Tag Archives: High Energy Astrophysical Phenomena

On the nature of M31 gamma-ray halo in its relation to dark matter annihilation [HEAP]

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http://arxiv.org/abs/2305.07590


The present work analyzes various aspects of M31 gamma-ray halo emission in its relation to annihilating dark matter (DM). The main aspect is the predicted effect of asymmetry of the intensity of emission due to inverse Compton scattering (ICS) of a possible population of relativistic electrons and positrons ($e^\pm$) in the galactic halo on starlight photons. This asymmetry is expected to exist around the major galactic axis, and arises due to anisotropy of the interstellar radiation field and the inclination of M31. ICS emission and its asymmetry were modeled by GALPROP code for the trial case of $e^\pm$ generated by annihilating weakly interacting massive particles (WIMPs) with various properties. The asymmetry was obtained to appear at photon energies above $\sim$ 0.1 MeV. Morphological and spectral properties of the asymmetry were studied in detail. Potential observational detection of the asymmetry may allow to infer the leptonic fraction in the emission generation mechanism, thus providing valuable inferences for understanding the nature of M31 gamma-ray halo emission. Specific asymmetry predictions were made for the recently claimed DM interpretation of the outer halo emission. The paper also studied the role of secondary — ICS and bremsstrahlung — emissions due to DM annihilation for that interpretation. And, finally, the latter was shown to be in significant tension with the recently derived WIMP constraints by radio data on M31.

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A. Egorov
Mon, 15 May 23
16/53

Comments: 15 pages, 5 figures, 4 tables, submitted to Phys. Rev. D

Modelling the variable emission states of $γ$-ray emitting Narrow-Line Seyfert 1 galaxies [HEAP]

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http://arxiv.org/abs/2305.07443


$\gamma$-ray-emitting narrow-line Seyfert 1 galaxies ($\gamma$-NLS1) constitute an intriguing small population of Active Galactic Nuclei with $\gamma$-ray emission resembling low power flat-spectrum radio quasars (FSRQ), but with differing physical properties. They are jetted, $\gamma$/radio-loud Seyfert galaxies, with relatively low black hole masses, accreting at exceptionally high, near-Eddington rates. Certain of these sources exhibit highly variable emission states on relatively short time scales, the physical origin of which remains elusive. In this work, varying emission states of two bona-fide NLS1s, 1H 0323+342 and PMN J0948+0022, and one little studied FSRQ/intermediate object, B2 0954+25A, are examined. For each source, we analyzed quasi-simultaneous multiwavelength data for different states of $\gamma$-ray activity and present the results of their broad-band emission modelling, taking into account all available physical constraints to limit the range of the model parameters. Two different scenarios are discussed, in the framework of a one-zone leptonic model, where the high energy emission is due to the inverse Compton scattering of the disc and broad line region (BLR) or torus photons by relativistic electrons within the jet. The transition from low to high state is well described by variations of the jet parameters, leaving the external photon fields unchanged. The parameterisation favours an emission scenario with particle injection on a stationary shock inside the jet. When considering all physical constraints, the disc & BLR scenario is preferred for all three sources. We use the multi-epoch modelling to characterize total jet powers and discuss the intrinsic nature of $\gamma$-NLS1 galaxies and FSRQs.

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A. Luashvili, C. Boisson, A. Zech, et. al.
Mon, 15 May 23
18/53

Comments: Accepted for publication in MNRAS

Drop in the hard pulsed fraction and a candidate cyclotron line in IGR J16320-4751 seen by NuSTAR [HEAP]

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http://arxiv.org/abs/2305.07068


We report on a timing and spectral analysis of a 50-ks NuSTAR observation of IGR J16320-4751 (= AX J1631.9-4752); a high-mass X-ray binary hosting a slowly-rotating neutron star. In this observation from 2015, the spin period was 1,308.8+/-0.4 s giving a period derivative dP/dt ~ 2E-8 s s-1 when compared with the period measured in 2004. In addition, the pulsed fraction decreased as a function of energy, as opposed to the constant trend that was seen previously. This suggests a change in the accretion geometry of the system during the intervening 11 years. The phase-averaged spectra were fit with the typical model for accreting pulsars: a power law with an exponential cutoff. This left positive residuals at 6.4 keV attributable to the known iron K-alpha line, as well as negative residuals around 14 keV from a candidate cyclotron line detected at a significance of 5-sigma. We found no significant differences in the spectral parameters across the spin period, other than the expected changes in flux and component normalizations. A flare lasting around 5 ks was captured during the first half of the observation where the X-ray emission hardened and the local column density decreased. Finally, the binary orbital period was refined to 8.9912+/-0.0078 d thanks to Swift/BAT monitoring data from 2005-2022.

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A. Bodaghee, A. Chiu, J. Tomsick, et. al.
Mon, 15 May 23
21/53

Comments: 17 pages, 11 figures, Referee-revised version accepted for publication in the Astrophysical Journal

IceCube: Neutrinos from Active Galaxies [HEAP]

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http://arxiv.org/abs/2305.07086


The IceCube project transformed a cubic kilometer of transparent, natural Antarctic ice into a Cherenkov detector. It discovered neutrinos of TeV-PeV energy originating beyond our Galaxy with an energy flux that exceeds the one of high-energy gamma rays of extragalactic origin. Unlike at any other wavelength of light, extragalactic neutrinos outshine the nearby sources in our own Milky way. Updated measurements of the diffuse cosmic neutrino flux indicate that the high-energy gamma rays produced by the neutral pions that accompany cosmic neutrinos lose energy in the sources and are likely to be observed at MeV energy, or below. After the reanalysis of 10 years of archival data with an improved data selection and enhanced data analysis methods, the active galaxy NGC 1068 emerged as the hottest spot in the neutrino sky map. It is also the most significant source in a search at the positions of 110 preselected high-energy gamma-ray sources. Additionally, we find evidence for neutrino emission from the active galaxies PKS 1424+240 and TXS 0506+056. TXS 0506+056 had already been identified as a neutrino source in a multimessenger campaign triggered by a neutrino of 290 TeV energy and, by the independent observation of a neutrino burst in 2014 from this source in archival IceCube data. The observations point to active galaxies as the sources of cosmic neutrinos, and cosmic rays, with the gamma-ray-obscured dense cores near the supermassive black holes at their center as the sites where neutrinos originate, typically within $10\sim100$ Schwarzschild radii.

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F. Halzen
Mon, 15 May 23
26/53

Comments: contribution to the 2023 Electroweak session of the 57th Rencontres de Moriond

Prospects of detecting soft X-ray emission from typical WHIM filaments around massive clusters and the Coma cluster soft excess [HEAP]

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http://arxiv.org/abs/2305.07579


While hot ICM in galaxy clusters makes these objects powerful X-ray sources, the cluster’s outskirts and overdense gaseous filaments might give rise to much fainter sub-keV emission. Cosmological simulations show a prominent “focusing” effect of rich clusters on the space density of the Warm-Hot Intergalactic Medium (WHIM) filaments up to a distance of $\sim 10\,{\rm Mpc}$ ($\sim$ turnaround radius, $r_{ta}$) and beyond. Here, we use Magneticum simulations to characterize their properties in terms of integrated emission measure for a given temperature and overdensity cut and the level of contamination by the more dense gas. We suggest that the annuli $(\sim 0.5-1)\times \,r_{ta}$ around massive clusters might be the most promising sites for the search of the gas with overdensity $\lesssim 50$. We model spectral signatures of the WHIM in the X-ray band and identify two distinct regimes for the gas at temperatures below and above $\sim 10^6\,{\rm K}$. Using this model, we estimate the sensitivity of X-ray telescopes to the WHIM spectral signatures. We found that the WHIM structures are within reach of future high spectral resolution missions, provided that the low-density gas is not extremely metal-poor. We then consider the Coma cluster observed by SRG/eROSITA during the CalPV phase as an example of a nearby massive object. We found that beyond the central $r\sim 40’$ ($\sim 1100\,{\rm kpc}$) circle, where calibration uncertainties preclude clean separation of the extremely bright cluster emission from a possible softer component, the conservative upper limits are about an order of magnitude larger than the levels expected from simulations.

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E. E.Churazov, I. I.I.Khabibullin, K. K.Dolag, et. al.
Mon, 15 May 23
27/53

Comments: Submitted to MNRAS

How do supernova remnants cool? — I. Morphology, optical emission lines, and shocks [HEAP]

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http://arxiv.org/abs/2305.07652


Supernovae (SNe) inject $\sim 10^{51}$ erg in the interstellar medium, thereby shocking and heating the gas. A substantial fraction of this energy is later lost via radiative cooling. We present a post-processing module for the FLASH code to calculate the cooling radiation from shock-heated gas using collisional excitation data from MAPPINGS V. When applying this tool to a simulated SN remnant (SNR), we find that most energy is emitted in the EUV. However, optical emission lines ($[$O III$]$, $[$N II$]$, $[$S II$]$, H${\alpha}$, H${\beta}$) are usually best observable. Our shock detection scheme shows that [S II] and [N II] emissions arise from the thin shell surrounding the SNR, while [O III], H$\rm \alpha$, and H$\rm \beta$ originate from the volume-filling hot gas inside the SNR bubble. We find that the optical emission lines are affected by the SNR’s complex structure and its projection onto the plane of the sky because the escaping line luminosity can be reduced by 10 — 80\% due to absorption along the line-of-sight. Additionally, the subtraction of contaminating background radiation is required for the correct classification of an SNR on the oxygen or sulphur BPT diagrams. The electron temperature and density obtained from our synthetic observations match well with the simulation but are very sensitive to the assumed metallicity.

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E. Makarenko, S. Walch, S. Clarke, et. al.
Mon, 15 May 23
30/53

Comments: 18 pages, 13 figures, accepted for publication in MNRAS

A QPO in Mkn 421 from Archival RXTE Data [HEAP]

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http://arxiv.org/abs/2305.07510


We report a 325(-7, +8) day quasi-periodic oscillation (QPO) in the X-ray emission of the blazar Mkn 421, based on data obtained with the Rossi X-ray Timing Explorer (RXTE). The QPO is seen prominently in the ASM data (at least 15 cycles), due to the fact that it has had near-continuous sampling for more than a decade. The PCA data, where the sampling is not uniform and shows many large gaps, provide supporting evidence at lower significance. This QPO is present in both the Proportional Counter Array (PCA) and All-Sky Monitor (ASM) light curves, however it is far more secure (32 sigma significance) in the ASM data since much of the PCA data are from target-of-opportunity flare observations and thus have substantial gaps. QPOs are an important observable in accretion disks, can be modulated by various orbital timescales, and may be generated by a number of mechanisms. They have been studied extensively in X-ray binaries, and should be present in active galactic nuclei (AGN) if they are governed by a common set of physical principles. In jetted sources, QPOs can probe jet-disk interactions or helical oscillations. This QPO previously has been claimed intermittently in X-ray, radio and gamma-ray data, but the continuous, 15-year extent (1996-2011) of the ASM observations (in which Mkn 421 is the brightest AGN observed) provides a unique window. The QPO appears present for nearly the entire extent of the ASM observations. We explore various physical origins and modulating mechanisms, particularly interpretations of the QPO as a result of disk-jet interactions, either due to an accretion disk limit cycle, jet instabilities or helical motions. Limit-cycle related oscillations would not interact with either Keplerian or Lense-Thirring modulated oscillations, however those associated with jet instabilities or helical motions in the jet would likely be modulated by Lense-Thirring precession.

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E. Smith, L. Oramas and E. Perlman
Mon, 15 May 23
33/53

Comments: 10 pages, 8 figures, ApJ, in press

Probing the Origin of Primordial Black Holes through Novel Gravitational Wave Spectrum [CL]

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http://arxiv.org/abs/2305.07569


In this article we investigate the cumulative stochastic gravitational wave spectra as a tool to gain insight on the creation mechanism of primordial black holes. We consider gravitational waves from the production mechanism of primordial black holes and from the gravitational interactions of those primordial black holes among themselves and other astrophysical black holes. We specifically focus on asynchronous bubble nucleation during a first order phase transition as the creation mechanism. We have used two benchmark phase transitions through which the primordial black holes and the primary gravitational wave spectra have been generated. We have considered binary systems and close hyperbolic interactions of primordial black holes with other primordial and astrophysical black holes as the source of the secondary part of the spectra. We have shown that this unique cumulative spectra have features which directly and indirectly depend on the specifics of the production mechanism.

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I. Banerjee and U. Dey
Mon, 15 May 23
35/53

Comments: 22 pages, 9 figures, 2 tables

X-ray surface brightness and gas density profiles of galaxy clusters up to 3*R500c with SRG/eROSITA [CEA]

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http://arxiv.org/abs/2305.07080


Using the data of the SRG/eROSITA all-sky survey, we stacked a sample of ~40 galaxy cluster images in the 0.3–2.3 keV band, covering the radial range up to $10\times R_{\rm 500c}$. The excess emission on top of the galactic and extragalactic X-ray backgrounds and foregrounds is detected up to $\sim 3\times R_{\rm 500c}$. At these distances, the surface brightness of the stacked image drops below $\sim 1$% of the background. The density profile reconstructed from the X-ray surface brightness profile agrees well (within $\sim30$%) with the mean gas profile found in numerical simulations, which predict the local gas overdensity of $\sim$ 20–30 at $3\times R_{\rm 500c}$ and the gas fraction close to the universal value of $\frac{\Omega_b}{\Omega_m}\approx 0.15$ in the standard $\Lambda$CDM model. Taking at face value, this agreement suggests that up to $\sim 3\times R_{\rm 500c}$ the X-ray signal is not strongly boosted by the gas clumpiness, although a scenario with a moderately inhomogeneous gas cannot be excluded. A comparison of the derived gas density profile with the electron pressure profile based on the SZ measurements suggests that by $r\sim 3\times R_{\rm 500c}$ the gas temperature drops by a factor of $\sim$ 4–5 below the characteristic temperature of a typical cluster in the sample within $R_{\rm 500c}$, while the entropy keeps growing up to this distance. Better constraints on the gas properties just beyond $3\times R_{\rm 500c}$ should be possible with a sample larger than used for this pilot study.

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N. Lyskova, E. Churazov, I. Khabibullin, et. al.
Mon, 15 May 23
38/53

Comments: submitted to MNRAS

Evolutionary Increase of the orbital Separation and Change of the Roche Lobe Size in SS433 [HEAP]

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http://arxiv.org/abs/2305.07093


We present results of long-term photometric monitoring of SS433 which proves a secular evolutionary increase of the orbital period of SS433 at a rate of $(1.14\pm 0.25)\times 10^{-7}$ s~s$^{-1}$. Using a physical model of non-conservative mass transfer in SS433 through a supercritical accretion disc around the compact companion, we reliably confirm that the binary mass ratio in SS433, $q=M_x/M_v$ is $\gtrsim 0.8$. For an optical star mass $M_v\sim 10 M_\odot$ the compact object in SS433 is a black hole with mass $M_{BH}\gtrsim 8 M_\odot$. We discuss evolutionary implications of the found orbital period increase in SS433 — a secular change in the orbital separation and a size of the Roche lobe of the optical star. We show that for the mass-loss rate $dM_v/dt\sim 10^{-4}-3\times 10^{-5} M_\odot$ per year and an optical star mass $M_v \sim 10-15 M_\odot$ the found orbital period increase implies the corresponding orbital separation increase while the Roche lobe size can shrink or expand around a mean constant value depending on the optical star mass-loss rate which may be modulated with the precessional period.

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A. Cherepashchuk, A. Belinski, A. Dodin, et. al.
Mon, 15 May 23
41/53

Comments: 19 pages, 3 figures, accepted for publication in New Astronomy

Deducing Neutron Star Equation of State from Telescope Spectra with Machine-learning-derived Likelihoods [HEAP]

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http://arxiv.org/abs/2305.07442


The interiors of neutron stars reach densities and temperatures beyond the limits of terrestrial experiments, providing vital laboratories for probing nuclear physics. While the star’s interior is not directly observable, its pressure and density determine the star’s macroscopic structure which affects the spectra observed in telescopes. The relationship between the observations and the internal state is complex and partially intractable, presenting difficulties for inference. Previous work has focused on the regression from stellar spectra of parameters describing the internal state. We demonstrate a calculation of the full likelihood of the internal state parameters given observations, accomplished by replacing intractable elements with machine learning models trained on samples of simulated stars. Our machine-learning-derived likelihood allows us to perform maximum a posteriori estimation of the parameters of interest, as well as full scans. We demonstrate the technique by inferring stellar mass and radius from an individual stellar spectrum, as well as equation of state parameters from a set of spectra. Our results are more precise than pure regression models, reducing the width of the parameter residuals by 11.8% in the most realistic scenario. The neural networks will be released as a tool for fast simulation of neutron star properties and observed spectra.

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D. Farrell, P. Baldi, J. Ott, et. al.
Mon, 15 May 23
42/53

Comments: 18 pages, 8 figures

Interplanetary scintillation and pulsar pulse statistics [HEAP]

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http://arxiv.org/abs/2305.07422


The effect of interplanetary plasma on pulsed pulsar radiation passing through is considered. The pulses of two rotating radio transients (J0609+16, J1132+25) and a pulsar (B0320+39) detected on the Large Phased Array (Pushchino observatory) were analyzed. It is shown that in observations at the frequency of 111 MHz, on elongations of 20o-40o, both an increase and a decrease in the number of received pulses are observed. The change in the number of pulses is explained by the distortion of the energy distribution of pulses due to interplanetary scintillation. These changes in the number of observed pulses are in qualitative agreement with the expected dependence of the scintillation index on the observed sources elongation. Analytical expressions are obtained that allow estimating the effective modulation index from observations of individual pulses for the power distribution of pulses by energy.

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S. Tyul’bashev, I. Chashei and M. Kitaeva
Mon, 15 May 23
43/53

Comments: accepted to MNRAS, 5 pages, 3 figures

The nuclear reaction network WinNet [IMA]

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http://arxiv.org/abs/2305.07048


We present the state-of-the-art single-zone nuclear reaction network WinNet that is capable of calculating the nucleosynthetic yields of a large variety of astrophysical environments and conditions. This ranges from the calculation of the primordial nucleosynthesis where only a few nuclei are considered to the ejecta of neutron star mergers with several thousands of involved nuclei. Here we describe the underlying physics and implementation details of the reaction network. We additionally present the numerical implementation of two different integration methods, the implicit Euler method and Gears method along with their advantages and disadvantages. We furthermore describe basic example cases of thermodynamic conditions that we provide together with the network and demonstrate the reliability of the code by using simple test cases. Once the manuscript has been accepted for publication, WinNet will be publicly available and open source.

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M. Reichert, C. Winteler, O. Korobkin, et. al.
Mon, 15 May 23
44/53

Comments: N/A

The Spatially Resolved Properties of the GW170817 Host Galaxy [HEAP]

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http://arxiv.org/abs/2305.07281


GW170817 is the unique gravitational-wave (GW) event that is associated to the electromagnetic (EM) counterpart GRB 170817A. NGC 4993 is identified as the host galaxy of GW170817/GRB 170817A. In this paper, we particularly focus on the spatially resolved properties of NGC 4993. We present the photometric results from the comprehensive data analysis of the high spatial-resolution images in the different optical bands. The morphological analysis reveals that NGC 4993 is a typical early-type galaxy without significant remnants of major galaxy merger. The spatially resolved stellar population properties of NGC 4993 suggest that the galaxy center has passive evolution with the outskirt formed by gas accretion. We derive the merging rate of the compact object per galaxy by a co-evolution scenario of supermassive black hole and its host galaxy. If the galaxy formation is at redshift 1.0, the merging rate per galaxy is $3.2\times 10^{-4}$ to $7.7\times 10^{-5}$ within the merging decay time from 1.0 to 5.0 Gyr. The results provide the vital information for the ongoing GW EM counterpart detections. The HST data analysis presented in this paper can be also applied for the Chinese Space Station Telescope (CSST) research in the future.

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Y. Li, J. Mao, J. Qin, et. al.
Mon, 15 May 23
45/53

Comments: RAA accepted

Observational predictions for Thorne-Żytkow objects [SSA]

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http://arxiv.org/abs/2305.07337


Thorne-$.Z$ytkow objects (T$.Z$O) are potential end products of the merger of a neutron star with a non-degenerate star. In this work, we have computed the first grid of evolutionary models of T$.Z$Os with the MESA stellar evolution code. With these models, we predict several observational properties of T$.Z$Os, including their surface temperatures and luminosities, pulsation periods, and nucleosynthetic products. We expand the range of possible T$.Z$O solutions to cover $3.45 \lesssim \log \left(T/K\right) \lesssim 3.65$ and $4.85 \lesssim \log \left(L/L_{\odot}\right) \lesssim 5.5$. Due to the much higher densities our T$.Z$Os reach compared to previous models, if T$.Z$Os form we expect them to be stable over a larger mass range than previously predicted, without exhibiting a gap in their mass distribution. Using the GYRE stellar pulsation code we show that T$.Z$Os should have fundamental pulsation periods of 1000–2000 days, and period ratios of $\approx$0.2–0.3. Models computed with a large 399 isotope fully-coupled nuclear network show a nucleosynthetic signal that is different to previously predicted. We propose a new nucleosynthetic signal to determine a star’s status as a T$.Z$O: the isotopologues $^{44}\rm{Ti} \rm{O}_2$ and $^{44}\rm{Ti} \rm{O}$, which will have a shift in their spectral features as compared to stable titanium-containing molecules. We find that in the local Universe (~SMC metallicities and above) T$.Z$Os show little heavy metal enrichment, potentially explaining the difficulty in finding T$.Z$Os to-date.

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R. Farmer, M. Renzo, Y. Götberg, et. al.
Mon, 15 May 23
46/53

Comments: 17 pages, 16 figures, 3 Tables, Sumbitedd to MNRAS, Zenodo data available this https URL

Drop in the hard pulsed fraction and a candidate cyclotron line in IGR J16320-4751 seen by NuSTAR [HEAP]

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http://arxiv.org/abs/2305.07068


We report on a timing and spectral analysis of a 50-ks NuSTAR observation of IGR J16320-4751 (= AX J1631.9-4752); a high-mass X-ray binary hosting a slowly-rotating neutron star. In this observation from 2015, the spin period was 1,308.8+/-0.4 s giving a period derivative dP/dt ~ 2E-8 s s-1 when compared with the period measured in 2004. In addition, the pulsed fraction decreased as a function of energy, as opposed to the constant trend that was seen previously. This suggests a change in the accretion geometry of the system during the intervening 11 years. The phase-averaged spectra were fit with the typical model for accreting pulsars: a power law with an exponential cutoff. This left positive residuals at 6.4 keV attributable to the known iron K-alpha line, as well as negative residuals around 14 keV from a candidate cyclotron line detected at a significance of 5-sigma. We found no significant differences in the spectral parameters across the spin period, other than the expected changes in flux and component normalizations. A flare lasting around 5 ks was captured during the first half of the observation where the X-ray emission hardened and the local column density decreased. Finally, the binary orbital period was refined to 8.9912+/-0.0078 d thanks to Swift/BAT monitoring data from 2005-2022.

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A. Bodaghee, A. Chiu, J. Tomsick, et. al.
Mon, 15 May 23
48/53

Comments: 17 pages, 11 figures, Referee-revised version accepted for publication in the Astrophysical Journal

Spectroscopic Searches for Evolutionary Orbital Period Changes in WR+OB Binaries: The case of CQ Cep and CX Cep [HEAP]

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http://arxiv.org/abs/2305.07105


We present the results of spectroscopic observations of two eclipsing WR+OB-type systems – CQ Cep and CX Cep, performed in 2020-2023 with a low-resolution slit spectrograph TDS ($\lambda\lambda= 3660-7410$\AA, $R = 1300-2500$) on 2.5-m telescope of the SAI MSU Caucasian Mountain Observatory. For CQ Cep, the radial velocity curves of a WN6 star are constructed, the problem of visibility of spectroscopic traces of an OB star is discussed and the components’ mass ratio $q\sim 0.6$ is estimated. For CX Cep, the radial velocity curves are constructed for both the WN5 and O5 components enabling their masses and circular orbit elements to be refined. The comparison of the radial velocity curves of these systems obtained in different epochs allowed us to derive the orbital period change rate $\dot{P}$ by the spectroscopic method, which is found to be in good agreement with estimates obtained by comparing the moments of primary eclipse minima: $\dot{P} = -0.0151\pm0.0013$ s yr$^{-1}$ for CQ Cep and $\dot{P} = 0.054\pm0.009$ s yr$^{-1}$ for CX Cep. The prospects of applicability of the spectroscopic dynamical method for studying the orbital evolution of Galactic WR+OB binaries and related objects are considered. We also discuss the effect of finite sizes of stars with stellar wind mass loss in close binary systems on their orbital evolution.

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I. Shaposhnikov, A. Cherepashchuk, A. Dodin, et. al.
Mon, 15 May 23
52/53

Comments: 13 pages, 8 figures, 11 tables, accepted for publication in MNRAS

Phase Transition Phenomenology with Nonparametric Representations of the Neutron Star Equation of State [HEAP]

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http://arxiv.org/abs/2305.07411


Astrophysical observations of neutron stars probe the structure of dense nuclear matter and have the potential to reveal phase transitions at high densities. Most recent analyses are based on parametrized models of the equation of state with a finite number of parameters and occasionally include extra parameters intended to capture phase transition phenomenology. However, such models restrict the types of behavior allowed and may not match the true equation of state. We introduce a complementary approach that extracts phase transitions directly from the equation of state without relying on, and thus being restricted by, an underlying parametrization. We then constrain the presence of phase transitions in neutron stars with astrophysical data. Current pulsar mass, tidal deformability, and mass-radius measurements disfavor only the strongest of possible phase transitions (latent energy per particle $\gtrsim 100\,\mathrm{MeV}$). Weaker phase transitions are consistent with observations. We further investigate the prospects for measuring phase transitions with future gravitational-wave observations and find that catalogs of \result{$O(100)$} events will (at best) yield Bayes factors of $\sim 10:1$ in favor of phase transitions even when the true equation of state contains very strong phase transitions. Our results reinforce the idea that neutron star observations will primarily constrain trends in macroscopic properties rather than detailed microscopic behavior. Fine-tuned equation of state models will likely remain unconstrained in the near future.

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R. Essick, I. Legred, K. Chatziioannou, et. al.
Mon, 15 May 23
53/53

Comments: 18 pages (+12 pages of references and appendix), 17 figures, 5 tables

Galactic diffuse gamma-ray emission from GeV to PeV energies in light of up-to-date cosmic ray measurements [HEAP]

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http://arxiv.org/abs/2305.06948


The diffuse gamma-ray emission between 10 and 1000 TeV from the Galactic plane was recently measured precisely by the Large High Altitude Air Shower Observatory (LHAASO), which is very useful in constraining the propagation and interaction of cosmic rays in the Milky Way. On the other hand, new measurements of CR spectra reach a very high precision up to 100 TeV energies, revealing multiple spectral structures of various species. In this work, we confront the model prediction of the diffuse gamma-ray emission, based on up-to-date measurements of the local cosmic ray spectra and simplified propagation setup, with the measurements of diffuse gamma-rays. To better constrain the low-energy part of the model, we analyze Fermi-LAT data to extract the diffuse emission between 1 and 500 GeV from the same sky regions of LHAASO. Compared with the prediction, we find that clear excesses between several GeV and ~60 TeV of the diffuse emission exist. Possible reasons to explain the excesses may include unresolved sources or more complicated propagation models. We illustrate that an exponential-cutoff-power-law component with an index of -2.40 and cutoff energy of ~30 TeV is able to account for such excesses.

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R. Zhang, X. Huang, Z. Xu, et. al.
Fri, 12 May 23
7/53

Comments: N/A

Propagation effects at low frequencies seen in the LOFAR long-term monitoring of the periodically active FRB 20180916B [HEAP]

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http://arxiv.org/abs/2305.06393


LOFAR (LOw Frequency ARray) has previously detected bursts from the periodically active, repeating fast radio burst (FRB) source FRB 20180916B down to unprecedentedly low radio frequencies of 110 MHz. Here we present 11 new bursts in 223 more hours of continued monitoring of FRB 20180916B in the 110-188 MHz LOFAR band. We place new constraints on the LOFAR activity width $w = 4.3^{+0.7}{-0.2}$ day, and phase centre $\phi{\mathrm{c}}^{\mathrm{LOFAR}} = 0.67^{+0.03}_{-0.02}$ in its 16.33-day activity cycle, strengthening the evidence for its frequency-dependent activity cycle. Propagation effects like Faraday rotation and scattering are especially pronounced at low frequencies and constrain properties of FRB 20180916B’s local environment. We track variations in scattering and time-frequency drift rates, and find no evidence for trends in time or activity phase. Faraday rotation measure (RM) variations seen between June 2021 and August 2022 show a fractional change $>$50% with hints of flattening of the gradient of the previously reported secular trend seen at 600 MHz. The frequency-dependent window of activity at LOFAR appears stable despite the significant changes in RM, leading us to deduce that these two effects have different causes. Depolarization of and within individual bursts towards lower radio frequencies is quantified using LOFAR’s large fractional bandwidth, with some bursts showing no detectable polarization. However, the degree of depolarization seems uncorrelated to the scattering timescales, allowing us to evaluate different depolarization models. We discuss these results in the context of models that invoke rotation, precession, or binary orbital motion to explain the periodic activity of FRB 20180916B.

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A. Gopinath, C. Bassa, Z. Pleunis, et. al.
Fri, 12 May 23
13/53

Comments: 17 pages, 10 figures, Submitted to MNRAS

What are neutron stars made of? Gravitational waves may reveal the answer [CL]

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http://arxiv.org/abs/2305.06606


Neutron stars are one of the most mysterious wonders in the Universe. Their extreme densities hint at new and exotic physics at work within. Gravitational waves could be the key to unlocking their secrets. In particular, a first detection of gravitational waves from rapidly-spinning, deformed neutron stars could yield new insights into the physics of matter at extreme densities and under strong gravity. Once a first detection is made, a critical challenge will be to robustly extract physically interesting information from the detected signals. In this essay, we describe initial research towards answering this challenge, and thereby unleashing the full power of gravitational waves as an engine for the discovery of new physics.

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N. Lu, S. Scott and K. Wette
Fri, 12 May 23
16/53

Comments: 14 pages, 2 figures. This essay was awarded 5th Place in the Gravity Research Foundation 2023 Awards for Essays on Gravitation. To appear in International Journal of Modern Physics D

Searching for temporary gamma-ray dark blazars associated with IceCube neutrinos [HEAP]

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http://arxiv.org/abs/2305.06729


Tensions between the diffuse gamma-ray sky observed by the Fermi Large Area Telescope (LAT) and the diffuse high-energy neutrino sky detected by the IceCube South Pole Neutrino Observatory question our knowledge about high-energy neutrino sources in the gamma-ray regime. While blazars are among the most energetic persistent particle accelerators in the Universe, studies suggest that they could account for up to for 10-30% of the neutrino flux measured by IceCube. Our recent results highlighted that the associated IceCube neutrinos arrived in a local gamma-ray minimum (dip) of three strong neutrino point-source candidates. We increase the sample of neutrino-source candidates to study their gamma-ray light curves. We generate the one-year Fermi-LAT light curve for 8 neutrino source candidate blazars (RBS 0958, GB6 J1040+0617, PKS 1313-333, TXS 0506+056, PKS 1454-354, NVSS J042025-374443, PKS 0426-380 and PKS 1502+106), centered on the detection time of the associated IceCube neutrinos. We apply the Bayesian block algorithm on the light curves to characterize their variability. Our results indicate that GB6 J1040+0617 was in the phase of high gamma-ray activity, while none of the other 7 neutrino source candidates were statistically bright during the detection of the corresponding neutrinos and that indeed even most of the times neutrinos arrived in a faint gamma-ray phase of the light curves. This suggests that the 8 source-candidate blazars (associated with 7 neutrino events) in our reduced sample are either not the sources of the corresponding IceCube neutrinos, or that an in-source effect (e.g. suppression of gamma rays due to high gamma-gamma opacity) complicates the multimessenger scenario of neutrino emission for these blazars.

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E. Kun, I. Bartos, J. Tjus, et. al.
Fri, 12 May 23
17/53

Comments: 13 pages, 8 figures, 4 tables. Submitted to A&A

A Leptonic Model for Neutrino Emission From Active Galactic Nuclei [HEAP]

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http://arxiv.org/abs/2305.06375


It is often stated that the observation of high-energy neutrinos from an astrophysical source would constitute a smoking gun for the acceleration of hadronic cosmic rays. Here, we point out that there exists a purely leptonic mechanism to produce TeV-scale neutrinos in astrophysical environments. In particular, very high energy synchrotron photons can scatter with X-rays, exceeding the threshold for muon-antimuon pair production. When these muons decay, they produce neutrinos without any cosmic-ray protons or nuclei being involved. In order for this mechanism to be efficient, the source in question must feature both kG-scale magnetic fields and a high density of keV-scale photons. As an example, we consider the active galaxy NGC 1068, which IceCube has recently detected as a source of TeV-scale neutrinos. We find that the neutrino emission observed from this source could potentially be generated through muon pair production for reasonable choices of physical parameters.

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D. Hooper and K. Plant
Fri, 12 May 23
18/53

Comments: 4 pages, 2 figures

Merger Conditions of Population III Protostar Binaries [SSA]

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http://arxiv.org/abs/2305.06843


Massive close binary stars with extremely small separations have been observed, and they are possible progenitors of gravitational-wave sources. The evolution of massive binaries in the protostellar accretion stage is key to understanding their formation process. We, therefore, investigate how close the protostars, consisting of a high-density core and a vast low-density envelope, can approach each other but not coalesce. To investigate the coalescence conditions, we conduct smoothed particle hydrodynamics simulations following the evolution of equal-mass binaries with different initial separations. Since Population (Pop) I and III protostars have similar interior structures, we adopt a specific Pop~III model with the mass and radius of $7.75\;M_{\odot}$ and $61.1\;R_{\odot}$ obtained by the stellar evolution calculations. Our results show that the binary separation decreases due to the transport of the orbital angular momentum to spin angular momentum. If the initial separation is less than about 80 per~cent of the sum of the protostellar radius, the binary coalesces in a time shorter than the tidal lock timescale. The mass loss up to the merging is $\lesssim 3$ per~cent. After coalescence, the star rotates rapidly, and its interior structure is independent of the initial separation. We conclude that there must be some orbital shrinking mechanism after the protostars contract to enter the zero-age main-sequence stage.

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T. Kirihara, H. Susa, T. Hosokawa, et. al.
Fri, 12 May 23
19/53

Comments: 17 pages, 13 figures, Accepted for Publication in ApJ

Effect of the cosmological model on LIV constraints from GRB Time-Delays datasets [CL]

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http://arxiv.org/abs/2305.06504


Putting constraints on a possible Lorentz Invariance Violation (LIV) from astrophysical sources such as gamma-ray bursts (GRBs) is an essential tool for finding evidences of new theories of quantum gravity (QG) that predict energy-dependent speed of light. Such a search has its own difficulties, so usually, the effect of the cosmological model is understudied and the default model is a fixed-parameters $\Lambda$CDM. In this work, we use different astrophysical datasets to study the effect of a number of dark energy models on the LIV constrains. To this end, we combine two public time-delay GRB datasets with the supernovae Pantheon dataset, a number of angular baryonic acoustic oscillations (BAO), the cosmic microwave background (CMB) distance prior and a GRB or quasars dataset. We find for $\alpha$ the expected average value of $\sim 4 \times 10^{-4}$, corresponding to $E_{QG}\ge 10^{17}$ GeV for both time-delay (TD) datasets, with the second one being more sensitive to the cosmological model. We find that the cosmology amounts to at least 20\% deviation in our constraints on the energy. Also interestingly, adding the TD points makes the DE models less-preferable statistically and shifts the value of the parameter $c/(H_0 r_d)$ down, making it smaller than the expected value. We see that possible LIV measurements depend critically on the transparency of the assumptions behind the published data with respect to cosmology and that taking it into account may be important contribution in the case of possible detection.

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D. Staicova
Fri, 12 May 23
26/53

Comments: 19 pages, prepared for the Classical and Quantum Gravity focus issue “Focus on Quantum Gravity Phenomenology in the Multi-Messenger Era: Challenges and Perspectives”

Interpreting the GeV-TeV Gamma-Ray Spectra of Local Giant Molecular Clouds using GEANT4 Simulation [HEAP]

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http://arxiv.org/abs/2305.06693


Recently, the Fermi-LAT gamma-ray satellite has detected six Giant Molecular Clouds (GMCs) located in the Gould Belt and the Aquila Rift regions. In half of these objects (Taurus, Orion A, Orion B), the observed gamma-ray spectrum can be explained using the Galactic diffused Cosmic Ray (CR) interactions with the gas environments. In the remaining three GMCs (Rho Oph, Aquila Rift, Cepheus), the origin of the gamma-ray spectrum is still not well established. We use the GEometry ANd Tracking (GEANT4) simulation framework in order to simulate gamma-ray emission due to CR/GMC interaction in these three objects, taking into account the gas density distribution inside the GMCs. We find that propagation of diffused Galactic CRs inside these GMCs can explain the Fermi-LAT detected gamma-ray spectra. Further, our estimated TeV-PeV fluxes are consistent with the HAWC upper limits, available for the Aquila Rift GMC. As last step, we compute the total neutrino flux estimated for these GMCs and compare it with the IceCube detection sensitivity.

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A. Roy, J. Joshi, M. Cardillo, et. al.
Fri, 12 May 23
30/53

Comments: 17 pages, 9 figures, Comments Welcome

XTE J1906+090: a persistent low luminosity Be X-ray Binary [HEAP]

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http://arxiv.org/abs/2305.06689


We present new results from INTEGRAL and Swift observations of the hitherto poorly studied and unidentified X-ray source XTE J1906+090. A bright hard X-ray outburst (luminosity of $\sim$10$^{36}$ erg s$^{-1}$ above 20 keV) has been discovered with INTEGRAL observations in 2010, this being the fourth outburst ever detected from the source. Such events are sporadic, the source duty cycle is in the range (0.8–1.6)% as inferred from extensive INTEGRAL and Swift monitoring in a similar hard X-ray band. Using five archival unpublished Swift/XRT observations, we found that XTE J1906+090 has been consistently detected at a persistent low X-ray luminosity value of $\sim$10$^{34}$ erg s$^{-1}$, with limited variability (a factor as high as 4). Based on our findings, we propose that XTE J1906+090 belongs to the small and rare group of persistent low luminosity Be X-ray Binaries.

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V. Sguera, L. Sidoli, A. Bird, et. al.
Fri, 12 May 23
33/53

Comments: Accepted for publication in MNRAS. 7 pages, 6 figures, 5 tables

Swift J1644+57 as an off-axis Jet [HEAP]

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http://arxiv.org/abs/2305.06370


One of the intriguing puzzles concerning Swift J1644+57, the first jetted tidal disruption event (TDE) discovered, is the constant increase in its jet energy, as implied by radio observations. During the first two hundred days the jet energy has increased by an order of magnitude. We suggest that the jet was viewed slightly off-axis. In this case, the apparent energy increase arises due to the slowing down of the jet and the corresponding broadening of its beaming cone. Using equipartition analysis, we infer an increasing jet energy as a larger region of the jet is observed. A simple off-axis model accounts nicely for the multi-wavelength radio observations, resolving this long-standing puzzle. The model allows us to self-consistently evolve the synchrotron signature from an off-axis jet as a function of time. It also allows us to estimate, for the first time, the beaming angle of the jet, $\theta_0 \approx 21^{\circ}$. This implies that the prompt phase of Swift J1644+57 involved super Eddington jet luminosity. We also present a closure relation between the spectral and temporal flux for off-axis jets, which can be used to test whether a given radio transient is off-axis or not.

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P. Beniamini, T. Piran and T. Matsumoto
Fri, 12 May 23
34/53

Comments: 9 pages, 8 figures. Submitted

Does Nature allow formation of ultra-compact black hole X-ray binaries via accretion-induced collapse of neutron stars? [HEAP]

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http://arxiv.org/abs/2305.06550


The formation path to ultra-compact X-ray binaries (UCXBs) with black hole (BH) accretors is still unclear. In the classical formation scenario, it is difficult to eject the massive envelope of the progenitor star of the BH via common envelope process. Given that some neutron stars (NSs) in binary systems evidently have birth masses close to $\sim 2.0\;M_\odot$, we explore here the possibility that BH-UCXBs may form via accretion-induced collapse (AIC) of accreting NSs, assuming that these previously evolved in LMXBs to masses all the way up to the maximum limit of a NS. We demonstrate this formation path by modelling a few cases of NS-UCXBs with initial NS masses close to the maximum mass of a NS that evolve into BH-UCXBs after the NS accretes material from its He~WD companion. We follow the evolution of the post-AIC BH-UCXB and, based on simple arguments, we anticipate that there is about one BH-UCXB with an AIC origin and a He~WD donor within the current sample of known UCXBs and that 2–5 such BH-UCXBs may be detected in gravitational waves by LISA. In addition, we find that the X-ray luminosity of NS-UCXBs near their orbital period minimum exceeds $\sim 10^{39}\;{\rm erg\;s^{-1}}$ and thus such systems may appear as ultraluminous X-ray sources.

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H. Chen, T. Tauris, X. Chen, et. al.
Fri, 12 May 23
38/53

Comments: ApJ accepted, 12 pages, 3 figures

Testing the linear relationship between black hole mass and variability timescale in low-luminosity AGN at submillimeter wavelengths [HEAP]

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http://arxiv.org/abs/2305.06529


The variability of submillimeter emission provides a useful tool to probe the accretion physics in low-luminosity active galactic nuclei. We accumulate four years of observations using Submillimeter Array for Centaurus A, NGC 4374, NGC 4278, and NGC 5077 and one year of observations for NGC 4552 and NGC 4579. All sources are variable. We measure the characteristic timescale at which the variability is saturated by modeling these sources’ light curve as a damped random walk. We detect a timescale for all the sources except NGC 4552. The detected timescales are comparable to the orbital timescale at the event horizon scale for most sources. Combined with previous studies, we show a correlation between the the timescale and the black hole mass over three orders of magnitude. This discovery suggests the sub-mm emission is optically thin with the emission originating from the event horizon. The mass scaling relationship further suggests that a group of radio sources with a broadband spectrum that peaks at submillimeter wavelengths have similar inner accretion physics. Sources that follow this relationship may be good targets for high-resolution imaging with the Event Horizon Telescope.

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B. Chen, G. Bower, J. Dexter, et. al.
Fri, 12 May 23
41/53

Comments: 18 pages, 7 figures, 4 tables, accepted for publication by ApJ

X-Shooting ULLYSES: massive stars at low metallicity. I. Project Description [SSA]

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http://arxiv.org/abs/2305.06376


Observations of individual massive stars, super-luminous supernovae, gamma-ray bursts, and gravitational-wave events involving spectacular black-hole mergers, indicate that the low-metallicity Universe is fundamentally different from our own Galaxy. Many transient phenomena will remain enigmatic until we achieve a firm understanding of the physics and evolution of massive stars at low metallicity (Z).
The Hubble Space Telescope has devoted 500 orbits to observe 250 massive stars at low Z in the ultraviolet (UV) with the COS and STIS spectrographs under the ULLYSES program.
The complementary “X-Shooting ULLYSES” (XShootU) project provides enhanced legacy value with high-quality optical and near-infrared spectra obtained with the wide-wavelength coverage X-shooter spectrograph at ESO’s Very Large Telescope.
We present an overview of the XShootU project, showing that combining ULLYSES UV and XShootU optical spectra is critical for the uniform determination of stellar parameters such as effective temperature, surface gravity, luminosity, and abundances, as well as wind properties such as mass-loss rates in function of Z. As uncertainties in stellar and wind parameters percolate into many adjacent areas of Astrophysics, the data and modelling of the XShootU project is expected to be a game-changer for our physical understanding of massive stars at low Z.
To be able to confidently interpret James Webb Space Telescope (JWST) spectra of the first stellar generations, the individual spectra of low Z stars need to be understood, which is exactly where XShootU can deliver.

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V. S., M. A., C. P.A., et. al.
Fri, 12 May 23
42/53

Comments: Accepted in A&A – 35 Pages, 12 Figures, 4 Tables, 2 Large Tables

XUV emission of the young planet-hosting star V1298\,Tau from coordinated observations with XMM-Newton and HST [SSA]

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http://arxiv.org/abs/2305.06931


Atmospheric mass loss plays a major role in the evolution of exoplanets. This process is driven by the stellar high-energy irradiation, especially in the first hundreds of millions of years after dissipation of the proto-planetary disk. A major source of uncertainty in modeling atmospheric photo-evaporation and photo-chemistry is due to the lack of direct measurements of the stellar flux at EUV wavelengths. Several empirical relationships have been proposed in the past to link EUV fluxes to emission levels in X-rays, but stellar samples employed for this aim are heterogeneous, and available scaling laws provide significantly different predictions, especially for very active stars. We present new UV and X-ray observations of V1298 Tau with HST/COS and XMM-Newton, aimed to determine more accurately the XUV emission of this solar-mass pre-Main Sequence star, which hosts four exoplanets. Spectroscopic data were employed to derive the plasma emission measure distribution vs.\ temperature, from the chromosphere to the corona, and the possible variability of this irradiation on short and year-long time scales, due to magnetic activity. As a side result, we have also measured the chemical abundances of several elements in the outer atmosphere of V1298 Tau. We employ our results as a new benchmark point for the calibration of the X-ray to EUV scaling laws, and hence to predict the time evolution of the irradiation in the EUV band, and its effect on the evaporation of exo-atmospheres.

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A. Maggio, I. Pillitteri, C. Argiroffi, et. al.
Fri, 12 May 23
46/53

Comments: 17 pages, 14 figures. Accepted for pubblication on ApJ

Exploring connections between the VLBI and optical morphology of AGNs and their host galaxies [GA]

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http://arxiv.org/abs/2305.06713


We analyse VLBI and optical images of AGNs and their host galaxies and look for statistical correlations between the shape and orientation of the galaxy and the direction of the jet. We utilise the Astrogeo catalogue, which has over 9000 VLBI sources, many of those with a clear core-jet like structure that allows for the jet position angle to be reliably determined. We then use the VLBI source positions to search for optical counterparts within various optical surveys. In order to parameterise the orientation and shape of the host galaxy, we fitted a Gaussian elliptical model to the optical image, taking the PSF into account. We check our own shape parameters from this fit against the ones provided by the optical surveys. As of yet, no clear correlation between the galaxy morphology and the jet direction is seen.

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D. Gil, J. Hodgson and B. L’Huillier
Fri, 12 May 23
47/53

Comments: IAU Symposium No. 375 Proceedings, 4 pages, 4 figures, 1 table

Ultra low-mass and small-radius white dwarfs made of heavy elements [SSA]

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http://arxiv.org/abs/2305.05847


Seven ultra low-mass and small-radius white dwarfs (LSPM J0815+1633, LP 240-30, BD+20 5125B, LP 462-12, WD J1257+5428, 2MASS J13453297+4200437, and SDSS J085557.46+053524.5) have been recently identified with masses ranging from $\sim$0.02 $M_\odot$ to $\sim$0.08 $M_\odot$ and radii from $\sim$ 4270 km to 10670 km. The mass-radius measurements of these white dwarfs pose challenges to traditional white dwarf models assuming they are mostly made of nuclei lighter than $^{56}$Fe. In this work we consider the possibility that those white dwarfs are made of heavier elements. Due to the small charge-to-mass ratios in heavy elements, the electron number density in white dwarf matter is effectively reduced, which reduces the pressure with additional contributions of lattice energy and electron polarization corrections. This consequently leads to white dwarfs with much smaller masses and radii, which coincide with the seven ultra low-mass and small-radius white dwarfs. The corresponding equation of state and matter contents of dense stellar matter with and without reaching the cold-catalyzed ground state are presented, which are obtained using the latest Atomic Mass Evaluation (AME 2020). Further observations are necessary to unveil the actual matter contents in those white dwarfs via, e.g., spectroscopy, asteroseismology, and discoveries of other ultra low-mass and small-radius white dwarfs.

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C. Xia, Y. Huang, H. Li, et. al.
Thu, 11 May 23
2/55

Comments: N/A

Constraining gravitational wave amplitude birefringence with GWTC-3 [CL]

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http://arxiv.org/abs/2305.05844


The propagation of gravitational waves can reveal fundamental features of the structure of space-time. For instance, differences in the propagation of gravitational-wave polarizations would be a smoking gun for parity violations in the gravitational sector, as expected from birefringent theories like Chern-Simons gravity. Here we look for evidence of amplitude birefringence in the latest LIGO-Virgo catalog (GWTC-3) through the use of birefringent templates inspired by dynamical Chern-Simons gravity. From 71 binary-black-hole signals, we obtain the most precise constraints on gravitational-wave amplitude birefringence yet, measuring a birefringent attenuation of $\kappa = – 0.019^{+0.038}{-0.029}\, \mathrm{Gpc}^{-1}$ at 100 Hz with 90% credibility, equivalent to a parity-violation energy scale of $M{PV} \gtrsim 6.8\times 10^{-21}\, \mathrm{GeV}$.

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T. Ng, M. Isi, K. Wong, et. al.
Thu, 11 May 23
3/55

Comments: N/A

3D evolution of neutron star magnetic-fields from a realistic core-collapse turbulent topology [HEAP]

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http://arxiv.org/abs/2305.06342


We present the first 3D fully coupled magneto-thermal simulations of neutron stars (including the most realistic background structure and microphysical ingredients so far) applied to a very complex initial magnetic field topology in the crust, similar to what recently obtained by proto-neutron star dynamo simulations. In such configurations, most of the energy is stored in the toroidal field, while the dipolar component is a few percent of the mean magnetic field. This initial feature is maintained during the long-term evolution (1e6 yr), since the Hall term favours a direct cascade (compensating for Ohmic dissipation) rather than a strong inverse cascade, for such an initial field topology. The surface dipolar component, responsible for the dominant electromagnetic spin-down torque, does not show any increase in time, when starting from this complex initial topology. This is at contrast with the timing properties of young pulsars and magnetars which point to higher values of the surface dipolar fields. A possibility is that the deep-seated magnetic field (currents in the core) is able to self-organize in large scales (during the collapse or in the early life of a neutron star). Alternatively, the dipolar field might be lower than is usually thought, with magnetosphere substantially contributing to the observed high spin-down, via e.g., strong winds or strong coronal magnetic loops, which can also provide a natural explanation to the tiny surface hotspots inferred from X-ray data.

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C. Dehman, D. Viganò, S. Ascenzi, et. al.
Thu, 11 May 23
4/55

Comments: 8 pages, 6 figures, submitted for publication in MNRAS, comments are welcome

Flavor-dependent long-range neutrino interactions in DUNE & T2HK: alone they constrain, together they discover [CL]

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http://arxiv.org/abs/2305.05184


Discovering new neutrino interactions would represent evidence of physics beyond the Standard Model. We focus on new flavor-dependent long-range neutrino interactions mediated by ultra-light mediators, with masses below $10^{-10}$ eV, introduced by new lepton-number gauge symmetries $L_e-L_\mu$, $L_e-L_\tau$, and $L_\mu-L_\tau$. Because the interaction range is ultra-long, nearby and distant matter – primarily electrons and neutrons – in the Earth, Moon, Sun, Milky Way, and the local Universe, may source a large matter potential that modifies neutrino oscillation probabilities. The upcoming Deep Underground Neutrino Experiment (DUNE) and the Tokai-to-Hyper-Kamiokande (T2HK) long-baseline neutrino experiments will provide an opportunity to search for these interactions, thanks to their high event rates and well-characterized neutrino beams. We forecast their probing power. Our results reveal novel perspectives. Alone, DUNE and T2HK may strongly constrain long-range interactions, setting new limits on their coupling strength for mediators lighter than $10^{-18}$ eV. However, if the new interactions are subdominant, then both DUNE and T2HK, together, will be needed to discover them, since their combination lifts parameter degeneracies that weaken their individual sensitivity. DUNE and T2HK, especially when combined, provide a valuable opportunity to explore physics beyond the Standard Model.

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M. Singh, M. Bustamante and S. Agarwalla
Thu, 11 May 23
8/55

Comments: 35 pages, 12 figures, 7 tables, 4 appendices. Comments are welcome

1100 Days in the Life of the Supernova 2018ibb — the Best Pair-Instability Supernova Candidate, to date [HEAP]

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http://arxiv.org/abs/2305.05796


Abridged – Stars with ZAMS masses between 140 and $260 M_\odot$ are thought to explode as pair-instability supernovae (PISNe). During their thermonuclear runaway, PISNe can produce up to several tens of solar masses of radioactive nickel, resulting in luminous transients similar to some superluminous supernovae (SLSNe). Yet, no unambiguous PISN has been discovered so far. SN2018ibb is a H-poor SLSN at $z=0.166$ that evolves extremely slowly compared to the hundreds of known SLSNe. Between mid 2018 and early 2022, we monitored its photometric and spectroscopic evolution from the UV to the NIR with 2-10m class telescopes. SN2018ibb radiated $>3\times10^{51} \rm erg$ during its evolution, and its bolometric light curve reached $>2\times10^{44} \rm erg\,s^{-1}$ at peak. The long-lasting rise of $>93$ rest-frame days implies a long diffusion time, which requires a very high total ejected mass. The PISN mechanism naturally provides both the energy source ($^{56}$Ni) and the long diffusion time. Theoretical models of PISNe make clear predictions for their photometric and spectroscopic properties. SN2018ibb complies with most tests on the light curves, nebular spectra and host galaxy, potentially all tests with the interpretation we propose. Both the light curve and the spectra require 25-44 $M_\odot$ of freshly nucleosynthesised $^{56}$Ni, pointing to the explosion of a metal-poor star with a He-core mass of 120-130 $M_\odot$ at the time of death. This interpretation is also supported by the tentative detection of [Co II]$\lambda$1.025$\mu$m, which has never been observed in any other PISN candidate or SLSN before. Powering by a central engine, such as a magnetar or a black hole, can be excluded with high confidence. This makes SN2018ibb by far the best candidate for being a PISN, to date.

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S. Schulze, C. Fransson, A. Kozyreva, et. al.
Thu, 11 May 23
9/55

Comments: Submitted to A&A, 44 pages, main text 38 pages, 37 figures, 16 Tables

Implications of pulsar timing array observations for LISA detections of massive black hole binaries [HEAP]

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http://arxiv.org/abs/2305.05955


Pulsar timing arrays (PTAs) and the Laser Interferometer Space Antenna (LISA) will open complementary observational windows on massive black-hole binaries (MBHBs), i.e., with masses in the range $\sim 10^6 – 10^{10}\,$ M${\odot}$. While PTAs may detect a stochastic gravitational-wave background from a population of MBHBs, during operation LISA will detect individual merging MBHBs. To demonstrate the profound interplay between LISA and PTAs, we estimate the number of MBHB mergers that one can expect to observe with LISA by extrapolating direct observational constraints on the MBHB merger rate inferred from PTA data. For this, we postulate that the common noise currently detected in PTAs is an astrophysical background sourced by a single MBHB population. We then constrain the LISA detection rate, $\mathcal{R}$, in the mass-redshift space by combining our Bayesian-inferred merger rate with LISA’s sensitivity to spin-aligned, inspiral-merger-ringdown waveforms. Using an astrophysically-informed formation model, we predict a 95$\%$ upper limit on the detection rate of $\mathcal{R} < 134\,{\rm yr}^{-1}$ for binaries with total masses in the range $10^7 – 10^8\,$ M${\odot}$. For higher masses, i.e., $>10^8\,$ M$_{\odot}$, we find $\mathcal{R} < 2\,(1)\,\mathrm{yr}^{-1}$ using an astrophysically-informed (agnostic) formation model, rising to $11\,(6)\,\mathrm{yr}^{-1}$ if the LISA sensitivity bandwidth extends down to $10^{-5}$ Hz. Forecasts of LISA science potential with PTA background measurements should improve as PTAs continue their search.

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N. Steinle, H. Middleton, C. Moore, et. al.
Thu, 11 May 23
10/55

Comments: N/A

Obscured AGN enhancement in galaxy pairs at cosmic noon: evidence from a probabilistic treatment of photometric redshifts [GA]

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http://arxiv.org/abs/2305.05692


Observations of the nearby universe reveal an increasing fraction of active galactic nuclei (AGN) with decreasing projected separation for close galaxy pairs, relative to control galaxies. This implies galaxy interactions play a role in enhancing AGN activity. However, the picture at higher redshift is less established, partly due to limited spectroscopic redshifts. We combine spectroscopic surveys with photometric redshift probability distribution functions for galaxies in the CANDELS and COSMOS surveys, to produce the largest ever sample of galaxy pairs used in an AGN fraction calculation for cosmic noon ($0.5<z<3$). We present a new technique for assessing galaxy pair probability (based on line-of-sight velocities +/-1000 km/s) from photometric redshift posterior convolutions and use these to produce weighted AGN fractions. Over projected separations 5-100kpc we find no evidence for enhancement, relative to isolated control galaxies, of X-ray (L_X > 10^42 erg/s) or infrared-selected AGN in major (mass ratios up to 4:1) or minor (4:1 to 10:1) galaxy pairs. However, defining the most obscured AGN as those detected in the infrared but not in X-rays, we observe a trend of increasing obscured AGN enhancement at decreasing separations. The peak enhancement, relative to isolated controls, is a factor of 2.08+/-0.61 for separations <25kpc. Our simulations with mock data, indicates this could be a lower limit of the true enhancement. If confirmed with improved infrared imaging (e.g., with JWST) and redshifts (e.g., with forthcoming multi-object spectrograph surveys), this would suggest that galaxy interactions play a role in enhancing the most obscured black hole growth at cosmic noon.

Read this paper on arXiv…

S. Dougherty, C. Harrison, D. Kocevski, et. al.
Thu, 11 May 23
17/55

Comments: Accepted for publication in MNRAS

CREX- and PREX-II-motivated relativistic interactions and their implications for the bulk properties of nuclear matter and neutron stars [CL]

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http://arxiv.org/abs/2305.05937


We investigate the implications of parity-violating electron scattering experiment on neutron skin thickness of $^{48}$Ca (CREX) and $^{208}$Pb (PREX-II) data on the bulk properties of finite nuclei, nuclear matter, and neutron stars. The neutron skin thickness from the CREX and PREX-II data is employed to constrain the parameters of relativistic mean field models which includes different non-linear, self and cross-couplings among isoscalar-scalar $\sigma$, isoscalar-vector $\omega$, isovector-scalar $\delta$ and isovector-vector $\rho$ meson fields up to the quartic order. Three parametrizations of RMF model are proposed by fitting CREX, PREX-II and both CREX as well as PREX-II data to assess their implications. A covariance analysis is performed to assess the theoretical uncertainties of model parameters and nuclear matter observables along with correlations among them. The RMF model parametrization obtained with the CREX data acquires much smaller value of symmetry energy (J= 28.97$\pm$ 0.99 MeV), its slope parameter (L= 30.61$\pm 6.74$ MeV) in comparison to those obtained with PREX-II data. The neutron star properties are studied by employing the equations of state (EoSs) composed of nucleons and leptons in $\beta$ equilibrium.

Read this paper on arXiv…

M. Kumar, S. Kumar, V. Thakur, et. al.
Thu, 11 May 23
19/55

Comments: 15 pages,15 figures. arXiv admin note: text overlap with arXiv:2210.02793

Unpacking merger jets: a Bayesian analysis of GW170817, GW190425 and electromagnetic observations of short gamma-ray bursts [HEAP]

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http://arxiv.org/abs/2305.06275


We present a novel fully Bayesian analysis to constrain short gamma-ray burst jet structures associated with cocoon, wide-angle and simple top-hat jet models, as well as the binary neutron star merger rate. These constraints are made given the distance and inclination information from GW170817, observed flux of GRB170817A, observed rate of short gamma-ray bursts detected by Swift, and the neutron star merger rate inferred from LIGO’s first and second observing runs. A separate analysis is conducted where a fitted short gamma-ray burst luminosity function is included to provide further constraints. The jet structure models are further constrained using the observation of GW190425 and we find that the assumption that it produced a GRB170817-like short gamma-ray burst that went undetected due to the jet geometry is consistent with previous observations. We find and quantify evidence for low luminosity and wide-angled jet structuring in the short gamma-ray burst population, independently from afterglow observations, with log Bayes factors of $0.45{-}0.55$ for such models when compared to a classical top-hat jet. Slight evidence is found for a Gaussian jet structure model over all others when the fitted luminosity function is provided, producing log Bayes factors of $0.25{-}0.9\pm0.05$ when compared to the other models. However without considering GW190425 or the fitted luminosity function, the evidence favours a cocoon-like model with log Bayes factors of $0.14\pm0.05$ over the Gaussian jet structure. We provide new constraints to the binary neutron star merger rates of $1{-}1300$Gpc$^{-3}$yr$^{-1}$ or $2{-}680$Gpc$^{-3}$yr$^{-1}$ when a fitted luminosity function is assumed.

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F. Hayes, I. Heng, G. Lamb, et. al.
Thu, 11 May 23
20/55

Comments: 18 pages, 8 figures

Exploring the spectrum of stochastic gravitational-wave anisotropies with pulsar timing arrays [CEA]

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http://arxiv.org/abs/2305.05690


Anisotropies in the nanohertz gravitational-wave background are a compelling next target for pulsar timing arrays (PTAs). Measurements or informative upper limits to the anisotropies are expected in the near future and can offer important clues about the origin of the background and the properties of the sources. Given that each source is expected (in the simplest scenario of circular inspirals) to emit at a fixed frequency, the anisotropy will most generally vary from one frequency to another. The main result presented in this work is an analytical model for the anisotropies produced by a population of inspiralling supermassive black-hole binaries (SMBHBs). This model can be immediately connected with parametrizations of the SMBHB mass function and can be easily expanded to account for new physical processes taking place within the PTA frequency band. We show that a variety of SMBHB models predict significant levels of anistropy at the highest frequencies accessible to PTA observations and that measurements of anisotropies can offer new information regarding this population beyond the isotropic component. We also model the impact of additional dynamical effects driving the binary towards merger and show that, if these processes are relevant within the PTA band, the detectability of anisotropies relative to the isotropic background will be enhanced. Finally, we use the formalism presented in this work to predict the level anisotropy of the circular and linear polarizations of the SGWB due to the distribution of binary orientation angles with respect to the line of sight.

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G. Sato-Polito and M. Kamionkowski
Thu, 11 May 23
25/55

Comments: 10 pages, 4 figures

Jet-powered turbulence in common envelope evolution [HEAP]

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http://arxiv.org/abs/2305.06266


We conduct a three-dimensional hydrodynamical simulation of a common envelope evolution (CEE) where a neutron star (NS) spirals-in inside the envelope of a red supergiant (RSG) star in a predetermined orbit. We find that the jets shed pairs of vortices in an expanding spiral pattern, inflate two expanding spirally-shaped low-density bubbles, one above and one below the equatorial plane, and deposit angular momentum to the envelope. In the simulation we do not include the gravity of the NS such that all effects we find are solely due to the jets that the spiralling-in NS launches. The angular momentum that the jets deposit to the envelope is of the same order of magnitude as the orbital angular momentum and has the same direction. The turbulence that the jets induce in the common envelope might play a role in transporting energy and angular momentum. The jet-deposited energy that is radiated away (a process not studied here) leads to a transient event that is termed common envelope jets supernova (CEJSN) and might mimic an energetic core collapse supernova. The turbulence and the spiral pattern that we explore here might lead to bumps in the late light curve of the CEJSN when different segments of the ejected envelope collide with each other. This study emphasises the roles that jets can play in CEE (including jets launched by black hole companions) and adds to the rich variety of processes in CEJSN events.

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S. Hillel, R. Schreier and N. Soker
Thu, 11 May 23
26/55

Comments: Will be submitted in two days to allow for comments

Extreme-mass-ratio inspirals into rotating boson stars: nonintegrability, chaos, and transient resonances [CL]

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http://arxiv.org/abs/2305.05691


General relativity predicts that black holes are described by the Kerr metric, which has integrable geodesics. This property is crucial to produce accurate waveforms from extreme-mass-ratio inspirals. Astrophysical environments, modifications of gravity and new fundamental fields may lead to nonintegrable geodesics, inducing chaotic effects. We study geodesics around self-interacting rotating boson stars and find robust evidence of nonintegrability and chaos. We identify islands of stability around resonant orbits, where the orbital radial and polar oscillation frequency ratios, known as rotation numbers, remain constant throughout the island. These islands are generically present both in the exterior and the interior of compact boson stars. A monotonicity change of rotation curves takes place as orbits travel from the exterior to the interior of the star. Therefore, configurations with neutron-star-like compactness can support degenerate resonant islands. This anomaly is reported here for the first time and it is not present in black holes. Such configurations can also support extremely prolonged resonant islands that span from the exterior to the interior of the star and are shielded by thick chaotic layers. We adiabatically evolve inspirals using approximated post-Newtonian fluxes and find time-dependent plateaus in the rotation curves which are associated with island-crossing orbits. Crossings of external islands give rise to typical gravitational-wave glitches found in non-Kerr objects. Furthermore, when an inspiral is traversing an internal island that is surrounded by a thick chaotic layer, a new type of simultaneous multifrequency glitch occurs that may be detectable with space interferometers such as LISA, and can serve as evidence of an extreme-mass-ratio inspiral around a supermassive boson star.

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K. Destounis, F. Angeloni, M. Vaglio, et. al.
Thu, 11 May 23
28/55

Comments: 22 pages, 17 figures, higher resolution plots available upon request

Multi-Messenger Diagnostics of the Engine behind Core-Collapse Supernovae [HEAP]

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http://arxiv.org/abs/2305.06134


Core-collapse supernova explosions play a wide role in astrophysics by producing compact remnants (neutron stars, black holes) and the synthesis and injection of many heavy elements into their host Galaxy. Because they are produced in some of the most extreme conditions in the universe, they can also probe physics in extreme conditions (matter at nuclear densities and extreme temperatures and magnetic fields). To quantify the impact of supernovae on both fundamental physics and our understanding of the Universe, we must leverage a broad set of observables of this engine. In this paper, we study a subset of these probes using a suite of 1-dimensional, parameterized mixing models: ejecta remnants from supernovae, ultraviolet, optical and infra-red lightcurves, and transient gamma-ray emission. We review the other diagnostics and show how the different probes tie together to provide a more clear picture of the supernova engine.

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C. Fryer, E. Burns, A. Hungerford, et. al.
Thu, 11 May 23
34/55

Comments: 21 pages, 11 figures

The spin measurement of MAXI J0637-430: a black hole candidate with high disk density [HEAP]

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http://arxiv.org/abs/2305.05914


The Galactic black hole candidate MAXI J0637-430 was first discovered by $\textit{MAXI/GSC}$ on 2019 November 02. We study the spectral properties of MAXI J0637-430 by using the archived $\textit{NuSTAR}$ data and $\textit{Swift}$/XRT data. After fitting the eight spectra by using a disk component and a powerlaw component model with absorption, we select the spectra with relatively strong reflection components for detailed X-ray reflection spectroscopy. Using the most state-of-art reflection model $\tt{relxillCp}$, the spectral fitting measures a black hole spin $\textit{a}{\rm{*}} > 0.72$ and the inclination angle of the accretion disk $i$ = $46.1{-5.3}^{+4.0}$ degrees, at 90 per cent confidence level. In addition, the fitting results show an extreme supersolar iron abundance. Combined with the fitting results of the reflection model $\tt{reflionx_hd}$, we consider that this unphysical iron abundance may be caused by a very high density accretion disk ( $n_{\rm{e}} > 2.34 \times 10^{21}$ $\rm{cm}^{-3}$ ) or a strong Fe K$\alpha$ emission line. The soft excess is found in the soft state spectral fitting results, which may be an extra free-free heating effect caused by high density of the accretion disk. Finally, we discuss the robustness of black hole spin obtained by X-ray reflection spectroscopy. The result of relatively high spin is self-consistent with broadened Fe K$\alpha$ line. Iron abundance and disk density have no effect on the spin results.

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N. Jia, Y. Feng, Y. Song, et. al.
Thu, 11 May 23
35/55

Comments: submitted to Research in Astronomy and Astrophysics

MeerKAT caught a Mini Mouse: serendipitous detection of a young radio pulsar escaping its birth sit [HEAP]

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http://arxiv.org/abs/2305.06130


In MeerKAT observations pointed at a Galactic X-ray binary located on the Galactic plane we serendipitously discovered a radio nebula with cometary-like morphology. The feature, which we named the Mini Mouse' based on its similarity with the previously discoveredMouse’ nebula, points back towards the previously unidentified candidate supernova remnant G45.24$+$0.18. We observed the location of the Mini Mouse with MeerKAT in two different observations, and we localised with arcsecond precision the 138 ms radio pulsar PSR J1914+1054g, recently discovered by the FAST telescope, to a position consistent with the head of the nebula. We confirm a dispersion measure of about 418 pc cm$^{-3}$ corresponding to a distance between 7.8 and 8.8 kpc based on models of the electron distribution. Using our accurate localisation and 2 period measurements spaced 90 days apart we calculate a period derivative of (2.7 $\pm$ 0.3) $\times$ 10 $^{-14}$ s s$^{-1}$. We derive a characteristic age of approximately 82 kyr and a spin down luminosity of 4$\times$10$^{35}$ erg s$^{-1}$, respectively. For a pulsar age comparable with the characteristic age, we find that the projected velocity of the neutron star is between 320 and 360 km/s if it was born at the location of the supernova remnant. The size of the proposed remnant appears small if compared with the pulsar characteristic age, however the relatively high density of the environment near the Galactic plane could explain a suppressed expansion rate and thus a smaller remnant.

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S. Motta, J. Turner, B. Stappers, et. al.
Thu, 11 May 23
44/55

Comments: 8 pages, 4 figures, accepted for publication on MNRAS

Dynamical He Flashes in Double White Dwarf Binaries [SSA]

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http://arxiv.org/abs/2305.05695


The detonation of an overlying helium layer on a $0.8-1.1\,\mathrm{M}{\odot}$ carbon-oxygen (CO) white dwarf (WD) can detonate the CO WD and create a thermonuclear supernova (SN). Many authors have recently shown that when the mass of the He layer is low ($\lesssim 0.03\,\mathrm{M}{\odot}$), the ashes from its detonation minimally impact the spectra and light-curve from the CO detonation, allowing the explosion to appear remarkably similar to Type Ia SNe. These new insights motivate our investigation of dynamical He shell burning, and our search for a binary scenario that stably accumulates thermally unstable He shells in the $0.01-0.08\,\mathrm{M}{\odot}$ range, thick enough to detonate, but also often thin enough for minimal impact on the observables. We first show that our improved non-adiabatic evolution of convective He shell burning in this shell mass range leads to conditions ripe for a He detonation. We also find that a stable mass-transfer scenario with a high entropy He WD donor of mass $0.15-0.25\,\mathrm{M}\odot$ yields the He shell masses needed to achieve the double detonations. This scenario also predicts that the surviving He donor leaves with a space velocity consistent with the unusual runaway object, D6-2. We find that hot He WD donors originate in common envelope events when a $1.3-2.0\,\mathrm{M}_\odot$ star fills its Roche lobe at the base of the red giant branch at orbital periods of $1-10$ days with the CO WD.

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T. Wong and L. Bildsten
Thu, 11 May 23
45/55

Comments: 12 pages, 6 figures; Accepted to ApJ

Detectability of a phase transition in neutron star matter with third-generation gravitational wave interferometers [HEAP]

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http://arxiv.org/abs/2305.05999


Possible strong first-order hadron-quark phase transitions in neutron star interiors leave an imprint on gravitational waves, which could be detected with planned third-generation interferometers. Given a signal from the late inspiral of a binary neutron star (BNS) coalescence, %the possibility of assessing the presence of such a phase transition depends on the precision that can be attained in the determination of the tidal deformability parameter, as well as on the model used to describe the hybrid star equation of state. For the latter, we employ here a phenomenological meta-modelling of the equation of state that largely spans the parameter space associated with both the low density phase and the quark high density compatible with current constraints. We show that with a network of third-generation detectors, a single loud BNS event might be sufficient to infer the presence of a phase transition at low baryon densities with an average Bayes factor $B\approx 100$, up to a luminosity distance ($\mathcal{D}_L \lesssim$ 300 Mpc).

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C. Mondal, M. Antonelli, F. Gulminelli, et. al.
Thu, 11 May 23
52/55

Comments: N/A

QLUSTER: quick clusters of merging binary black holes [HEAP]

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http://arxiv.org/abs/2305.04987


This short document illustrates QLUSTER: a toy model for populations of binary black holes in dense astrophysical environments. QLUSTER is a simple tool to investigate the occurrence and properties of hierarchical black-hole mergers detectable by gravitational-wave interferometers. QLUSTER is not meant to rival the complexity of state-of-the-art population synthesis and N-body codes but rather provide a fast, approximate, and easy-to-interpret framework to investigate some of the key ingredients of the problem. These include the binary pairing probability, the escape speed of the host environment, and the merger generation. We also introduce the “hierarchical-merger efficiency” — an estimator that quantifies the relevance of hierarchical black-hole mergers in a given astrophysical environment.

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D. Gerosa and M. Mould
Wed, 10 May 23
2/65

Comments: Contribution to the 2023 Gravitation session of the 57th Rencontres de Moriond

Shocks Power Tidal Disruption Events [HEAP]

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http://arxiv.org/abs/2305.05333


Accretion of debris seems to be the natural mechanism to power the radiation emitted during a tidal disruption event (TDE), in which a supermassive black hole tears apart a star. However, this requires the prompt formation of a compact accretion disk. Here, using a fully relativistic global simulation for the long-term evolution of debris in a TDE with realistic initial conditions, we show that at most a tiny fraction of the bound mass enters such a disk on the timescale of observed flares. To “circularize” most of the bound mass entails an increase in the binding energy of that mass by a factor $\sim 30$; we find at most an order unity change. Our simulation suggests it would take a time scale comparable to a few tens of the characteristic mass fallback time to dissipate enough energy for “circularization”. Instead, the bound debris forms an extended eccentric accretion flow with eccentricity $\simeq 0.4-0.5$ by $\sim 2$ fallback times. Although the energy dissipated in shocks in this large-scale flow is much smaller than the “circularization” energy, it matches the observed radiated energy very well. Nonetheless, the impact of shocks is not strong enough to unbind initially bound debris into an outflow.

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T. Ryu, J. Krolik, T. Piran, et. al.
Wed, 10 May 23
5/65

Comments: 20 pages, 16 figures, Submitted to ApJ, comments welcome!

AREPO White Dwarf merger simulations resulting in edge-lit detonation and run-away hypervelocity companion [SSA]

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http://arxiv.org/abs/2305.05192


We present a series of high-resolution simulations generated with the moving-mesh code AREPO to model the merger of a $1.1 \, \mathrm{M_\odot}$ carbon-oxygen primary white dwarf with an outer helium layer and a $0.35\,\mathrm{M_\odot}$ secondary helium white dwarf. Our simulations lead to detonations that are consistent with the edge-lit scenario, where a helium detonation is ignited at the base of the helium layer of the primary WD, which triggers an off-centre carbon detonation. This produces an asymmetric ejecta pattern and differences in line-of-sight observables (e.g. mean atomic weight). The ejecta that are flung into space are dominated by $^{56}\mathrm{Ni}$, $^{4}\mathrm{He}$, $^{28}\mathrm{Si}$, and $^{32}\mathrm{S}$. Our simulations result in a surviving degenerate companion of mass $0.22-0.25$ $\mathrm{M_\odot}$ moving at $>1\,700$ $\mathrm{km}\,\mathrm{s}^{-1}$, consistent with the observational findings of hypervelocity WDs. The secondary’s surface layers are enriched by heavy metals, with $^{56}\mathrm{Ni}$ making up approximately $0.8 \%$ of the remaining mass. We also analyse the sensitivity of the outcome on simulation parameters, including the “inspiral time”, which defines a period of accelerated angular momentum loss. We find that the choice of “inspiral time” qualitatively influences the simulation result, including the survival of the secondary. We argue that the shorter inspiral cases result in qualitatively and quantitatively similar outcomes. We also investigate the sensitivity of our results on the primary’s chemical profile by comparing simulations using isothermal, constant composition models with the same mass and central composition and characterised by either a bare carbon-oxygen core (no helium) or a carbon-oxygen core enveloped by a thick helium layer.

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U. Burmester, L. Ferrario, R. Pakmor, et. al.
Wed, 10 May 23
6/65

Comments: The submission has been accepted for publication in the Monthly Notices of the Royal Astronomical Society (MNRAS). 20 pages, 12 figures

Calculating the Gravitational Waves Emitted from High-speed Sources [CL]

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http://arxiv.org/abs/2305.04969


The possibility of forming gravitational-wave sources with high center-of-mass (c.m.) velocities in the vicinity of supermassive black holes requires us to develop a method of deriving the waveform in the observer’s frame. Here we show that in the limit where the c.m. velocity is high but the relative velocities of the components of the source are small, we can solve the problem by directly integrating the relaxed Einstein field equation. In particular, we expand the result into multipole components which can be conveniently calculated given the orbit of the source in the observer’s frame. Our numerical calculations using arbitrary c.m. velocities show that the result is consistent with the Lorentz transformation of GWs to the leading order of the radiation field. Moreover, we show an example of using this method to calculate the waveform of a scattering event between the high-speed ($\sim 0.1c$) stellar objects embedded in the accretion disk of an active galactic nucleus. Our multipole-expansion method not only has advantages in analyzing the results from stellar-dynamical models but also provides new insight into the multipole properties of the GWs emitted from a high-speed source.

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H. Yan, X. Chen and A. Torres-Orjuela
Wed, 10 May 23
7/65

Comments: 9 pages, 2 figures. Accepted by PRD

Investigating the impact of vertically extended coronae on X-ray reverberation mapping [HEAP]

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http://arxiv.org/abs/2305.05039


Accreting black holes commonly exhibit hard X-ray emission, originating from a region of hot plasma near the central engine referred to as the corona. The origin and geometry of the corona are poorly understood, and models invoking either inflowing or outflowing material (or both) can successfully explain only parts of the observed phenomenology. In particular, recent works indicate that the time-averaged and variability property might originate in different regions of the corona. In this paper we present a model designed to move beyond the lamp post paradigm, with the goal of accounting for the vertical extent of the corona. In particular, we highlight the impact of including self consistently a second lamp post, mimicking for example an extended jet base. We fully include the effect that the second source has on the time-dependent disk ionization, reflection spectrum, and reverberation lags. We also present an application of this new model to NICER observations of the X-ray binary MAXI J1820+070 near its hard-to-soft state transition. We demonstrate that in these observations, a vertically extended corona can capture both spectral and timing properties, while a single lamp post model can not. In this scenario, the illumination responsible for the time-averaged spectrum originates close to the black hole, while the variability is likely associated with the ballistic jet.

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M. Lucchini, G. Mastroserio, J. Wang, et. al.
Wed, 10 May 23
9/65

Comments: 17 pages, 12 figures, accepted for publication on ApJ

A renewed search for radio emission from the variable $γ$-ray pulsar PSR J2021$+$4026 [HEAP]

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http://arxiv.org/abs/2305.05261


We undertake the first targeted search at 1.5 GHz for radio emission from the variable $\gamma$-ray pulsar PSR J2021$+$4026. This radio-quiet pulsar assumes one of two stable $\gamma$-ray emission states, between which it transitions on a timescale of years. These transitions, in both $\gamma$-ray flux and pulse profile shape, are accompanied by contemporaneous changes to the pulsar’s spin-down rate. A number of radio pulsars are known to exhibit similar correlated variability, which in some cases involves an emission state in which the radio emission ceases to be detectable. In this paper, we perform a search for radio emission from PSR J2021$+$4026, using archival radio observations recorded when the pulsar was in each of its emission/spin-down states. Using improved techniques, we search for periodic radio emission as well as single pulse phenomena such as giant radio pulses and RRAT-like emission. Our search reveals no evidence of radio emission from PSR J2021$+$4026. We estimate that the flux density for periodic emission from PSR J2021$+$4026 does not exceed 0.2 mJy at this frequency. We also estimate single-pulse flux limits for RRAT-like bursts and giant radio pulses to be 0.3 and 100 Jy respectively. We discuss the transitioning behaviour of PSR J2021$+$4026 in the context of pulsar glitches, intermittent pulsars and the increasingly common emission-rotation correlation observed in radio pulsars.

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B. Shaw, B. Stappers, P. Weltevrede, et. al.
Wed, 10 May 23
15/65

Comments: 10 pages, 5 figures, 3 tables

Search for astrophysical electron antineutrinos in Super-Kamiokande with 0.01wt% gadolinium loaded water [HEAP]

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http://arxiv.org/abs/2305.05135


We report the first search result for the flux of astrophysical electron antineutrinos for energies O(10) MeV in the gadolinium-loaded Super-Kamiokande (SK) detector. In June 2020, gadolinium was introduced to the ultra-pure water of the SK detector in order to detect neutrons more efficiently. In this new experimental phase, SK-Gd, we can search for electron antineutrinos via inverse beta decay with efficient background rejection and higher signal efficiency thanks to the high efficiency of the neutron tagging technique. In this paper, we report the result for the initial stage of SK-Gd with a $22.5\times552$ $\rm kton\cdot day$ exposure at 0.01% Gd mass concentration. No significant excess over the expected background in the observed events is found for the neutrino energies below 31.3 MeV. Thus, the flux upper limits are placed at the 90% confidence level. The limits and sensitivities are already comparable with the previous SK result with pure-water ($22.5 \times 2970 \rm kton\cdot day$) owing to the enhanced neutron tagging.

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M. Harada, K. Abe, C. Bronner, et. al.
Wed, 10 May 23
22/65

Comments: N/A

Measurement of ultra-high-energy diffuse gamma-ray emission of the Galactic plane from 10 TeV to 1 PeV with LHAASO-KM2A [HEAP]

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http://arxiv.org/abs/2305.05372


The diffuse Galactic $\gamma$-ray emission, mainly produced via interactions between cosmic rays and the diffuse interstellar medium, is a very important probe of the distribution, propagation, and interaction of cosmic rays in the Milky Way. In this work we report the measurements of diffuse $\gamma$-rays from the Galactic plane between 10 TeV and 1 PeV energies, with the square kilometer array of the Large High Altitude Air Shower Observatory (LHAASO). Diffuse emissions from the inner ($15^{\circ}<l<125^{\circ}$, $|b|<5^{\circ}$) and outer ($125^{\circ}<l<235^{\circ}$, $|b|<5^{\circ}$) Galactic plane are detected with $29.1\sigma$ and $12.7\sigma$ significance, respectively. The outer Galactic plane diffuse emission is detected for the first time in the very- to ultra-high-energy domain ($E>10$~TeV). The energy spectrum in the inner Galaxy regions can be described by a power-law function with an index of $-2.99\pm0.04$, which is different from the curved spectrum as expected from hadronic interactions between locally measured cosmic rays and the line-of-sight integrated gas content. Furthermore, the measured flux is higher by a factor of $\sim3$ than the prediction. A similar spectrum with an index of $-2.99\pm0.07$ is found in the outer Galaxy region, and the absolute flux for $10\lesssim E\lesssim60$ TeV is again higher than the prediction for hadronic cosmic ray interactions. The latitude distributions of the diffuse emission are consistent with the gas distribution, while the longitude distributions show slight deviation from the gas distribution. The LHAASO measurements imply that either additional emission sources exist or cosmic ray intensities have spatial variations.

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Z. Cao, F. Aharonian, Q. An, et. al.
Wed, 10 May 23
25/65

Comments: 11 pages, 7 figures, 5 tables

Binary neutron star populations in the Milky Way [HEAP]

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http://arxiv.org/abs/2305.04955


Galactic binary neutron stars (BNSs) are a unique laboratory to probe the evolution of BNSs and their progenitors. Here, we use a new version of the population synthesis code SEVN to evolve the population of Galactic BNSs, by modeling the spin up and down of pulsars self-consistently. We analyze the merger rate $\mathcal{R}{\rm MW}$, orbital period $P{\rm orb}$, eccentricity $e$, spin period $P$, and spin period derivative $\dot{P}$ of the BNS population. Values of the common envelope parameter $\alpha=1 – 3$ and an accurate model of the Milky Way star formation history best reproduce the BNS merger rate in our Galaxy ($\mathcal{R}{\rm MW}\approx{}30$ Myr$^{-1}$). We apply radio-selection effects to our simulated BNSs and compare them to the observed population. Using a Dirichlet process Gaussian mixture method, we evaluate the four-dimensional likelihood in the $(P{\rm orb}, e, P, \dot{P})$ space, by comparing our radio-selected simulated pulsars against Galactic BNSs. Our analysis favours an uniform initial distribution for both the magnetic field ($10^{10-13}$ G) and the spin period ($10-100$ ms). The implementation of radio selection effects is critical to match not only the spin period and period derivative, but also the orbital period and eccentricity of Galactic BNSs. According to our fiducial model, the Square Kilometre Array will detect $\sim 20$ new BNSs in the Milky Way.

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C. Sgalletta, G. Iorio, M. Mapelli, et. al.
Wed, 10 May 23
33/65

Comments: 20 pages, 8 figures, 8 tables, comments welcome

R-modes as a New Probe of Dark Matter in Neutron Stars [HEAP]

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http://arxiv.org/abs/2305.05664


In this work, we perform the first systematic investigation of effects of the presence of dark matter on r-mode oscillations in neutron stars (NSs). Using a self-interacting dark matter (DM) model based on the neutron decay anomaly and a hadronic model obtained from the posterior distribution of a recent Bayesian analysis, we impose constraints on the DM self-interaction strength using recent multimessenger astrophysical observations. The constrained DM interaction strength is then used to estimate DM self-interaction cross section and shear viscosity resulting from DM, which is found to be several orders of magnitude smaller than shear viscosity due to hadronic matter. Assuming that the DM fermion is in chemical equilibrium with the neutrons in the neutron star, we estimate the bulk viscosity resulting from the dark decay of neutrons, and find it to be much smaller than the hadronic bulk viscosity. We also conclude that the instability window with minimal hadronic damping mechanisms can become smaller when including DM shear and bulk viscosity but remains incompatible with the X-ray and pulsar observational data for the chosen DM model.

Read this paper on arXiv…

S. Shirke, S. Ghosh, D. Chatterjee, et. al.
Wed, 10 May 23
34/65

Comments: 29 pages, 12 figures, 1 table. To be submitted to JCAP. Comments are welcome

Multi-messenger observations of double neutron stars in Galactic disk with gravitational and radio waves [HEAP]

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http://arxiv.org/abs/2305.05202


We evaluate the prospects for radio follow-up of the double neutron stars (DNSs) in the Galactic disk that could be detected through future space-borne gravitational wave (GW) detectors. We first simulate the DNS population in the Galactic disk that is accessible to space-borne GW detectors according to the merger rate from recent LIGO results. Using the inspiraling waveform for the eccentric binary, the average number of the DNSs detectable by TianQin (TQ), LISA, and TQ+LISA are 217, 368, and 429, respectively. For the joint GW detection of TQ+LISA, the forecasted parameter estimation accuracies, based on the Fisher information matrix, for the detectable sources can reach the levels of $\Delta P_{\mathrm b}/P_{\mathrm b} \lesssim 10^{-6}$, $\Delta \Omega \lesssim 100~{\mathrm {deg}}^2$, $\Delta e/e \lesssim 0.3$, and $\Delta \dot{P}{\mathrm b} / \dot{P}{\mathrm b} \lesssim 0.02$. These estimation accuracies are fitted in the form of power-law function of signal-to-noise ratio. Next, we simulate the radio pulse emission from the possible pulsars in these DNSs according to pulsar beam geometry and the empirical distributions of spin period and luminosity. For the DNSs detectable by TQ+LISA, the average number of DNSs detectable by the follow-up pulsar searches using the Parkes, FAST, SKA1, and SKA are 8, 10, 43, and 87, respectively. Depending on the radio telescope, the average distances of these GW-detectable pulsar binaries vary from 1 to 7 kpc. Considering the dominant radiometer noise and phase jitter noise, the timing accuracy of these GW-detectable pulsars can be as low as 70 ${\rm ns}$ while the most probable value is about 100 $\mu {\rm s}$.

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W. Feng, J. Chen, Y. Wang, et. al.
Wed, 10 May 23
41/65

Comments: 15 pages, 9 figures, 3 tables. To be published in PRD

Constraining $p$-wave Dark Matter Annihilation with Gamma-ray Observations of M87 [CL]

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http://arxiv.org/abs/2305.05155


We consider constraints on $p$-wave dark matter in a dark matter spike surrounding the supermassive black hole at the center of M87. Owing to the large mass of the black hole, and resulting large velocity dispersion for the dark matter particles in the spike, it is possible for Fermi-LAT and MAGIC data to place tight constraints on $p$-wave annihilation, which would be far more stringent than those placed by observations of dwarf spheroidal galaxies. Indeed, for optimistic choices of the spike parameters, gamma-ray data would exclude thermal $p$-wave dark matter models with a particle mass $\lesssim {10}~\rm TeV$. But there is significant uncertainty in the properties and parameters of the spike, and for less optimistic scenarios, thermal dark matter candidates would be completely unconstrained. In addition to better understanding the spike parameters, a second key to improving constraints on dark matter annihilation is an accurate astrophysical background model.

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K. Christy, J. Kumar and P. Sandick
Wed, 10 May 23
47/65

Comments: 10 pages, 4 figures

A Low-Mass Helium Star Progenitor Model for the Type Ibn SN 2020nxt [HEAP]

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http://arxiv.org/abs/2305.05015


A growing number of supernovae (SNe) are now known to exhibit evidence for significant interaction with a dense, pre-existing, circumstellar medium (CSM). SNe Ibn comprise one such class that can be characterised by both rapidly evolving light curves and persistent narrow He I lines. The origin of such a dense CSM in these systems remains a pressing question, specifically concerning the progenitor system and mass-loss mechanism. In this paper, we present multi-wavelength data of the Type Ibn SN 2020nxt, including $HST$/STIS ultraviolet spectra. We fit the data with recently updated CMFGEN models designed to handle configurations for SNe Ibn. The UV coverage yields strong constraints on the energetics and, when combined with the CMFGEN models, offer new insight on potential progenitor systems. We find the most successful model is a $\lesssim4 {\rm M}\odot$ helium star that lost its $\sim 1\,{\rm M}\odot$ He-rich envelope in the years preceding core collapse. We also consider viable alternatives, such as a He white dwarf merger. Ultimately, we conclude at least some SNe Ibn do not arise from single, massive ($>30 {\rm M}_\odot$) Wolf-Rayet-like stars.

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Q. Wang, A. Goel, L. Dessart, et. al.
Wed, 10 May 23
53/65

Comments: 17 pages, 13 figures, 1 table, submitted to MNRAS

Discovery of Radial Spectral Hardening in the Hot Bubble of Planetary Nebula BD+30 3639 with Median Energy Imaging [SSA]

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http://arxiv.org/abs/2305.04948


We introduce a new imaging analysis technique to study the spatial distribution of the X-ray emission from the hot bubble of planetary nebula BD+30 3639. Hot bubble emission is typically photon-starved, thus limiting the methods for spatial-spectral analysis, however, this new technique uses the statistics of photon energies across the nebula to identify spatial variations. Using the median energy value of the X-ray photons, we identified a rise in median energy values towards the projected edge of the nebula, which we refer to as radial spectral hardening. We explored the origin of this radial spectral hardening with X-ray spectral analysis of distinct regions of high- and low-median energy values. Given that the hot bubble is embedded within a young, dense, planetary nebula, we argue that the radial spectral hardening is due to an increased column density at the projected nebular edge. Median energy imaging provides a promising new methodology for exploring the spatial variations in faint extended X-ray sources.

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R. Jr
Wed, 10 May 23
55/65

Comments: 10 pages, 6 figures, and one potentially embarrassing last minute revision. Submitted to ApJ

Pulsar Observations at low latitudes and low frequencies [IMA]

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http://arxiv.org/abs/2305.05458


The Pulsar Monitoring in Argentina (PuMA) is a collaboration between the Argentine Institute for Radioastronomy (IAR) and the Rochester Institute of Technology (RIT) that since 2017 has been observing southern sky pulsars with high cadence using the two restored IAR antennas in the L-Band (1400MHz). We briefly review the first set of results of this program to study transient phenomena, such as magnetars and glitching pulsars, as well as to perform precise timing of millisecond pulsars. Access to lower frequency bands, where most of the pulsars are brighter, would allow us to reach additional pulsars, currently buried into the background noise. We identify two dozen additional glitching pulsars that could be observable in the 400MHz band by the IAR’s projected Multipurpose Interferometer Array (MIA). We also discuss the relevance and challenges of single-pulse pulsar timing at low frequencies and the search for Fast Radio Burst (FRB) in the collected data since 2017 using machine learning techniques.

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C. Lousto, R. Missel, E. Zubieta, et. al.
Wed, 10 May 23
58/65

Comments: 11 pages, 10 figures, 5 tables. arXiv admin note: text overlap with arXiv:2108.13462

GRB 221009A: Spectral signatures based on ALPs candidates [HEAP]

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http://arxiv.org/abs/2305.05145


GRB 221009A has posed a significant challenge to our current understanding of the mechanisms that produce TeV photons in gamma-ray bursts (GRB). On one hand, the Klein-Nishina (KN) effect of the inverse Compton scattering leads to less efficient energy losses of high-energy electrons. In the other hand, at a redshift of 0.151, the TeV spectrum of GRB 221009A undergoes significant absorption by the Extragalactic Background Light (EBL). Therefore, the observation of 18-TeV and 250-TeV photons in this event implies the presence of enormous photon fluxes at the source, which cannot be easily generated by the Synchrotron Self-Compton mechanism in external shocks. As an alternative, some authors have suggested the possibility of converting the TeV-photons into Axion-like particles (ALPs) at the host galaxy, in order to avoid the effects of EBL absorption, and then reconverting them into photons within the Milky Way. While this solution relaxes the requirement of very-high photon fluxes, the KN effect still poses a challenge. Previously, we have showed that the injections of ALPs could explain the observation of 18-TeV photons. Here, we include the energy dependence of the survival probability to determine the spectral conditions that would be required for the injection of such ALPs, limit the ALP’s candidate region, and discuss the implications in the maximum particle rate for different light-curve assumptions.

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D. Rojas, S. Hernández-Cadena, M. González, et. al.
Wed, 10 May 23
65/65

Comments: N/A

Exploring departures from Schwarzschild black hole geometry in $f(R)$ gravity [CL]

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http://arxiv.org/abs/2305.04695


Different astrophysical methods can be combined to detect possible deviations from General Relativity. In this work, we consider a class of $f(R)$ gravity models selected by the existence of Noether symmetries. In this framework, it is possible to determine a set of static and spherically symmetric black hole solutions, encompassing small departures from the Schwarzschild geometry. In particular, when gravity is the only dominating interaction, we exploit the ray-tracing technique to reconstruct the image of a black hole, the epicyclic frequencies, and the black hole shadow profile. Moreover, when matter dynamics is also affected by an electromagnetic radiation force, we take into account the general relativistic Poynting-Robertson effect. In light of the obtained results, the proposed strategy results to be robust and efficient: on the one hand, it allows to investigate gravity from strong to weak field regimes; on the other hand, it is capable of detecting small departures from General Relativity, depending on the current observational sensitivity.

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V. Falco, F. Bajardi, R. D’Agostino, et. al.
Tue, 9 May 23
1/88

Comments: 19 pages; 7 figures; 2 tables; accepted for publication on EPJ C

Memory matters : Gravitational wave memory of compact binary coalescence in the presence of matter effects [CL]

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http://arxiv.org/abs/2305.04761


Binary neutron stars (BNS) and neutron star-black hole (NSBH) binaries are one of the most promising gravitational wave (GW) sources to probe matter effects. Upcoming observing runs of LIGO-Virgo-KAGRA detectors and future third generation detectors like Einstein Telescope and Cosmic Explorer will allow the extraction of detailed information on these matter effects from the GW signature of BNS and NSBH systems. One subtle effect which may be helpful to extract more information from the detection of compact binary systems is the non-linear memory. In this work, we investigate the observational consequences of gravitational wave non-linear memory in the presence of matter effects.
We start by quantifying the impact of non-linear memory on distinguishing BNS mergers from binary black holes (BBH) or NSBH mergers. We find that for the third generation detectors, the addition of non-linear memory to the GW signal model expands the parameter space where BNS signals become distinguishable from the BBH and NSBH signals. Using numerical relativity simulations, we also study the non-linear memory generated from the post-merger phase of BNS systems. We find that it does not show a strong dependence on the equation of state of the NS. However, the non-linear memory from the BNS post-merger phase is much lower than the one from BBH systems of the same masses. Furthermore, we compute the detection prospects of non-linear memory from the post-merger phase of NS systems by accumulating signal strength from a population of BNS mergers for the current and future detectors. Finally, we discuss the impact of possible linear memory from the dynamical ejecta of BNS and NSBH systems and its signal strength relative to the non-linear memory. We find that linear memory almost always has a much weaker effect than non-linear memory.

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D. Lopez, S. Tiwari and M. Ebersold
Tue, 9 May 23
4/88

Comments: N/A

Exploring the nature of black hole and gravity with an imminent merging binary of supermassive black holes [CL]

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http://arxiv.org/abs/2305.04478


A supermassive binary black-hole candidate SDSS J1430+2303 reported recently motivates us to investigate an imminent binary of supermassive black holes as potential gravitational wave source, the radiated gravitational waves at the end of the merger are shown to be in the band of space-borne detectors. We provide a general analysis on the required detecting sensitivity needed for probing such type gravitational wave sources and make a full discussion by considering two typically designed configurations of space-borne antennas. If a source is so close, it is possible to be detected with Taiji pathfinder-plus which is proposed to be an extension for the planned Taiji pathfinder by just adding an additional satellite to the initial two satellites. The gravitational wave detection on such kind of source enables us to explore the properties of supermassive black holes and the nature of gravity.

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X. Zhong, W. Han, Z. Luo, et. al.
Tue, 9 May 23
6/88

Comments: N/A

No Surviving SN Ia Companion In SNR 0509-67.5: Stellar Population Characterization and Comparison To Models [SSA]

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http://arxiv.org/abs/2305.03750


The community agrees that Type Ia supernovae arise from Carbon/Oxygen white dwarfs undergoing thermonuclear runaway. However, the full progenitor system and the process that prompts the white dwarf to explode remain unknown. Most current models suggest that the white dwarf explodes because of interaction with a binary companion which may survive the process and remain within the resulting remnant of the exploded star. Furthermore, both the pre-supernova interaction process and the explosion of the primary are expected to imprint a significant departure from ordinary stellar radii and temperatures onto the secondary, making the star identifiable against the unrelated stellar population. Identification of a surviving companion inside an SN Ia remnant might confirm a specific corresponding SN Ia progenitor channel based on the identity of the companion. We conducted a surviving companion search of the Type Ia remnant SNR 0509-67.5 based in the Large Magellanic Cloud. The well-constrained distance to and foreground extinction of the Large Magellanic Cloud allow for Bayesian inference of stellar parameters with low correlation and uncertainties. We present a deep catalog of fully characterized stars interior to SNR 0509-67.5 with radii, effective temperatures, and metallicities inferred using combined Hubble Space Telescope photometric observations across multiple visits. We then compile a list of surviving companion models appropriate for the age of the remnant (roughly 400 years after the explosion). We compare these predictions with the inferred stellar parameters and conclude that none of the stars are consistent with the predicted signatures of a surviving companion.

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J. Shields, P. Arunachalam, W. Kerzendorf, et. al.
Tue, 9 May 23
8/88

Comments: 16 pages, 8 figures, 4 tables

Scaling and Universality in the Temporal Occurrence of Repeating FRBs [HEAP]

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http://arxiv.org/abs/2305.04738


The dynamics of repeating fast radio bursts (FRBs) are driven by their physical nature and central engine, however their event rate, energy distribution and temporal occurrence behaviour are still remain uncertain due to the server lack of information of bursts. Recently, the available of high-frequency observation data for the Five-hundred-meter Aperture Spherical radio Telescope (FAST) has made it possible to statistically study the temporal occurrence on timescales from several milliseconds to over several thousand seconds. In this research we studied both the FRB121102 and FRB20201124A temporal occurrence and report here a statistical result about the behaviour of the waiting time (or recurrence-time) between successive bursts. The results exhibit novel scaling and universality which have not reported in the field yet. Specifically, we find the scaling law for FRBs recurrence-time distribution which is a clear indication of the importance of correlations in the structure of its physical nature and central engine. The scaling relationships were observed for time scales spanning three orders of magnitude. Given that they are sharing the same scaling law between two repeating FRBs, we infer that the scaling law of waiting time distribution should acts as a indicator which provides insights into the physical nature and the development of the central engine model.

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Y. Du, P. Wang, L. Song, et. al.
Tue, 9 May 23
11/88

Comments: N/A

On the nature of the planet-powered transient event ZTF SLRN-2020 [SSA]

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http://arxiv.org/abs/2305.04909


The Red Nova ZTF SLRN-2020 is the third transient event with properties that are compatible with the merger of a planet with a main sequence (or close to) star on a dynamical timescale. While the two first transient events occurred in young systems, ZTF SLRN-2020 occurred in an old system. Nonetheless, I show that the three star-planet intermediate luminosity optical transients (ILOTs, also termed Red Novae) occupy the same area in the energy-time diagram of ILOTs. Based on models for ILOTs that are power by stellar binary interaction I suggest that the planet in ZTF SLRN-2020 launched jets at about its escape speed before it was engulfed by the star. Interestingly, the escape speed from the planet is similar to the orbital speed of the planet. This leads to an outflow with a very low terminal velocity, much below the escape velocity from the star, and in concentration around ~45 degrees to the equatorial plane. As well, the planet might have lost back some of the accreted mass just before engulfment, forming an accretion disk around the star. This disk might have launched jets during the main outburst of the event. The jets form a bipolar expanding nebula.

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N. Soker
Tue, 9 May 23
12/88

Comments: Will be submitted in 3 days to allow for comments before submission and press release (including of missing references and transients)

Gravity modes on rapidly rotating accreting white dwarfs and their variation after dwarf novae [SSA]

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http://arxiv.org/abs/2305.03809


Accreting white dwarfs in Cataclysmic variables (CVs) show short-period (tens of minutes) brightness variations that are consistent with non-radial oscillations similar to gravity (g) modes observed in isolated white dwarfs (WDs). GW Librae, a dwarf nova, was the first CV in which non-radial oscillations were observed and continues to be the best studied accreting WD displaying these pulsations. Unlike isolated WDs, accreting WDs rotate rapidly, with spin periods comparable to or shorter than typical low-order oscillation periods. Accreting WDs also have a different relationship between their interior temperature and surface temperature. The surface temperature of an accreting WD varies on a months to year timescale between dwarf novae accretion events, allowing study of how this temperature change effects g-mode behavior. Here we show results from adiabatic seismological calculations for accreting WDs, focusing on low-order ($\ell=1$) modes. We demonstrate how g-modes vary in response to temperature changes in the subsurface layers due to a dwarf nova accretion event. These calculations include rotation non-perturbatively, required by the high spin rate. We discuss the thermal history of these accreting WDs, and compare the seismological properties with and without rotation. Comparison of $g$-mode frequencies to observed objects may allow inference of features of the structure of the WD such as mass, surface abundance, accretion history, and more. The variation of mode frequencies during cooling after an outburst provides a novel method of identifying modes.

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P. Kumar and D. Townsley
Tue, 9 May 23
14/88

Comments: 18 pages, 13 figures, Accepted to ApJ

Non-thermal emissions from a head-tail radio galaxy in 3D magnetohydrodynamic simulations [HEAP]

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http://arxiv.org/abs/2305.04795


We present magnetohydrodynamic simulations of a jet-wind interaction in a galaxy cluster and the radio to gamma-ray and the neutrino emissions from this “head-tail galaxy”. Our simulation follows the evolution of cosmic-ray (CR) particle spectra with energy losses and the stochastic turbulence acceleration. We find that the reacceleration is essential to explain the observed radio properties of head-tail galaxies, in which the radio flux and spectral index do not drastically change. Our models suggest that hard X-ray emissions can be detected around the head-tail galaxy in the Perseus cluster by the hard X-ray satellites, such as FORCE, and it will potentially constrain the acceleration efficiency. We also explore the origin of the collimated synchrotron threads, which are found in some head-tail galaxies by recent high-quality radio observations. Thin and elongated flux tubes, connecting the two tails, are formed by strong backflows at an early phase. We find that these threads advect with the wind for over 300 Myr without disrupting. The radio flux from the flux tubes is much lower than the typical observed flux. An efficient CR diffusion process along the flux tubes, however, may solve this discrepancy.

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T. Ohmura, K. Asano, K. Nishiwaki, et. al.
Tue, 9 May 23
17/88

Comments: 16 pages, 10 figures, accepted for publication in ApJ

Magnetically Threaded Thin Disks in the Presence of the Quadrupole Magnetic Field [HEAP]

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http://arxiv.org/abs/2305.04849


Neutron stars might have multipole magnetic fields as implied by recent observations of pulsars. The presence of the quadrupole field might have an effect on the interaction between the disc and the neutron star depending on the location of the inner radius of the disc and the strength of the quadrupole field. For a quadrudipole stellar field, we calculate the toroidal field generated within the disc, the magnetospheric radius and the torque exerted onto the star. Also, we deduce the effect of the rotation of the star on the magnetospheric radius which is relevant even for pure dipole magnetic fields.

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S. Çıkıntoğlu
Tue, 9 May 23
18/88

Comments: 7 pages, 4 figures, submitted to MNRAS

Horizon fluxes of binary black holes in eccentric orbits [CL]

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http://arxiv.org/abs/2305.03771


I compute the rate of change of mass and angular momentum of a black hole, namely tidal heating, in an eccentric orbit. The change is caused due to the tidal field of the orbiting companion. I compute the result for both the spinning and non-spinning black holes in the leading order of the mean motion, namely $\xi$. I demonstrate that the rates get enhanced significantly for nonzero eccentricity. Since eccentricity in a binary evolves with time I also express the results in terms of an initial eccentricity and azimuthal frequency $\xi_{\phi}$. In the process, I developed a prescription that can be used to compute all physical quantities in a series expansion of initial eccentricity, $e_0$. This result was only known in the leading order while ignoring the contribution of the spin on the eccentricity evolution. Although the eccentricity evolution result still ignores the spin effect in the current work, the prescription can be used to compute higher-order corrections of initial eccentricity post-leading order. Using this result I computed the rate of change of mass and angular momentum of a black hole in terms of initial eccentricity and azimuthal frequency up to $\mathcal{O}(e_0^2)$.

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S. Datta
Tue, 9 May 23
21/88

Comments: N/A

The lively accretion disc in NGC 2992. III. Tentative evidence of rapid Ultra Fast Outflow variability [GA]

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http://arxiv.org/abs/2305.03754


We report on the 2019 XMM-Newton+NuSTAR monitoring campaign of the Seyfert galaxy NGC 2992, observed at one of its highest flux levels in the X-rays. The time-averaged spectra of the two XMM-Newton orbits show Ultra Fast Outflows (UFOs) absorbing structures above 9 keV with $> 3 \sigma$ significance. A detailed investigation of the temporal evolution on a $\sim$5 ks time scale reveals UFO absorption lines at a confidence level $>$95% (2$\sigma$) in 8 out of 50 XMM-Newton segments, estimated via Monte Carlo simulations. We observe a wind variability corresponding to a length scale of 5 Schwarzschild radii $r_S$. Adopting the novel Wind in the Ionised Nuclear Environment (WINE) model, we estimate the outflowing gas velocity ($v=0.21-0.45 c$), column density ($N_H=4-8\cdot 10^{24} cm^{-2}$) and ionisation state ($\log(\xi_0/erg\ cm\ s^{-1})=3.7-4.7$), taking into account geometrical and special relativity corrections. These parameters lead to instantaneous mass outflow rates $\dot{M}{out}\simeq0.3-0.8 M{\odot} yr^{-1}$, with associated outflow momentum rates $\dot{p}{out}\simeq 20-90 L{Bol}/c$ and kinetic energy rates $\dot{E}K \simeq 2-25 L{Bol}$. We estimate a wind duty cycle $\approx$ 12% and a total mechanical power $\approx$ 2 times the AGN bolometric luminosity, suggesting the wind may drive significant feedback effects between the AGN and the host galaxy. Notably, we also provide an estimate for the wind launching radius and density $\approx 5 r_S, 10^{11} {cm}^{-3}$, respectively.

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A. Luminari, A. Marinucci, S. Bianchi, et. al.
Tue, 9 May 23
22/88

Comments: Accepted for publication in the Astrophysical Journal. 21 pages, 11 figures

IceCube and the origin of ANITA-IV events [HEAP]

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http://arxiv.org/abs/2305.03746


Recently, the ANITA collaboration announced the detection of new, unsettling upgoing Ultra-High-Energy (UHE) events. Understanding their origin is pressing to ensure success of the incoming UHE neutrino program. In this work, we study their internal consistency and the implications of the lack of similar events in IceCube. We introduce a generic, simple parametrization to study the compatibility between these two observatories in Standard Model-like and Beyond Standard Model scenarios: an incoming flux of particles that interact with Earth nucleons with cross section $\sigma$, producing particle showers along with long-lived particles that decay with lifetime $\tau$ and generate a shower that explains ANITA observations. We find that the ANITA angular distribution imposes significant constraints, and when including null observations from IceCube only $\tau \sim 10^{-3}$ – $10^{-2} \,\mathrm{s}$ and $\sigma \sim 10^{-33}$ – $10^{-32}\,\mathrm{cm^2}$ can explain the data. This hypothesis is testable with future IceCube data. Finally, we discuss a specific model that can realize this scenario. Our analysis highlights the importance of simultaneous observations by high-energy optical neutrino telescopes and new UHE radio detectors to uncover cosmogenic neutrinos or discover new physics.

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T. Bertólez-Martínez, C. Argüelles, I. Esteban, et. al.
Tue, 9 May 23
24/88

Comments: 11 pages, 7 figures + Appendices. Comments welcome!

Generalized Linear Models of T$_{90}$-T$_{50}$ relation to classify GRBs [HEAP]

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http://arxiv.org/abs/2305.03947


Gamma-ray bursts (GRBs) can be classified with their linearly dependent parameters alongside the standard $T_{90}$ distribution. The Generalized linear mixture model(GLM) identifies the number of linear dependencies in a two-parameter space. Classically, GRBs are classified into two classes by the presence of bimodality in the histogram of T${90}$. However, additional classes and sub-classes of GRBs are fascinating topics to explore. In this work, we investigate the GRBs classes in the $ T{90} {-}T_{50}$ plane using the Generalized Linear Models(GLM) for \textit{Fermi} GBM and BATSE catalogs. This study shows five linear features for the \textit{Fermi} GBM catalog and four linear features for the BATSE catalog, directing towards the possibility of more than two GRB classes.

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S. Dutta, S. Sunanda, R. Moharana, et. al.
Tue, 9 May 23
49/88

Comments: 8 figures, 1 table

Updated Orbital Ephemeris and Detection of Superhump Modulation in X-ray Band for the Ultra-Compact Low Mass X-ray Binary 4U 1820-30 [HEAP]

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http://arxiv.org/abs/2305.04419


The 4U 1820-30 is a ultra-compact low mass X-ray binary (LMXB) near the center of the globular cluster NGC 6624. Its negative orbital period derivative, observed from the phase evolution of its sinusoidal-like orbital variation, contradicts the positive value obtained from the theoretical prediction. In this paper, we present the analysis of the 4U 1820-30 orbital modulation from light curves obtained from the {\it Neutron star Interior Composition ExploreR (NICER)} observations from 2017 to mid 2022. Combined with historical records, the orbital derivative is measured from the orbital phase evolution between 1976 and 2002 is $\dot P /P =(-5.21 \pm 0.13) \times 10^{-8}$ yr$^{-1}$. No significant second order orbital period derivative is detected with a 2$\sigma$ upper limit of $|\ddot P|<5.48 \times 10^{-22}$ s s$^{-2}$. We discuss the possible intrinsic orbital period derivative of 4U 1820-30 and suggest that this binary system may have a significant mass outflow similar to some other LMXBs. In addition, a periodic modulation with a period of $691.6 \pm 0.7$ s, which is consistent with the superhump period discovered in the far ultraviolet band of the {\it Hubble Space Telescope}, was also detected in in the X-ray light curves collected by {\it NICER}. We conclude that such modulation is probably caused by a period of $0.8 \pm 0.1$ day apsidal precession of accretion disk similar to the SU UMa type dwarf novae and some LMXBs. However we cannot exclude the possibility that it is induced by a hierarchical third star orbiting around the binary system.

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Y. Chou and Y. Jhang
Tue, 9 May 23
52/88

Comments: 27 pages, 10 figures, accepted for publication by Astrophysical Journal

Strong-Field Physics in QED and QCD: From Fundamentals to Applications [CL]

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http://arxiv.org/abs/2305.03865


We provide a pedagogical review article on fundamentals and applications of the quantum dynamics in strong electromagnetic fields in QED and QCD. The fundamentals include the basic picture of the Landau quantization and the resummation techniques applied to the class of higher-order diagrams that are enhanced by large magnitudes of the external fields. We then discuss observable effects of the vacuum fluctuations in the presence of the strong fields, which consist of the interdisciplinary research field of nonlinear QED. We also discuss extensions of the Heisenberg-Euler effective theory to finite temperature/density and to non-Abelian theories with some applications. Next, we proceed to the paradigm of the dimensional reduction emerging in the low-energy dynamics in the strong magnetic fields. The mechanisms of superconductivity, the magnetic catalysis of the chiral symmetry breaking, and the Kondo effect are addressed from a unified point of view in terms of the renormalization-group method. We provide an up-to-date summary of the lattice QCD simulations in magnetic fields for the chiral symmetry breaking and the related topics as of the end of 2022. Finally, we discuss novel transport phenomena induced by chiral anomaly and the axial-charge dynamics. Those discussions are supported by a number of appendices.

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K. Hattori, K. Itakura and S. Ozaki
Tue, 9 May 23
53/88

Comments: Prepared for an invited review article

Probing the Sub-Parsec Dust of a Supermassive Black Hole with the Tidal Disruption Event AT 2020mot [HEAP]

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http://arxiv.org/abs/2305.03767


AT 2020mot is a typical UV/optical tidal disruption event (TDE) with no radio or X-ray signatures in a quiescent host. We find an i-band excess and re-brightening along the decline of the light curve which could be due to two consecutive dust echoes from a TDE. We model our observations following van Velzen et al. (2016) and find that the near-infrared light curve can be explained by concentric rings of thin dust within $\sim$0.1 parsecs of a 6e6 M$_{\odot}$ supermassive black hole (SMBH), among the smallest scales at which dust has been inferred near SMBHs. We find dust covering factors of order fc $\leq$ 2%, much lower than found for dusty tori of active galactic nuclei. These results highlight the potential of TDEs for uncovering the environments around black holes when including near-infrared observations in high-cadence transient studies.

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M. Newsome, I. Arcavi, D. Howell, et. al.
Tue, 9 May 23
54/88

Comments: N/A

Toward robust detections of nanohertz gravitational waves [IMA]

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http://arxiv.org/abs/2305.04464


The recent observation of a common red-noise process in pulsar timing arrays (PTAs) suggests that the detection of nanohertz gravitational waves might be around the corner. However, in order to confidently attribute this red process to gravitational waves, one must observe the Hellings-Downs curve — the telltale angular correlation function associated with a gravitational-wave background. This effort is complicated by the complex modelling of pulsar noise. Without proper care, mis-specified noise models can lead to false-positive detections. Background estimation using bootstrap methods such as sky scrambles and phase shifts, which use the data to characterize the noise, are therefore important tools for assessing significance. We investigate the ability of current PTA experiments to estimate their background with “quasi-independent” scrambles — characterized by a statistical “match” below the fiducial value: $|M|<0.1$. We show that sky scrambling is affected by “saturation” after ${\cal O}(10)$ quasi-independent realizations; subsequent scrambles are no longer quasi-independent. We show phase scrambling saturates after ${\cal O}(100)$ quasi-independent realizations. With so few independent scrambles, it is difficult to make reliable statements about the $\gtrsim 5 \sigma$ tail of the null distribution of the detection statistic. We discuss various methods by which one may increase the number of independent scrambles. We also consider an alternative approach wherein one re-frames the background estimation problem so that the significance is calculated using statistically \textit{dependent} scrambles. The resulting $p$-value is in principle well-defined but may be susceptible to failure if assumptions about the data are incorrect.

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V. Marco, A. Zic, M. Miles, et. al.
Tue, 9 May 23
59/88

Comments: N/A

Stability of interlinked neutron vortex and proton flux-tube arrays in a neutron star — III. Proton feedback [HEAP]

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http://arxiv.org/abs/2305.04482


The coupled, time-dependent Gross-Pitaevskii and Ginzburg-Landau equations are solved simultaneously in three dimensions to investigate the equilibrium state and far-from-equilibrium, spin-down dynamics of an interpenetrating neutron superfluid and proton type-II superconductor, as an idealized description of the outer core of a neutron star. The simulations generalize previous calculations without the time-dependent Ginzburg-Landau equation, where proton feedback is absent. If the angle $\theta$ between the rotation and magnetic axes does not equal zero, the equilibrium state consists of geometrically complicated neutron vortex and proton flux-tube tangles, as the topological defects pin to one another locally but align with different axes globally. During spin-down, new types of motion are observed. For $\theta = 0$, entire vortices pair rectilinearly with flux tubes and move together while pinned. For $\theta \neq 0$, vortex segments pair with segments from one or more flux tubes, and the paired segments move together while pinned. The degree to which proton feedback impedes the deceleration of the crust is evaluated as a function of $\theta$ and the pinning strength, $\eta$. Key geometric properties of vortex-flux-tube tangles, such as filament length, mean curvature, and polarity are analysed. It is found that proton feedback smooths the deceleration of the crust, reduces the rotational glitch sizes, and stabilizes the vortex tangle dynamics. The dimensionless control parameters in the simulations are mutually ordered to match what is expected in a real neutron star, but their central values and dynamics ranges differ from reality by many orders of magnitude due to computational limitations.

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K. Thong, A. Melatos and L. Drummond
Tue, 9 May 23
60/88

Comments: N/A

Flight of the Bumblebee: the Early Excess Flux of Type Ia Supernova 2023bee revealed by $TESS$, $Swift$ and Young Supernova Experiment Observations [HEAP]

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http://arxiv.org/abs/2305.03779


We present high-cadence ultraviolet through near-infrared observations of the Type Ia supernova (SN Ia) 2023bee in NGC~2708 ($D = 32 \pm 3$ Mpc), finding excess flux in the first days after explosion relative to the expected power-law rise from an expanding fireball. This deviation from typical behavior for SNe Ia is particularly obvious in our 10-minute cadence $TESS$ light curve and $Swift$ UV data. Compared to a few other normal SNe Ia with detected early excess flux, the excess flux in SN 2023bee is redder in the UV and less luminous. We present optical spectra of SN 2023bee, including two spectra during the period where the flux excess is dominant. At this time, the spectra are similar to those of other SNe Ia but with weaker Si II, C II and Ca II absorption lines, perhaps because the excess flux creates a stronger continuum. We compare the data to several theoretical models that have been proposed to explain the early flux excess in SNe Ia. Interaction with either a nearby companion star or close-in circumstellar material is expected to produce a faster evolution than seen in the data. Radioactive material in the outer layers of the ejecta, either from a double detonation explosion or simply an explosion with a $^{56}$Ni clump near the surface, can not fully reproduce the evolution either, likely due to the sensitivity of early UV observable to the treatment of the outer part of ejecta in simulation. We conclude that no current model can adequately explain the full set of observations. We find that a relatively large fraction of nearby, bright SNe Ia with high-cadence observations have some amount of excess flux within a few days of explosion. Considering potential asymmetric emission, the physical cause of this excess flux may be ubiquitous in normal SNe Ia.

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Q. Wang, A. Rest, G. Dimitriadis, et. al.
Tue, 9 May 23
64/88

Comments: 20 pages, 12 figures

High energy gamma-ray emission powered by a young protostar: the case of S255 NIRS 3 [HEAP]

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http://arxiv.org/abs/2305.04571


Evidence of efficient acceleration of cosmic rays in massive young stellar objects has been recently reported. Among these massive protostars, S255 NIRS 3 for which extreme flaring events associated with radio jets have been detected, is one of the best objects to test this hypothesis. We search for gamma-ray emission associated with this object in Fermi-LAT data and inspect the gas content in different molecular lines using the MWISP survey. A GeV source dubbed 4FGL J0613.1+1749c lies on top of the MYSO region, where two filamentary ~10 pc CO structures extend along the same direction of the sub-parsec radio jets. We investigate the spectrum, morphology, and light curve of the gamma-ray source and compare it with the theoretical emission expected from hadronic and leptonic populations accelerated in the radio jets. We argue that the gamma-ray source could be powered by particles accelerated in the S255 NIRS 3 jets, radiating via Bremsstrahlung or proton-proton interaction, and with a synchrotron component shinning in radio from primary or secondary electrons in the case of a leptonic or hadronic population.

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E. Wilhelmi, R. López-Coto and Y. Su
Tue, 9 May 23
66/88

Comments: accepted for publication in Monthly Notices of the Royal Astronomical Society

Near-Infrared Spectroscopy of Dense Ejecta Knots in the Outer Eastern Area of the Cassiopeia A Supernova Remnant [HEAP]

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http://arxiv.org/abs/2305.04484


The Cassiopeia A supernova remnant has a complex structure, manifesting the multidimensional nature of core-collapse supernova explosions. To further understand this, we carried out near-infrared multi-object spectroscopy on the ejecta knots located in the “northeastern (NE) jet” and the “Fe K plume” regions, which are two distinct features in the outer eastern area of the remnant. Our study reveals that the knots exhibit varying ratios of [S II] 1.03 $\mu$m, [P II] 1.189 $\mu$m, and [Fe II] 1.257 $\mu$m lines depending on their locations within the remnant, suggesting regional differences in elemental composition. Notably, the knots in the NE jet are mostly ‘S-rich’ with weak or no [P II] lines, implying that they originated below the explosive Ne burning layer, consistent with the results of previous studies. We detected no ejecta knots exhibiting only [Fe II] lines in the NE jet area that are expected in the jet-driven SN explosion model. Instead, we discovered a dozen ‘Fe-rich’ knots in the Fe K plume area. We propose that they are dense knots produced by a complete Si burning with $\alpha$-rich freezeout in the innermost region of the progenitor and ejected with the diffuse X-ray emitting Fe ejecta but decoupled after crossing the reverse shock. In addition to these metal-rich ejecta knots, several knots emitting only He I 1.083 $\mu$m lines were detected, and their origin remains unclear. We also detected three extended H emission features of circumstellar or interstellar origin in this area and discuss its association with the supernova remnant.

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B. Koo, Y. Lee, J. Lee, et. al.
Tue, 9 May 23
69/88

Comments: 30 pages, 16 figures, submitted to ApJ

Exploring the viability of pseudo Nambu-Goldstone boson as ultralight dark matter in a mass range relevant for strong gravity applications [CL]

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http://arxiv.org/abs/2305.03776


We study a simple extension of the Standard Model featuring a dark sector with an ultralight pseudo Nambu-Goldstone boson as dark matter candidate. We focus on the mass range $\mathcal{O}(10^{-20} – 10^{-10})$ eV, relevant for strong gravity applications, and explore its production and evolution in the early Universe. The model is formulated in such a way that dark matter does not couple directly to photons or other Standard Model particles avoiding some of the most stringent cosmological bounds related to axion-like particles. In this work, two different scenarios are considered depending on whether dark matter is produced in a pre-inflationary or post-inflationary regime. We also discuss the effect from emergent topological defects such as cosmic strings and domain walls, and estimate the spectrum of stochastic gravitational waves produced by their decay, enabling to test the model at current and future gravitational-wave experiments.

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A. Morais, V. Oliveira, A. Onofre, et. al.
Tue, 9 May 23
72/88

Comments: 22 pages, 5 figures

Revealing the intrinsic X-ray reverberation lags in IRAS 13224-3809 through the Granger causality test [HEAP]

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http://arxiv.org/abs/2305.04185


The Granger causality is an econometric test for determining whether one time series is useful for forecasting another one with a certain Granger lag. Here, the light curves in the 0.3-1 keV (reflection dominated, soft) and 1.2-5 keV (continuum dominated, hard) bands of Active Galactic Nuclei (AGNs) are produced, and the Granger lags are estimated and compared to the traditional lag-frequency spectra. We find that the light curves in the hard band Granger-cause (lead) those in the soft band, whereas the obtained Granger lags could be interpreted as the intrinsic reverberation lags. Then, we extract the Granger-lag profiles from 14 XMM-Newton observations of IRAS 13224-3809, and find that the lags are significant in 12 observations. The majority of the obtained Granger (intrinsic) lags are ~ 200-500 s. With the IRAS 13224-3809 mass of 2 $\times 10^6$ $M_{\odot}$, these lags correspond to the true light-travel distance of ~ 20-50 $r_g$. Hence, by assuming a lamp-post geometry and a face-on disc, this places the corona at ~ 10-25 $r_{g}$ above the central black hole. Moreover, multiple Granger lags consisting of the small and large lags of < 500 s and > 1000 s are detected in 4 observations. This means that the corona height can significantly evolve from ~ 10-25 $r_{g}$ to ~ 55 $r_{g}$, or vice versa, towards the end of the observation. Granger lags are a promising way to measure the intrinsic lags, and provide evidence of coronal height variability within each individual observation.

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P. Chainakun, N. Nakhonthong, W. Luangtip, et. al.
Tue, 9 May 23
80/88

Comments: 13 pages, 10 figures, 1 Table, accepted for publication in MNRAS

Core Collapse Supernova Explosions in Active Galactic Nucleus Accretion Disks [HEAP]

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http://arxiv.org/abs/2305.04010


Astrophysical events that occur in active galactic nucleus (AGN) disks are believed to differ significantly from the ordinary in the interstellar medium. We show that stars located in the outer region of the AGN disk would explode near the original migration starting points instead of being accreted by the central supermassive black hole due to the effect of viscosity. AGN disks provide a dense environment for supernova (SN) explosions, which inevitably involve ejecta-disk interactions. In this paper, we investigate the light curves (LCs) of core-collapse SN exploded in AGN disks. In addition to the fundamental energy source of $^{56} \mathrm{Ni}$–$^{56} \mathrm{Co}$–$^{56} \mathrm{Fe}$ decay reaction powering the SN LCs, the forward-reverse shock produced during interactions may contribute significantly to the observed flux. If the stellar winds manage to create a cavity surrounded by a shell near the star before the SN explosion, the ejecta-winds-disk configurations are expected. We present various SN LCs from different types of progenitors and find that the SN LCs are dominated by the radiation of ejecta-disk interaction-induced shocks. The resulting SNe in the AGN disk is a promising transient source for UV and optical band detection by the Neil Gehrels Swift Observatory (Swift), the Ultraviolet Explorer (UVEX) and wide field survey telescopes such as Ultraviolet Transient Astronomy Satellite (ULTRASAT), Wide Field Survey Telescope (WFST) and Legacy Survey of Space and Time (LSST) at the Vera C. Rubin Observatory. These detections could aid in the investigation of AGN discs and the associated high-energy transient occurrences.

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F. Li, Y. Liu, X. Fan, et. al.
Tue, 9 May 23
81/88

Comments: ApJ in press, 16 pages, 6 figures

Spectral distortions of astrophysical blackbodies as axion probes [CL]

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http://arxiv.org/abs/2305.03749


Recent studies reveal that more than a dozen of white dwarfs displaying near-perfect blackbody spectra in the optical range have been lurking in the Sloan Digital Sky Survey catalog. We point out that, in a way analogous to the Cosmic Microwave Background, these stars serve as excellent testbeds for new physics. Specifically, we show how their observed lack of spectral distortions translates into limits on the parameter space of axions with electromagnetic coupling. The prospects for future improvements are also discussed.

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J. Chang, R. Ebadi, X. Luo, et. al.
Tue, 9 May 23
85/88

Comments: 14 pages, 8 figures

Neutrino many-body correlations [CL]

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http://arxiv.org/abs/2305.04916


This paper responds to suggestions that the standard approach to collective neutrino oscillations leaves out potentially important quantum many-body correlations. Arguments in favor of this idea have been based on calculations that, on close scrutiny, offer no evidence either way. Inadequacies of the usual quantum-kinetic formalism are not currently supported by the literature.

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L. Johns
Tue, 9 May 23
86/88

Comments: 8 pages, 0 figures

MAXI J1848-015: The First Detection of Relativistically Moving Outflows from a Globular Cluster X-ray Binary [HEAP]

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http://arxiv.org/abs/2305.03764


Over the past decade, observations of relativistic outflows from outbursting X-ray binaries in the Galactic field have grown significantly. In this work, we present the first detection of moving and decelerating radio-emitting outflows from an X-ray binary in a globular cluster. MAXI J1848-015 is a recently discovered transient X-ray binary in the direction of the globular cluster GLIMPSE-C01. Using observations from the VLA, and a monitoring campaign with the MeerKAT observatory for 500 days, we model the motion of the outflows. This represents some of the most intensive, long-term coverage of relativistically moving X-ray binary outflows to date. We use the proper motions of the outflows from MAXI J1848-015 to constrain the component of the intrinsic jet speed along the line of sight, $\beta_\textrm{int} \cos \theta_\textrm{ejection}$, to be $=0.19\pm0.02$. Assuming it is located in GLIMPSE-C01, at 3.4 kpc, we determine the intrinsic jet speed, $\beta_\textrm{int}=0.79\pm0.07$, and the inclination angle to the line of sight, $\theta_\textrm{ejection}=76^\circ\pm2^{\circ}$. This makes the outflows from MAXI J1848-015 somewhat slower than those seen from many other known X-ray binaries. We also constrain the maximum distance to MAXI J1848-015 to be $4.3$ kpc. Lastly, we discuss the implications of our findings for the nature of the compact object in this system, finding that a black hole primary is a viable (but as-of-yet unconfirmed) explanation for the observed properties of MAXI J1848-015. If future data and/or analysis provide more conclusive evidence that MAXI J1848-015 indeed hosts a black hole, it would be the first black hole X-ray binary in outburst identified in a Galactic globular cluster.

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A. Bahramian, E. Tremou, A. Tetarenko, et. al.
Tue, 9 May 23
88/88

Comments: 14 pages, 5 figures, ApJL in press

Mildly Relativistic Motion in the Radio Quiet Quasar PG 1351+640 [GA]

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http://arxiv.org/abs/2305.03470


Measuring the proper motion of the emission component in radio-quiet quasars (RQQs) could help to distinguish between the origins of the radio emission and to understand whether the jet production mechanism is the same in radio-loud quasars (RLQs) and RQQs. PG 1351+640 is one of the few RQQs suitable for proper motion studies: it has two compact components on milli-arcsecond scales, a flat-spectrum core and a steep-spectrum jet; both components are >2 mJy at 5 GHz and are well suited for Very Long Baseline Array (VLBA) observations. We compare recent VLBA observations with that made seventeen years ago and find no significant change in the core-jet separation between 2005 and 2015 (a proper motion of 0.003 mas yr-1). However, the core-jet separation increased significantly between 2015 and 2022, inferring a jet proper motion velocity of 0.063 mas yr-1, which corresponds to an apparent transverse velocity of 0.37c. The result suggests that the jet of the RQQ PG 1351+640 is mildly relativistic and oriented at a relatively small viewing angle.

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A. Wang, T. An, S. Guo, et. al.
Mon, 8 May 23
6/63

Comments: The article has been published by Oxford University Press: this https URL&utm_campaign=mnrasl&utm_medium=email

Anisotropic Star Clusters around Recoiling Supermassive Black Holes [GA]

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http://arxiv.org/abs/2305.03054


Gravitational wave recoil kicks from merging supermassive black hole binaries can have a profound effect on the surrounding stellar population. In this work, we study the dynamic and kinematic properties of nuclear star clusters following a recoil kick. We show that these post-kick structures present unique signatures that can provide key insight to observational searches for recoiling supermassive black holes. In Akiba & Madigan (2021), we showed that an in-plane recoil kick turns a circular disk into a lopsided, eccentric disk such as the one we observe in the Andromeda nucleus. Building on this work, here we explore many recoil kick angles as well as initial stellar configurations. For a circular disk of stars, an in-plane kick causes strong apsidal alignment with a significant fraction of the disk becoming retrograde at large radii. If initial orbits are highly eccentric, an in-plane kick forms a bar-like structure made up of two anti-aligned lopsided disks. An out-of-plane kick causes clustering in the argument of periapsis, $\omega$, regardless of the initial eccentricity distribution. Initially isotropic configurations form anisotropies in the form of a torus of eccentric orbits oriented perpendicular to the recoil kick. Post-kick surface density and velocity maps are presented in each case to highlight the distinct, observable structures of these systems.

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T. Akiba and A. Madigan
Mon, 8 May 23
7/63

Comments: 43 pages, 29 figures, submitted to ApJ

Searching for Quasi-Periodic Eruptions using Machine Learning [IMA]

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http://arxiv.org/abs/2305.03629


Quasi-Periodic Eruptions (QPEs) are a rare phenomenon in which the X-ray emission from the nuclei of galaxies shows a series of large amplitude flares. Only a handful of QPEs have been observed but the possibility remains that there are as yet undetected sources in archival data. Given the volume of data available a manual search is not feasible, and so we consider an application of machine learning to archival data to determine whether a set of time-domain features can be used to identify further lightcurves containing eruptions. Using a neural network and 14 variability measures we are able to classify lightcurves with accuracies of greater than 94% with simulated data and greater than 98% with observational data on a sample consisting of 12 lightcurves with QPEs and 52 lightcurves without QPEs. An analysis of 83,531 X-ray detections from the XMM Serendipitous Source Catalogue allowed us to recover lightcurves of known QPE sources and examples of several categories of variable stellar objects.

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R. Webbe and A. Young
Mon, 8 May 23
8/63

Comments: 18 pages. 16 figures

The first massive compact companion in a wide orbit around a hot subdwarf star [SSA]

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http://arxiv.org/abs/2305.03475


We report the discovery of the first hot subdwarf B (sdB) star with a massive compact companion in a wide ($P=892.5\pm60.2\,{\rm d}$) binary system. It was discovered based on an astrometric binary solution provided by the Gaia mission Data Release 3. We performed detailed analyses of the spectral energy distribution (SED) as well as spectroscopic follow-up observations and confirm the nature of the visible component as a sdB star. The companion is invisible despite of its high mass of $M_{\rm comp}=1.50_{-0.45}^{+0.37}\,M_{\rm \odot}$. A main sequence star of this mass would significantly contribute to the SED and can be excluded. The companion must be a compact object, either a massive white dwarf or a neutron star. Stable Roche lobe overflow to the companion likely led to the stripping of a red giant and the formation of the sdB, the hot and exposed helium core of the giant. Based on very preliminary data, we estimate that $\sim9\%$ of the sdBs might be formed through this new channel. This binary might also be the prototype for a new progenitor class of supernovae type Ia, which has been predicted by theory.

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S. Geier, M. Dorsch, H. Dawson, et. al.
Mon, 8 May 23
10/63

Comments: 11 pages, accepted for publication in A&A

Early excess emission in Type Ia supernovae from the interaction between supernova ejecta and their circumstellar wind [HEAP]

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http://arxiv.org/abs/2305.03363


The effects of the interaction between Type Ia supernova ejecta and their circumstellar wind on the photometric properties of Type Ia supernovae are investigated. We assume that a hydrogen-rich, dense, and extended circumstellar matter (CSM) is formed by the steady mass loss of their progenitor systems. The CSM density is assumed to be proportional to r^{-2}. When the mass-loss rate is above 1e-4 Msun/yr with a wind velocity of 100 km/s, CSM interaction results in an early flux excess in optical light-curves within 4 days of explosion. In these cases, the optical colour quickly evolves to the blue. The ultraviolet flux below 3000 A is found to have a persistent flux excess compared to Type Ia supernovae as long as CSM interaction continues. Type Ia supernovae with progenitor mass-loss rates between 1e-4 and 1e-3 Msun/yr may not have a CSM that is dense enough to affect spectra to make them Type Ia-CSM, but they may still result in Type Ia supernovae with an early optical flux excess. Because they have a persistent ultraviolet flux excess, ultraviolet light curves around the luminosity peak would be significantly different from those with a low-density CSM.

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T. Moriya, P. Mazzali, C. Ashall, et. al.
Mon, 8 May 23
11/63

Comments: 8 pages, 8 figures, accepted by Monthly Notices of the Royal Astronomical Society

Cosmic rays from heavy particle decays [CL]

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http://arxiv.org/abs/2305.03313


Multidimensional modification of gravity with a smaller mass scale of the gravitational interaction is considered. Stable by assumption dark matter particles could decay via interactions with virtual black holes. The decay rates of such processes are estimated. It is shown that with the proper fixation of the parameters the decays of these ultra-massive particles can give noticeable contribution to the flux of high energy cosmic rays in particular, near the Greisen-Zatsepin-Kuzmin limit. Such particles can also create neutrinos of very high energies observed in the existing huge underwater or ice-cube detectors.

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E. Arbuzova, A. Dolgov and A. Nikitenko
Mon, 8 May 23
12/63

Comments: 7 pages, 3 figures

An independent determination of the distance to supernova SN 1987A by means of the light echo AT 2019xis [HEAP]

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http://arxiv.org/abs/2305.03456


Accurate distance determination to astrophysical objects is essential for the understanding of their intrinsic brightness and size. The distance to SN 1987A has been previously measured by the expanding photosphere method, and by using the angular size of the circumstellar rings with absolute sizes derived from light curves of narrow UV emission lines, with reported distances ranging from 46.77 kpc to 55 kpc. In this study, we independently determined the distance to SN 1987A using photometry and imaging polarimetry observations of AT 2019xis, a light echo of SN 1987A, by adopting a radiative transfer model of the light echo developed in Ding et al. (2021). We obtained distances to SN 1987A in the range from 49.09 $\pm$ 2.16 kpc to 59.39 $\pm$ 3.27 kpc, depending on the interstellar polarization and extinction corrections, which are consistent with the literature values. This study demonstrates the potential of using light echoes as a tool for distance determination to astrophysical objects in the Milky Way, up to kiloparsec level scales.

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A. Cikota, J. Ding, L. Wang, et. al.
Mon, 8 May 23
22/63

Comments: Accepted for publication in ApJL