density in the steady state. Applying the analytic formulas to the massive protostellar disk of GGD27-MM1, where the grain size is constrained from a millimeter polarimetric observation, we infer that the silicate grains in this disk fragment at collision velocities above ~ 10 m/s. The inferred fragmentation threshold velocity is lower than the maximum grain collision velocity in typical protoplanetary disks around low-mass stars, implying that coagulation alone may not lead to the formation of rocky planetesimals in those disks. With future measurements of grain sizes in massive protostellar disks, our model will provide more robust constraints on the sticking property of silicate grains.

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R. Yamamuro, K. Tanaka and S. Okuzumi
Fri, 17 Mar 23
17/67

Comments: 17 pages, 5 figures,accepted for publication to The Astrophysical Journal

ALMA detection of CO rotational line emission in red supergiant stars of the massive young star cluster RSGC1 — Determination of a new mass-loss rate prescription for red supergiants [SSA]

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http://arxiv.org/abs/2303.09385


[Abridged] Aim: We aim to derive a new mass-loss rate prescription for RSGs that is not afflicted with some uncertainties inherent in preceding studies. Methods: We have observed CO rotational line emission towards a sample of RSGs in the open cluster RSGC1 that all are of similar initial mass. The ALMA CO(2-1) line detections allow to retrieve the gas mass-loss rates (Mdot_CO). In contrast to mass-loss rates derived from the analysis of dust spectral features (Mdot_SED), the data allow a direct determination of the wind velocity and no uncertain dust-to-gas correction factor is needed. Results: Five RSGs in RSGC1 have been detected in CO(2-1). The retrieved Mdot_CO values are systematically lower than Mdot_SED. Although only five RSGs in RSGC1 have been detected, the data allow to propose a new mass-loss rate relation for M-type red supergiants that is dependent on luminosity and initial mass. The new mass-loss rate relation is based on the new Mdot_CO values for the RSGs in RSGC1 and on prior Mdot_SED values for RSGs in 4 clusters, including RSGC1. The new Mdot-prescription yields a good prediction for the mass-loss rate of some well-known Galactic RSGs that are observed in multiple CO rotational lines, including alpha Ori, mu Cep and VX Sgr. However, there are indications that a stronger, potentially eruptive, mass-loss process – different than captured by our new mass-loss rate prescription – is occurring during some fraction of the RSG lifetime. Implementing a lower mass-loss rate in evolution codes for massive stars has important consequences for the nature of their end-state. A reduction of the RSG mass-loss rate implies that quiescent RSG mass loss is not enough to strip a single star’s hydrogen-rich envelope. Upon core-collapse such single stars would explode as RSG.

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L. Decin, A. Richards, P. Marchant, et. al.
Fri, 17 Mar 23
21/67

Comments: 26 pages, submitted to Astronomy & Astrophysics, minor revisions already implemented

Detection and Characterisation of a Coronal Mass Ejection using Interplanetary Scintillation measurements from the Murchison Widefield Array [SSA]

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http://arxiv.org/abs/2303.09134


We have shown previously that the Murchison Widefield Array (MWA), can detect hundreds of Interplanetary Scintillation (IPS) sources simultaneously across a field of view $\sim30^\circ$ in extent. To test if we can use this capability to track heliospheric structures, we undertook a search of 88 hours of MWA IPS data, and identified an observation likely to have a significant Coronal Mass Ejection (CME) in the field of view. We demonstrate that in a single 5-minute MWA observation we are able to localise and image a CME $\sim$33 hours after launch at an elongation of $\sim37^\circ$ from the Sun. We use IPS observables to constrain the kinematics of the CME, and describe how MWA IPS observations can be used in the future to make a unique contribution to heliospheric modelling efforts.

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J. Morgan, P. McCauley, A. Waszewski, et. al.
Fri, 17 Mar 23
22/67

Comments: 12 pages, 4 figures. Accepted for publication in “Space Weather” (ISSN:1542-7390)

Quiescence of an Outburst of a Low-Mass Young Stellar Object: LDN1415-IRS [SSA]

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http://arxiv.org/abs/2303.09118


LDN1415-IRS, a low-mass young stellar object (YSO) went into an outburst between 2001 and 2006, illuminating a surrounding nebula, LDN1415-Neb. LDN1415-Neb was found to have brightened by I=3.77 mag by April 2006. The optical light curve covering $\sim$ 15.5 years, starting from October 2006 to January 2022, is presented in this study. The initial optical spectrum indicated the presence of winds in the system but the subsequent spectra have no wind indicators. The declining light curve and the absence of the P-Cygni profile in later epoch spectra indicate that the star and nebula system is retrieving back from its outburst state. Two Herbig-Haro objects (HHOs) are positioned linearly with respect to the optical brightness peak of the nebula, probably indicating the circumstellar disk being viewed edge-on. Our recent deep near-infrared (NIR) imaging using TANSPEC has revealed the presence of a nearby star-like source, south of the LDN1415-IRS, at an angular distance of $\sim$ 5.4 arcsec.

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K. Singh, D. Ojha, J. Ninan, et. al.
Fri, 17 Mar 23
25/67

Comments: Accepted for publication in the Journal of Astrophysics and Astronomy

OGLE-2016-BLG-1195 AO: Lens, Companion to Lens or Source, or None of the Above? [EPA]

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http://arxiv.org/abs/2303.08876


We systematically investigate the claim by Vandorou et al. (2023) to have detected the host star of the low mass-ratio ($q<10^{-4}$) microlensing planet OGLE-2016-BLG-1195Lb, via Keck adaptive optics (AO) measurements $\Delta t=4.12\,$yr after the peak of the event ($t_0$). If correct, this measurement would contradict the microlens parallax measurement derived from Spitzer observations in solar orbit taken near $t_0$. We show that this host identification would be in $4\,\sigma$ conflict with the original ground-based lens-source relative proper-motion measurements. By contrast, Gould (2022) estimated a probability $p=10\%$ that the other star'' resolved by single-epoch late-time AO would be a companion to the host or the microlensed source, which is much more probable than a 4$\,\sigma$ statistical fluctuation. In addition, independent of this proper-motion discrepancy, the kinematics of this host-identification are substantially less probable than those of the Spitzer solution. Hence, this identification should not be accepted, pending additional observations that would either confirm or contradict it, which could be taken in 2023. Motivated by this tension, we present two additional investigations. We explore the possibility that Vandorou et al. (2023) identified the wrongstar” (or stellar asterism) on which to conduct their analysis. We find that astrometry of KMT and Keck images favors a star (or asterism) lying about 175 mas northwest of the one that they chose. We also present event parameters from a combined fit to all survey data, which yields, in particular, a more precise mass ratio, $q=(4.6\pm 0.4)\times 10^{-5}$. Finally, we discuss the broader implications of minimizing such false positives for the first measurement of the planet mass function, which will become possible when AO on next-generation telescopes are applied to microlensing planets.

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A. Gould, Y. Shvartzvald, J. Zhang, et. al.
Fri, 17 Mar 23
28/67

Comments: 31 pages, 7 figures, 3 tables, 2 appendices, submitted to AAS Journals

Repeating Outbursts from the Young Stellar Object Gaia23bab (= SPICY 97589) [SSA]

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http://arxiv.org/abs/2303.09409


The light curve of Gaia23bab (= SPICY 97589) shows two significant ($\Delta G>2$ mag) brightening events, one in 2017 and an ongoing event starting in 2022. The source’s quiescent spectral energy distribution indicates an embedded ($A_V>5$ mag) pre-main-sequence star, with optical accretion emission and mid-infrared disk emission. This characterization is supported by the source’s membership in an embedded cluster in the star-forming cloud DOBASHI 1604 at a distance of $900\pm45$~pc. Thus, the brightening events are probable accretion outbursts, likely of EX Lup-type.

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M. Kuhn, R. Benjamin, E. Ishida, et. al.
Fri, 17 Mar 23
30/67

Comments: 4 pages and 1 figure. Submitted to Research Notes of the AAS

Extinction towards the cluster R136 in the Large Magellanic Cloud: An extinction law from the near-infrared to the ultraviolet [GA]

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http://arxiv.org/abs/2303.09374


The cluster R136 in the giant star-forming region 30 Doradus in the Large Magellanic Cloud (LMC) offers a unique opportunity to resolve a stellar population in a starburst-like environment. We obtain the near-infrared to ultraviolet extinction towards 50 stars in the core of R136, employing the `extinction without standards’ method. To assure good fits over the full wavelength range, we combine and modify existing extinction laws. We detect a strong spatial gradient in the extinction properties across the core of R136, coinciding with a gradient in density of cold gas that is part of a molecular cloud lying northeast of the cluster. In line with previous measurements of R136 and the 30 Doradus region, we obtain a high total-to-relative extinction ($R_V = 4.38 \pm 0.87$). However, the high values of $R_V$ are accompanied by relatively strong extinction in the ultraviolet, contrary to what is observed for Galactic sightlines. The relatively strong ultraviolet extinction suggests that the properties of the dust towards R136 differ from those in the Milky Way. For $R_{V} \sim 4.4$, about three times fewer ultraviolet photons can escape from the ambient dust environment relative to the canonical Galactic value of $R_{V} \sim 3.1$ at the same $A_{V}$. Therefore, if dust in the R136 star-bursting environment is characteristic for cosmologically distant star-bursting regions, the escape fraction of ultraviolet photons from such regions is overestimated by a factor of three relative to the standard Milky Way assumption for the total-to-selective extinction. Furthermore, a comparison with average curves tailored to other regions of the LMC shows that large differences in ultraviolet extinction exist within this galaxy. Further investigation is required in order to decipher whether or not there is a relation between $R_V$ and ultraviolet extinction in the LMC.

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S. Brands, A. Koter, J. Bestenlehner, et. al.
Fri, 17 Mar 23
33/67

Comments: Accepted for publication in A&A (18 pages, 12 figures)

Solar center-to-limb variation in Rossiter-McLaughlin and exoplanet transmission spectroscopy [SSA]

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http://arxiv.org/abs/2303.09169


Line profiles from spatially unresolved stellar observations consist of a superposition of local line profiles that result from observing the stellar atmosphere under specific viewing angles. Line profile variability caused by stellar magnetic activity or planetary transit selectively varies the weight and/or shape of profiles at individual surface positions. The effect is usually modeled with radiative transfer calculations because observations of spatially resolved stellar surfaces are not available. For the Sun, we recently obtained a broadband spectroscopic atlas of the solar center-to-limb variation (CLV). We use the atlas to study systematic differences between largely used radiative transfer calculations and solar observations. We concentrate on four strong lines useful for exoplanet transmission analysis, and we investigate the impact of CLV on transmission and Rossiter-McLaughlin (RM) curves. Solar models used to calculate synthetic spectra tend to underestimate line core depths but overestimate the effect of CLV. Our study shows that CLV can lead to significant systematic offsets in transmission curves and particularly in RM curves; transmission curves centered on individual lines are overestimated by up to a factor of two by the models, and simulations of RM curves yield amplitudes that are off by up to 5–10\,m\,s$^{-1}$ depending on the line. For the interpretation of transit observations, it is crucial for model spectra that accurately reproduce the solar CLV to become available which, for now, is the only calibration point available.

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A. Reiners, F. Yan, M. Ellwarth, et. al.
Fri, 17 Mar 23
38/67

Comments: 10 pages, accepted for publication in A&A, solar spectra library available at this http URL

The First Multiband Photometric Light Curve Solutions of the V Gru Binary System from the Southern Hemisphere [SSA]

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http://arxiv.org/abs/2303.09109


The first multiband photometric solutions of the short-period V Gru eclipsing binary from the southern hemisphere is presented in this study. Light curves of the system were observed through BVI filters at the Congarinni Observatory in Australia for 15 nights. In addition to the new ground-based data, we also used the TESS observations in two sectors. We analyzed the light curves of the system using the PHysics Of Eclipsing BinariEs (PHOEBE) 2.4.7 version code to achieve the best accordance with the photometric observations. The solutions suggest that V Gru is a near-contact binary system with q=1.302(81) mass ratio, f1=0.010(23), f2=-0.0.009(21), and i=73.45(38). We considered the two hot spots on the hotter and cooler components for the light curve analysis. We extracted the minima times from the light curves based on the Markov Chain Monte Carlo (MCMC) approach. Using our new light curves, TESS, and additional literature minima, we computed the ephemeris of V Gru. The system’s eclipse timing variation trend was determined using the MCMC method. This system is a good and challenging case for future studies.

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M. Tanriver, A. Poro, A. Bulut, et. al.
Fri, 17 Mar 23
45/67

Comments: Accepted by the Research in Astronomy and Astrophysics (RAA) journal

Modeling contact binaries, II. The effect of energy transfer [SSA]

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http://arxiv.org/abs/2303.09328


Context. It is common for massive stars to engage in binary interaction. In close binaries, the components can enter a contact phase, where both stars overflow their respective Roche lobes simultaneously. While there exist observational constraints on the stellar properties of such systems, the most detailed stellar evolution models that feature a contact phase are not fully reconcilable with those measurements. Aims. We aim to consistently model contact phases of binary stars in a 1D stellar evolution code. To this end, we develop the methodology to account for energy transfer in the common contact layers. Methods. We implement an approximative model for energy transfer between the components of a contact binary based on the von Zeipel theorem in the stellar evolution code MESA. We compare structure and evolution models with and without this transfer and analyze the implications for the observable properties of the contact phase. Results. Implementing energy transfer helps eliminating baroclinicity in the common envelope between the components of a contact binary, which, if present, would drive strong thermal flows. We find that accounting for energy transfer in massive contact binaries significantly alters the mass ratio evolution and can extend the lifetime of an unequal mass ratio contact system.

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M. Fabry, P. Marchant, N. Langer, et. al.
Fri, 17 Mar 23
47/67

Comments: 11 pages, 5 figures. Accepted to A&A

The Empirical Limits of Gyrochronology [SSA]

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http://arxiv.org/abs/2303.08830


The promise of gyrochronology is that given a star’s rotation period and mass, its age can be inferred. The reality of gyrochronology is complicated by effects other than ordinary magnetized braking that alter stellar rotation periods. In this work, we present an interpolation-based gyrochronology framework that reproduces the time- and mass-dependent spin-down rates implied by the latest open cluster data, while also matching the rate at which the dispersion in initial stellar rotation periods decreases as stars age. We validate our technique for stars with temperatures of 3800-6200 K and ages of 0.08-2.6 gigayears (Gyr), and use it to reexamine the empirical limits of gyrochronology. In line with previous work, we find that the uncertainty floor varies strongly with both stellar mass and age. For Sun-like stars (5800 K), the statistical age uncertainties improve monotonically from $\pm$38% at 0.2 Gyr to $\pm12$% at 2 Gyr, and are caused by the empirical scatter of the cluster rotation sequences combined with the rate of stellar spin-down. For low-mass K-dwarfs (4200 K), the posteriors are highly asymmetric due to stalled spin-down, and $\pm$1$\sigma$ age uncertainties vary non-monotonically between 10% and 50% over the first few gigayears. High-mass K-dwarfs (5000 K) older than 1.5 Gyr yield the most precise ages, with limiting uncertainties currently set by possible changes in the spin-down rate (12% systematic), the calibration of the absolute age scale (8% systematic), and the width of the slow sequence (4% statistical). An open-source implementation, called gyro-interp, is available online at https://github.com/lgbouma/gyro-interp

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L. Bouma, E. Palumbo and L. Hillenbrand
Fri, 17 Mar 23
48/67

Comments: ApJL accepted. Data behind Fig1 are uploaded. Code documentation is at this https URL

Optical and near-infrared spectroscopy of the black hole transient 4U 1543-47 during its 2021 ultra-luminous state [HEAP]

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http://arxiv.org/abs/2303.08837


We present simultaneous optical and near-infrared spectra obtained during the 2021 outburst of the black hole transient 4U 1543-47. The X-ray hardness-intensity diagram and the comparison with similar systems reveal a luminous outburst, probably reaching the Eddington luminosity, as well as a long-lasting excursion to the so-called ultra-luminous state. VLT/X-shooter spectra were taken in two epochs 14 days apart during the early and brightest part of the outburst, while the source was in this ultra-luminous accretion state. The data show strong H and HeI emission lines, as well as high-excitation HeII and OIII transitions. Most lines are single-peaked in both spectra, except for the OIII lines that exhibit evident double-peaked profiles during the second epoch. The Balmer lines are embedded in broad absorption wings that we believe are mainly produced by the contribution of the A2V donor to the optical flux, which we estimate to be in the range of 11 to 14 per cent in the $r$ band during our observations. Although no conspicuous outflow features are found, we observe some wind-related line profiles, particularly in the near-infrared. Such lines include broad emission line wings and skewed red profiles, suggesting the presence of a cold (i.e. low ionisation) outflow with similar observational properties to those found in other low-inclination black hole transients.

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J. Sánchez-Sierras, T. Muñoz-Darias, J. Casares, et. al.
Fri, 17 Mar 23
52/67

Comments: Accepted for publication in A&A

Improved prior for adaptive optics point spread function estimation from science images: Application for deconvolution [IMA]

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http://arxiv.org/abs/2303.09422


Access to knowledge of the point spread function (PSF) of adaptive optics(AO)-assisted observations is still a major limitation when processing AO data. This limitation is particularly important when image analysis requires the use of deconvolution methods. As the PSF is a complex and time-varying function, reference PSFs acquired on calibration stars before or after the scientific observation can be too different from the actual PSF of the observation to be used for deconvolution, and lead to artefacts in the final image. We improved the existing PSF-estimation method based on the so-called marginal approach by enhancing the object prior in order to make it more robust and suitable for observations of resolved extended objects. Our process is based on a two-step blind deconvolution approach from the literature. The first step consists of PSF estimation from the science image. For this, we made use of an analytical PSF model, whose parameters are estimated based on a marginal algorithm. This PSF was then used for deconvolution. In this study, we first investigated the requirements in terms of PSF parameter knowledge to obtain an accurate and yet resilient deconvolution process using simulations. We show that current marginal algorithms do not provide the required level of accuracy, especially in the presence of small objects. Therefore, we modified the marginal algorithm by providing a new model for object description, leading to an improved estimation of the required PSF parameters. Our method fulfills the deconvolution requirement with realistic system configurations and different classes of Solar System objects in simulations. Finally, we validate our method by performing blind deconvolution with SPHERE/ZIMPOL observations of the Kleopatra asteroid.

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A. Lau, R. Fétick, B. Neichel, et. al.
Fri, 17 Mar 23
55/67

Comments: accepted for publication in Astronomy & Astrophysics (A&A)

Seismological Studies of Pulsating DA White Dwarfs Observed with the Kepler Space Telescope and K2 Campaigns 1-8 [SSA]

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http://arxiv.org/abs/2303.08887


All single stars that are born with masses up to 8.5 – 10 $M_\odot$ will end their lives as a white dwarf (WD) star. In this evolutionary stage, WDs enter the cooling sequence, where the stars radiate away their thermal energy, and are basically cooling. As these stars cool, they reach temperatures and conditions that cause the stars to pulsate. Using differential photometry to produce light curves, we can determine the observed periods of pulsation from the WD. We used the White Dwarf Evolution Code (WDEC) to calculate a grid of over one million models with various temperature, stellar mass and mass of helium and hydrogen layers, and calculated their theoretical pulsation periods. In this paper, we describe our approach to WD asteroseismology using WDEC models and we present seismological studies for 29 observed DAVs in the Kepler and K2 datasets, 25 of which have never been analyzed using these observations, and 19 of which have never been seismically analyzed in any capacity before. Learning about the internal structure of WDs place important constraints on the WD cooling sequence and our overall understanding of stellar evolution for low mass stars.

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W. Hall, B. Castanheira and A. Bischoff-Kim
Fri, 17 Mar 23
58/67

Comments: 22 pages, 9 Tables and 12 Figures, ApJ accepted

Azimuthal C/O Variations in a Planet-Forming Disk [EPA]

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http://arxiv.org/abs/2303.08927


The elemental carbon-to-oxygen ratio (C/O) in the atmosphere of a giant planet is a promising diagnostic of that planet’s formation history in a protoplanetary disk. Alongside efforts in the exoplanet community to measure C/O in planetary atmospheres, observational and theoretical studies of disks are increasingly focused on understanding how the gas-phase C/O varies both with radial location and between disks. This is mostly tied to the icelines of major volatile carriers such as CO and H2O. Using ALMA observations of CS and SO, we have unearthed evidence for an entirely novel type of C/O variation in the protoplanetary disk around HD 100546: an azimuthal variation from a typical, oxygen-dominated ratio (C/O=0.5) to a carbon-dominated ratio (C/O>1.0). We show that the spatial distribution and peculiar line kinematics of both CS and SO molecules can be well-explained by azimuthal variations in the C/O ratio. We propose a shadowing mechanism that could lead to such a chemical dichotomy. Our results imply that tracing the formation history of giant exoplanets using their atmospheric C/O ratios will need to take into account time-dependent azimuthal C/O variations in a planet’s accretion zone.

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L. Keyte, M. Kama, A. Booth, et. al.
Fri, 17 Mar 23
59/67

Comments: Accepted in Nature Astronomy

Physics-based model of solar wind stream interaction regions: Interfacing between Multi-VP and 1D MHD for operational forecasting at L1 [SSA]

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http://arxiv.org/abs/2303.09221


Our current capability of space weather prediction in the Earth’s radiation belts is limited to only an hour in advance using the real-time solar wind monitoring at the Lagrangian L1 point. To mitigate the impacts of space weather on telecommunication satellites, several frameworks were proposed to advance the lead time of the prediction. We develop a prototype pipeline called “Helio1D” to forecast ambient solar wind conditions (speed, density, temperature, tangential magnetic field) at L1 with a lead time of 4 days. This pipeline predicts Corotating Interaction Regions (CIRs) and high-speed streams that can increase high-energy fluxes in the radiation belts. The Helio1D pipeline connects the Multi-VP model, which provides real-time solar wind emergence at 0.14 AU, and a 1D MHD model of solar wind propagation. We benchmark the Helio1D pipeline for solar wind speed against observations for the intervals in 2004 – 2013 and 2017 – 2018. We developed a framework based on the Fast Dynamic Time Warping technique that allows us to continuously compare time-series outputs containing CIRs to observations to measure the pipeline’s performance. In particular, we use this framework to calibrate and improve the pipeline’s performance for operational forecasting. To provide timing and magnitude uncertainties, we model several solar wind conditions in parallel, for a total of 21 profiles corresponding to the various virtual targets including the Earth. This pipeline can be used to feed real-time, daily solar wind forecasting that aims to predict the dynamics of the inner magnetosphere and the radiation belts.

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R. Kieokaew, R. Pinto, E. Samara, et. al.
Fri, 17 Mar 23
60/67

Comments: 24 pages, 9 figures. The appendix is available upon request

Detection of a high-velocity sodium feature on the ultra-hot Jupiter WASP-121 b [EPA]

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http://arxiv.org/abs/2303.09376


Ultra-hot Jupiters, with their high equilibrium temperatures and resolved spectral lines, have emerged as a perfect testbed for new analysis techniques in the study of exoplanet atmospheres. In particular, the resolved sodium doublet as a resonant line has proven a powerful indicator to probe the atmospheric structure over a wide pressure range. We explore an atmospheric origin of the observed blueshifted feature next to the sodium doublet of the ultra-hot Jupiter WASP-121~b, using a partial transit obtained with the 4-UT mode of ESPRESSO. We study its atmospheric dynamics visible across the terminator by splitting the data into mid-transit and egress. We determine that the blueshifted high-velocity absorption component is generated only during the egress part of the transit when a larger fraction of the day side of the planet is visible. For the egress data, MERC retrieves the blueshifted high-velocity absorption component as an equatorial day-to-night side wind across the evening limb, with no zonal winds visible on the morning terminator with weak evidence compared to a model with only vertical winds. For the mid-transit data, the observed line broadening is attributed to a vertical, radial wind. We attribute the equatorial day-to-night side wind over the evening terminator to a localised jet and restrain its existence between the substellar point and up to $10^\circ$ to the terminator in longitude, an opening angle of the jet of at most $60^\circ$ in latitude, and a lower boundary in altitude between [1.08, 1.15] $R_p$. Due to the partial nature of the transit, we cannot make any statements on whether the jet is truly super-rotational and one-sided or part of a symmetric day-to-night side atmospheric wind from the hotspot.

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J. Seidel, F. Borsa, L. Pino, et. al.
Fri, 17 Mar 23
65/67

Comments: 15 pages, 10 figures, 2 appendixes, accepted for publication in A&A on March 10th, 2023

The parallax and 3D kinematics of water masers in the massive star-forming region G034.43+0.24 [GA]

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http://arxiv.org/abs/2303.09129


We report a trigonometric parallax measurement of 22 GHz water masers in the massive star-forming region G034.43+0.24 as part of the Bar and Spiral Structure Legacy (BeSSeL) Survey using the Very Long Baseline Array. The parallax is 0.330$\pm$50.018 mas, corresponding to a distance of $3.03^{+0.17}_{-0.16}$ kpc. This locates G034.43+0.24 near the inner edge of the Sagittarius spiral arm and at one end of a linear distribution of massive young stars which cross nearly the full width of the arm. The measured 3-dimensional motion of G034.43+0.24 indicates a near-circular Galactic orbit. The water masers display arc-like distributions, possibly bow shocks, associated with winds from one or more massive young stars.

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X. Mai, B. Zhang, M. Reid, et. al.
Fri, 17 Mar 23
67/67

Comments: N/A

Biosignature Line Ratios of [P II] in Exoplanetary and Nebular Environments [EPA]

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http://arxiv.org/abs/2301.07736


Being the backbone element of DNA, phosphorus is a key component in the search for life in the Universe. To aid in its detection, we present line emissivity ratios for the five lowest-lying forbidden [P~II] transitions, namely those among the levels $3s^23p^2(^3P_0,^3P_1, ^3P_2,^1D_2,^1S_0)$. The wavelengths range between 0.44-70 \mum, and several lie within the spectroscopic domain observable with the James Webb Space Telescope (JWST). These line ratios have been calculated using a new collisional-radiative-recombination (CRR) model combining calculated collision strengths and level-specific recombination rate coefficients; with both datasets computed using the accurate Breit-Pauli R-Matrix method. The CRR model includes a new scheme for \eion recombination to emission line formation. We compare its effect to models incorporating only electron impact excitation and spontaneous radiative decay. We find that electron-ion recombination has a significant impact on all line ratios, and represents a major improvement in physical accuracy of emission line models.

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K. Hoy, S. Nahar and A. Pradhan
Fri, 20 Jan 23
1/72

Comments: 5 pages, 4 figures

Tracing the history of an unusual compound presolar grain from progenitor star to asteroid parent body host [EPA]

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http://arxiv.org/abs/2301.08228


We conducted a TEM study of an unusual oxide-silicate composite presolar grain (F2-8) from the unequilibrated ordinary chondrite Semarkona. The presolar composite grain is relatively large, has an amoeboidal shape, and contains Mg-rich olivine, Mg-Al spinel, and Ca-rich pyroxene. The shape and phase assemblage are reminiscent of amoeboid-olivine-aggregates and add to the growing number of TEM observations of presolar refractory inclusion-like (CAIs and AOAs) grains. In addition to the dominant components, F2-8 also contains multiple subgrains, including an alabandite-oldhamite composite grain within the olivine and several magnetite subgrains within the Mg-Al spinel. We argue that the olivine, Mg-Al spinel, and alabandite-oldhamite formed by equilibrium condensation, whereas the Ca-rich pyroxene formed by non-equilibrium condensation, all in an M-type AGB star envelope. On the other hand, the magnetite subgrains are likely the result of aqueous alteration on the Semarkona asteroidal parent body. Additional evidence of secondary processing includes Fe-enrichment in the Mg-Al spinel and olivine, elevated Al contents in the olivine, and beam sensitivity and a modulated structure for the olivine. Compound presolar grains record condensation conditions over a wide range of temperatures. Additionally, the presence of several different presolar phases in a composite grain can impart information on the relative rates and effects of post-condensation processing in a range of environments, including the interstellar medium, solar nebula, and the host asteroid parent body. The TEM observations of F2-8 provide insights across the lifetime of the grain from its formation by condensation in an M-type AGB star envelope, its transit through the interstellar medium, and aqueous alteration during its residence on Semarkona’s asteroidal parent body.

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S. Singerling, L. Nittler, J. Barosch, et. al.
Fri, 20 Jan 23
6/72

Comments: 36 total pages, including 6 figures, 3 supplemental figures, 4 tables, and 2 supplemental tables

Multifrequency microwave imaging of weak transients from the quiet solar corona [SSA]

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http://arxiv.org/abs/2301.07840


Understanding the dynamics of the quiet solar corona is important for answering key questions including the coronal heating problem. Multiple studies have suggested small-scale magnetic reconnection events may play a crucial role. These reconnection events are expected to involve accelerating electrons to suprathermal energies, which can then produce nonthermal observational signatures. However, due to the paucity of sensitive high-fidelity observations capable of probing these nonthermal signatures, most studies were unable to quantify their nonthermal nature. Here we use joint radio observations from the Very Large Array (VLA) and the Expanded Owens Valley Solar Array (EOVSA) to detect transient emissions from the quiet solar corona in the microwave (GHz) domain. While similar transients have been reported in the past, their nonthermal nature could not be adequately quantified due to the unavailability of broadband observations. Using a much larger bandwidth available now with the VLA and EOVSA, in this study, we are able to quantify the nonthermal energy associated with two of these transients. We find that the total nonthermal energy associated with some of these transients can be comparable to or even larger than the total thermal energy of a nanoflare, which underpins the importance of nonthermal energy in the total coronal energy budget.

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S. Mondal, B. Chen and S. Yu
Fri, 20 Jan 23
9/72

Comments: Submitted to ApJ

An XMM-Newton view of the Symbiotic Stars HM Sge, NQ Gem, and PU Vul [SSA]

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http://arxiv.org/abs/2301.08191


We present the analysis of archival XMM-Newton observations of the symbiotic stars (SySts) HM Sge, NQ Gem, and PU Vul. The EPIC-pn spectra reveal the presence of emission lines and spectral modeling reveal unprecedented characteristics. For instance, the best fit to the EPIC-pn spectrum of the $\beta$-type SySt PU Vul reveals the presence of two plasma components. We report the discovery of an extremely soft spectral component in the EPIC-pn spectrum of the $\beta$-type Syst HM Sge which we suggest is produced by periodic mass ejections such as jets. We suggest that a simple $\beta$-type classification no longer applies to HM Sge. Finally, the spectrum of the $\beta/\delta$-type SySt NQ Gem can not be fitted by a two-temperature plasma model as performed by previous authors. The model requires extra components to fit the 1.0–4.0 keV energy range. More sophisticated models to $\beta/\delta$-type SySt are needed in order to peer into the accretion process from such systems.

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J. Toalá, M. Botello and L. Sabin
Fri, 20 Jan 23
21/72

Comments: 6 pages, 2 Tables, 2 Figures; Submitted to ApJ

Stereoscopic Observation of Simultaneous Longitudinal and Transverse Oscillations in a Single Filament Driven by Two-sided-loop Jet [SSA]

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http://arxiv.org/abs/2301.07989


We report the first observations of simultaneous large-amplitude longitudinal and transverse oscillations of a quiescent filament trigged by a two-sided-loop jet formed by the magnetic reconnection between the filament and an emerging loop in the filament channel, recorded by the Solar Dynamics Observatory and the Solar TErrestrial RElations Observatory. The north arm of the jet firstly pushed the filament mass moving northwardly along the magnetic field lines consisting of the coronal cavity, then some elevated filament mass fell back and started to oscillate longitudinally at the bottom of the cavity (i.e., the magnetic dip). The northernmost part of the filament also showed transverse oscillation simultaneously. The amplitude and period of the longitudinal (transverse) oscillation are 12.96 (2.99) Mm and 1.18 (0.33) hours, respectively. By using the method of filament seismology, the radius of curvature of the magnetic dip is about 151 Mm, consistent with that obtained by the 3D reconstruction (166 Mm). Using different physical parameters of the observed longitudinal and transverse oscillations, the magnetic field strength of the filament is estimated to be about 23 and 21 Gauss, respectively. By calculating the energy of the moving filament mass, the minimum energy of the jet is estimated to be about 1.96 x 10^28 erg. We conclude that the newly formed jet can not only trigger simultaneous longitudinal and transverse oscillations in a single filament, but also can be used as a seismology tool for diagnosing filament information, such as the magnetic structure, magnetic field strength, and magnetic twists.

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S. Tan, Y. Shen, X. Zhou, et. al.
Fri, 20 Jan 23
26/72

Comments: 9 pages, 7 figures, accept by MNRAS

Timing the formation of the Galactic thin disc with asteroseismic stellar ages [GA]

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http://arxiv.org/abs/2301.07990


The formation of the extended thin disc is the most spectacular event of our Galaxy in the past $\sim8$\,Gyr. To unveil this process, obtaining precise and accurate stellar ages for a large sample of stars is essential although challenging. In this work, we present the asteroseismic age determination of 5306 red giant branch stars using \kepler{} and LAMOST data, with a thorough examination of how the age determination is affected by the choice of different temperature scales and stellar models. Thanks to the high precision of the asteroseismic and spectroscopic parameters of our sample stars, we are able to achieve age determination with an average accuracy of 12 per cent. However, the age determination is sensitively dependent on the adopted temperature scale, as 50\,K difference in effective temperature may cause larger than 10 per cent systematic uncertainty in the age estimates. Using the ages derived with the most plausible set of the temperature scale, we study the age distribution of the chemical thin disc stars, and present an estimate of the formation epoch of the first Galactic thin disc stars. We find that the first (oldest) thin disc stars have an age of $9.5^{+0.5(\rm rand.)+0.5(\rm sys.)}_{-0.4(\rm rand.)-0.3(\rm sys.)}$\,Gyr, where the systematic uncertainties reflect ages estimated using different stellar evolutionary models. At this epoch, the Galactic thick disc was still forming stars, indicating there is a time window when both the thin and thick discs of our Galaxy were forming stars together. Moreover, we find that the first thin disc stars exhibit a broad distribution of Galactocentric radii, suggesting that the inner and outer thin discs began to form simultaneously.

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W. Yaqian, X. Maosheng, Z. Gang, et. al.
Fri, 20 Jan 23
27/72

Comments: 17 pages, 13 figures, accepted by MNRAS

Photometric Calibrations of M-dwarf Metallicity with Markov Chain Monte Carlo and Bayesian Inference [SSA]

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http://arxiv.org/abs/2301.08036


Knowledge of stellar atmospheric parameters ($T_{\rm eff}$, $\log{g}$, [Fe/H]) of M dwarfs can be used to constrain both theoretical stellar models and Galactic chemical evolutionary models, and guide exoplanet searches, but their determination is difficult due to the complexity of the spectra of their cool atmospheres. In our ongoing effort to characterize M dwarfs, and in particular their chemical composition, we carried out multiband photometric calibrations of metallicity for early- and intermediate-type M dwarfs. The third Gaia data release provides high-precision astrometry and three-band photometry. This information, combined with the 2MASS and CatWISE2020 infrared photometric surveys and a sample of 4919 M dwarfs with metallicity values determined with high-resolution spectroscopy by The Cannon and APOGEE spectra, allowed us to study the effect of the metallicity in color-color and color-magnitude diagrams. We divided this sample into two subsamples: we used 1000 stars to train the calibrations with Bayesian statistics and Markov Chain Monte Carlo techniques, and the remaining 3919 stars to check the accuracy of the estimations. We derived several photometric calibrations of metallicity applicable to M dwarfs in the range of $-0.45\leq\text{[Fe/H]}\leq +0.45$ dex and spectral types down to M5.0 V that yield uncertainties down to the $0.10$ dex level. Lastly, we compared our results with other photometric estimations published in the literature for an additional sample of 46 M dwarfs in wide binary systems with FGK-type primary stars, and found a great predictive performance.

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C. Duque-Arribas, D. Montes, H. Tabernero, et. al.
Fri, 20 Jan 23
31/72

Comments: Accepted for publication in ApJ, 24 pages, 14 figures and 7 tables

Grid-Based Simulations of Polar Circumbinary Disks: Polar Alignment and Vortex Formation [EPA]

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http://arxiv.org/abs/2301.07796


We describe the first grid-based simulations of the polar alignment of a circumbinary disk. We simulate the evolution of an inclined disk around an eccentric binary using the grid-based code ATHENA++. The use of a grid-based numerical code allows us to explore lower disk viscosities than have been examined in previous studies. We find that the disk aligns to a polar orientation when the $\alpha$ viscosity is high, while disks with lower viscosity nodally precess with little alignment over 1000 binary orbital periods. The timescales for polar alignment and disk precession are compared as a function of disk viscosity, and are found to be in agreement with previous studies. At very low disk viscosities (e.g. $\alpha = 10^{-5}$), anticyclonic vortices are observed along the inner edge of the disk. These vortices can persist for thousands of binary orbits, creating azimuthally localized overdensities as well as multiple pairs of spiral arms. The vortex is formed at $\sim 3-4$ times the binary semi-major axis, close to the inner edge of the disk, and orbits at roughly the local Keplerian speed. The presence of a vortex in the disk may play an important role in the evolution of circumbinary systems, such as driving episodic accretion and accelerating the formation of polar circumbinary planets.

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I. Rabago, Z. Zhu, R. Martin, et. al.
Fri, 20 Jan 23
37/72

Comments: 10 pages, 11 figures, Accepted for publication in MNRAS. Visualizations of the simulations in this paper can be found online at this https URL

Where are the missing symbiotic stars? Uncovering hidden Symbiotic Stars in public catalogues [SSA]

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http://arxiv.org/abs/2301.08201


Theoretical predictions of the population of Galactic symbiotic stars (SySts) are highly inconsistent with the current known population. Despite intense effort over the past decades, observations are still far below the predictions. The majority of known SySts so far are identified based on selection criteria established in the optical regime. The recent discovery of SU Lyn with very faint optical emission lines uncloaked a subgroup of SySts with accreting-only white dwarfs. In this particular case, the luminous red giant may overshadow the dimmed white dwarf companion. A new approach to search for this subgroup of SySts is presented, employing GALEX UV and 2MASS/AllWISE IR photometry. The FUV-NUV colour index is an indicator, direct or indirect, for the presence of hot compact companions. The cross-match of the Catalogue of Variable Stars III obtained from the All-Sky Automated Survey for SuperNovae with the GALEX, 2MASS and AllWISE catalogues result in a sample of 814 potential SySt candidates. From them, 105 sources have photometric measurements from both FUV and NUV bands and 35 exhibit FUV-NUV<1, similar to what it is expected from known SySts. Five known SySts are recovered, while two new genuine SySts are discovered in spectroscopic follow-up observations after the detection of the typical emission lines.

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S. Akras
Fri, 20 Jan 23
48/72

Comments: 11 pages, 5 figures, 1 table, accepted for Publication in MNRAS

Internal and external alignment of carbonaceous grains within the radiative torque paradigm [GA]

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http://arxiv.org/abs/2301.07832


We study the internal and external alignment of carbonaceous grains, including graphite and hydrogenated amorphous carbon (HAC), in the interstellar medium (ISM) within the RAdiative Torque (RAT) paradigm. For internal alignment (IA), we find that HAC grains having nuclear paramagnetism due to hydrogen protons can have efficient nuclear relaxation, whereas both HAC and graphite grains can have efficient inelastic relaxation for grains aligned both at low$-J$ and high$-J$ attractors. For external alignment, HAC and graphite grains can align with the radiation direction ($k$-RAT) at low$-J$ attractors but cannot have stable alignment at high$-J$ attractors due to the suppression of radiative precession. HAC also has slow Larmor precession compared to the randomization by gas collisions and cannot be aligned with the magnetic field ($B$-RAT). Small HAC grains of $a<0.05\mu$m drifting through the diffuse ISM can be weakly aligned along the induced electric field ($E$-RAT) at high$-J$ attractors due to its fast precession. Paramagnetic relaxation by nuclear magnetism is found inefficient for HAC grains due to the rapid suppression of nuclear susceptibility when grains rotate at high$-J$ attractors. We then study the alignment of carbon dust in the envelope of a typical C-rich Asymptotic Giant Branch star, IRC+10216. We find that grains aligned at low$-J$ attractors can occur via $k$-RAT with the wrong IA in the inner region but via $B$-RAT in the outermost region. However, grains aligned at high$-J$ attractors have the right IA alignment via $k$-RAT due to efficient inelastic relaxation. The polarization pattern observed toward IRC+10216 by SOFIA/HAWC+ can reproduced when only grains at low$-J$ attractors are present due to removal of grains at high$-J$ attractors by the RAT disruption.

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T. Hoang, V. Phan and L. Tram
Fri, 20 Jan 23
49/72

Comments: 24 pages, 15 figures

Texture of average solar photospheric flows and the donut-like pattern [SSA]

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http://arxiv.org/abs/2301.07988


Detailed knowledge of surface dynamics is one of the key points in understanding magnetic solar activity. The motions of the solar surface, to which we have direct access via the observations, tell us about the interaction between the emerging magnetic field and the turbulent fields.
The flows computed with the coherent structure tracking (CST) technique on the whole surface of the Sun allow for the texture of the velocity modulus to be analyzed and for one to locate the largest horizontal flows and determine their organization. The velocity modulus maps show structures more or less circular and closedwhich are visible at all latitudes; here they are referred to as donuts. They reflect the most active convective cells associated with supergranulation. These annular flows are not necessarily joined as would seem to indicate the divergence maps. The donuts have identical properties (amplitude, shape, inclination, etc.) regardless of their position on the Sun. The kinematic simulation of the donuts’ outflow applied to passive scalar (corks) indicates the preponderant action of the selected donuts which are, from our analysis, one of the major actors for the magnetic field diffusion on the quiet Sun. The absence of donuts in the magnetized areas (plages) indicates the action of the magnetic field on the strongest supergranular flows and thus modifies the diffusion of the magnetic field in that location. The detection of the donuts is a way to locate in the quiet Sun the vortex and the link with the jet, blinkers, coronal bright points (campfires), or other physical structures. Likewise, the study of the influence of donuts on the evolution of active events, such as the destruction of sunspots, filament eruptions, and their influences on upper layers via spicules and jets, could be done more efficiently via the detection of that structures.

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T. Roudier, J. Ballot, J. Malherbe, et. al.
Fri, 20 Jan 23
51/72

Comments: 14 pages, 17 figures

BD+30$^\circ$549: young helium-weak silicon star in NGC 1333 star-forming region [SSA]

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http://arxiv.org/abs/2301.07856


We present results of the spectroscopic study of the chemically peculiar star BD+30$^\circ$549 which is bona-fide member of young NGC 1333 star forming region. We found that the star possesses negligible rotation and helium-weak spectroscopic pattern with strongly enhanced Si II and Si III lines. The fundamental parameters of the star $T_{eff}$=13100~K and $\log (L/L_{\odot})$=2.1 indicate its age of about 2.7 Myr and position on the Hertzsprung-Russell diagram at the end of the Pre-Main Sequence evolutionary track, close to the Zero Age Main Sequence. Abundance analysis reveals the modest deficit of almost all elements with exception of Si, Fe, Ca and P which are overabundant. We performed the non-LTE calculations for Si II/Si III, Mg II and Ca II in order to check the influence of departures from LTE on line formation. Non-LTE calculations lead to much better reproduction of individual silicon line profiles, but does not completely remove the abundance discrepancy between Si II and Si III lines. We also investigate the effects of possible chemical stratification in BD+30$^\circ$549. We suspect that the “Si II/Si III anomaly”, observed in BD+30$^\circ$549 spectrum arises under the combined action of the vertical and horizontal abundance gradients and non-LTE effects. We suppose that evolutionary status and phenomena observed in BD+30$^\circ$549 indicate that conditions favorable for the selective diffusion and formation of the surface chemical composition peculiarities (slow rotation and stabilization of the atmosphere) can be built up already at the Pre-Main Sequence phase.

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I. Potravnov, L. Mashonkina and T. Ryabchikova
Fri, 20 Jan 23
52/72

Comments: N/A

Planet Search with the Keck/NIRC2 Vortex Coronagraph in Ms-band for Vega [EPA]

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http://arxiv.org/abs/2301.07714


Gaps in circumstellar disks can signal the existence of planetary perturbers, making such systems preferred targets for direct imaging observations of exoplanets. Being one of the brightest and closest stars to the Sun, the photometric standard star Vega hosts a two-belt debris disk structure. Together with the fact that its planetary system is being viewed nearly face-on, Vega has been one of the prime targets for planet imaging efforts. Using the vector vortex coronagraph on Keck/NIRC2 in Ms-band at 4.67 $\mu$m, we report the planet detection limits from 1 au to 22 au for Vega with an on-target time of 1.8 h. We reach a 3 Jupiter mass limit exterior to 12 au, which is nearly an order of magnitude deeper than existing studies. Combining with existing radial velocity studies, we can confidently rule out the existence of companions more than ~8 Jupiter mass from 22 au down to 0.1 au for Vega. Interior and exterior to ~4 au, this combined approach reaches planet detection limits down to ~2-3 Jupiter mass using radial velocity and direct imaging, respectively. By reaching multi-Jupiter mass detection limits, our results are expected to be complemented by the planet imaging of Vega in the upcoming observations using the James Webb Space Telescope to obtain a more holistic understanding of the planetary system configuration around Vega.

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B. Ren, N. Wallack, S. Hurt, et. al.
Fri, 20 Jan 23
54/72

Comments: 6 pages, 3 figures, 1 table, A&A accepted. Contrast curve for 2018 observation available in anc folder. Happy Rabbit Year!

Structure and evolution of a tidally heated star [SSA]

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http://arxiv.org/abs/2301.07878


The shearing motion of tidal flows that are excited in non-equilibrium binary stars transform kinetic energy into heat via a process referred to as tidal heating. In this paper we aim to explore the way tidal heating affects the stellar structure. We used the TIDES code, which solves the equations of motion of the three-dimensional (3D) grid of volume elements that conform multiple layers of a rotating binary star to obtain an instantaneous value for the angular velocity, $\omega”$, as a function of position in the presence of gravitational, centrifugal, Coriolis, gas pressure, and viscous forces. The released energy, $\dot{E,}$ was computed using a prescription for turbulent viscosity that depends on the instantaneous velocity gradients. The $\dot{E}$ values for each radius were injected into a MESA stellar structure calculation. The method is illustrated for a 1.0+0.8 M$_\odot$ binary system, with an orbital period of $P$=1.44d and departures from synchronous rotation of 5% and 10%. We find that heated models have a larger radius and surface luminosity, a smaller surface convection zone, and lower nuclear reaction rates than the equivalent standard stellar models, and their evolutionary tracks extend to higher temperatures. The magnitude of these effects depends on the amount of injected energy, which, for a fixed set of stellar, rotation and orbital parameters, depends on the perturbed star’s density structure and turbulent viscosity. Tidal heating offers a possible alternative for describing phenomena such as bloated or overluminous binary components, age discrepancies, and aspherical mass ejection, as well as the extended main sequence turnoff in clusters. However, establishing its actual role requires 3D stellar structure models commensurate with the nonspherically symmetric properties of tidal perturbations.

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D. Estrella-Trujillo, S. Arthur, G. Koenigsberger, et. al.
Fri, 20 Jan 23
56/72

Comments: 16 pages, 7 figures, appendix with 9 figures, A&A in Press

Constraining fundamental parameters in modified gravity using Gaia-DR2 massive white dwarf observation [CL]

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http://arxiv.org/abs/2301.07645


Various experiments and observations have led researchers to suggest different bounds on fundamental constants like the fine-structure constant and the proton-to-electron mass ratio. These bounds differ mostly due to the energy scale of the systems where the experiments are performed. In this article, we obtain bounds on these parameters in the modified gravity context using the Gaia-DR2 massive white dwarf data and show that the bounds alter as the gravity theory changes. This exploration not only indicates strong support for non-negligible influences of modified gravity in astrophysical scenarios in high-density regimes but also reveals that the bounds on fundamental parameters can be much stronger under alternate gravity theories.

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S. Kalita and A. Uniyal
Fri, 20 Jan 23
57/72

Comments: 6 pages with 3 figures; comments welcome

Characterising fast-time variations in the hard X-ray time profiles of solar flares using Solar Orbiter's STIX [SSA]

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http://arxiv.org/abs/2301.08040


Aims: The aim of this work is to develop a method to systematically detect and characterise fast-time variations ($\gtrsim 1$s) in the non-thermal hard X-ray (HXR) time profiles of solar flares using high-resolution data from Solar Orbiter’s Spectrometer/Telescope for Imaging X-rays (STIX).
Methods: The HXR time profiles were smoothed using Gaussian Process (GP) regression. The time profiles were then fitted with a linear combination of Gaussians to decompose the time profile. From the Gaussian decomposition, key characteristics such as the periodicity, full width at half maximum (FWHM), time evolution, and amplitude can be derived.
Results: We present the outcome of applying this method to four M and X GOES-class flares from the first year of Solar Orbiter science operations. The HXR time profiles of these flares were decomposed into individual Gaussians and their periods were derived. The quality of fit is quantified by the standard deviation of the residuals (difference between observed and fitted curve, normalised by the error on the observed data), for which we obtain $\leq 1.8$ for all flares presented. In this work, the first detection of fast-time variations with Solar Orbiter’s STIX instrument has been made on timescales across the range of 4-128s.
Conclusions: A new method for identifying and characterising fast-time variations in the non-thermal HXR profiles of solar flares has been developed, in which the time profiles are fit with a linear combination of Gaussian bursts. The opportunity to study time variations in flares has greatly improved with the new observations from STIX on Solar Orbiter.

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H. Collier, L. Hayes, A. Battaglia, et. al.
Fri, 20 Jan 23
60/72

Comments: 12 pages, 10 figures, A&A journal

Plasma broadening of autoionizing resonances [SSA]

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http://arxiv.org/abs/2301.07734


A general formulation is developed to demonstrate that atomic autoionizing (AI) resonances are broadened and shifted significantly due to plasma effects across bound-free continua. The theoretical and computational method presented accounts for broadening mechanisms: electron collisional, ion microfields (Stark), thermal Doppler, core excitations, and free-free transitions. {\it Extrinsic} plasma broadening redistributes and shifts AI resonance strengths while broadly preserving naturally {\it intrinsic} asymmetries of resonance profiles. Integrated oscillator strengths are conserved as resonance structures dissolve into continua with increasing electron density. As exemplar, the plasma attenuation of photoionization cross sections computed using the R-matrix method is studied in neon-like Fe~XVII in a critical range $N_e = 10^{21-24}$cc along isotherms $T = 1-2 \times 10^6$K, and its impact on Rosseland Mean opacities. The energy-temperature-density dependent cross sections would elicit and introduce physical features in resonant processes in photoionization, \eion excitation and recombination. The method should be generally applicable to atomic species in high-energy-density (HED) sources such as fusion plasmas and stellar interiors.

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A. Pradhan
Fri, 20 Jan 23
62/72

Comments: 5 pages, 3 figures

Core-envelope decoupling drives radial shear dynamos in cool stars [SSA]

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http://arxiv.org/abs/2301.07716


Differential rotation is thought to be responsible for the dynamo process in stars like our Sun, driving magnetic activity and star spots. We report that star spot measurements in the Praesepe open cluster are strongly enhanced only for stars which depart from standard models of rotational evolution. A decoupling of the spin down history between the core and envelope explains both the activity and rotation anomalies: surface rotational evolution is stalled by interior angular momentum redistribution, and the resultant radial shears enhance star spot activity. These anomalies provide evidence for an evolving front of shear-enhanced activity affecting the magnetic and rotational evolution of cool stars and the high-energy environments of their planetary companions for hundreds of millions to billions of years on the main sequence.

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L. Cao, M. Pinsonneault and J. Saders
Fri, 20 Jan 23
63/72

Comments: 12 pages, 8 figures. Submitted to ApJ Letters

A disk-wind driving the rotating molecular outflow in CB 26 [SSA]

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http://arxiv.org/abs/2301.07877


We present 12CO (J=2-1) sensitive molecular line and 1.3 mm continuum observations made with the Submillimeter Array (SMA) of the bipolar outflow associated with the young star located in the Bok globule known as CB 26. The SMA observations were carried out in its extended configuration allowing us to study the kinematics and structure of the outflow with about 1 arcsec or 140 au resolution. We find that the dusty and edge-on circumstellar disk related with the outflow has an projected spatial (deconvolved) size of 196 au x 42 au with a total (gas and dust) mass of 0.031 Msun. We estimated a dynamical mass for the central object of 0.66 Msun, and the mass of the molecular outflow of 5×10-5 Msun. The observations confirm that the outflow rotation has a similar orientation to that of the edge-on disk. For the outflow, we find that the following quantities: the rotation velocity, the specific angular momentum, and the launching radius, decrease with the height above mid-plane, as observed in other molecular rotating outflows. The radius, and expansion velocity also increase with the height above the disk midplane. Estimations for the outflow linear momentum rate, the outflow angular momentum rate, and the accretion luminosity seem to be well explained by a disk wind present in CB26.

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J. López-Vázquez, L. Zapata and C. Lee
Fri, 20 Jan 23
71/72

Comments: 9 pages, 8 figures

A search for mid-IR bands of amino acids in the Perseus Molecular Cloud [GA]

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http://arxiv.org/abs/2301.07252


Amino acids are building-blocks of proteins, basic constituents of all organisms and essential to life on Earth. They are present in carbonaceous chondrite meteorites and comets, but their origin is still unknown. We present Spitzer spectroscopic observations in the star-forming region IC 348 of the Perseus Molecular Cloud showing the possible detections of mid-IR emission lines consistent with the most intense laboratory bands of the three aromatic amino acids, tyrosine, phenylalanine and tryptophan and the aliphatic amino acids isoleucine and glycine. Based on these tentative identifications, preliminary estimates of column densities give values 10-100 times higher for isoleucine and glycine than for the aromatic amino acids as in some meteorites. Potential counterparts of the strongest laboratory bands of each amino acid are also found in the combined spectrum of 32 interstellar locations obtained in diverse unrelated star-forming regions.

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S. Iglesias-Groth
Thu, 19 Jan 23
2/100

Comments: 8 pages, 2 figures, 1 table. Accepted Mem. S.A.It. Vol. 75, 282 \c{opyright} SAIt 2023. arXiv admin note: substantial text overlap with arXiv:2104.12026

Exploring the Temporal Variation of the Solar Quadrupole Moment J2 [SSA]

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http://arxiv.org/abs/2301.07506


Recently, Rozelot & Eren pointed out that the first solar gravitational moment (J2) might exhibit a temporal variation. The suggested explanation is through the temporal variation of the solar rotation with latitude. This issue is deeper developed due to an accurate knowledge of the long-term variations in solar differential rotation regarding solar activity. Here we analyze solar cycles 12-24, investigating the long-term temporal variations in solar differential rotation. It is shown that J2 exhibits a net modulation over the 13 studied cycles of approximately (89.6 +- 0.1) yr, with a peak-to-peak amplitude of approximately 0.1 x 10-7 for a reference value of 2.07 x 10-7). Moreover, J2 exhibits a positive linear trend in the period of minima solar activity (sunspot number up to around 40) and a marked declining trend in the period of maxima (sunspot number above 50). In absolute magnitude, the mean value of J2 is more significant during periods of minimum than in periods of maximum. These findings are based on observational results that are not free of errors and can be refined further by considering torsional oscillations for example. They are comforted by identifying a periodic variation of the J2 term evidenced through the analysis of the perihelion precession of planetary orbits either deduced from ephemerides or computed in the solar equatorial coordinate system instead of the ecliptic coordinate one usually used.

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S. Eren and J. Rozelot
Thu, 19 Jan 23
3/100

Comments: 7 pages, 5 figures

Resurrection of type IIL supernova 2018ivc: Implications for a binary evolution sequence connecting hydrogen-rich and -poor progenitors [HEAP]

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http://arxiv.org/abs/2301.07357


Long-term observations of synchrotron emission from supernovae (SNe), covering more than a year after the explosion, provide a unique opportunity to study the poorly-understood evolution of massive stars in the final millennium of their lives via changes in the mass-loss rate. Here, we present a result of our long-term monitoring of a peculiar type IIL SN 2018ivc, using the Atacama Large Millimeter/submillimeter Array (ALMA). Following the initial decay, it showed unprecedented rebrightening starting at ~ a year after the explosion. This is one of the rare examples showing such rebrightening in the synchrotron emission, and the first case at millimeter wavelengths. We find it to be in the optically-thin regime unlike the optically-thick centimeter emission. As such, we can robustly reconstruct the distribution of the circumstellar matter (CSM) and thus the mass-loss history in the final ~1,000 years. We find that the progenitor of SN 2018ivc had experienced a very high mass-loss rate >~10^{-3} Msun/yr ~1,500 years before the explosion, which was followed by a moderately high mass-loss rate (>~10^{-4} Msun/yr) up until the explosion. From this behavior, we suggest SN 2018ivc represents an extreme version of a binary evolution toward SNe IIb, which bridges the hydrogen-poor SNe (toward SNe Ib/c, without a hydrogen envelope) and hydrogen-rich SNe (SNe IIP, with a massive envelope).

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K. Maeda, T. Michiyama, P. Chandra, et. al.
Thu, 19 Jan 23
6/100

Comments: 13 pages, 4 figures, 1 table. Accepted for publication in ApJL

Data-Driven Radiative Magnetohydrodynamics Simulations with the MURaM code [SSA]

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http://arxiv.org/abs/2301.07621


We present a method of conducting data-driven simulations of solar active regions and flux emergence with the MURaM radiative magnetohydrodynamics (MHD) code. The horizontal electric field derived from the full velocity and magnetic vectors, is implemented at the photospheric (bottom) boundary to drive the induction equation. The energy equation accounts for thermal conduction along magnetic fields, optically-thin radiative loss, and heating of coronal plasma by viscous and resistive dissipation, which allows for a realistic presentation of the thermodynamic properties of coronal plasma that are key to predicting the observational features of solar active regions and eruptions. To validate the method, the photospheric data from a comprehensive radiative MHD simulation of solar eruption (the ground truth) are used to drive a series of numerical experiments. The data-driven simulation reproduces the accumulation of free magnetic energy over the course of flux emergence in the ground truth with an error of 3\%. The onset time is approximately 8\,min delayed compared to the ground truth. However, a precursor-like signature can be identified at the correct onset time. The data-driven simulation captures key eruption-related emission features and plasma dynamics of the ground truth flare over a wide temperature span from $\log_{10}T{=}4.5$ to $\log_{10}T{>}8$. The evolution of the flare and coronal mass ejection as seen in synthetic extreme ultraviolet images is also reproduced with high fidelity. The method helps to understand the evolution of magnetic field in a more realistic coronal environment and to link the magnetic structures to observable diagnostics.

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F. Chen, M. Cheung, M. Rempel, et. al.
Thu, 19 Jan 23
10/100

Comments: 34 pages, 23 figures, submitted to ApJ

Variation of small scale magnetic fields over a century using Ca-K images as proxy [SSA]

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http://arxiv.org/abs/2301.07350


A combined uniform and long-time series of Ca-K images from the Kodaikanal Observatory (KO), Mount Wilson Observatory (MWO), and Mauna Loa Solar Observatory (MLSO) were used to identify and study the Ca-K small-scale features and their solar cycle variations over a century. The small scale features are classified into three distinct categories: enhanced network (EN), active network (AN), and quiet network (QN). All these features show that their areas vary according to the 11-year solar cycle. The relative amplitude of the Ca-K network variations agree with that of the sunspot cycle. The total area of these small-scale features varies from about 5% during the minimum phase of the solar cycle to about 20% during its maximum phase. Considering the average intensity and the amplitude of their area variations, we find that the total contribution of EN, AN and QN to the irradiance variation of the Sun is about 3%.

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J. Singh, M. Priyal, B. Ravindra, et. al.
Thu, 19 Jan 23
17/100

Comments: Submitted article in RAA. It is under review. 15 pages, 8 figures

ABYSS I: Targeting strategy for APOGEE & BOSS young star survey in SDSS-V [GA]

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http://arxiv.org/abs/2301.07186


The fifth iteration of the Sloan Digital Sky Survey (SDSS-V) is set to obtain optical and near-infrared spectra of $\sim$5 million stars of all ages and masses throughout the Milky Way. As a part of these efforts, APOGEE & BOSS Young Star Survey (ABYSS) will observe $\sim10^5$ stars with ages $<$30 Myr that have been selected using a set of homogeneous selection functions that make use of different tracers of youth. The ABYSS targeting strategy we describe in this paper is aimed to provide the largest spectroscopic census of young stars to-date. It consists of 8 different types of selection criteria that take the position on the HR diagram, infrared excess, variability, as well as the position in phase space in consideration. The resulting catalog of $\sim$200,000 sources (of which a half are expected to be observed) provides representative coverage of the young Galaxy, including both nearby diffuse associations as well as more distant massive complexes, reaching towards the inner Galaxy and the Galactic center.

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M. Kounkel, E. Zari, K. Covey, et. al.
Thu, 19 Jan 23
25/100

Comments: 18 pages, 12 pages. Submitted to ApJS. Part of SDSS DR18

A black widow population dissection through HiPERCAM multi-band light curve modelling [HEAP]

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http://arxiv.org/abs/2301.07132


Black widows are extreme millisecond pulsar binaries where the pulsar wind ablates their low-mass companion stars. Their optical light curves vary periodically due to the high irradiation and tidal distortion of the companion, which allows us to infer the binary parameters. We present simultaneous multi-band observations obtained with the HIPERCAM instrument at the 10.4-m GTC telescope for six of these systems. The combination of this five-band fast photometer with the world’s largest optical telescope enables us to inspect the light curve range near minima. We present the first light curve for PSR J1641+8049, as well as attain a significant increase in signal-to-noise and cadence compared with previous publications for the remaining 5 targets: PSR J0023+0923, PSR J0251+2606, PSR J0636+5129, PSR J0952-0607 and PSR J1544+4937. We report on the results of the light curve modelling with the Icarus code for all six systems, which reveals some of the hottest and densest companion stars known. We compare the parameters derived with the limited but steadily growing black widow population for which optical modelling is available. We find some expected correlations, such as that between the companion star mean density and the orbital period of the system, but also a puzzling positive correlation between the orbital inclination and the irradiation temperature of the companion. We propose such a correlation would arise if pulsars with magnetic axis orthogonal to their spin axis are capable of irradiating their companions to a higher degree.

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D. Sánchez, M. Kennedy, C. Clark, et. al.
Thu, 19 Jan 23
28/100

Comments: 18 pages (+12 pages for appendix), 12 figures (+13 in the appendix), 3 tables (1 in the appendix). Accepted for publication in MNRAS on 2023 January 17th

Parametric instability in warped astrophysical discs: growth, saturation and feedback [SSA]

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http://arxiv.org/abs/2301.07176


Attempts to understand the dynamics of warped astrophysical discs have garnered significant attention, largely motivated by the growing catalogue of observed distorted systems. Previous studies have shown that the evolution of the warp is crucially regulated by the internal flow fields established by the undulating geometry. These are typically modelled as laminar horizontal, shearing flows which oscillate back and forth at approximately the orbital frequency. However this shearing motion is known to be susceptible to a hydrodynamic, parametric instability of inertial waves which might modify the warped dynamics. Whilst the linear growth phase is well understood, the subsequent nonlinear saturation combined with the self-consistent feedback onto the warp has not been studied. In this work, we implement a novel numerical setup using the recent ring model framework of Fairbairn and Ogilvie, within the Lagrangian code GIZMO. We formally identify several locally growing modes in the simulation, as predicted by a three-mode coupling analysis of the instability, and find decent agreement with the theoretical growth rates. We understand the saturation mechanism as a wave breaking process which suppresses the growth of shorter wavelength parametric couplings first, whilst allowing the longest mode to dominate the final quasi-steady, wavelike turbulence. The Reynolds stresses, transporting energy from the warp to the small scales, can be effectively modelled using a time-dependent, anisotropic viscous alpha model which closely captures the amplitude and phase evolution of the warp. Consequently, this model might help inform future global studies which are commonplace but typically don’t resolve the parametric instability.

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C. Fairbairn and G. Ogilvie
Thu, 19 Jan 23
40/100

Comments: Accepted MNRAS, 22 pages, 17 figures

The orbits of visual binary and multiple stars obtained by the Apparent Motion Parameters method during the last 40 years [SSA]

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http://arxiv.org/abs/2301.07602


Summed many years of work at Pulkovo, the orbits of 67 wide pairs of visual double and multiple stars (included in 64 systems) which were obtained by the Apparent Motion Parameters (AMP) method are presented. This short arc orbit determination method is based on the most reliable astrometric and astrophysical data corresponding to one instant of time. The rest of the observations accumulated in the world serve to control the quality of the orbit and refine some parameters. All early determined AMP-orbits were compared with new observations, some of them were recalculated, new ones were added. For the stars of Pulkovo program of observations with a 26-inch refractor, the Gaia DR2 data were analised. Based on these data, the orbits of 16 stars were calculated. In 20 cases from 67, the quasi-instant motion according to the Gaia DR2 data at the instant 2015.5 contradicts the motion according to all-world observations. A possible reason is the presence of inner subsystems. The orientation of the obtained orbits in the galactic coordinate system is also given.

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L. Romanenko, O. Kiyaeva, I. Izmailov, et. al.
Thu, 19 Jan 23
42/100

Comments: 12 pages

ALMA-IMF. VI. Prestellar and protostellar core populations in the W43 cloud complex [GA]

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http://arxiv.org/abs/2301.07238


The origin of the stellar initial mass function (IMF) and its relation with the core mass function (CMF) are actively debated issues with important implications in astrophysics. Recent observations in the W43 molecular complex of top-heavy CMFs, with an excess of high-mass cores compared to the canonical mass distribution, raise questions about our understanding of the star formation processes and their evolution in space and time. We aim to compare populations of protostellar and prestellar cores in three regions imaged in the ALMA-IMF Large Program. We created an homogeneous core catalogue in W43, combining a new core extraction in W43-MM1 with the catalogue of W43-MM2&MM3 presented in a previous work. Our detailed search for protostellar outflows enabled us to identify between 23 and 30 protostellar cores out of 127 cores in W43-MM1 and between 42 and 51 protostellar cores out of 205 cores in W43-MM2&MM3. Cores with neither outflows nor hot core emission are classified as prestellar candidates. We found a similar fraction of cores which are protostellar in the two regions, about 35%. This fraction strongly varies in mass, from 15-20% at low mass, between 0.8 and 3$M_{\odot} $ up to about 80% above 16$M_{\odot}$. Protostellar cores are found to be, on average, more massive and smaller in size than prestellar cores. Our analysis also revealed that the high-mass slope of the prestellar CMF in W43, $\alpha=-1.46_{-0.19}^{+0.12}$, is consistent with the Salpeter slope, and thus the top-heavy form measured for the global CMF, $\alpha=-0.96$, is due to the protostellar core population. Our results could be explained by clump-fed models in which cores grow in mass, especially during the protostellar phase, through inflow from their environment. The difference between the slopes of the prestellar and protostellar CMFs moreover implies that high-mass cores grow more in mass than low-mass cores.

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T. Nony, R. Galvan-Madrid, F. Motte, et. al.
Thu, 19 Jan 23
43/100

Comments: 27 pages, 18 figures. Accepted for publication in A&A

Imaging faint sources with the extended solar gravitational lens [IMA]

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http://arxiv.org/abs/2301.07495


We consider resolved imaging of faint sources with the solar gravitational lens (SGL) while treating the Sun as an extended gravitating body. We use our new diffraction integral that describes how a spherical electromagnetic wave is modified by the static gravitational field of an extended body, represented by series of multipole moments characterizing its interior mass distribution. Dominated by the solar quadrupole moment, these deviations from spherical symmetry significantly perturb the image that is projected by the Sun into its focal region, especially at solar equatorial latitudes. To study the optical properties of the quadrupole SGL, we develop an approximate solution for the point spread function of such an extended lens. We also derive semi-analytical expressions to estimate signal levels from extended targets. With these tools, we study the impact of solar oblateness on imaging with the SGL. Given the small value of the solar quadrupole moment, the majority of the signal photons arriving from an extended target still appear within the image area projected by the monopole lens. However, these photons are scrambled, thus reducing the achievable signal-to-noise ratio during image recovery process (i.e., deconvolution). We also evaluate the spectral sensitivity for high-resolution remote sensing of exoplanets with the extended SGL. We assess the impact on image quality and demonstrate that despite the adverse effects of the quadrupole moment, the SGL remains uniquely capable of delivering high-resolution imaging and spectroscopy of faint, small and distant targets, notably terrestrial exoplanets within ~30–100 parsec from us.

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S. Turyshev and V. Toth
Thu, 19 Jan 23
47/100

Comments: 23 pages, 2 figures

New parameters for star cluster dynamics: the effect of primordial binaries and dark remnants [GA]

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http://arxiv.org/abs/2301.07706


By studying the normalized cumulative radial distribution (nCRD) of the stars in the central region of a Monte Carlo-simulated globular cluster, we recently defined three parameters able to pinpoint the stage of internal dynamical evolution reached by the system: $A_5$ (i.e., the area subtended by the nCRD within 5$\%$ the half-mass radius, $r_h$), $P_5$ (the value of the nCRD at 5$\%$ $r_h$), and $S_{2.5}$ (the slope of the nCRD at 2.5$\%$ $r_h$). Here we extend the analysis and explore the effects that different fractions (0$\%$, 10$\%$, and 20$\%$) of primordial binaries and stellar-mass black holes (BHs) induce on the dynamical history of the system. As expected, the gradual contraction of the cluster becomes milder and core collapse shallower for increasing binary fraction. Nevertheless, the cluster dynamical evolution is still properly traced by the three parameters. For models with a larger initial retention of stellar mass BHs the evolution depends on the timescale of their subsequent dynamical ejection. An early dynamical ejection of BHs results in a long-term evolution of the three parameters similar to that found in systems with no initial BH retention. Conversely, in the model that retains a large number of BHs for extended time (slow dynamical ejection of BHs), the system is characterized by a less concentrated structure and by the lack of significant temporal evolution of the three parameters. The smaller values of the three parameters found in this case might be used to indirectly infer the possible presence of BHs in the cluster.

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B. Bhat, B. Lanzoni, F. Ferraro, et. al.
Thu, 19 Jan 23
50/100

Comments: 15 pages, 12 figures, 1 table

First total recovery of Sun global Alfven resonance: least-squares spectra of decade-scale dynamics of N-S-separated fast solar wind reveal solar-type stars act as revolving-field magnetoalternators [SSA]

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http://arxiv.org/abs/2301.07219


The Sun reveals itself in the 385.8-2.439-nHz band of polar ({\phi}Sun>|70{\deg}|) fast (>700 km s^-1) solar wind’s decade-scale dynamics as a globally completely vibrating, revolving-field magnetoalternator rather than a proverbial engine. Thus North-South separation of 1994-2008 Ulysses <10 nT wind polar samplings spanning ~1.6 10^7-2.5 10^9-erg base energies reveals Gauss-Vanicek spectral signatures of an entirely >99%-significant Sun-borne global sharp Alfven resonance (AR), Pi=PS/i, imprinted into the winds to the order n=100+ and co-triggered by the PS=~11-yr Schwabe global mode northside, its ~10-yr degeneration equatorially, and ~9-yr degeneration southside. The Sun is a typical ~3-dB-attenuated ring-system of differentially rotating and contrarily (out-of-phase) vibrating conveyor belts and layers with a continuous spectrum and resolution (<81.3 nHz (S), <55.6 nHz (N)) in lowermost frequencies (<2 {\mu}Hz in most modes). AR is accompanied by an also sharp symmetrical antiresonance P(-) whose both N/S tailing harmonics P(-17) are the well-known PR=~154-day Rieger period dominating planetary dynamics and space weather. Unlike a resonating motor restrained from separating its casing, the freely resonating Sun exhausts the wind in an axial shake-off beyond L1 at highly coherent discrete wave modes generated in the Sun, so to understand solar-type stars, only global decadal scales matter. The result verified against remote data and the experiment, so it instantly replaces dynamo with magnetoalternator and advances Standard Stellar Models, improving fundamental understanding of billions of trillions of solar-type stars. Gauss-Vanicek spectral analysis revolutionizes planetary & space sciences by rigorously simulating multiple spacecraft or fleet formations from a single spacecraft and physics by directly computing nonlinear global dynamics (rendering spherical approximation obsolete).

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M. Omerbashich
Thu, 19 Jan 23
51/100

Comments: 31 pages, 7 figures, 3 tables

Quasi-periodic Variations of Coronal Mass Ejections with Different Angular Widths [SSA]

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http://arxiv.org/abs/2301.07379


Coronal mass ejections (CMEs) are energetic expulsions of organized magnetic features from the Sun. The study of CME quasi-periodicity helps establish a possible relationship between CMEs, solar flares, and geomagnetic disturbances. We used the angular width of CMEs as a criterion for classifying the CMEs in the study. Based on 25 years of observational data, we systematically analyzed the quasi-periodic variations corresponding to the CME occurrence rate of different angular widths in the northern and southern hemispheres, using frequency and time-frequency analysis methods. There are various periods for CMEs of different angular widths: 9 months, 1.7 years, and 3.3-4.3 years. Compared with previous studies based on the occurrence rate of CMEs, we obtained the same periods of 1.2(+-0.01) months, 3.1(+-0.04) months, ~6.1(+-0.4) months, 1.2(+-0.1) years, and 2.4(+-0.4) years. We also found additional periods of all CMEs that appear only in one hemisphere or during a specific solar cycle. For example, 7.1(+-0.2) months and 4.1(+-0.2) years in the northern hemisphere, 1(+-0.004) months, 5.9(+-0.2) months, 1(+-0.1) years, 1.4(+-0.1) years, and 2.4(+-0.4) years in the southern hemisphere, 6.1(+-0.4) months in solar cycle 23 (SC23) and 6.1(+-0.4) months, 1.2(+-0.1) years, and 3.7(+-0.2) years in solar cycle 24 (SC24). The analysis shows that quasi-periodic variations of the CMEs are a link among oscillations in coronal magnetic activity, solar flare eruptions, and interplanetary space.

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X. Li, H. Deng, F. Wang, et. al.
Thu, 19 Jan 23
53/100

Comments: 18 pages, 8 figures, 4 tables, Accepted by APJ

Turning point principle for stability of viscous gaseous stars [CL]

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http://arxiv.org/abs/2301.07328


We consider stability of non-rotating viscous gaseous stars modeled by the Navier-Stokes-Poisson system. Under general assumptions on the equations of states, we proved that the number of unstable modes for the linearized Navier-Stokes-Poisson system equals that of the linearized Euler-Poisson system modeling inviscid gaseous stars. In particular, the turning point principle holds true for non-rotating stars with or without viscosity. That is, the transition of stability only occurs at the extrema of the total mass and the number of unstable modes is determined by the mass-radius curve. For the proof, we establish an infinite dimensional Kelvin-Tait-Chetaev theorem for a class of linear second order PDEs with dissipation. Moreover, we prove that linear stability implies nonlinear asymptotic stability and linear instability implies nonlinear instability for Navier-Stokes-Poisson system.

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M. Cheng, Z. Lin and Y. Wang
Thu, 19 Jan 23
54/100

Comments: N/A

Solaris: A Focused Solar Polar Discovery-class Mission to achieve the Highest Priority Heliophysics Science Now [IMA]

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http://arxiv.org/abs/2301.07647


Solaris is a transformative Solar Polar Discovery-class mission concept to address crucial outstanding questions that can only be answered from a polar vantage. Solaris will image the Sun’s poles from ~75 degree latitude, providing new insight into the workings of the solar dynamo and the solar cycle, which are at the foundation of our understanding of space weather and space climate. Solaris will also provide enabling observations for improved space weather research, modeling and prediction, revealing a unique, new view of the corona, coronal dynamics and CME eruptions from above.

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D. Hassler, S. Gibson, J. Newmark, et. al.
Thu, 19 Jan 23
55/100

Comments: This White Paper was submitted in 2022 to the United States National Academies Solar and Space Physics (Heliophysics) Decadal Survey

No evidence for synchronization of the solar cycle by a "clock" [SSA]

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http://arxiv.org/abs/2301.07469


The length of the solar activity cycle fluctuates considerably. The temporal evolution of the corresponding cycle phase, that is, the deviation of the epochs of activity minima or maxima from strict periodicity, provides relevant information concerning the physical mechanism underlying the cyclic magnetic activity. An underlying strictly periodic process (akin to a perfect “clock”), with the observer seeing a superposition of the perfect clock and a small random phase perturbation, leads to long-term phase stability in the observations. Such behavior would be expected if cycles were synchronized by tides caused by orbiting planets or by a hypothetical torsional oscillation in the solar radiative interior. Alternatively, in the absence of such synchronization, phase fluctuations accumulate and a random walk of the phase ensues, which is a typical property of randomly perturbed dynamo models. Based on the sunspot record and the reconstruction of solar cycles from cosmogenic C14, we carried out rigorous statistical tests in order to decipher whether there exists phase synchronization or random walk. Synchronization is rejected at significance levels of between 95% (28 cycles from sunspot data) and beyond 99% (84 cycles reconstructed from C14, while the existence of random walk in the phases is consistent with all data sets. This result strongly supports randomly perturbed dynamo models with little inter-cycle memory.

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E. Weisshaar, M. Schüssler and R. Cameron
Thu, 19 Jan 23
63/100

Comments: Astronomy & Astrophysics, in press

Transit timing variation analysis of the low-mass brown dwarf KELT-1 b [SSA]

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http://arxiv.org/abs/2301.07619


We investigate whether there is a variation in the orbital period of the short-period brown dwarf-mass KELT-1\,b, which is one of the best candidates to observe orbital decay. We obtain 19 high-precision transit light curves of the target using six different telescopes. We add all precise and complete transit light curves from open databases and the literature, as well as the available TESS observations from sectors 17 and 57, to form a transit timing variation (TTV) diagram spanning more than 10 years of observations. The analysis of the TTV diagram, however, is inconclusive in terms of a secular or periodic variation, hinting that the system might have synchronized. We update the transit ephemeris and determine an informative lower limit for the reduced tidal quality parameter of its host star of Q$_{\star}^{\prime} > (8.5 \pm 3.9) \times 10^{6}$ assuming that the stellar rotation is not yet synchronised. Using our new photometric observations, published light curves, the TESS data, archival radial velocities and broadband magnitudes, we also update the measured parameters of the system. Our results are in good agreement with those found in previous analyses.

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&. Baştürk, J. Southworth, S. Yalçınkaya, et. al.
Thu, 19 Jan 23
66/100

Comments: Accepted for publication by the MNRAS on 2023/01/16

Rossby waves on stellar equatorial beta-planes: uniformly rotating radiative stars [SSA]

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http://arxiv.org/abs/2301.07446


Rossby waves arise due to the conservation of total vorticity in rotating fluids and may govern the large-scale dynamics of stellar interiors. Recent space missions collected huge information about the light curves and activity of many stars, which triggered observations of Rossby waves in stellar surface and interiors. We aim to study the theoretical properties of Rossby waves in stratified interiors of uniformly rotating radiative stars with sub-adiabatic vertical temperature gradient. We use the equatorial beta-plane approximation and linear vertical gradient of temperature to study the linear dynamics of equatorially trapped Rossby and inertia-gravity waves in interiors of radiative stars. The governing equation is solved by the method of separation of variables in the vertical and latitudinal directions. Vertical and latitudinal solutions of the waves are found to be governed by Bessel functions and Hermite polynomials, respectively. Appropriate boundary conditions at stellar surface and poles define analytical dispersion relations for Rossby, Rossby-gravity and inertia-gravity waves. The waves are confined in surface layers of 30-50 $H_0$, where $H_0$ is surface density scale height, and trapped between the latitudes of $\pm 60^0$. Observable frequencies (normalized by the angular frequency of the stellar rotation) of Rossby waves with $m=1$ ($m=2$), where $m$ is the toroidal wavenumber, are in the interval of 0.65-1 (1.4-2), depending on stellar rotation, radius and surface temperature. Rossby-type waves can be systematically observed using light curves of Kepler and TESS stars. Observations and theory then can be used for the sounding of stellar interiors.

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M. Albekioni, T. Zaqarashvili and V. Kukhianidze
Thu, 19 Jan 23
70/100

Comments: N/A

Correcting Stellar Flare Frequency Distributions Detected by TESS and Kepler [SSA]

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http://arxiv.org/abs/2301.07552


The habitability of planets is closely connected with the stellar activity, mainly the frequency of flares and the distribution of flare energy. Kepler and TESS find many flaring stars are detected via precise time-domain photometric data, and the frequency and energy distribution of stellar flares on different types of stars are studied statistically. However, the completeness and observational bias of detected flare events from different missions (e.g. Kepler and TESS) vary a lot. We use a unified data processing and detection method for flares events based on the light curve from Kepler and TESS. Then we perform injection and recovery tests in the original light curve of each star for each flare event to correct the completeness and energy of flares. Three samples of flaring stars are selected from Kepler and TESS, with rotating periods from 1 to $\sim$ 5 days. Adopting a hot-blackbody assumption, our results show that the cumulative flare frequency distributions (FFDs) of the same stars in Kepler and TESS bands tend to be consistent after correction, revealing a more natural flaring frequency and energy distribution. Our results also extend the low-energy limit in cumulative FFD fitting to $10^{31.5-33}$ erg on different types of stars. For solar-type stars, the average power-law index of cumulative FFD ($\alpha_{\rm cum}$) is $-0.84$, which indicates that low-energy flares contribute less to the total flare energy. With a piecewise correlation between $\alpha_{\rm cum}$ and $T_{\rm eff}$, $\alpha_{\rm cum}$ first rises with $T_{\rm eff}$ from M2 to K1 stars, then slightly decreases for stars hotter than K1.

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D. Gao, H. Liu, M. Yang, et. al.
Thu, 19 Jan 23
71/100

Comments: 22 pages, 12 figures, 4 tables. Published in AJ

A rich molecular chemistry in the gas of the IC 348 star cluster of the Perseus Molecular Cloud [GA]

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http://arxiv.org/abs/2301.07224


We present Spitzer 10-34 {\mu}m spectroscopic observations of the diffuse gas in the inner region of the star-forming region IC 348 of the Perseus Molecular Cloud. We find evidence for the strongest mid-IR bands of common molecules as H\textsubscript{2}, OH, H\textsubscript{2}O,CO\textsubscript{2} and NH\textsubscript{3} and of several carbonaceous molecules which may play an important role in the production of more complex hydrocarbons: HCN, C\textsubscript{2}H\textsubscript{2}, C\textsubscript{4}H\textsubscript{2}, HC\textsubscript{3}N, HC\textsubscript{5}N, C\textsubscript{2}H\textsubscript{6}, C\textsubscript{6}H\textsubscript{2}, C\textsubscript{6}H\textsubscript{6}. The excitation diagram of H\textsubscript{2} reveals the presence of warm gas (270 +- 30 K) at the observed locations. Assuming this temperature, the derived abundances of CO\textsubscript{2} and NH\textsubscript{3} relative to H\textsubscript{2} are 10\textsuperscript{-8} and 10\textsuperscript{-7}, respectively. From the water lines we obtain an abundance of order 10\textsuperscript{-6} and higher gas temperatures. The abundances derived for HCN and C\textsubscript{2}H\textsubscript{2}, key molecules in the development of prebiotic building blocks, are of order 10\textsuperscript{-7} and 10\textsuperscript{-9}, respectively. More complex molecules such as PAHs and the fullerenes C\textsubscript{60} and C\textsubscript{70} are also present. IC 348 appears to be very rich and diverse in molecular content. The JWST spectroscopic capabilities may provide details on the spatial distribution of all these molecules and extend the present search to more complex hydrocarbons.

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S. Iglesias-Groth and M. Marin-Dobrincic
Thu, 19 Jan 23
73/100

Comments: 33 pages, 24 figures, 4 tables, ACCEPTED in MNRAS

Identification of late-type stars of class I [SSA]

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http://arxiv.org/abs/2301.07415


Aims. Gaia DR3 GSP-Phot and GSP-Spec parameters of known K- and M-type stars with luminosity class I are examined and compared with parameters collected from the literature, to assess their accuracy and their potential for stellar classification of unknown intrinsically bright late-types. Gaia DR3 GSP-Phot and GSP-Spec parameters were generated by the Astrophysical Parameters Inference Software (Apsis). Methods. In the Gaia DR3 catalog, there are about 40,000 entries with Apsis parameters similar to those of known red supergiants, RSGs, good parallaxes, and infrared 2MASS and WISE data. By using parallactic distances, infrared photometry, and variability information, only 203 new entries are found with luminosities and temperatures similar to that of known RSGs and G-band amplitudes smaller than 0.5 mag. Their low-resolution BP/RP spectra are compared with an empirically made spectral library of BP/RP spectra of known bright late-type stars (C-rich, S-type, O-rich asymptotic giant branch stars (AGBs), and RSGs) to obtain their spectral types. Results. Among them, 15 S-type stars are identified by peculiar absorption features due to ZrO and LaO visible in their BP/RP spectra, one S/C star, and nine C-rich stars by their strong CN absorption bands. K- and M-types can be reproduced with an accuracy of two subtypes. 20 new RSGs are confirmed, of which six have bolometric magnitudes brighter than those of the AGB limit: 2MASS J21015501+4517205, 2MASS J16291280-4956384, 2MASS J10192621-5818105, 2MASS J20230860+3651450, 2MASS J17084131-4026595, and 2MASS J16490055-4217328. The flag for C-rich stars of the Gaia DR3 LPV pipeline is erroneously true for some RSGs and a visual inspection of the BP/RP spectra is mandatory.

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M. Messineo
Thu, 19 Jan 23
86/100

Comments: 17 figures, 18 pages, accepted by A&A

Explosive Events in the Quiet Sun Near and Beyond the Solar Limb Observed with the Interface Region Imaging Spectrograph (IRIS) [SSA]

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http://arxiv.org/abs/2301.07190


We study point-like explosive events (EE), characterized by emission in the far wings of spectral lines, in a quiet region near the South Pole, using Interface Region Imaging Spectrograph (IRIS) spectra at two slit positions, slit-jaw (SJ) observations and Atmospheric Imaging Assembly (AIA) images. The events were best visible in SiIV spectra; they were weak in SJs, occasionally visible in 1600 A and 304 A AIA images, and invisible in higher temperature AIA images. We identified EEs from position–time images in the far wings of the SiIV lines and measured their distance from the limb. A Gaussian model of the height distribution showed that EEs occur in a narrow (0.9″) height range, centered at 3.2″ above the continuum limb at 2832.0 A. On the disk, we found that they occur in network boundaries. Further, we studied the line profiles of two bright EEs above the limb and one on the disk. We found that what appears as broad-band emission, is actually a superposition of 2–3 narrow-band Gaussian components with well-separated line profiles, indicating that material is expelled towards and/or away from the observer in discrete episodes in time and in space. The expelled plasma accelerates quickly, reaching line-of-sight (LOS) velocities up to 90 km/s. Overall, the motion was practically along the LOS, as the velocity on the plane of sky was small. In some cases tilted spectra were observed that could be interpreted in terms of rotating motions of up to 30 km/s. We did not find any strong absorption features in the wing of the SiIV lines, although in one case a very weak absorption feature was detected. No motions, indicative of jets, were detected in SJ or AIA images. Reconnection in an asymmetric magnetic-field geometry, in the middle or near the top of small loops is a plausible explanation of their observational characteristics.

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C. Alissandrakis and J. Vial
Thu, 19 Jan 23
89/100

Comments: Accepted, Solar Physics

A Unified Model for Bipolar Outflows from Young Stars: Kinematic Signatures of Jets, Winds, and Their Magnetic Interplay with the Ambient Toroids [SSA]

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http://arxiv.org/abs/2301.07447


Kinematic signatures of the jet, winds, multicavities, and episodic shells arising in the unified model of bipolar outflows developed in Shang et al.\ (2020), in which an outflow forms by radially directed, wide-angle toroidally magnetized winds interacting with magnetized isothermal toroids, are extracted in the form of position–velocity diagrams. Elongated outflow lobes, driven by magnetized winds and their interplay with the environment, are dominated by extended bubble structures with mixing layers beyond the conventional thin-shell models. The axial cylindrically stratified density jet carries a broad profile near the base, across the projected velocity of the wide-angle wind, and narrows down along the axis with the collimated flow. The reverse shock encloses the magnetized free wind, forms an innermost cavity, and deflects the flow pattern. Shear, Kelvin–Helmholtz instabilities, and pseudopulses add fine and distinctive features between the jet–shell components, and the fluctuating jet velocities. The broad webbed velocity features connect the extremely high and the low velocities across the multicavities, mimicking nested outflowing slower-wind components. Rings and ovals in the perpendicular cuts trace multicavities at different heights, and the compressed ambient gap regions enrich the low-velocity features with protruding spikes. Our kinematic signatures capture the observed systematics of the high-, intermediate-, and low-velocity components from Class 0 to II jet–outflow systems in molecular and atomic lines. The nested shells observed in HH 212, HH 30, and DG Tau B are naturally explained. Outflows as bubbles are ubiquitous and form an inevitable integrative outcome of the interaction between wind and ambient media.

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H. Shang, C. Liu, R. Krasnopolsky, et. al.
Thu, 19 Jan 23
92/100

Comments: 66 pages, 26 figures, 3 tables, to appear in the Astrophysical Journal (2023)

Periodicities of solar activity and solar radiation derived from observations and their links with the terrestrial environment [SSA]

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http://arxiv.org/abs/2301.07480


Solar magnetic activity is expressed via variations of sunspots and active regions varying on different timescales. The most accepted is an 11-year period supposedly induced by the electromagnetic solar dynamo mechanism. There are also some shorter or longer timescales detected: the biennial cycle (2-2.7 years), Gleisberg cycle (80-100 years), and Hallstatt’s cycle (2100-2300 years). Recently, using Principal Component Analysis (PCA) of the observed solar background magnetic field (SBMF), another period of 330-380 years, or Grand Solar Cycle (GSC), was derived from the summary curve of two eigenvectors of SBMF. In this paper, a spectral analysis of the averaged sunspot numbers, solar irradiance, and the summary curve of eigenvectors of SBMF was carried out using Morlet wavelet and Fourier transforms. We detect a 10.7-year cycle from the sunspots and modulus summary curve of eigenvectors as well a 22 years cycle and the grand solar cycle of 342-350-years from the summary curve of eigenvectors. The Gleissberg centennial cycle is only detected on the full set of averaged sunspot numbers for 400 years or by adding a quadruple component to the summary curve of eigenvectors. Another period of 2200-2300 years is detected in the Holocene data of solar irradiance measured from the abundance of $^{14}$C isotope. This period was also confirmed with the period of 2100 years derived from a baseline of the summary curve, supposedly, caused by the solar inertial motion (SIM) induced by the gravitation of large planets. The implication of these findings for different deposition of solar radiation into the northern and southern hemispheres of the Earth caused by the combined effects of the solar activity and solar inertial motion on the terrestrial atmosphere are also discussed.

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V. Zharkova, I. Vasilieva, S. Shepherd, et. al.
Thu, 19 Jan 23
93/100

Comments: 30 pages, 15 figures

Revisiting the stability of strange-dwarf stars and strange planets [CL]

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http://arxiv.org/abs/2301.07654


The dynamical stability of strange-dwarf hybrid stars and strange planets, constituted by strange-quark-matter cores and dilute-nuclear-matter crusts, is revisited by analyzing the fundamental mode eigenfrequencies of the radial oscillation equations with non-trivial boundary conditions for slow and fast conversions characterizing distinct microphysical scales originating at the density-discontinuous interface. Our calculations indicate that in the case of rapid conversions the so-called {\it reaction mode} plays the fundamental role in these non-compact objects and allow their existence in nature. Interestingly, slow conversions display the same stability window as the seminal work of Glendenning-Kettner-Weber. The robustness of our findings is demonstrated for different transition densities and also using an equation of state from perturbative QCD for the ultra-dense core.

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V. Goncalves, J. Jimenez and L. Lazzari
Thu, 19 Jan 23
96/100

Comments: 6 pages, 3 figures

Stellar Initial Mass Function Varies with Metallicities and Time [GA]

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http://arxiv.org/abs/2301.07029


Most structural and evolutionary properties of galaxies strongly rely on the stellar initial mass function (IMF), namely the distribution of the stellar mass formed in each episode of star formation. As the IMF shapes the stellar population in all stellar systems, it turns out to become one of the most fundamental concepts of modern astronomy. Both constant and variable IMFs across different environments have been claimed despite a large number of theoretical and observational efforts. However, the measurement of the IMF in Galactic stellar populations has been limited by the relatively small number of photometrically observed stars, leading to high uncertainties. Here we report a star-counting result based on ~93,000 spectroscopically observed M-dwarf stars, an order of magnitude more than previous studies, in the 100–300 parsec (pc) Solar neighbourhood. We find unambiguous evidence of a variable IMF that depends on both metallicity and stellar age. Specifically, the stellar population formed at the early time contains fewer low-mass stars compared to the canonical IMF, independent of stellar metallicities. In present days, on the other hand, the proportion of low-mass stars increases with stellar metallicity. The variable abundance of low-mass stars in our Milky Way establishes a powerful benchmark for models of star formation and can heavily impact results in Galactic chemical enrichment modelling, mass estimation of galaxies, and planet formation efficiency.

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J. Li, C. Liu, Z. Zhang, et. al.
Wed, 18 Jan 23
12/133

Comments: Main text (3 Figures, 6 pages) and Supplementary Information (16 pages, 6 Figures). Nature accepted

Massive pre-main-sequence stars in M17 — Modelling hydrogen and dust in MYSO disks [SSA]

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http://arxiv.org/abs/2301.06819


The young massive-star-forming region M17 contains optically visible massive pre-main-sequence stars that are surrounded by circumstellar disks. Such disks are expected to disappear when these stars reach the main sequence. The physical and dynamical structure of these remnant disks are poorly constrained, especially the inner regions where accretion, photo-evaporation, and companion formation and migration may be ongoing. We aim to constrain the physical properties of the inner parts of the circumstellar disks of massive young stellar objects B243 (6 Msun) and B331 (12 Msun), two systems for which the central star has been detected and characterized previously despite strong dust extinction. Two-dimensional radiation thermo-chemical modelling with ProDiMo of double-peaked hydrogen lines of the Paschen and Brackett series observed with X-shooter was used to probe the properties of the inner disks. Additionally, the dust structure was studied by fitting the optical and near-infrared spectral energy distribution. B243 features a hot gaseous inner disk with dust at the sublimation radius at 3 AU. The disk appears truncated at roughly 6.5 AU; a cool outer disk of gas and dust may be present, but it cannot be detected with our data. B331 also has a hot gaseous inner disk. A gap separates the inner disk from a colder dusty outer disk starting at up to 100 AU. In both sources the inner disk extends to almost the stellar surface. Chemistry is essential for the ionization of hydrogen in these disks. The lack of a gap between the central objects and these disks suggests that they accrete through boundary-layer accretion. This would exclude the stars having a strong magnetic field. Their structures suggest that both disks are transitional in nature, that is to say they are in the process of being cleared, either through boundary-layer accretion, photo-evaporation, or through companion activity.

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F. Backs, J. Poorta, C. Rab, et. al.
Wed, 18 Jan 23
17/133

Comments: 18 pages, 16 figures. Accepted for publication in A&A

Coronal Hole Analysis and Prediction using Computer Vision and LSTM Neural Network [SSA]

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http://arxiv.org/abs/2301.06732


As humanity has begun to explore space, the significance of space weather has become apparent. It has been established that coronal holes, a type of space weather phenomenon, can impact the operation of aircraft and satellites. The coronal hole is an area on the sun characterized by open magnetic field lines and relatively low temperatures, which result in the emission of the solar wind at higher than average rates. In this study, To prepare for the impact of coronal holes on the Earth, we use computer vision to detect the coronal hole region and calculate its size based on images from the Solar Dynamics Observatory (SDO). We then implement deep learning techniques, specifically the Long Short-Term Memory (LSTM) method, to analyze trends in the coronal hole area data and predict its size for different sun regions over 7 days. By analyzing time series data on the coronal hole area, this study aims to identify patterns and trends in coronal hole behavior and understand how they may impact space weather events. This research represents an important step towards improving our ability to predict and prepare for space weather events that can affect Earth and technological systems.

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J. Yun
Wed, 18 Jan 23
18/133

Comments: 15 pages

Takeout and Delivery: Erasing the Dusty Signature of Late-stage Terrestrial Planet Formation [EPA]

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http://arxiv.org/abs/2301.05719


The formation of planets like Earth is expected to conclude with a series of late-stage giant impacts that generate warm dusty debris, the most anticipated visible signpost of terrestrial planet formation in progress. While there is now evidence that Earth-sized terrestrial planets orbit a significant fraction of solar-type stars, the anticipated dusty debris signature of their formation is rarely detected. Here we discuss several ways in which our current ideas about terrestrial planet formation imply transport mechanisms capable of erasing the anticipated debris signature. A tenuous gas disk may be regenerated via “takeout” (i.e., the liberation of planetary atmospheres in giant impacts) or “delivery” (i.e., by asteroids and comets flung into the terrestrial planet region) at a level sufficient to remove the warm debris. The powerful stellar wind from a young star can also act, its delivered wind momentum producing a drag that removes warm debris. If such processes are efficient, terrestrial planets may assemble inconspicuously, with little publicity and hoopla accompanying their birth. Alternatively, the rarity of warm excesses may imply that terrestrial planets typically form very early, emerging fully formed from the nebular phase without undergoing late-stage giant impacts. In either case, the observable signposts of terrestrial planet formation appear more challenging to detect than previously assumed. We discuss observational tests of these ideas.

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J. Najita and S. Kenyon
Wed, 18 Jan 23
26/133

Comments: 20 pages, 3 figures, accepted for publication in ApJ

Slowly rotating Tolman VII solution [CL]

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http://arxiv.org/abs/2301.06960


We present a model of a slowly rotating Tolman VII (T-VII) fluid sphere, at second order in the angular velocity. The structure of this configuration is obtained by integrating the Hartle-Thorne equations for slowly rotating relativistic masses. We model a sequence in adiabatic and quasi-stationary contraction, by varying the tenuity parameter $R/R_{\mathrm{S}}$, where $R$ is the radius of the configuration and $R_{\mathrm{S}}$ is its Schwarzschild radius. We determined the moment of inertia $I$, mass quadrupole moment $Q$, and the ellipticity $\varepsilon$, for various configurations. Similar to previous results for Maclaurin and polytropic spheroids, in slow rotation, we found a change in the behaviour of the ellipticity when the tenuity reaches a certain critical value. We compared our results of $I$ and $Q$ for the T-VII model with those predicted by the universal fittings proposed for realistic neutron stars. For the relevant range of compactness, we found that relative errors are within $10\%$, thus suggesting the T-VII solution as a very good approximation for the description of the interior of neutron stars.

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C. Posada and Z. Stuchlík
Wed, 18 Jan 23
30/133

Comments: 20 pages, 10 figures

Speckle-interferometric study of close visual binary system Hip 11253 (HD14874) using Gaia (DR2) and (EDR3) [SSA]

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http://arxiv.org/abs/2301.05968


We present a comprehensive set of physical and geometrical parameters for each of the components of the close visual binary system Hip 11253 (HD14874). We present an analysis for the binary and multiple stellar systems with the aim to obtain a match between the overall observational spectral energy distribution of the system and the spectral synthesis created from model atmospheres. The epoch positions are used to determine the orbital parameters and the total mass.

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H. Aljboor and A. Taani
Wed, 18 Jan 23
31/133

Comments: Accepted for publication in RAA

Cluster Population Demographics in NGC 628 Derived from Stochastic Population Synthesis Models [GA]

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http://arxiv.org/abs/2301.05912


The physical properties of star cluster populations offer valuable insights into their birth, evolution, and disruption. However, individual stars in clusters beyond the nearest neighbours of the Milky Way are unresolved, forcing analyses of star cluster demographics to rely on integrated light, a process that is fraught with uncertainty. Here infer the demographics of the cluster population in the benchmark galaxy NGC 628 using data from the Legacy Extra-galactic UV Survey (LEGUS) coupled to a novel Bayesian forward-modelling technique. Our method allows analysis of a total of 1178 clusters in the LEGUS catalogue, roughly a factor of 4 more than previous studies that required severe completeness cuts to the data. Our results indicate that the cluster mass function is truncated at $\sim 10^4$ $ \mathrm{M}_{\odot}$, consistent with proposed relations between truncation mass and star formation surface density. We find that cluster disruption begins early, $\sim 10$ Myr after formation, but that it is relatively mild, with clusters requiring on average $2-3$ times their present age to disrupt; we do not find any evidence for mass dependent disruption. We also do not find convincing evidence for any radial variations in these conclusions, though we find suggestive hints that inner galaxy clusters may be more prone to disruption. Confirming or refuting these hints will require future observations to increase the sample size of outer galaxy clusters.

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J. Tang, K. Grasha and M. Krumholz
Wed, 18 Jan 23
32/133

Comments: N/A

Deciphering Faint Gyrosynchrotron Emission from Coronal Mass Ejection using Spectro-polarimetric Radio Imaging [SSA]

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http://arxiv.org/abs/2301.06522


Measurements of the plasma parameters of coronal mass ejections (CMEs), particularly the magnetic field and non-thermal electron population entrained in the CME plasma, are crucial to understand their propagation, evolution, and geo-effectiveness. Spectral modeling of gyrosynchrotron (GS) emission from CME plasma has been regarded as one of the most promising remote sensing technique for estimating spatially resolved CME plasma parameters. Imaging the very low flux density CME GS emission in close proximity to the Sun with orders of magnitude higher flux density, however, has proven to be rather challenging. This challenge has only recently been met using the high dynamic range imaging capability of the Murchison Widefield Array (MWA). Although routine detection of GS is now within reach, the challenge has shifted to constraining the large number of free parameters in GS models, a few of which are degenerate, using the limited number of spectral points at which the observations are typically available. These degeneracies can be broken using polarimetric imaging. For the first time, we demonstrate this using our recently developed capability of high fidelity polarimetric imaging on the data from the MWA. We show that, in addition to breaking the degeneracies, spectro-polarimetric spectroscopic imaging also yields tighter constraints on the plasma parameters of key interest than possible with total intensity spectroscopic imaging alone.

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D. Kansabanik, S. Mondal and D. Oberoi
Wed, 18 Jan 23
33/133

Comments: Submitted to the Astrophysical Journal, under review (21 pages, 15 figures, 2 tables)

Dynamical tides in Jupiter and other rotationally flattened planets and stars with stable stratification [EPA]

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http://arxiv.org/abs/2301.07097


We develop a numerical method for directly computing the dissipative dynamical tidal response of rapidly rotating, oblate stars and gaseous planets with realistic internal structures. Applying these calculations to neutrally and stably stratified polytropes, we identify the most relevant resonances in models with rotation rates up to nearly the mass-shedding limit. We then compute the dynamical tidal response for Jupiter interior models including both stably stratified and convective regions. These calculations show that resonances involving waves with both gravito-inertial and purely inertial character are capable of explaining a discrepancy between observations and hydrostatic calculations of Jupiter’s response to tidal forcing by Io. This result contrasts with recent work that excluded Jupiter’s rotational flattening, and opens the door to resonances involving a wider range of internal oscillation modes than previously considered.

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J. Dewberry
Wed, 18 Jan 23
34/133

Comments: 14 pages, 10 figures, submitted to MNRAS (comments welcome)

Modelling the early mass-ejection in jet driven protostellar outflows. Lessons from Cep\,E [SSA]

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http://arxiv.org/abs/2301.06146


We have used the axisymmetric chemo-hydrodynamical code WALKIMYA-2D to numerically model and reproduce the physical and CO emission properties of the jet-driven outflow from the intermediate-mass protostar Cep E, which was observed at $\sim 800$au resolution in the CO $J=2\to 1$ line with the IRAM interferometer. Our simulations take into account the observational constraints available on the physical structure of the protostellar envelope to provide constraints on the dynamics of the inner protostellar environment from the study of the outflow/jet propagation away from the launch region. WALKIMYA-2D successfully reproduces the main qualitative and quantitative features of the Cep E outflow and the jet kinematics, naturally accounting for their time variability. Signatures of internal shocks are detected as knots along the jet. In the early times of the ejection process, the young emitted knots interact with the dense circumstellar envelope through high-velocity, dissociative shocks, which strongly decrease the CO gas abundance in the jet. As time proceeds, the knots propagate more smoothly through the envelope and dissociative shocks disappear after $\sim 10^3$ yr. The distribution of CO abundance along the jet shows that the latter bears memory of the early dissociative phase in the course of its propagation. Analysis of the velocity field shows that the jet material mainly consists of gas entrained from the circumstellar envelope and accelerated away from the protostar at 700 au scale. As a result, the overall jet mass loss rate appears higher than the actual mass ejection rate by a factor $\sim 3$. Numerical modelling of the Cep E jet-driven outflow and comparison with the CO observations have allowed us to peer into the outflow formation mechanism with unprecedented detail and to retrieve the history of the mass-loss events that have shaped the outflow.

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P. Rivera-Ortiz, A. Schutzer, B. Lefloch, et. al.
Wed, 18 Jan 23
37/133

Comments: N/A

The Breakthrough Listen Search for Intelligent Life: A Laser Search Pipeline for the Automated Planet Finder [IMA]

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http://arxiv.org/abs/2301.06971


The Search for Extraterrestrial Intelligence (SETI) has traditionally been conducted at radio wavelengths, but optical searches are well-motivated and increasingly feasible due to the growing availability of high-resolution spectroscopy. We present a data analysis pipeline to search Automated Planet Finder (APF) spectroscopic observations from the Levy Spectrometer for intense, persistent, narrow bandwidth optical lasers. We describe the processing of the spectra, the laser search algorithm, and the results of our laser search on 1983 spectra of 388 stars as part of the Breakthrough Listen search for technosignatures. We utilize an empirical spectra-matching algorithm called SpecMatch-Emp to produce residuals between each target spectrum and a set of best-matching catalog spectra, which provides the basis for a more sensitive search than previously possible. We verify that SpecMatch-Emp performs well on APF-Levy spectra by calibrating the stellar properties derived by the algorithm against the SpecMatch-Emp library and against Gaia catalog values. We leverage our unique observing strategy, which produces multiple spectra of each target per night of observing, to increase our detection sensitivity by programmatically rejecting events which do not persist between observations. With our laser search algorithm we achieve a sensitivity equivalent to the ability to detect an 84 kW laser at the median distance of a star in our dataset (78.5 ly). We present the methodology and vetting of our laser search, finding no convincing candidates consistent with potential laser emission in our target sample.

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A. Zuckerman, Z. Ko, H. Isaacson, et. al.
Wed, 18 Jan 23
39/133

Comments: 24 pages, 12 figures. Accepted to The Astronomical Journal

Spectrophotometric analysis of magnetic white dwarf II: Helium-rich compositions [SSA]

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http://arxiv.org/abs/2301.06605


We present an analysis of all single white dwarf stars known to exhibit spectroscopic signatures of neutral helium line splitting due to the presence of a strong magnetic field. Using state-of-the-art models taking into account the effects of magnetic fields on the synthetic spectra, we determine effective temperatures, surface gravities and masses for the stars in our sample. Our analysis uses data from the second and third Gaia (early) data release, photometric data from diverse surveys such as the Sloan Digital Sky Survey and Pan-STARRS, and archived spectroscopic data. We are able to successfully reproduce the spectra of 8 objects using an offset dipole geometry while several others seem to require either a more complexe geometry or a different chemical composition. We also highlight a group of hot featureless white dwarfs that are most probably highly magnetic objects whose spectra are completely smeared due to the field strength distribution across the surface.

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F. Hardy, P. Dufour and S. Jordan
Wed, 18 Jan 23
41/133

Comments: 38 pages. Part 2 of 2. To be published in Monthly Notices of the Royal Astronomical Society

Has the dust clump in the debris disk of Beta Pictoris moved? [EPA]

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http://arxiv.org/abs/2301.06891


The edge-on debris disk of the nearby young star Beta Pictoris shows an unusual brightness asymmetry in the form of a clump. The clump has been detected in both the mid-IR and CO and its origin has so far remained uncertain. Here we present new mid-IR observations of Beta Pic to track any motion of the dust clump. Together with previous observations, the data span a period of 12 years. We measured any projected displacement of the dust clump over the 12-yr period to be $0.2^{+1.3}_{-1.4}$ au away from the star based on the median and 1$\sigma$ uncertainty, and constrain this displacement to be <11 au at the 3$\sigma$ level. This implies that the observed motion is incompatible with Keplerian motion at the 2.8$\sigma$ level. It has been posited that a planet migrating outwards may trap planetesimals into a 2:1 resonance, resulting in the observed clump at pericentre of their orbits that trails the planet. The observed motion is also incompatible with such resonant motion at the 2.6$\sigma$ level. While Keplerian motion and resonant motion is still possible, the data suggest that the dust clump is more likely stationary. Such a stationary dust clump could originate from the collision or tidal disruption of a planet-sized body, or from secular perturbations due to a planet that create regions with enhanced densities in the disk.

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Y. Han, M. Wyatt and W. Dent
Wed, 18 Jan 23
44/133

Comments: 14 pages, 8 figures, 5 tables. Published in MNRAS