Tag Archives: Earth and Planetary Astrophysics

Interstellar Objects [EPA]

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http://arxiv.org/abs/2304.00568


Since 2017, two macroscopic interstellar objects have been discovered in the inner Solar System, both of which are distinct in nature. The first interstellar object, 1I/Oumuamua, passed within $\sim63$ lunar distances of the Earth, appeared asteroidal lacking detectable levels of gas or dust loss, yet exhibited a nongravitational acceleration. 1I/Oumuamua’s brief visit left open questions regarding its provenance which has given rise to many theoretical hypotheses, including an icy comet lacking a dust coma, an elongated fragment of a planet or planetesimal that was tidally disrupted, and an ultra-porous fractal aggregate. The second interstellar object, 2I/Borisov, was distinct from 1I/Oumuamua in terms of its bulk physical properties and displayed a definitive cometary tail. We review the discoveries of these objects, the subsequent observations and characterizations, and the theoretical hypotheses regarding their origins. We describe 1I/Oumuamua and 2I/Borisov in the context of active asteroids and comets in the Solar System. The discovery of these two objects implies a galactic-wide population of $\sim10^{26}$ similar bodies. Forthcoming observatories should detect many more interstellar planetesimals which may offer new insights into how planetary formation processes vary throughout the Galaxy.

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D. Seligman and A. Moro-Martín
Tue, 4 Apr 23
12/111

Comments: 51 pages, 10 figures, invited review for Contemporary Physics, comments welcome

Detection of TiO and VO in the atmosphere of WASP-121b and Evidence for its temporal variation [EPA]

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http://arxiv.org/abs/2304.00461


We report the transit observations of the ultra hot Jupiter WASP-121b using the Goodman High Throughput Spectrograph (GHTS) at the 4-meter ground-based telescope Southern Astrophysical Research Telescope (SOAR), covering the wavelength range $502-900$ nm. By dividing the target and reference star into 19 spectroscopic passbands and applying differential spectrophotometry, we derive spectroscopic transit light curves and fit them using Gaussian process framework to determine transit depths for every passbands. The obtained optical transmission spectrum shows a steep increased slope toward the blue wavelength, which seems to be too steep to be accounted for by the Rayleigh scattering alone. We note that the transmission spectrum from this work and other works differ obviously from each other, which was pointed out previously by \citet{Wilson2021} as evidence for temporal atmospheric variation. We perform a free chemistry retrieval analysis on the optical transmission spectra from this work and the literature HST/WFC3 NIR spectrum. We determine TiO, VO and H${2}$O with abundances of $-5.95{-0.42}^{+0.47}$ dex, $-6.72_{-1.79}^{+0.51}$ dex, and $-4.13_{-0.46}^{+0.63}$ dex, respectively. We compare the abundances of all these three molecules derived from this work and previous works, and find that they are not consistent with each other, indicating the chemical compositions of the terminator region may change over long timescales. Future multi-epoch and high-precision transit observations are required to further confirm this phenomena. We note that when combining the transmission spectra in the optical and in NIR in retrieval analysis, the abundances of V and VO, the NIR-to-optical offset and the cloud deck pressure may be coupled with each other.

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Q. Ouyang, W. Wang, M. Zhai, et. al.
Tue, 4 Apr 23
19/111

Comments: 23 pages, 13 figures, 6 tables. Accepted for publication in Research in Astronomy and Astrophysics

Towards 3D Retrieval of Exoplanet Atmospheres: Assessing Thermochemical Equilibrium Estimation Methods [EPA]

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http://arxiv.org/abs/2304.00073


Characterizing exoplanetary atmospheres via Bayesian retrievals requires assuming some chemistry model, such as thermochemical equilibrium or parameterized abundances. The higher-resolution data offered by upcoming telescopes enables more complex chemistry models within retrieval frameworks. Yet, many chemistry codes that model more complex processes like photochemistry and vertical transport are computationally expensive, and directly incorporating them into a 1D retrieval model can result in prohibitively long execution times. Additionally, phase-curve observations with upcoming telescopes motivate 2D and 3D retrieval models, further exacerbating the lengthy runtime for retrieval frameworks with complex chemistry models. Here, we compare thermochemical equilibrium approximation methods based on their speed and accuracy with respect to a Gibbs energy-minimization code. We find that, while all methods offer orders of magnitude reductions in computational cost, neural network surrogate models perform more accurately than the other approaches considered, achieving a median absolute dex error <0.03 for the phase space considered. While our results are based on a 1D chemistry model, our study suggests that higher dimensional chemistry models could be incorporated into retrieval models via this surrogate modeling approach.

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M. Himes, J. Harrington and A. Baydin
Tue, 4 Apr 23
31/111

Comments: 22 pages, 14 figures, submitted to PSJ 2022/11/22, revised 2023/3/7, accepted 2023/3/23

Modified Newtonian Dynamics as an Alternative to the Planet Nine Hypothesis [CL]

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http://arxiv.org/abs/2304.00576


A new class of Kuiper belt objects that lie beyond Neptune with semimajor axes greater than 250 astronomical units show orbital anomalies that have been interpreted as evidence for an undiscovered ninth planet. We show that a modified gravity theory known as MOND (Modified Newtonian Dynamics) provides an alternative explanation for the anomalies using the well-established secular approximation. We predict that the major axes of the orbits will be aligned with the direction towards the galactic center and that the orbits cluster in phase space, in agreement with observations of Kuiper belt objects from the new class. Thus MOND, which can explain galactic rotation without invoking dark matter, might also be observable in the outer solar system.

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K. Jones-Smith and H. Mathur
Tue, 4 Apr 23
46/111

Comments: Under review at the Astronomical Journal. Complementary to the findings of Migaszewski in arXiv:2303.13339

The X-ray activity of F stars with hot Jupiters: KELT-24 versus WASP-18 [SSA]

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http://arxiv.org/abs/2304.00854


X-rays emitted by the coronae of solar-type stars are a feature present in up to late-A types during the main sequence phase. F stars, either with or without hot Jupiters, are usually X-ray emitters. The very low level of X-ray emission of the F5 star WASP-18 despite its relatively young age and spectral type is thus quite peculiar. [Abridged] We observed KELT-24 with \xmm\ for a total of 43 ks in order to test if the X-ray activity of this star is depressed by the interaction with its massive hot Jupiter, as is the case of WASP-18. KELT-24 is detected in combined EPIC images with a high significance level. Its average coronal spectrum is well described by a cool component at 0.36 keV and a hotter component at 0.98 keV. We detected a flare with a duration of about 2 ks, during which the coronal temperature reached 3.5 keV. The unabsorbed quiescent flux in 0.3-8.0 keV is $\sim1.33\times10^{-13}$ erg s$^{-1}$ cm$^{-2}$, corresponding to a luminosity of $1.5\times10^{29}$ erg s$^{-1}$ at the distance of the star. The luminosity is well within the range of the typical X-ray luminosity of F stars in Hyades, which are coeval. We conclude that the activity of KELT-24 appears normal, as expected, and is not affected by any star–planet interaction. From the analysis of TESS light curves, we infer a distribution of optical flares for KELT-24 and WASP-18. Small optical flickering similar to flares is recognized in WASP-18 but at lower levels of energy and amplitude than in KELT-24. We discuss the causes of the low activity of WASP-18. Either WASP-18b could hamper the formation of a corona bright in X-rays in its host star through some form of tidal interaction, or the star has entered a minimum of activity similar to the solar Maunder minimum. This latter hypothesis would make WASP-18 among the few candidates showing such a quench of stellar activity.

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I. Pillitteri, S. Colombo, G. Micela, et. al.
Tue, 4 Apr 23
55/111

Comments: 6 pages, 7 figures, A&A accepted

Electrostatic Model for Antenna Signal Generation From Dust Impacts [CL]

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http://arxiv.org/abs/2304.00452


Dust impacts on spacecraft are commonly detected by antenna instruments as transient voltage perturbations. The signal waveform is generated by the interaction between the impact-generated plasma cloud and the elements of the antenna-spacecraft system. A general electrostatic model is presented that includes the two key elements of the interaction, namely the charge recollected from the impact plasma by the spacecraft and the fraction electrons and cations that escape to infinity. The clouds of escaping electrons and cations generate induced signals, and their vastly different escape speeds are responsible for the characteristic shape of the waveforms. The induced signals are modeled numerically for the geometry of the system and the location of the impact. The model employs a Maxwell capacitance matrix to keep track of the mutual interaction between the elements of the system. A new reduced-size model spacecraft is constructed for laboratory measurements using the dust accelerator facility. The model spacecraft is equipped with four antennas: two operating in a monopole mode, and one pair configured as a dipole. Submicron-sized iron dust particles accelerated to > 20 km/s are used for test measurements, where the waveforms of each antenna are recorded. The electrostatic model provides a remarkably good fit to the data using only a handful of physical fitting parameters, such as the escape speeds of electrons and cations. The presented general model provides the framework for analyzing antenna waveforms and is applicable for a range of space missions investigating the distribution of dust particles in relevant environments.

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M. Shen, Z. Sternovsky, A. Garzelli, et. al.
Tue, 4 Apr 23
60/111

Comments: Manuscript accepted online by JGR: Space Physics on 13 August 2021

Eight exoplanet candidates in SAO survey [EPA]

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http://arxiv.org/abs/2304.01076


Here we present eight new candidates for exoplanets detected by the transit method at the Special Astrophysical Observatory of the Russian Academy of Sciences. Photometric observations were performed with a 50-cm robotic telescope during the second half of 2020. We detected transits with depths of $\Delta m = 0.056-0.173^m$ and periods $P = 18.8^h-8.3^d$ in the light curves of stars with magnitudes of $m = 14.3-18.8^m$. All considered stars are classified as dwarfs with radii of $R_* = 0.4-0.6 R_{sun}$ (with the uncertainty for one star up to $1.1 R_{sun}$). We estimated the candidate radii (all are greater than 1.4 times the Jovian radius), semi-major axes of their orbits ($0.012-0.035 AU$), and other orbital parameters by modelling. We report the light curves with transits for two stars obtained in 2022 based on individual observations.

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O. Yakovlev, A. Valeev, G. Valyavin, et. al.
Tue, 4 Apr 23
63/111

Comments: 16 pages, 14 figures, 3 tables

Resonant mechanisms that produce near-Sun asteroids [EPA]

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http://arxiv.org/abs/2304.00561


All near-Earth asteroids (NEAs) that reach sufficiently small perihelion distances will undergo a so-called super-catastrophic disruption. The mechanisms causing such disruptions are currently unknown or, at least, undetermined. To help guide theoretical and experimental work to understand the disruption mechanism, we use numerical simulations of a synthetic NEA population to identify the resonant mechanisms that are responsible for driving NEAs close to the Sun, determine how these different mechanisms relate to their dynamical lifetimes at small heliocentric distances and calculate the average time they spend at different heliocentric distances. Typically, resonances between NEAs and the terrestrial and giant planets are able to dramatically reduce the perihelion distances of the former. We developed an algorithm that scans the orbital evolution of asteroids and automatically identifies occurrences of mean motion and secular resonances. We find that most near-Sun asteroids are pushed to small perihelion distances by the 3:1J and 4:1J mean-motion resonances with Jupiter, as well as the secular resonances v6, v5,v3 and v4. The time-scale of the small-perihelion evolution is fastest for the 4:1J, followed by the 3:1J, while v5 is the slowest.~7% of the test asteroids were not trapped in a resonance during the latest stages of their dynamical evolution, which suggests that the secular oscillation of the eccentricity due to the Kozai mechanism, a planetary close encounter or a resonance that we have not identified pushed them below the estimated average disruption distance.

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A. Toliou and M. Granvik
Tue, 4 Apr 23
79/111

Comments: 20 pages

The CARMENES search for exoplanets around M dwarfs — A deep transfer learning method to determine Teff and [M/H] of target stars [SSA]

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http://arxiv.org/abs/2304.00224


The large amounts of astrophysical data being provided by existing and future instrumentation require efficient and fast analysis tools. Transfer learning is a new technique promising higher accuracy in the derived data products, with information from one domain being transferred to improve the accuracy of a neural network model in another domain. In this work, we demonstrate the feasibility of applying the deep transfer learning (DTL) approach to high-resolution spectra in the framework of photospheric stellar parameter determination. To this end, we used 14 stars of the CARMENES survey sample with interferometric angular diameters to calculate the effective temperature, as well as six M dwarfs that are common proper motion companions to FGK-type primaries with known metallicity. After training a deep learning (DL) neural network model on synthetic PHOENIX-ACES spectra, we used the internal feature representations together with those 14+6 stars with independent parameter measurements as a new input for the transfer process. We compare the derived stellar parameters of a small sample of M dwarfs kept out of the training phase with results from other methods in the literature. Assuming that temperatures from bolometric luminosities and interferometric radii and metallicities from FGK+M binaries are sufficiently accurate, DTL provides a higher accuracy than our previous state-of-the-art DL method (mean absolute differences improve by 20 K for temperature and 0.2 dex for metallicity from DL to DTL when compared with reference values from interferometry and FGK+M binaries). Furthermore, the machine learning (internal) precision of DTL also improves as uncertainties are five times smaller on average. These results indicate that DTL is a robust tool for obtaining M-dwarf stellar parameters comparable to those obtained from independent estimations for well-known stars.

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A. Bello-García, V. Passegger, J. Ordieres-Meré, et. al.
Tue, 4 Apr 23
89/111

Comments: N/A

Updated Planetary Mass Constraints of the Young V1298 Tau System Using MAROON-X [EPA]

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http://arxiv.org/abs/2304.00797


The early K-type T-Tauri star, V1298 Tau ($V=10\,{\rm mag}$, ${\rm age}\approx20-30\,{\rm Myr}$) hosts four transiting planets with radii ranging from $4.9-9.6\,R_\oplus$. The three inner planets have orbital periods of $\approx8-24\,{\rm d}$ while the outer planet’s period is poorly constrained by single transits observed with \emph{K2} and \emph{TESS}. Planets b, c, and d are proto-sub-Neptunes that may be undergoing significant mass loss. Depending on the stellar activity and planet masses, they are expected to evolve into super-Earths/sub-Neptunes that bound the radius valley. Here we present results of a joint transit and radial velocity (RV) modelling analysis, which includes recently obtained \emph{TESS} photometry and MAROON-X RV measurements. Assuming circular orbits, we obtain a low-significance ($\approx2\sigma$) RV detection of planet c implying a mass of $19.8_{-8.9}^{+9.3}\,M_\oplus$ and a conservative $2\sigma$ upper limit of $<39\,M_\oplus$. For planets b and d, we derive $2\sigma$ upper limits of $M_{\rm b}<159\,M_\oplus$ and $M_{\rm d}<41\,M_\oplus$. For planet e, plausible discrete periods of $P_{\rm e}>55.4\,{\rm d}$ are ruled out at a $3\sigma$ level while seven solutions with $43.3<P_{\rm e}/{\rm d}<55.4$ are consistent with the most probable $46.768131\pm000076\,{\rm d}$ solution within $3\sigma$. Adopting the most probable solution yields a $2.6\sigma$ RV detection with mass a of $0.66\pm0.26\,M_{\rm Jup}$. Comparing the updated mass and radius constraints with planetary evolution and interior structure models shows that planets b, d, and e are consistent with predictions for young gas-rich planets and that planet c is consistent with having a water-rich core with a substantial ($\sim5\%$ by mass) H$_2$ envelope.

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J. Sikora, J. Rowe, S. Barat, et. al.
Tue, 4 Apr 23
91/111

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

Coherent radio bursts from known M-dwarf planet host YZ Ceti [SSA]

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http://arxiv.org/abs/2304.00031


Observing magnetic star-planet interactions (SPI) offers promise for determining magnetic fields of exoplanets. Models of sub-Alfv\’enic SPI predict that terrestrial planets in close-in orbits around M~dwarfs can induce detectable stellar radio emission, manifesting as bursts of strongly polarized coherent radiation observable at specific planet orbital positions. We present 2-4 GHz detections of coherent radio bursts on the slowly-rotating M dwarf YZ Ceti, which hosts a compact system of terrestrial planets, the innermost orbiting with a 2-day period. Two coherent bursts occur at similar orbital phases of YZ Cet b, suggestive of an enhanced probability of bursts near that orbital phase. We model the system’s magnetospheric environment in the context of sub-Alfv\’enic SPI and determine that YZ Ceti b can plausibly power the observed flux densities of the radio detections. However, we cannot rule out stellar magnetic activity, without a well characterized rate of non-planet-induced coherent radio bursts on slow rotators. YZ Ceti is therefore a candidate radio SPI system, with unique promise as a target for the long-term monitoring.

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J. Pineda and J. Villadsen
Tue, 4 Apr 23
92/111

Comments: Authors’ version of article published in Nature Astronomy, see their website for official version of scientific record

The common trend of saltation particles on the surface of fast-rotating asteroids [EPA]

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http://arxiv.org/abs/2304.00205


An asteroid spun up to its critical limit has unique surface mechanical properties that its gravity and the centrifugal force largely balance, creating a relaxation environment where low-energy events such as mass shedding may trigger subsequent long complex motion of an asteroid’s regolith grains. Exploring such an evolution process may provide key clues for understanding the early formation of multi-asteroid systems. This paper investigates the complex evolution process of loose particles becoming triggered by shedding events and the dependency of their dynamical propagation on the contact mechanical properties of the asteroid surface. We present a numerical model for tracking the trajectory of a shed particle that considers the collision between the particle and the surface of an asteroid. Monte Carlo simulations are performed to reflect the statistical behavior of shed particles. We also introduce zero-velocity surfaces to our data-based analysis in order to reveal the intrinsic invariance of the evolutionary processes. We used the average mechanical energy of the particle cloud to check the connection between contact property and the temporal-spatial distribution of the shed particles. We sketch a common evolutionary path of the particle in the vicinity of a fast-rotating asteroid, that is, particles dislodged from the unstable region will eventually enter, through several collisions with the surface, non-return orbits that launch from the minimum geopotential area of the unstable region. The common trend is independent of any particular asteroid morphology, and all shed particles enter the same evolutionary path. We also find that the orbital energy of the particle cloud is statistically independent of the surface contact property, meaning that the collision coefficient of restitution is a nonsensitive parameter in the outward spreading process of the shed particles.

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Z. Song, Y. Yu, B. Cheng, et. al.
Tue, 4 Apr 23
94/111

Comments: Accepted for publication in A&A

The Kepler Giant Planet Search. I: A Decade of Kepler Planet Host Radial Velocities from W. M. Keck Observatory [EPA]

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http://arxiv.org/abs/2304.00071


Despite the importance of Jupiter and Saturn to Earth’s formation and habitability, there has not yet been a comprehensive observational study of how giant exoplanets correlate with the architectural properties of close-in, sub-Neptune sized exoplanets. This is largely because transit surveys are particularly insensitive to planets at orbital separations > 1 AU, and so their census of Jupiter-like planets is incomplete, inhibiting our study of the relationship between Jupiter-like planets and the small planets that do transit. To establish the relationship between small and giant planets, we conducted the Kepler Giant Planet Survey (KGPS). Using W. M. Keck Observatory HIRES, we spent over a decade collecting 2858 RVs (2181 of which are presented here for the first time) of 63 sun-like stars that host 157 transiting planets. We had no prior knowledge of which systems would contain giant planets beyond 1 AU, making this survey unbiased in detected Jovians. In this paper, we announce RV-detected companions to 20 stars from our sample. These include 13 Jovians (0.3 MJ < M sin i < 13 MJ, 1 < a < 10 AU), 7 non-transiting sub-Saturns, and 3 stellar-mass companions. We also present updated masses and densities of 84 transiting planets. The KGPS project leverages the longest-running and most data-rich collection of RVs of the NASA Kepler systems yet, and will provide a basis for addressing whether giant planets help or hinder the growth of sub-Neptune sized and terrestrial planets. Future KGPS papers will examine the relationship between small, transiting planets and their companions.

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L. Weiss, H. Isaacson, G. Marcy, et. al.
Tue, 4 Apr 23
97/111

Comments: 118 pages, 69 figures, submitted to ApJS. Machine-readable versions of Tables 3 and 4 are hosted at www.astroweiss.com/Publications

Features of Gaia DR3 Spectroscopic Binaries I. Tidal circularization of Main-Sequence Stars [SSA]

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http://arxiv.org/abs/2304.00043


Previous studies pointed out that many observed samples of short-period binaries display a cutoff period, $P_{\rm cut}$, such that almost all binaries with periods shorter than $P_{\rm cut}$ have circular orbits. This feature is probably due to long-term circularization processes induced by tidal interaction between the two stars of each binary. It seemed as if coeval main-sequence (MS) samples of open clusters display $P_{\rm cut}$ that depends on the sample age. Using the unprecedentedly large sample of MS spectroscopic orbits recently released by $\textit{Gaia}$ we have found that the $P_{\rm cut}$ does not depend on the stellar age but, instead, varies with stellar temperature, decreasing linearly from $6.5$ day at $T_{\rm eff}\sim 5700$ K to $\sim 2.5$ day at $6800$ K. $P_{\rm cut}$ was derived by a new algorithm that relied on clear upper envelopes displayed in the period-eccentricity diagrams. Our $P_{\rm cut}$ determines both the border between the circular and eccentric binaries and the location of the upper envelope. The results are inconsistent with the theory which assumes circularization occurs during the stellar MS phase, a theory that was adopted by many studies. The circularization has probably taken place at the pre-main-sequence phase, as suggested already in 1989 by Zahn and Bouchet, and later by Khaluillin and Khaluillina in 2011. Our results suggest that the weak dependence of $P_{\rm cut}$ on the cluster age is not significant, and/or might be due to the different temperatures of the samples. If indeed true, this has far-reaching implications for the theory of binary and exoplanet circularization, synchronization, and alignment.

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D. Bashi, T. Mazeh and S. Faigler
Tue, 4 Apr 23
106/111

Comments: 13 pages, 12 figures, 2 tables. Accepted for publication in MNRAS

Laboratory Study of Antenna Signals Generated by Dust Impacts on Spacecraft [CL]

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http://arxiv.org/abs/2304.00453


Space missions often carry antenna instruments that are sensitive to dust impacts, however, the understanding of signal generation mechanisms remained incomplete. A signal generation model in an analytical form is presented that provides a good agreement with laboratory measurements. The model is based on the direct and induced charging of the spacecraft from the collected and escaping fraction of free charges from the impact-generated plasma cloud. A set of laboratory experiments is performed using a 20:1 scaled-down model of the Cassini spacecraft in a dust accelerator facility. The results show that impact plasmas can be modeled as a plume of ions streaming away from the impact location and a cloud of isotropically expanding electrons. The fitting of the model to the collected antenna waveforms provides some of the key parameters of the impact plasma. The model also shows that the amplitudes of the impact signals can be significantly reduced in typical space environments due to the discharging effects in the ambient plasma.

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M. Shen, Z. Sternovsky, M. Horányi, et. al.
Tue, 4 Apr 23
107/111

Comments: Manuscript accepted online by JGR: Space Physics on 05 April 2021

Variability of Antenna Signals From Dust Impacts [CL]

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http://arxiv.org/abs/2304.00454


Electric field instruments carried by spacecraft (SC) are complementary to dedicated dust detectors by registering transient voltage perturbations caused by impact-generated plasma. The signal waveform contains information about the interaction between the impact-generated plasma cloud and the elements of SC-antenna system. The variability of antenna signals from dust impacts has not yet been systematically characterized. A set of laboratory measurements are performed to characterize signal variations in response to SC parameters (bias voltage and antenna configuration) and impactor parameters (impact speed and composition). The measurements demonstrate that dipole antenna configurations are sensitive to dust impacts and that the detected signals vary with impact location. When dust impacts occur at low speeds, the antennas typically register smaller amplitudes and less characteristic impact signal shapes. In this case, impact event identification may be more challenging due to lower signal-to-noise ratios and/or more variable waveforms shapes, indicating the compound nature of nonfully developed impact-generated plasmas. To investigate possible variations in the impacting materials, the measurements are carried out using two dust samples with different mass densities: iron and aluminum. No significant variations of the measured waveform or plasma parameters obtained from data analysis are observed between the two materials used.

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M. Shen, Z. Sternovsky and D. Malaspina
Tue, 4 Apr 23
110/111

Comments: Manuscript accepted online by JGR: Space Physics on 22 March 2023

Early Bombardment of the Moon: Connecting the Lunar Crater Record to the Terrestrial Planet Formation [EPA]

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http://arxiv.org/abs/2303.17736


The lunar crater record features $\sim 50$ basins. The radiometric dating of Apollo samples indicates that the Imbrium basin formed relatively late — from the planet formation perspective — some $\simeq 3.9$ Ga. Here we develop a dynamical model for impactors in the inner solar system to provide context for the interpretation of the lunar crater record. The contribution of cometary impactors is found to be insignificant. Asteroids produced most large impacts on the terrestrial worlds in the last $\simeq 3$ Gyr. The great majority of early impactors were rocky planetesimals left behind at $\sim 0.5$–1.5 au after the terrestrial planet accretion. The population of terrestrial planetesimals was reduced by disruptive collisions in the first $t \sim 20$ Myr after the gas disk dispersal. We estimate that there were $\sim 4 \times 10^5$ diameter $d>10$ km bodies when the Moon formed (total planetesimal mass $\sim 0.015$ $M_{\rm Earth}$ at $t \sim 50$ Myr). The early bombardment of the Moon was intense. To accommodate $\sim 50$ known basins, the lunar basins that formed before $\simeq 4.35$–4.41 Ga must have been erased. The late formation of Imbrium occurs with a $\sim 15$–35\% probability in our model. About 20 $d>10$-km bodies were expected to hit the Earth between 2.5 and 3.5 Ga, which is comparable to the number of known spherule beds in the late Archean. We discuss implications of our model for the lunar/Martian crater chronologies, Late Veneer, and noble gases in the Earth atmosphere.

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D. Nesvorny, F. Roig, D. Vokrouhlicky, et. al.
Mon, 3 Apr 23
5/53

Comments: Icarus, in press

Planet formation in the PDS 70 system: Constraining the atmospheric chemistry of PDS 70b and c [EPA]

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http://arxiv.org/abs/2303.17899


Understanding the chemical link between protoplanetary disks and planetary atmospheres is complicated by the fact that the popular targets in the study of disks and planets are widely separated both in space and time. The 5 Myr PDS 70 systems offers a unique opportunity to directly compare the chemistry of a giant planet’s atmosphere to the chemistry of its natal disk. To that end, we derive our current best physical and chemical model for the PDS 70 disk through forward modelling of the $^{12}$CO, C$^{18}$O, and C$_2$H emission radial profiles with the thermochemical code DALI and find a volatile C/O ratio above unity in the outer disk. Using what we know of the PDS 70 disk today, we analytically estimate the properties of the disk as it was 4 Myr in the past when we assume that the giant planets started their formation, and compute a chemical model of the disk at that time. We compute the formation of PDS 70b and PDS 70c using the standard core accretion paradigm and account for the accretion of volatile and refractory sources of carbon and oxygen to estimate the resulting atmospheric carbon-to-oxygen number ratio (C/O) for these planets. Our inferred C/O ratio of the gas in the PDS 70 disk indicates that it is marginally carbon rich relative to the stellar C/O = 0.44 which we derive from an empirical relation between stellar metallicity and C/O. Under the assumption that the disk has been carbon rich for most of its lifetime, we find that the planets acquire a super-stellar C/O in their atmospheres. If the carbon-rich disk is a relatively recent phenomenon (i.e. developed after the formation of the planets at $\sim 1$ Myr) then the planets should have close to the stellar C/O in their atmospheres. This work lays the groundwork to better understand the disk in the PDS 70 system as well as the planet formation scenario that produce its planets.

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A. Cridland, S. Facchini, E. Dishoeck, et. al.
Mon, 3 Apr 23
11/53

Comments: 18 pages, 14 figures, 5 tables, accepted for publication in A&A

Nuggets of Wisdom: Determining an Upper Limit on the Number Density of Chickens in the Universe [EPA]

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http://arxiv.org/abs/2303.17626


The lower limit on the chicken density function (CDF) of the observable Universe was recently determined to be approximately 10$^{-21}$ chickens pc$^{-3}$. For over a year, however, the scientific community has struggled to determine the upper limit to the CDF. Here we aim to determine a reasonable upper limit to the CDF using multiple observational constraints. We take a holistic approach to considering the effects of a high CDF in various domains, including the Solar System, interstellar medium, and effects on the cosmic microwave background. We find the most restrictive upper limit from the domains considered to be 10$^{23}$ pc$^{-3}$, which ruffles the feathers of long-standing astrophysics theory.

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R. Losacco and Z. Claytor
Mon, 3 Apr 23
12/53

Comments: 5 pages, 1 figure, 1 table, 0 chickens were harmed

Sodium Brightening of (3200) Phaethon Near Perihelion [EPA]

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http://arxiv.org/abs/2303.17625


Sunskirting asteroid (3200) Phaethon has been repeatedly observed in STEREO HI1 imagery to anomalously brighten and produce an antisunward tail for a few days near each perihelion passage, phenomena previously attributed to the ejection of micron-sized dust grains. Color imaging by the SOHO LASCO coronagraphs during the 2022 May apparition indicate that the observed brightening and tail development instead capture the release of sodium atoms, which resonantly fluoresce at the 589.0/589.6 nm D lines. While HI1’s design bandpass nominally excludes the D lines, filter degradation has substantially increased its D line sensitivity, as quantified by the brightness of Mercury’s sodium tail in HI1 imagery. Furthermore, the expected fluorescence efficiency and acceleration of sodium atoms under solar radiation readily reproduce both the photometric and morphological behaviors observed by LASCO and HI1 during the 2022 apparition and the 17 earlier apparitions since 1997. This finding connects Phaethon to the broader population of sunskirting and sungrazing comets observed by SOHO, which often also exhibit bright sodium emission with minimal visible dust, but distinguishes it from other sunskirting asteroids without detectable sodium production under comparable solar heating. These differences may reflect variations in the degree of sodium depletion of near-surface material, and thus the extent and/or timing of any past or present resurfacing activity.

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Q. Zhang, K. Battams, Q. Ye, et. al.
Mon, 3 Apr 23
21/53

Comments: 30 pages, 14 figures, 6 tables; PSJ, in press

Volatile-to-sulfur Ratios Can Recover a Gas Giant's Accretion History [EPA]

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http://arxiv.org/abs/2303.17622


The newfound ability to detect SO2 in exoplanet atmospheres presents an opportunity to measure sulfur abundances and so directly test between competing modes of planet formation. In contrast to carbon and oxygen, whose dominant molecules are frequently observed, sulfur is much less volatile and resides almost exclusively in solid form in protoplanetary disks. This dichotomy leads different models of planet formation to predict different compositions of gas giant planets. Whereas planetesimal-based models predict roughly stellar C/S and O/S ratios, pebble accretion models more often predict superstellar ratios. To explore the detectability of SO2 in transmission spectra and its ability to diagnose planet formation, we present a grid of atmospheric photochemical models and corresponding synthetic spectra for WASP-39b (where SO2 has been detected). Our 3D grid contains 11^3 models (spanning 1–100x the solar abundance ratio of C, O, and S) for thermal profiles corresponding to the morning and evening terminators, as well as mean terminator transmission spectra. Our models show that for a WASP-39b-like O/H and C/H enhancement of ~10x Solar, SO2 can only be seen for C/S and O/S <~1.5, and that WASP-39b’s reported SO2 abundance of 1–10 ppm may be more consistent with planetesimal accretion than with pebble accretion models (although some pebble models also manage to predict similarly low ratios). More extreme C/S and O/S ratios may be detectable in higher-metallicity atmospheres, suggesting that smaller and more metal-rich gas and ice giants may be particularly interesting targets for testing planet formation models. Future studies should explore the dependence of SO2 on a wider array of planetary and stellar parameters, both for the prototypical SO2 planet WASP-39b, as well as for other hot Jupiters and smaller gas giants.

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I. Crossfield
Mon, 3 Apr 23
25/53

Comments: 9 pages, 6 figures, 1 table, and 1331 models and spectra at this https URL Submitted to ApJL

MO0NFALL: The Great Filter and Exo-Moon Occurrence [EPA]

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http://arxiv.org/abs/2303.18227


We observe neither life beyond Earth, nor moons around exoplanets, despite the prevalence of Earth-like planets across the galaxy. We suggest Moonfall as a possible mechanism to explain both simultaneously.

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C. Brinkman, K. Gootkin, R. Lee, et. al.
Mon, 3 Apr 23
28/53

Comments: N/A

A Unified Nomenclature and Taxonomy for Planets, Stars, and Moons [EPA]

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http://arxiv.org/abs/2303.18217


I solve the problem of nomenclature of planets, stars, and moons, and in doing so repair two of the IAU’s blunders. Drawing and improving upon foundational work by Chen & Kipping, I describe a single, physics-based taxonomy that christens all objects in hydrostatic equilibrium as “stars,” a category that contains several subcategories based on the relevant pressure terms in the equation of state. I also acknowledge dynamical considerations, which allow me to describe a single designation scheme for all “stars” following the Washington Multiplicity Catalog convention. Under this unified scheme, what we used to call “Planet Earth” is now the moon rock “star” Sun Da.

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J. Wright
Mon, 3 Apr 23
37/53

Comments: 5 pages, 2 figures, 5 sections (1 of them is boring)

Party Planning the Next True Happy New Year: Lunar Orbital Evolution Epochs with Integer Synodic Months Per Year [EPA]

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http://arxiv.org/abs/2303.17697


Humans like to party, and New Year celebrations are a great way to do that. However New Years celebrations that rely on an orbital year don’t line up with those that use a Lunar Calendar, as there are currently 12.368 synodic months (moonths) in a year. There is cyclostratigraphic, paleontological, and tidal rhythmite data that reveal that over billions of years the interplay of angular momentum between the Sun, Earth and Moon has changed the rate of rotation of Earth, and at the same time evolved the orbit of the Moon, and therefore the length of a Lunar month. Using a subset of this data and referencing literature models of the Moon’s orbital evolution, we create our own simple model to determine “True Happy New Years”, time periods when there were an integer number of lunar synodic months in an Earth orbital year. This would allow modern calendars to pick a shared New Year’s Day, and party accordingly. We then predict the next True Happy New Year to be in 252 million years, and offer suggestions to begin the party planning process early, so that we as a planet may be ready.

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M. Popinchalk
Mon, 3 Apr 23
38/53

Comments: 5 pages, 1 figure, submitted for 4/1/2023

Eccentricity Growth of Massive Planets inside Cavities of Protoplanetary Discs [EPA]

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http://arxiv.org/abs/2303.17784


We carry out hydrodynamical simulations to study the eccentricity growth of a 1-30 Jupiter mass planet located inside the fixed cavity of a protoplanetary disc. The planet exchanges energy and angular momentum with the disc at resonant locations, and its eccentricity grows due to Lindblad resonances. We observe several phases of eccentricity growth where different eccentric Lindblad resonances dominate from 1:3 up to 3:5. The maximum values of eccentricity reached in our simulations are 0.65-0.75. We calculate the eccentricity growth rate for different planet masses and disc parameters and derive analytical dependencies on these parameters. We observe that the growth rate is proportional to both the planet’s mass and the characteristic disc mass for a wide range of parameters. In a separate set of simulations, we derived the width of the 1:3 Lindblad resonance.

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M. Romanova, A. Koldoba, G. Ustyugova, et. al.
Mon, 3 Apr 23
42/53

Comments: 19 pages, 18 figures, accepted by MNRAS

Modeling meteorite craters by impacting melted tin on sand [EPA]

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http://arxiv.org/abs/2303.18016


To simulate the heated exterior of a meteorite, we impact a granular bed with melted tin. The morphology of tin remnant and crater is found to be sensitive to the temperature and solidification of tin. By employing deep learning and convolutional neural network, we can quantify and map the complex impact patterns onto network systems based on feature maps and Grad-CAM results. This gives us unprecedented details on how the projectile deforms and interacts with the granules, which information can be used to trace the development of different remnant shapes. Furthermore, full dynamics of granular system is revealed by the use of Particle Image Velocimetry. Kinetic energy, temperature and diameter of the projectile are used to build phase diagrams for the morphology of both crater and tin remnant. In addition to successfully reproducing key features of simple and complex craters, we are able to detect a possible artifact when compiling crater data from field studies. The depth of craters from high-energy impacts in our work is found to be independent of their width. However, when mixing data from different energy, temperature and diameter of projectile, a bogus power-law relationship appears between them. Like other controlled laboratory researches, our conclusions have the potential to benefit the study of paint in industry and asteroid sampling missions on the surface of celestial bodies.

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H. Huang, P. Tsai, C. Lu, et. al.
Mon, 3 Apr 23
44/53

Comments: 6 pages, 5 figures

Interstellar Objects and Exocomets [EPA]

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http://arxiv.org/abs/2303.17980


In this chapter we review our knowledge of our galaxy’s cometary population outside our Oort Cloud – exocomets and Interstellar Objects (ISOs). We start with a brief overview of planetary system formation, viewed as a general process around stars. We then take a more detailed look at the creation and structure of exocometary belts, as revealed by the unprecedented combination of theoretical and observational advances in recent years. The existence and characteristics of individual exocomets orbiting other stars is summarized, before looking at the mechanisms by which they may be ejected into interstellar space. The discovery of the first two ISOs is then described, along with the surprising differences in their observed characteristics. We end by looking ahead to what advances may take place in the next decade.

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A. Fitzsimmons, K. Meech, L. Matrà, et. al.
Mon, 3 Apr 23
51/53

Comments: 39 pages, 12 figures. Review chapter to appear in ‘Comets III’ book

Stirred but not shaken: a multi-wavelength view of HD 16743's debris disc [EPA]

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http://arxiv.org/abs/2303.17128


Planetesimals — asteroids and comets — are the building blocks of planets in protoplanetary discs and the source of dust, ice and gas in debris discs. Along with planets they comprise the left-over material after star formation that constitutes a planetary system. Planets influence the dynamics of planetesimals, sculpting the orbits of debris belts to produce asymmetries or gaps. We can constrain the architecture of planetary systems, and infer the presence of unseen planetary companions, by high spatial resolution imaging of debris discs. HD~16743 is a relatively young F-type star that hosts a bright edge-on debris disc. Based on far-infrared \textit{Herschel} observations its disc was thought to be stirred by a planetary companion. Here we present the first spatially resolved observations at near-infrared and millimetre wavelengths with \textit{HST} and ALMA, revealing the disc to be highly inclined at $87\fdg3~^{+1\fdg9}{-2\fdg5}$ with a radial extent of 157.7$^{+2.6}{-1.5}$~au and a FWHM of 79.4$^{+8.1}{-7.8}$~au ($\Delta R/R = 0.5$). The vertical scale height of the disc is $0.13~\pm~0.02$, significantly greater than typically assumed unstirred value of 0.05, and could be indicative of stirring of the dust-producing planetesimals within the disc by bodies at least a few times the mass of Pluto up to 18.3~$M{\oplus}$ in the single object limit.

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J. Marshall, J. Milli, E. Choquet, et. al.
Fri, 31 Mar 23
5/70

Comments: 12 pages, 7 figures, 4 tables, accepted for publication in MNRAS

Multi-wavelength aperture polarimetry of debris disc host stars [EPA]

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http://arxiv.org/abs/2303.17179


Debris discs around main sequence stars have been extensively characterised from infrared to millimetre wavelengths through imaging, spectroscopic, and total intensity (scattered light and/or thermal emission) measurements. Polarimetric observations have only been used sparingly to interpret the composition, structure, and size of dust grains in these discs. Here we present new multi-wavelength aperture polarisation observations with parts-per-million sensitivity of a sample of twelve bright debris discs, spanning a broad range of host star spectral types, and disc properties. These measurements were mostly taken with the HIgh Precision Polarimetric Instrument on the Anglo-Australian Telescope. We combine these polarisation observations with the known disc architectures and geometries of the discs to interpret the measurements. We detect significant polarisation attributable to circumstellar dust from HD 377 and HD 39060, and find tentative evidence for HD 188228 and HD 202628.

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J. Marshall, D. Cotton, K. Bott, et. al.
Fri, 31 Mar 23
7/70

Comments: 25 pages, 8 figures, 9 tables, accepted for publication in MNRAS

A re-investigation of debris disc halos [EPA]

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http://arxiv.org/abs/2303.17434


A significant fraction of debris discs consist of a bright ring beyond which extends a wide halo. Such a halo should be made of small grains produced in the ring of parent bodies (PB) and pushed on high-e orbits by radiation pressure. It has been shown that, under several simplifying assumptions, the surface brightness (SB) of this halo should radially decrease as $r^{-3.5}$ in scattered light. We aim to revisit the halo phenomenon and focus on two so far unexplored issues: 1) How the unavoidable presence of small unbound grains, non-isotropic scattering phase functions (SPF) and finite instrument resolution affect scattered light SB profiles, and 2) How the halo phenomenon manifests itself at longer wavelengths. We find that unbound grains account for a significant fraction of the halo’s luminosity in scattered light, and can significantly flatten the SB radial profile. Realistic size-dependent SPFs also have an effect, resulting here again in shallower SB profiles. For edge-on discs, non-resolving the vertical profile can also flatten the projected SB. We show that roughly half of the observationally-derived halo profiles found in the literature are compatible with our new results, and that roughly half of the remaining systems are probably shaped by additional processes. We also propose that, in future observational studies, the characteristics of PB belt and halos should be fitted separately. In thermal emission, wide halos should remain detectable up to the far-IR and, with the exception of the $\sim 8-15\mu$m domain, the halo accounts for more than half of the system’s total flux up to $\lambda\sim80-90\mu$m. The halo’s contribution strongly decreases in the sub-mm to mm but still represents a few percents of the system’s luminosity at $\lambda\sim 1$mm. For unresolved systems, the presence of a halo can also affect the determination of the disc’s radius from its SED.

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P. Thebault, J. Olofsson and Q. Kral
Fri, 31 Mar 23
9/70

Comments: accepted for publication in A&A (abstract significantly shortened to comply with arxiv limits)

A Modest Proposal for the Non-existence of Exoplanets: The Expansion of Stellar Physics to Include Squars [EPA]

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http://arxiv.org/abs/2303.16915


The search for exoplanets has become a focal point of astronomical research, captivating public attention and driving scientific inquiry; however, the rush to confirm exoplanet discoveries has often overlooked potential alternative explanations leading to a scientific consensus that is overly reliant on untested assumptions and limited data. We argue that the evidence in support of exoplanet observation is not necessarily definitive and that alternative interpretations are not only possible, but necessary. Our conclusion is therefore concise: exoplanets do not exist. Here, we present the framework for a novel type of cuboid star, or squar, which can precisely reproduce the full range of observed phenomena in stellar light curves, including the trapezoidal flux deviations (TFDs) often attributed to “exoplanets.” In this discovery paper, we illustrate the power of the squellar model, showing that the light curve of the well-studied “exoplanet” WASP-12b can be reconstructed simply from a rotating squar with proportions $1:1/8:1$, without invoking ad-hoc planetary bodies. Our findings cast serious doubt on the validity of current “exoplanetary” efforts, which have largely ignored the potential role of squars and have instead blindly accepted the exoplanet hypothesis without sufficient critical scrutiny. In addition, we discuss the sociopolitical role of climate change in spurring the current exoplanet fervor which has lead to the speculative state of “exoplanetary science” today. We strongly urge the astronomical community to take our model proposal seriously and treat its severe ramifications with the utmost urgency to restore rationality to the field of astronomy.

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C. Woodrum, R. Hviding, R. Amaro, et. al.
Fri, 31 Mar 23
16/70

Comments: 7 pages, 4 figures, publication pending litigation. For all intents and purposes this manuscript is dated April 1st, 2023

On The Planetary Theory of Everything [EPA]

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http://arxiv.org/abs/2303.17035


Here, we present a simple solution to problems that have plagued (extra)”galactic” astronomers and cosmologists over the last century. We show that “galaxy” formation, dark matter, and the tension in the expansion of the universe can all be explained by the natural behaviors of an overwhelmingly large population of exoplanets throughout the universe. Some of these ideas have started to be proposed in the literature, and we commend these pioneers revolutionizing our understanding of astrophysics. Furthermore, we assert that, since planets are obviously the ubiquitous answer to every current question that can be posed by astronomers, planetary science must then be the basis for all science, and therefore that all current funding for science be reserved for (exo)planetary science – we happily welcome all astronomers and other scientists.

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J. Jr., M. M.M.M., J. Dietrich, et. al.
Fri, 31 Mar 23
27/70

Comments: 7 pages, 4 figures, accepted to Acta Prima Aprila

JWST/NIRCam discovery of the first Y+Y brown dwarf binary: WISE J033605.05$-$014350.4 [SSA]

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http://arxiv.org/abs/2303.16923


We report the discovery of the first brown dwarf binary system with a Y dwarf primary, WISE J033605.05$-$014350.4, observed with NIRCam on JWST with the F150W and F480M filters. We employed an empirical point spread function binary model to identify the companion, located at a projected separation of 84 milliarcseconds, position angle of 295 degrees, and with contrast of 2.8 and 1.8 magnitudes in F150W and F480M, respectively. At a distance of 10$\,$pc based on its Spitzer parallax, and assuming a random inclination distribution, the physical separation is approximately 1$\,$au. Evolutionary models predict for that an age of 1-5 Gyr, the companion mass is about 4-12.5 Jupiter masses around the 7.5-20 Jupiter mass primary, corresponding to a companion-to-host mass fraction of $q=0.61\pm0.05$. Under the assumption of a Keplerian orbit the period for this extreme binary is in the range of 5-9 years. The system joins a small but growing sample of ultracool dwarf binaries with effective temperatures of a few hundreds of Kelvin. Brown dwarf binaries lie at the nexus of importance for understanding the formation mechanisms of these elusive objects, as they allow us to investigate whether the companions formed as stars or as planets in a disk around the primary.

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P. Calissendorff, M. Furio, M. Meyer, et. al.
Fri, 31 Mar 23
34/70

Comments: 8 pages, 3 figures, 1 table. Accepted for publication in Astrophysical Journal Letters

uGMRT observations of the hot-Saturn WASP 69b: Radio-Loud Exoplanet-Exomoon Survey II (RLEES II) [EPA]

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http://arxiv.org/abs/2303.17269


Exomoons have so far eluded ongoing searches. Several studies have exploited transit and transit timing variations and high-resolution spectroscopy to identify potential exomoon candidates. One method of detecting and confirming these exomoons is to search for signals of planet-moon interactions. In this work, we present the first radio observations of the exomoon candidate system WASP 69b. Based on the detection of alkali metals in the transmission spectra of WASP-69b, it was deduced that the system might be hosting an exomoon. WASP 69b is also one of the exoplanet systems that will be observed as part of JWST cycle-1 GTO. This makes the system an excellent target to observe and follow up. We observed the system for 32 hrs at 150 MHz and 218 MHz using the upgraded Giant Metrewave Radio Telescope (uGMRT). Though we do not detect radio emission from the systems, we place strong $3\sigma$ upper limits of 3.3 mJy at 150 MHz and 0.9 mJy at 218 MHz. We then use these upper limits to estimate the maximum mass loss from the exomoon candidate.

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M. Narang, A. Oza, K. Hakim, et. al.
Fri, 31 Mar 23
35/70

Comments: Accepted in MNRAS, 8 pages, 4 Figures

Surface Composition of Pluto's Kiladze Area and Relationship to Cryovolcanism [EPA]

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http://arxiv.org/abs/2303.17072


A link between exposures of water (H${}{2}$O) ice with traces of an ammoniated compound (e.g., a salt) and the probable effusion of a water-rich cryolava onto the surface of Pluto has been established in previous investigations (Dalle Ore et al. 2019). Here we present the results from the application of a machine learning technique and a radiative transfer model to a water-ice-rich exposure in Kiladze area and surroundings on Pluto. We demonstrate the presence of an ammoniated material suggestive of an undetermined but relatively recent emplacement event. Kiladze lies in a region of Pluto’s surface that is structurally distinct from that of the areas where similar evidence points to cryovolcanic activity at some undetermined time in the planet’s history. Although the Kiladze depression superficially resembles an impact crater, a close inspection of higher-resolution images indicates that the feature lacks the typical morphology of a crater. Here we suggest that a cryolava water carrying an ammoniated component may have come onto the surface at the Kiladze area via one or more volcanic collapses, as in a resurgent volcanic caldera complex. Large regions east of Kiladze also exhibit the presence of H${}{2}$O ice and have graben-like structures suggestive of cryovolcanic activity, but with existing data are not amenable to the detailed search that might reveal an ammoniated component.

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A. Emran, C. Ore, D. Cruikshank, et. al.
Fri, 31 Mar 23
37/70

Comments: 28 pages, 11 figures, submitted to Icarus

Correlation between activity indicators: H$α$ and Ca II lines in M-dwarf stars [SSA]

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http://arxiv.org/abs/2303.17237


Different approaches have been adopted to study short- and long-term stellar magnetic activity, and although the mechanisms by which low-mass stars generate large-scale magnetic fields are not well understood, it is known that stellar rotation plays a key role. There are stars that show a cyclical behaviour in their activity which can be explained by solar dynamo or $\alpha\Omega$ dynamo models. However, when studying late-type dwarf stars, it is necessary to implement other indicators to analyse their magnetic activity. In the present work, we perform a comparative study between the best-known activity indicators so far defined from the Ca II and H$\alpha$ lines to analyse M-dwarf stars. We studied a sample of 29 M stars with different chromospheric activity levels and spectral classes ranging from dM0 to dM6. To do so, we employed 1796 wide range spectra from different instruments with a median time span of observations of 21 yr. In addition, we complemented our data with photometric observations from the TESS space mission for better stellar characterisation and short-term analysis. We obtained a good and significant correlation ($rho = 0.91$) between the indexes defined from the two lines for the whole set of stars in the sample. However, we found that there is a deviation for faster rotators (with $P_{rot} < 4$ days) and higher flare activity (at least one flare per day). There is an overall positive correlation between Ca II and H$\alpha$ emission in dM stars, except during flare events. In particular, we found that low-energy high-frequency flares could be responsible for the deviation in the linear trend in fast-rotator M dwarfs. This implies that the rotation period could be a fundamental parameter to study the stellar activity and that the rotation could drive the magnetic dynamo in low-mass active stars.

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R. Bustos, A. Buccino, M. Flores, et. al.
Fri, 31 Mar 23
46/70

Comments: N/A

A novel survey for young substellar objects with the W-band filter VI: Spectroscopic census of sub-stellar members and the IMF of $σ$ Orionis cluster [SSA]

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http://arxiv.org/abs/2303.17424


Low-mass stars and sub-stellar objects are essential in tracing the initial mass function (IMF). We study the nearby young $\sigma$ Orionis cluster (d$\sim$408 pc; age$\sim$1.8 Myr) using deep NIR photometric data in J, W and H-bands from WIRCam on the Canada-France-Hawaii Telescope. We use the water absorption feature to photometrically select the brown dwarfs and confirm their nature spectroscopically with the IRTF-SpeX. Additionally we select candidate low-mass stars for spectroscopy and analyze their membership and that of literature sources using astrometry from Gaia DR3. We obtain the near-IR spectra for 28 very low-mass stars and brown dwarfs and estimate their spectral type between M3-M8.5 (mass ranging between 0.3-0.01 M${\odot}$). Apart from these, we also identify 5 new planetary mass candidates which require further spectroscopic confirmation of youth. We compile the comprehensive catalog of 170 spectroscopically confirmed members in the central region of the cluster, for a wide mass range of $\sim$19-0.004 M${\odot}$. We estimate the star/BD ratio to be $\sim$4, within the range reported for other nearby star forming regions. With the updated catalog of members we trace the IMF down to 4 M$_\mathrm{Jup}$ and we find that a two-segment power-law fits the sub-stellar IMF better than the log-normal distribution.

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B. Damian, J. Jose, B. Biller, et. al.
Fri, 31 Mar 23
52/70

Comments: Accepted for publication in The Astrophysical Journal (ApJ). 27 pages, 9 figures, 2 tables

Planetary seismology as a test of modified gravity proposals [CL]

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http://arxiv.org/abs/2303.17213


We demonstrate that it is possible to test models of gravity, such as Palatini $f(R)$ and Eddington-inspired Born-Infeld models, using seismic data from Earth. By incorporating additional limitations on Earth’s moment of inertia and mass given from observational data, the models’ parameters can be restricted to a $2\sigma$ level of accuracy. Our novel tool provides that $\beta\lesssim 10^9 \text{m}^2$ for Palatini and $\epsilon\lesssim 4\cdot 10^9 \text{m}^2$ for Eddington-inspired Born-Infeld gravity. We also discuss further enhancements to the proposed method, aimed at imposing even more stringent constraints on modified gravity proposals.

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A. Kozak and A. Wojnar
Fri, 31 Mar 23
67/70

Comments: 10 pages, 3 figures

UFOs: Just Hot Air or Something Meteor? [CL]

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http://arxiv.org/abs/2303.17103


For much of February 2023, the world was in panic as repeated balloon-like unidentified flying objects (UFOs) were reported over numerous countries by governments that often responded with military action. As a result, most of these craft either escaped or were destroyed, making any further observation of them nearly impossible. These were not the first time balloon-like objects have loomed over Earth, nor are they likely to be the last. This has prompted us to push for a better understanding of UFOs. First we demonstrate that the distribution of balloon incidents and other UFO reports are consistent with being drawn from the same geographic distribution, and further that both of these distributions are consistent with the areas of the Earth that feature the jet stream. Second we show that there are more UFO sightings during meteor showers, as we would expect if meteor showers, already a known source of extraterrestrial material, are being used to provide some manner of distraction to help alien craft enter the Earth’s atmosphere without drawing undue attention. These links between alleged balloon incidents, UFO reports, and meteor showers establish a transport pipeline for alien craft from interplanetary and possibly interstellar space to the Earth’s surface.

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M. Lund
Fri, 31 Mar 23
68/70

Comments: 9 pages, 4 figures, 2 tables, submission for Saturday’s Acta Prima Aprilia

Disk or Companion: Characterizing Excess Infrared Flux in Seven White Dwarf Systems with Near-Infrared Spectroscopy [SSA]

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http://arxiv.org/abs/2303.16330


Excess infrared flux from white dwarf stars is likely to arise from a dusty debris disk or a cool companion. In this work, we present near-infrared spectroscopic observations with Keck/MOSFIRE, Gemini/GNIRS, and Gemini/Flamingos-2 of seven white dwarfs with infrared excesses identified in previous studies. We confirmed the presence of dust disks around four white dwarfs (Gaia J0611-6931, Gaia J0006+2858, Gaia J2100+2122, and WD 0145+234) as well as two new white dwarf brown dwarf pairs (Gaia J0052+4505 and Gaia J0603+4518). In three of the dust disk systems, we detected for the first time near-infrared metal emissions (Mg I, Fe I, and Si I) from a gaseous component of the disk. We developed a new Markov Chain Monte Carlo framework to constrain the geometric properties of each dust disk. In three systems, the dust disk and the gas disk appear to coincide spatially. For the two brown dwarf white dwarf pairs, we identified broad molecular absorption features typically seen in L dwarfs. The origin of the infrared excess around Gaia J0723+6301 remains a mystery. Our study underlines how near-infrared spectroscopy can be used to determine sources of infrared excess around white dwarfs, which has now been detected in hundreds of systems photometrically.

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D. Owens, S. Xu, E. Manjavacas, et. al.
Thu, 30 Mar 23
4/66

Comments: 23 pages, 10 figures, 5 tables, AJ, in press

Thermoelastic properties and thermal evolution of the Martian core from ab initio calculated ferromagnetic Fe-S liquid [EPA]

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http://arxiv.org/abs/2303.16542


The accurate thermoelastic properties and thermal conductivity are crucial in understanding the thermal evolution of the Martian core. A fitting method based on the ab initio calculated pressure-volume-temperature data is proposed in the formulation of the equation of state with high accuracy, by which the pressure and temperature dependent thermoelastic properties can be directly calculated by definitions. The ab initio results show that the liquid Fe0.75S0.25 under Martian core condition is thoroughly in the ferromagnetic state, without existing spin crossover. The liquid Fe0.75S0.25 in magnetic calculation owns a low thermal conductivity (21~23 W/m/K) when compared with non-magnetic calculation at the same state. Based on the Insight estimated and ab initio calculated properties of the Martian core, the iron snow model is verified when the current temperature at the core-mantle boundary is below the core melting temperature, and the simply secular cooling model is verified on the contrary.

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W. Li, Z. Li, Z. Ma, et. al.
Thu, 30 Mar 23
11/66

Comments: N/A

Self-consistent Models of Y Dwarf Atmospheres with Water Clouds and Disequilibrium Chemistry [EPA]

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http://arxiv.org/abs/2303.16295


Y dwarfs are the coolest spectral class of brown dwarf. They have effective temperatures less than 500 K, with the coolest detection as low as ~250 K. Their spectra are shaped predominantly by gaseous water, methane, and ammonia. At the warmer end of the Y dwarf temperature range, spectral signatures of disequilibrium carbon monoxide have been observed. Cooler Y dwarfs could host water clouds in their atmospheres. Since they make up the low-mass tail of the star formation process, and are a valuable analogue to the atmospheres of giant gaseous exoplanets in a temperature range that is difficult to observe, understanding Y dwarf atmospheric compositions and processes will both deepen our understanding of planet and star formation, and provide a stepping stone towards characterizing cool exoplanets. JWST spectral observations are anticipated to provide an unprecedented level of detail for these objects, and yet published self-consistent model grids do not accurately replicate even the existing HST and ground-based observations. In this work, we present a new suite of 1-d radiative-convective equilibrium models to aid in the characterization of Y dwarf atmospheres and spectra. We compute clear, cloudy, equilibrium-chemistry and disequilibrium-chemistry models, providing a comprehensive suite of models in support of the impending JWST era of panchromatic Y dwarf characterization. Comparing these models against current observations, we find that disequilibrium CH4-CO and NH3-N2 chemistry and the presence of water clouds can bring models and observations into better, though still not complete, agreement.

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B. Lacy and A. Burrows
Thu, 30 Mar 23
14/66

Comments: main text: 27 pages, 19 figures, 4 tables; appendix + references: 13 pages, 3 figures, 4 tables; model grid available on zenodo this https URL

The orbits of outer planetary satellites using the Gaia data [EPA]

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http://arxiv.org/abs/2303.16377


Launch of the Gaia space observatory started a new era in astrometry when the accuracy of star coordinates increased by thousands of times. Significant improvement of accuracy was also expected for the coordinates of the Solar system bodies. Gaia DR3 provided us with the data which could be used to test our expectations. In this work, we refine the orbits of a number of outer planetary satellites using both ground-based and Gaia observations. From thirteen outer satellites observed by Gaia, we chose six to obtain their orbits. Some specific moments in using observations of outer satellites made by Gaia are demonstrated. These pecularities stem from scanning motion of Gaia, in particular from the fact that the accuracy of observations is significantly different along and across the scanning direction. As expected, Gaia observations proved to be more precise than those made from Earth, which results in more accurate satellite ephemerides. We estimate accuracy of the ephemerides of considered satellites for the interval between 1996 and 2030. As astrometric positions published in Gaia DR3 were not corrected for the relativistic light deflection by the Sun, we took into account this effect, which slightly diminished the rms residuals. In addition, relativistic light deflection by the giant planets was estimated, which, as it turned out, can be neglected with the given accuracy of Gaia observations.

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N. Emelyanov, M. Kovalev and M. Varfolomeev
Thu, 30 Mar 23
19/66

Comments: accepted in MNRAS 28.03.2023, 9 pages, 8 figures

FAUST VIII. The protostellar disk of VLA 1623-2417 W and its streamers imaged by ALMA [SSA]

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http://arxiv.org/abs/2303.16257


More than 50% of solar-mass stars form in multiple systems. It is therefore crucial to investigate how multiplicity affects the star and planet formation processes at the protostellar stage. We report continuum and C$^{18}$O (2-1) observations of the VLA 1623-2417 protostellar system at 50 au angular resolution as part of the ALMA Large Program FAUST. The 1.3 mm continuum probes the disks of VLA 1623A, B, and W, and the circumbinary disk of the A1+A2 binary. The C$^{18}$O emission reveals, for the first time, the gas in the disk-envelope of VLA 1623W. We estimate the dynamical mass of VLA 1623W, $M_{\rm dyn}=0.45\pm0.08$ M${\odot}$, and the mass of its disk, $M{\rm disk}\sim6\times10^{-3}$ M$_{\odot}$. C$^{18}$O also reveals streamers that extend up to 1000 au, spatially and kinematically connecting the envelope and outflow cavities of the A1+A2+B system with the disk of VLA 1623W. The presence of the streamers, as well as the spatial ($\sim$1300 au) and velocity ($\sim$2.2 km/s) offset of VLA 1623W suggest that either sources W and A+B formed in different cores, interacting between them, or that source W has been ejected from the VLA 1623 multiple system during its formation. In the latter case, the streamers may funnel material from the envelope and cavities of VLA 1623AB onto VLA 1623W, thus concurring to set its final mass and chemical content.

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S. Mercimek, L. Podio, C. Codella, et. al.
Thu, 30 Mar 23
20/66

Comments: 10 pages, 5 figures, accepted by MNRAS

Self-gravity in thin-disc simulations of protoplanetary discs: smoothing length rectified and generalised to bi-fluids [EPA]

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http://arxiv.org/abs/2303.16213


To mimic protoplanetary discs (PPDs) evolution, 2D simulations with self-gravity must introduce a softening prescription of the gravitational potential. When the disc is only made of gas the smoothing length is proportional to the gas scale height. On the other hand when a dust component is included, the question arises as whether the smoothing length approach can still be used to quantify not only the dust self-gravity but also its gravitational interaction with gas.
We identified grey areas in the standard smoothing length formalism for computing self-gravity in PPDs uniquely made of gas. We revisit the smoothing length approach which is then generalised to two phases when the dust component can be considered as a pressureless fluid.
Analytical developments are used to approximate the vertically averaged self-gravity when the smoothing length is not assumed to be constant but rather a spatial function.
We obtained an analytical expression for the space varying smoothing length, which strongly improves the accuracy of the self-gravity computation. For the first time, this method is generalised to address bi-fluid interactions in a PPD: two additional smoothing lengths are proposed for featuring an isolated dusty disc and gas-dust self-gravity interactions. We checked that our method remains compatible with standard fast Fourier transform algorithms and evaluated computational costs.
Our space varying smoothing length permits (i) to solve the contradictions inherent to a constant smoothing length hypothesis, (ii) to fit accurately the 3D vertically averaged self-gravity and (iii) is applicable to a bi-fluid description of PPDs with the use of two additional smoothing lengths. Such results are crucial to enable realistic 2D numerical simulations accounting for self-gravity and are important to deepen our understanding of planetesimals formation and type I migration.

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S. Restrepo and P. Barge
Thu, 30 Mar 23
25/66

Comments: 12 pages, 7 figures

Near-IR and optical radial velocities of the active M-dwarf star Gl 388 (AD Leo) with SPIRou at CFHT and SOPHIE at OHP [SSA]

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http://arxiv.org/abs/2303.16712


Context: The search for extrasolar planets around the nearest M-dwarfs is a crucial step towards identifying the nearest Earth-like planets. One of the main challenges in this search is that M-dwarfs can be magnetically active and stellar activity can produce radial velocity (RV) signals that could mimic those of a planet.
Aims: We aim to investigate whether the 2.2 day period observed in optical RVs of the nearby active M-dwarf star Gl 388 (AD Leo) is due to stellar activity or to a planet which co-rotates with the star as suggested in the past.
Methods: We obtained quasi-simultaneous optical RVs of Gl 388 from 2019 to 2021 with SOPHIE (R$\sim$75k) at the OHP in France, and near-IR RV and Stokes V measurements with SPIRou at the CFHT (R$\sim$70k).
Results: The SOPHIE RV time-series displays a periodic signal with 2.23$\pm$0.01 days period and 23.6$\pm$0.5 m/s amplitude, which is consistent with previous HARPS observations obtained in 2005-2006. The SPIRou RV time-series is flat at 5 m/s rms and displays no periodic signals. RV signals of amplitude higher than 5.3 m/s at a period of 2.23 days can be excluded with a confidence level higher than 99%. Using the modulation of the longitudinal magnetic field (Bl) measured with SPIRou, we derive a stellar rotation period of 2.2305$\pm$0.0016 days.
Conclusions: SPIRou RV measurements provide solid evidence that the periodic variability of the optical RVs of Gl 388 is due to stellar activity rather than to a co-rotating planet. The magnetic activity nature of the optical RV signal is further confirmed by the modulation of Bl with the same period. The SPIRou campaign on Gl 388 demonstrates the power of near-IR RV to confirm or infirm planet candidates discovered in the optical around active stars. SPIRou observations reiterate how effective spectropolarimetry is at determining the stellar rotation period.

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A. Carmona, X. Delfosse, S. Bellotti, et. al.
Thu, 30 Mar 23
29/66

Comments: 25 pages, 23 figures, Accepted by Astronomy and Astrophysics

Prospects for localising Planet 9 with a future Uranus mission [EPA]

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http://arxiv.org/abs/2303.16830


Past years have seen various publications attempting to explain the apparent clustering features of trans-Neptunian objects, the most popular explanation being an unconfirmed “Planet 9”. The recently proposed Uranus Orbiter and Probe mission by NASA’s Planetary Science and Astrobiology Decadal Survey could offer the opportunity to precisely determine Planet 9’s sky location and mass by carefully monitoring ranging data during the interplanetary cruise. We use Monte Carlo-Markov Chain methods to reconstruct simulated spacecraft trajectories in a simplified solar system model containing Planet 9, providing an estimate of the mission’s localisation capacity depending on sky location, Earth-spacecraft Doppler link noise level and data collection rate. We characterise the noise via the Allan deviation $\sigma_{\rm A}$, scaled to the Cassini-era value $\sigma_{\rm A}^{\rm \scriptscriptstyle Cass} = 3 \times 10^{-15}$, finding that daily measurements of the spacecraft position can lead to $\sim$0.2 deg$^2$ localisation of Planet 9 (assuming $M_9 = 6.3 M_{\oplus}$, $d_9 = 460$AU). As little as a 3-fold improvement in $\sigma_{\rm A}$ drastically decreases the sky localisation area size to $\sim$0.01 deg$^2$. Thus, we showcase that a future Uranus mission carries a significant potential also for non-Uranian science.

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J. Bucko, D. Soyuer and L. Zwick
Thu, 30 Mar 23
40/66

Comments: Submitted to MNRAS: Letters, 5 pages, 4 figures

The puzzle of the formation of T8 dwarf Ross 458c [SSA]

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http://arxiv.org/abs/2303.16863


At the lowest masses, the distinction between brown dwarfs and giant exoplanets is often blurred and literature classifications rarely reflect the deuterium burning boundary. Atmospheric characterisation may reveal the extent to which planetary formation pathways contribute to the population of very-low mass brown dwarfs, by revealing if their abundance distributions differ from those of the local field population or, in the case of companions, their primary stars. The T8 dwarf Ross 458c is a possible planetary mass companion to a pair of M dwarfs, and previous work suggests that it is cloudy. We here present the results of the retrieval analysis of Ross 458c, using archival spectroscopic data in the 1.0 to 2.4 micron range. We test a cloud free model as well as a variety of cloudy models and find that the atmosphere of Ross 458c is best described by a cloudy model (strongly preferred). The CH4/H2O is higher than expected at 1.97 +0.13 -0.14. This value is challenging to understand in terms of equilibrium chemistry and plausible C/O ratios. Comparisons to thermochemical grid models suggest a C/O of ~ 1.35, if CH4 and H2O are quenched at 2000 K, requiring vigorous mixing. We find a [C/H] ratio of +0.18, which matches the metallicity of the primary system, suggesting that oxygen is missing from the atmosphere. Even with extreme mixing, the implied C/O is well beyond the typical stellar regime, suggesting a either non-stellar formation pathway, or the sequestration of substantial quantities of oxygen via hitherto unmodeled chemistry or condensation processes.

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J. Gaarn, B. Burningham, J. Faherty, et. al.
Thu, 30 Mar 23
41/66

Comments: 16 pages, 9 figures

Saturn's Seismic Rotation Revisited [EPA]

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http://arxiv.org/abs/2303.16219


Normal mode seismology is a promising means of measuring rotation in gas giant interiors, and ring seismology presents a singular opportunity to do so at Saturn. We calculate Saturn’s normal modes of oscillation and zonal gravity field, using nonperturbative methods for normal modes in the rigidly rotating approximation, and perturbative methods for the shifts that Saturn’s deep winds induce in the mode frequencies and zonal gravity harmonics. The latter are calculated by solving the thermo-gravitational wind equation in an oblate geometry. Comparing many such models to gravity data and the frequencies of ring patterns excited by Saturn normal modes, we use statistical methods to estimate that Saturn’s cloud-level winds extend inward along cylinders before decaying at a depth 0.125-0.138 times Saturn’s equatorial radius, or 7,530-8,320 km, consistent with analyses of Cassini gravity and magnetic field data. The seismology is especially useful for pinning down Saturn’s poorly constrained deep rotation period, which we estimate at 634.7 min (median) with a 5/95% quantile range 633.8-635.5 min. Outstanding residuals in mode frequencies at low angular degree suggest a more complicated deep interior than has been considered to date. Smaller but still significant residuals at high angular degree also show that our picture for the thermal, composition, and/or rotation profile in Saturn’s envelope is not yet complete.

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C. Mankovich, J. Dewberry and J. Fuller
Thu, 30 Mar 23
42/66

Comments: Accepted to PSJ

The ultraviolet habitable zone of exoplanets [EPA]

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http://arxiv.org/abs/2303.16229


The dozens of rocky exoplanets discovered in the Circumstellar Habitable Zone (CHZ) currently represent the most suitable places to host life as we know it outside the Solar System. However, the presumed presence of liquid water on the CHZ planets does not guarantee suitable environments for the emergence of life. According to experimental studies, the building blocks of life are most likely produced photochemically in presence of a minimum ultraviolet (UV) flux. On the other hand, high UV flux can be life-threatening, leading to atmospheric erosion and damaging biomolecules essential to life. These arguments raise questions about the actual habitability of CHZ planets around stars other than Solar-type ones, with different UV to bolometric luminosity ratios. By combining the “principle of mediocricy” and recent experimental studies, we define UV boundary conditions (UV-habitable Zone, UHZ) within which life can possibly emerge and evolve. We investigate whether exoplanets discovered in CHZs do indeed experience such conditions. By analysing Swift-UV/Optical Telescope data, we measure the near ultraviolet (NUV) luminosities of 17 stars harbouring 23 planets in their CHZ. We derive an empirical relation between NUV luminosity and stellar effective temperature. We find that eighteen of the CHZ exoplanets actually orbit outside the UHZ, i.e., the NUV luminosity of their M-dwarf hosts is decisively too low to trigger abiogenesis – through cyanosulfidic chemistry – on them. Only stars with effective temperature >3900 K illuminate their CHZ planets with enough NUV radiation to trigger abiogenesis. Alternatively, colder stars would require a high-energy flaring activity.

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R. Spinelli, F. Borsa, G. Ghirlanda, et. al.
Thu, 30 Mar 23
44/66

Comments: 8 pages, 3 figures

The CORALIE survey for southern extrasolar planets XIX. Brown dwarfs and stellar companions unveiled by radial velocity and astrometry [EPA]

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http://arxiv.org/abs/2303.16717


A historical planet-search on a sample of 1647 nearby southern main sequence stars has been ongoing since 1998 with the CORALIE spectrograph at La Silla Observatory, with a backup subprogram dedicated to the monitoring of binary stars. We review 25 years of CORALIE measurements and search for Doppler signals consistent with stellar or brown dwarf companions to produce an updated catalog of both known and previously unpublished binary stars in the planet-search sample, assessing the binarity fraction of the stellar population and providing perspective for more precise planet-search in the binary sample. We perform new analysis on the CORALIE planet-search sample radial velocity measurements, searching for stellar companions and obtaining orbital solutions for both known and new binary systems. We perform simultaneous radial velocity and proper motion anomaly fits on the subset of these systems for which Hipparcos and Gaia astrometry measurements are available, obtaining accurate estimates of true mass for the companions. We find 218 stars in the CORALIE sample to have at least one stellar companion, 130 of which are not yet published in the literature and for which we present orbital solutions. The use of proper motion anomaly allow us to derive true masses for the stellar companions in 132 systems, which we additionally use to estimate stability regions for possible planetary companions on circumprimary or circumbinary orbits. Finally, we produce detection limit maps for each star in the sample and obtain occurrence rates of $0.43^{+0.23}{-0.11}\%$ and $12.69^{+0.87}{-0.77}\%$ for brown dwarf and stellar companions respectively in the CORALIE sample.

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D. Barbato, D. Ségransan, S. Udry, et. al.
Thu, 30 Mar 23
47/66

Comments: 34 pages, 15 figures, accepted for publication in A&A

The volcanic and radial expansion/contraction history of the Moon simulated by numerical models of magmatism in the convective mantle [EPA]

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http://arxiv.org/abs/2303.16517


To understand the evolution of the Moon, we numerically modeled mantle convection and magmatism in a two-dimensional polar rectangular mantle. Magmatism occurs as an upward permeable flow of magma generated by decompression melting through the convecting matrix. The mantle is assumed to be initially enriched in heat-producing elements (HPEs) and compositionally dense ilmenite-bearing cumulates (IBC) at its base. Here, we newly show that magma generation and migration play a crucial role in the calculated volcanic and radial expansion/contraction history. Magma is generated in the deep mantle by internal heating for the first several hundred million years. A large volume of the generated magma ascends to the surface as partially molten fingers and plumes driven by melt-buoyancy to cause a volcanic activity and radial expansion of the planet with the peak at 3.5-4 Gyr ago. Eventually, however, the planet begins to radially contract when the mantle solidifies by cooling from the surface boundary. As the mantle is cooled, the activity of partially molten plumes declines but continues for billions of years after the peak because some basal materials enriched in the dense IBC components hold HPEs. The calculated volcanic and radial expansion/contraction history is consistent with the observed history of the Moon. Our simulations suggest a substantial fraction of the mantle was solid, and there was a basal layer enriched in HPEs and the IBC components at the beginning of the history of the Moon.

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K. U, M. Kameyama and M. Ogawa
Thu, 30 Mar 23
48/66

Comments: 36 pages, 10 figures, and 3 tables

Magnetic fields inferred by Solar Orbiter: A comparison between SO/PHI-HRT and SDO/HMI [SSA]

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http://arxiv.org/abs/2303.16771


The High Resolution Telescope (HRT) of the Polarimetric and Helioseismic Imager on board the Solar Orbiter spacecraft (SO/PHI) and the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) both infer the photospheric magnetic field from polarised light images. SO/PHI is the first magnetograph to move out of the Sun–Earth line and will provide unprecedented access to the Sun’s poles. This provides excellent opportunities for new research wherein the magnetic field maps from both instruments are used simultaneously. We aim to compare the magnetic field maps from these two instruments and discuss any possible differences between them. We used data from both instruments obtained during Solar Orbiter’s inferior conjunction on 7 March 2022. The HRT data were additionally treated for geometric distortion and degraded to the same resolution as HMI. The HMI data were re-projected to correct for the $3^{\circ}$ separation between the two observatories. SO/PHI-HRT and HMI produce remarkably similar line-of-sight magnetograms, with a slope coefficient of $0.97$, an offset below $1$ G, and a Pearson correlation coefficient of $0.97$. However, SO/PHI-HRT infers weaker line-of-sight fields for the strongest fields. As for the vector magnetic field, SO/PHI-HRT was compared to both the $720$-second and $90$-second HMI vector magnetic field: SO/PHI-HRT has a closer alignment with the $90$-second HMI vector. In the weak signal regime ($< 600$ G), SO/PHI-HRT measures stronger and more horizontal fields than HMI, very likely due to the greater noise in the SO/PHI-HRT data. In the strong field regime ($\gtrsim 600$ G), HRT infers lower field strengths but with similar inclinations (a slope of $0.92$) and azimuths (a slope of $1.02$). The slope values are from the comparison with the HMI $90$-second vector.

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J. Sinjan, D. Calchetti, J. Hirzberger, et. al.
Thu, 30 Mar 23
50/66

Comments: 10 pages, 5 figures, accepted for publication in A&A; manuscript is a part of Astronomy & Astrophysics special issue: Solar Orbiter First Results (Nominal Mission Phase)

Systematic KMTNet Planetary Anomaly Search. IX. Complete Sample of 2016 Prime-Field Planets [EPA]

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http://arxiv.org/abs/2303.16881


As a part of the “Systematic KMTNet Planetary Anomaly Search” series, we report five new planets (namely, OGLE-2016-BLG-1635Lb, MOA-2016-BLG-532Lb, KMT-2016-BLG-0625Lb, OGLE-2016-BLG-1850Lb, and KMT-2016-BLG-1751Lb) and one planet candidate (KMT-2016-BLG-1855), which were found by searching $2016$ KMTNet prime fields. These $buried$ planets show a wide range of masses from Earth–class to Super–Jupiter–class, and are located in both the disk and the bulge. The ultimate goal of this series is to build a complete planet sample. Because our work provides a complementary sample to other planet detection methods, which have different detection sensitivities, our complete sample will help us to obtain a better understanding of planet demographics in our Galaxy.

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I. Shin, J. Yee, W. Zang, et. al.
Thu, 30 Mar 23
56/66

Comments: 38 pages, 17 figures, 12 Tables, submitted to the AAS journal

ASSIST: An Ephemeris-Quality Test Particle Integrator [EPA]

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http://arxiv.org/abs/2303.16246


We introduce ASSIST, a software package for ephemeris-quality integrations of test particles. ASSIST is an extension of the REBOUND framework and makes use of its IAS15 integrator to integrate test particle trajectories in the field of the Sun, Moon, planets, and 16 massive asteroids, with the positions of the masses coming from the JPL DE441 ephemeris and its associated asteroid perturber file. The package incorporates the most significant gravitational harmonics and general relativistic corrections. ASSIST also accounts for position- and velocity-dependent non-gravitational effects. The first order variational equations are included for all terms to support orbit fitting and covariance mapping. This new framework is meant to provide an open-source package written in a modern language to enable high-precision orbital analysis and science by the small body community. ASSIST is open source, freely distributed under the GNU General Public license, version 3.

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M. Holman, A. Akmal, D. Farnocchia, et. al.
Thu, 30 Mar 23
58/66

Comments: Submitted to PSJ (27 January 2023), Revised (28 March 2023)

Mid-Infrared Observations of the Giant Planets [EPA]

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http://arxiv.org/abs/2303.16264


The mid-infrared spectral region provides a unique window into the atmospheric temperature, chemistry, and dynamics of the giant planets. From more than a century of mid-infrared remote sensing, progressively clearer pictures of the composition and thermal structure of these atmospheres have emerged, along with a greater insight into the processes that shape them. Our knowledge of Jupiter and Saturn has benefitted from their proximity and relatively warm temperatures, while the details of colder and more distant Uranus and Neptune are limited, as these planets remain challenging targets. As the timeline of observations continues to grow, an understanding of the temporal and seasonal variability of the giant planets is beginning to develop, with promising new observations on the horizon.

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M. Roman
Thu, 30 Mar 23
59/66

Comments: 49 pages (including a long bibliography), 20 figures

Bayesian Computation in Astronomy: Novel methods for parallel and gradient-free inference [IMA]

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http://arxiv.org/abs/2303.16134


The goal of this thesis is twofold; introduce the fundamentals of Bayesian inference and computation focusing on astronomical and cosmological applications, and present recent advances in probabilistic computational methods developed by the author that aim to facilitate Bayesian data analysis for the next generation of astronomical observations and theoretical models. The first part of this thesis familiarises the reader with the notion of probability and its relevance for science through the prism of Bayesian reasoning, by introducing the key constituents of the theory and discussing its best practices. The second part includes a pedagogical introduction to the principles of Bayesian computation motivated by the geometric characteristics of probability distributions and followed by a detailed exposition of various methods including Markov chain Monte Carlo (MCMC), Sequential Monte Carlo (SMC), and Nested Sampling (NS). Finally, the third part presents two novel computational methods (Ensemble Slice Sampling and Preconditioned Monte Carlo) and their respective software implementations (zeus and pocoMC). [abridged]

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M. Karamanis
Wed, 29 Mar 23
4/73

Comments: PhD Thesis, 280 pages

The connection between starspots and superflares: a case study of two stars [SSA]

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http://arxiv.org/abs/2303.16051


How do the characteristics of starspots influence the triggering of stellar flares? Here we investigate the activity of two K-type stars, similar in every way from mass to rotation periods and planetary systems. Both stars exhibit about a hundred spots, however, Kepler-411 produced 65 superflares, while Kepler-210 presented none. The spots of both stars were characterized using the planetary transit mapping technique, which yields the intensity, temperature, and radius of starspots. The average radius was $(17\pm7) \times 10^3$ km and $(58 \pm 23) \times 10^3$ km, while the intensity ratio with respect to the photosphere was $(0.35\pm0.24)$ $I_{c}$ and $(0.64\pm0.15)$ $I_{c}$, and the temperature was $(3800 \pm 700)$ K and $(4180 \pm 240)$ K for spots of Kepler-411 and Kepler-210, respectively. Therefore, spots on the star with no superflares, Kepler-210, are mostly larger, less dark, and warmer than those on the flaring star, Kepler-411. This may indicate magnetic fields with smaller magnitude and complexity of the spots on Kepler-210 when compared to those on Kepler-411. Thus, starspot area appears not to be the main culprit of superflares triggering. Perhaps the magnetic complexity of active regions is more important.

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A. Araújo and A. Valio
Wed, 29 Mar 23
5/73

Comments: 5 pages,4 Figures

TOI-5375 B: A Very Low Mass Star at the Hydrogen-Burning Limit Orbiting an Early M-type Star [SSA]

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http://arxiv.org/abs/2303.16193


The TESS mission detected a companion orbiting TIC 71268730, categorized it as a planet candidate, and designated the system TOI-5375. Our follow-up analysis using radial velocity data from the Habitable-zone Planet Finder (HPF), photometric data from Red Buttes Observatory (RBO), and speckle imaging with NN-EXPLORE Exoplanet Stellar Speckle Imager (NESSI) determined that the companion is a very low mass star (VLMS) near the hydrogen-burning mass limit with a mass of 0.080$\pm{0.002} M_{\Sun}$ ($83.81\pm{2.10} M_{J}$), a radius of 0.1114$^{+0.0048}{-0.0050} R{\Sun}$ (1.0841$^{0.0467}{0.0487} R{J}$), and brightness temperature of $2600\pm{70}$ K. This object orbits with a period of 1.721553$\pm{0.000001}$ days around an early M dwarf star ($0.62\pm{0.016}M_{\Sun}$). TESS photometry shows regular variations in the host star’s TESS light curve, which we interpreted as activity-induced variation of $\sim$2\%, and used this variability to measure the host star’s stellar rotation period of 1.9716$^{+0.0080}_{-0.0083}$ days. The TOI-5375 system provides tight constraints on stellar models of low-mass stars at the hydrogen-burning limit and adds to the population in this important region.

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M. Lambert, C. Bender, S. Kanodia, et. al.
Wed, 29 Mar 23
8/73

Comments: 15 pages, 8 figures, Accepted to the Astronomical Journal

The impact of dust evolution on the dead zone outer edge in magnetized protoplanetary disks [EPA]

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http://arxiv.org/abs/2303.15675


[Abridged] Aims. We provide an important step toward a better understanding of the magnetorotational instability (MRI)-dust coevolution in protoplanetary disks by presenting a proof of concept that dust evolution ultimately plays a crucial role in the MRI activity. Methods. First, we study how a fixed power-law dust size distribution with varying parameters impacts the MRI activity, especially the steady-state MRI-driven accretion, by employing and improving our previous 1+1D MRI-driven turbulence model. Second, we relax the steady-state accretion assumption in this disk accretion model, and partially couple it to a dust evolution model in order to investigate how the evolution of dust (dynamics and grain growth processes combined) and MRI-driven accretion are intertwined on million-year timescales. Results. Dust coagulation and settling lead to a higher gas ionization degree in the protoplanetary disk, resulting in stronger MRI-driven turbulence as well as a more compact dead zone. On the other hand, fragmentation has an opposite effect because it replenishes the disk in small dust particles. Since the dust content of the disk decreases over million years of evolution due to radial drift, the MRI-driven turbulence overall becomes stronger and the dead zone more compact until the disk dust-gas mixture eventually behaves as a grain-free plasma. Furthermore, our results show that dust evolution alone does not lead to a complete reactivation of the dead zone. Conclusions. The MRI activity evolution (hence the temporal evolution of the MRI-induced $\alpha$-parameter) is controlled by dust evolution and occurs on a timescale of local dust growth, as long as there is enough dust particles in the disk to dominate the recombination process for the ionization chemistry. Once it is no longer the case, it is expected to be controlled by gas evolution and occurs on a viscous evolution timescale.

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T. Delage, M. Gárate, S. Okuzumi, et. al.
Wed, 29 Mar 23
19/73

Comments: 23 pages, 13 figures, Accepted for publication in A&A

Insights on the Sun birth environment in the context of star-cluster formation in hub-filament systems [GA]

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http://arxiv.org/abs/2303.15695


Cylindrical molecular filaments are observed to be the main sites of Sun-like star formation, while massive stars form in dense hubs, at the junction of multiple filaments. The role of hub-filament configurations has not been discussed yet in relation to the birth environment of the solar system and to infer the origin of isotopic ratios of Short-Lived Radionuclides (SLR, such as $^{26}$Al) of Calcium-Aluminum-rich Inclusions (CAIs) observed in meteorites. In this work, we present simple analytical estimates of the impact of stellar feedback on the young solar system forming along a filament of a hub-filament system. We find that the host filament can shield the young solar system from the stellar feedback, both during the formation and evolution of stars (stellar outflow, wind, and radiation) and at the end of their life (supernovae). We show that the young solar system formed along a dense filament can be enriched with supernova ejecta (e.g., $^{26}$Al) during the formation timescale of CAIs. We also propose that the streamers recently observed around protostars may be channeling the SLR-rich material onto the young solar system. We conclude that considering hub-filament configurations as the birth environment of the Sun is important when deriving theoretical models explaining the observed properties of the solar system.

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D. Arzoumanian, S. Arakawa, M. Kobayashi, et. al.
Wed, 29 Mar 23
23/73

Comments: Accepted for publication in The Astrophysical Journal Letters

Rebuilding the Habitable Zone from the Bottom Up with Computational Zones [EPA]

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http://arxiv.org/abs/2303.16111


Computation, if treated as a set of physical processes that act on information represented by states of matter, encompasses biological systems, digital systems, and other constructs, and may be a fundamental measure of living systems. The opportunity for biological computation, represented in the propagation and selection-driven evolution of information-carrying organic molecular structures, has been partially characterized in terms of planetary habitable zones based on primary conditions such as temperature and the presence of liquid water. A generalization of this concept to computational zones is proposed, with constraints set by three principal characteristics: capacity, energy, and instantiation (or substrate). Computational zones naturally combine traditional habitability factors, including those associated with biological function that incorporate the chemical milieu, constraints on nutrients and free energy, as well as element availability. Two example applications are presented by examining the fundamental thermodynamic work efficiency and Landauer limit of photon-driven biological computation on planetary surfaces and of generalized computation in stellar energy capture structures (a.k.a. Dyson structures). It is shown that computational zones involving nested structures or substellar objects could manifest unique observational signatures as cool far-infrared emitters. While this is an entirely hypothetical example, its simplicity offers a useful, complementary introduction to computational zones.

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C. Scharf and O. Witkowski
Wed, 29 Mar 23
27/73

Comments: 31 pages, 3 figures, submitted to The Astrobiology Journal

On Secular Gravitational Instability in Vertically Stratified Disks [EPA]

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http://arxiv.org/abs/2303.15607


Secular gravitational instability (GI) is one promising mechanism for explaining planetesimal formation. The previous studies on secular GI utilized a razor-thin disk model and derived the growth condition in terms of the vertically integrated physical values such as dust-to-gas surface density ratio. However, in weakly turbulent disks where secular GI can operate, a dust disk can be orders of magnitude thinner than a gas disk, and analyses treating the vertical structures are necessary to clarify the interplay of the midplane dust motion and the upper gas motion. In this work, we perform vertically global linear analyses of secular GI with the vertical domain size of a few gas scale heights. We find that dust grains accumulate radially around the midplane while gas circulates over the whole vertical region. We obtain well-converged growth rates when the outer gas boundary is above two gas scale heights. The growth rates are underestimated if we assume the upper gas to be steady and regard it just as the source of external pressure to the dusty lower layer. Therefore, treating the upper gas motion is important even when the dust disk is much thinner than the gas disk. Conducting a parameter survey, we represent the growth condition in terms of the Toomre’s $Q$ value for dust and dust-to-gas surface density ratio. The critical dust disk mass for secular GI is $\sim10^{-4}$ stellar mass for the dust-to-gas surface density ratio of 0.01, the Stokes number of 0.1, and dimensionless radial dust diffusivity of $10^{-4}$.

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R. Tominaga, S. Inutsuka and S. Takahashi
Wed, 29 Mar 23
53/73

Comments: 23 pages, 17 figures; Submitted to ApJ

The radiation environment over the African continent at aviation altitudes: First results of the RPiRENA-based dosimeter [CL]

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http://arxiv.org/abs/2303.15452


The radiation environment over the African continent, at aviation altitudes, remains mostly uncharacterized and unregulated. In this paper we present initial measurements made by a newly developed active dosimeter on-board long-haul flights between South Africa and Germany. Based on these initial tests, we believe that this low-cost and open-source dosimeter is suitable for continued operation over the Africa continent and can provide valuable long-term measurements to test dosimteric models and inform aviation policy

Read this paper on arXiv…

M. Mosotho, R. Strauss, S. S.Bottcher, et. al.
Wed, 29 Mar 23
68/73

Comments: Accepted to appear in Journal of Space Weather and Space Climate

The beta Pictoris system: Setting constraints on the planet and the disk structures at mid-IR wavelengths with NEAR [EPA]

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http://arxiv.org/abs/2303.15155


[abridged] We analyzed mid-infrared high-contrast coronagraphic images of the beta Pictoris system, taking advantage of the NEAR experiment using the VLT/VISIR instrument. The goal of our analysis is to investigate both the detection of the planet beta Pictoris b and of the disk features at mid-IR wavelengths. In addition, by combining several epochs of observation, we expect to constrain the position of the known clumps and improve our knowledge on the dynamics of the disk. To evaluate the planet b flux contribution, we extracted the photometry and compared it to the flux published in the literature. In addition, we used previous data from T-ReCS and VISIR, to study the evolution of the position of the southwest clump that was initially observed in the planetary disk back in 2003. While we did not detect the planet b, we were able to put constraints on the presence of circumplanetary material, ruling out the equivalent of a Saturn-like planetary ring around the planet. The disk presents several noticeable structures, including the known southwest clump. Using a 16-year baseline, sampled with five epochs of observations, we were able to examine the evolution of the clump: the clump orbits in a Keplerian motion with an sma of 56.1+-0.4 au. In addition to the known clump, the images clearly show the presence of a second clump on the northeast side of the disk and fainter and closer structures that are yet to be confirmed. We found correlations between the CO clumps detected with ALMA and the mid-IR images. If the circumplanetary material were located at the Roche radius, the maximum amount of dust determined from the flux upper limit around beta Pictoris b would correspond to the mass of an asteroid of 5 km in diameter. Finally, the Keplerian motion of the southwestern clump is possibly indicative of a yet-to-be-detected planet or signals the presence of a vortex.

Read this paper on arXiv…

N. Skaf, A. Boccaletti, E. Pantin, et. al.
Tue, 28 Mar 23
3/81

Comments: Accepted in Astronomy and Astrophysics

Fishing for Planets: A Comparative Analysis of EPRV Survey Performance in the Presence of Correlated Noise [EPA]

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http://arxiv.org/abs/2303.14571


With dedicated exoplanet surveys underway for multiple extreme precision radial velocity (EPRV) instruments, the near-future prospects of RV exoplanet science are promising. These surveys’ generous time allocations are expected to facilitate the discovery of Earth analogs around bright, nearby Sun-like stars. But survey success will depend critically on the choice of observing strategy, which will determine the survey’s ability to mitigate known sources of noise and extract low-amplitude exoplanet signals. Here, we present an analysis of the Fisher information content of simulated EPRV surveys, accounting for the most recent advances in our understanding of stellar variability on both short and long timescales (i.e., oscillations and granulation within individual nights, and activity-induced variations across multiple nights). In this analysis, we capture the correlated nature of stellar variability by parameterizing these signals with Gaussian Process kernels. We describe the underlying simulation framework as well as the physical interpretation of the Fisher information content, and we evaluate the efficacy of EPRV survey strategies that have been presented in the literature. We explore and compare strategies for scheduling observations over various timescales and we make recommendations to optimize survey performance for the detection of Earth-like exoplanets.

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A. Gupta and M. Bedell
Tue, 28 Mar 23
4/81

Comments: 24 Pages, 11 Figures

Three Saturn-mass planets transiting F-type stars revealed with TESS and HARPS [EPA]

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http://arxiv.org/abs/2303.15080


While the sample of confirmed exoplanets continues to increase, the population of transiting exoplanets around early-type stars is still limited. These planets allow us to investigate the planet properties and formation pathways over a wide range of stellar masses and study the impact of high irradiation on hot Jupiters orbiting such stars. We report the discovery of TOI-615b, TOI-622b, and TOI-2641b, three Saturn-mass planets transiting main sequence, F-type stars. The planets were identified by the Transiting Exoplanet Survey Satellite (TESS) and confirmed with complementary ground-based and radial velocity observations. TOI-615b is a highly irradiated ($\sim$1277 $F_{\oplus}$) and bloated Saturn-mass planet (1.69$^{+0.05}{-0.06}$$R{Jup}$ and 0.43$^{+0.09}{-0.08}$$M{Jup}$) in a 4.66 day orbit transiting a 6850 K star. TOI-622b has a radius of 0.82$^{+0.03}{-0.03}$$R{Jup}$ and a mass of 0.30$^{+0.07}{-0.08}$~$M{Jup}$ in a 6.40 day orbit. Despite its high insolation flux ($\sim$600 $F_{\oplus}$), TOI-622b does not show any evidence of radius inflation. TOI-2641b is a 0.37$^{+0.05}{-0.04}$$M{Jup}$ planet in a 4.88 day orbit with a grazing transit (b = 1.04$^{+0.05}{-0.06 }$) that results in a poorly constrained radius of 1.61$^{+0.46}{-0.64}$$R_{Jup}$. Additionally, TOI-615b is considered attractive for atmospheric studies via transmission spectroscopy with ground-based spectrographs and $\textit{JWST}$. Future atmospheric and spin-orbit alignment observations are essential since they can provide information on the atmospheric composition, formation and migration of exoplanets across various stellar types.

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A. Psaridi, F. Bouchy, M. Lendl, et. al.
Tue, 28 Mar 23
7/81

Comments: 16 pages, 17 figures, submitted to A&A

Spin of protoplanets generated by pebble accretion: Influences of protoplanet-induced gas flow [EPA]

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http://arxiv.org/abs/2303.15098


We investigate the spin state of a protoplanet during the pebble accretion influenced by the gas flow in the gravitational potential of the protoplanet and how it depends on the planetary mass, the headwind speed, the distance from the host star, and the pebble size. We perform nonisothermal three-dimensional hydrodynamical simulations in a local frame to obtain the gas flow around the planet. We then numerically integrate three-dimensional orbits of pebbles under the obtained gas flow. Finally, assuming uniform spatial distribution of incoming pebbles, we calculate net spin by summing up specific angular momentum that individual pebbles transfer to the protoplanet at impacts. We find that a protoplanet with the envelope acquires prograde net spin rotation regardless of the planetary mass, the pebble size, and the headwind speed of the gas. This is because accreting pebbles are dragged by the envelope that commonly has prograde rotation. As the planetary mass or orbital radius increases, the envelope is thicker and the prograde rotation is faster, resulting in faster net prograde spin. When the dimensionless thermal mass of the planet, $m = R_{\mathrm{Bondi}} / H$, where $R_{\mathrm{Bondi}}$ and $H$ are the Bondi radius and the disk gas scale height, is larger than a certain critical mass ($m \gtrsim 0.3$ at $0.1 \, \mathrm{au}$ or $m \gtrsim 0.1$ at $1 \, \mathrm{au}$), the spin rotation exceeds the breakup one. The predicted spin frequency reaches the breakup one at the planetary mass $m_{\mathrm{iso,rot}} \sim 0.1 \, (a / 1 \, \mathrm{au})^{-1/2}$ (where $a$ is the orbital radius), suggesting that the protoplanet cannot grow beyond $m_{\mathrm{iso,rot}}$. It is consistent with the Earth’s current mass and could help the formation of the Moon by a giant impact on fast-spinning proto-Earth.

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K. Takaoka, A. Kuwahara, S. Ida, et. al.
Tue, 28 Mar 23
8/81

Comments: 14 pages, 10 figures, Accepted for publication in Astronomy and Astrophysics (A&A)

A High-Eccentricity Warm Jupiter Orbiting TOI-4127 [EPA]

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http://arxiv.org/abs/2303.14570


We report the discovery of TOI-4127 b, a transiting, Jupiter-sized exoplanet on a long-period ($P = 56.39879^{+0.00010}{-0.00010}$ d), high-eccentricity orbit around a late F-type dwarf star. This warm Jupiter was first detected and identified as a promising candidate from a search for single-transit signals in TESS Sector 20 data, and later characterized as a planet following two subsequent transits (TESS Sectors 26 and 53) and follow-up ground-based RV observations with the NEID and SOPHIE spectrographs. We jointly fit the transit and RV data to constrain the physical ($R_p = 1.096^{+0.039}{-0.032} R_J$, $M_p = 2.30^{+0.11}{-0.11} M_J$) and orbital parameters of the exoplanet. Given its high orbital eccentricity ($e=0.7471^{+0.0078}{-0.0086}$), TOI-4127 b is a compelling candidate for studies of warm Jupiter populations and of hot Jupiter formation pathways. We show that the present periastron separation of TOI-4127 b is too large for high-eccentricity tidal migration to circularize its orbit, and that TOI-4127 b is unlikely to be a hot Jupiter progenitor unless it is undergoing angular momentum exchange with an undetected outer companion. Although we find no evidence for an external companion, the available observational data are insufficient to rule out the presence of a perturber that can excite eccentricity oscillations and facilitate tidal migration.

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A. Gupta, J. Jackson, G. Hebrard, et. al.
Tue, 28 Mar 23
9/81

Comments: N/A

Remarks on compressible convection in Super-Earths [EPA]

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http://arxiv.org/abs/2303.15153


The radial density of planets increases with depth due to compressibility, leading to impacts on their convective dynamics. To account for these effects, including the presence of a quasi-adiabatic temperature profile and entropy sources due to dissipation, the compressibility is expressed through a dissipation number, $\mathcal{D}$, proportional to the planet’s radius and gravity. In Earth’s mantle, compressibility effects are moderate, but in large rocky or liquid exoplanets (Super-Earths), the dissipation number can become very large. This paper explores the properties of compressible convection when the dissipation number is significant. We start by selecting a simple Murnaghan equation of state that embodies the fundamental properties of condensed matter at planetary conditions. Next, we analyze the characteristics of adiabatic profiles and demonstrate that the ratio between the bottom and top adiabatic temperatures is relatively small and probably less than 2. We examine the marginal stability of compressible mantles and reveal that they can undergo convection with either positive or negative superadiabatic Rayleigh numbers. Lastly, we delve into simulations of convection performed using the exact equations of mechanics, neglecting inertia (infinite Prandtl number case), and examine their consequences for Super-Earths dynamics.

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Y. Ricard and T. Alboussière
Tue, 28 Mar 23
19/81

Comments: 31 pages, 15 figures

Towards robust corrections for stellar contamination in JWST exoplanet transmission spectra [EPA]

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http://arxiv.org/abs/2303.15418


Transmission spectroscopy is still the preferred characterization technique for exoplanet atmospheres, although it presents unique challenges which translate into characterization bottlenecks when robust mitigation strategies are missing. Stellar contamination is one of such challenges that can overpower the planetary signal by up to an order of magnitude, and thus not accounting for stellar contamination can lead to significant biases in the derived atmospheric properties. Yet, accounting for stellar contamination may not be straightforward, as important discrepancies exist between state-of-the-art stellar models and measured spectra and between models themselves. Here we explore the extent to which stellar models can be used to reliably correct for stellar contamination and yield a planet’s uncontaminated transmission spectrum. We find that (1) discrepancies between stellar models can dominate the noise budget of JWST transmission spectra of planets around stars with heterogeneous photospheres; (2) the true number of unique photospheric spectral components and their properties can only be accurately retrieved when the stellar models have a sufficient fidelity; and (3) under such optimistic circumstances the contribution of stellar contamination to the noise budget of a transmission spectrum is considerably below that of the photon noise for the standard transit observation setup. Therefore, we suggest (1) increased efforts towards development of model spectra of stars and their active regions in a data-driven manner; and (2) the development of empirical approaches for deriving spectra of photospheric components using the observatories with which the atmospheric explorations are carried out.

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B. Rackham and J. Wit
Tue, 28 Mar 23
24/81

Comments: 15 pages, 8 figures, 2 tables

Detection Rate of <50-meter Interstellar Objects with LSST [IMA]

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http://arxiv.org/abs/2303.14766


The previous decade saw the discovery of the first four known interstellar objects due to advances in astronomical viewing equipment. Future sky surveys with greater sensitivity will allow for more frequent detections of such objects, including increasingly small objects. We consider the capabilities of the Legacy Survey of Space and Time (LSST) of the Vera C. Rubin Observatory to detect interstellar objects of small sizes during its period of operation over the next decade. We use LSST’s detection capabilities and simulate populations of interstellar objects in the range of 1-50m in diameter to calculate the expected number of small interstellar objects that will be detected. We use previous detections of interstellar objects to calibrate our object density estimates. We also consider the impact of the population’s albedo on detection rates by considering populations with two separate albedo distributions: a constant albedo of 0.06 and an albedo distribution that resembles near earth asteroids. We find that the number of detections increases with the diameter over the range of diameters we consider. We estimate a detection rate of up to a small ISO every two years of LSST’s operation with an increase by a factor of ten for future surveys that extend a magnitude deeper.

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C. Ezell and A. Loeb
Tue, 28 Mar 23
29/81

Comments: 17 pages, 7 figures

High atmospheric metal enrichment for a Saturn-mass planet [EPA]

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http://arxiv.org/abs/2303.14206


Atmospheric metal enrichment (i.e., elements heavier than helium, also called “metallicity”) is a key diagnostic of the formation of giant planets. The giant planets of the solar system exhibit an inverse relationship between mass and both their bulk metallicities and atmospheric metallicities. Extrasolar giant planets also display an inverse relationship between mass and bulk metallicity. However, there is significant scatter in the relationship and it is not known how atmospheric metallicity correlates with either planet mass or bulk metallicity. Here we show that the Saturn-mass exoplanet HD 149026b has an atmospheric metallicity 59 – 276 times solar (at 1 $\sigma$), which is greater than Saturn’s atmospheric metallicity of ~7.5 times solar at >4 $\sigma$ confidence. This result is based on modeling CO$_2$ and H$_2$O absorption features in the thermal emission spectrum of the planet measured by JWST. HD 149026b is the most metal-rich giant planet known, with an estimated bulk heavy element abundance of 66 $\pm$ 2% by mass. We find that the atmospheric metallicities of both HD 149026b and the solar system giant planets are more correlated with bulk metallicity than planet mass.

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J. Bean, Q. Xue, P. August, et. al.
Tue, 28 Mar 23
35/81

Comments: Published online in Nature on March 27, 2023; a JWST thermal emission spectrum of a planet that definitely has an atmosphere 😉

The GAPS Programme at TNG XLII. A characterisation study of the multi-planet system around the 400 Myr-old star HD 63433 (TOI-1726) [EPA]

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http://arxiv.org/abs/2303.15242


For more than two years, we monitored with the HARPS-N spectrograph the 400 Myr-old star HD\,63433, which hosts two close-in (orbital periods $P_b\sim7.1$ and $P_c\sim20.5$ days) sub-Neptunes detected by the TESS space telescope, and it was announced in 2020. Using radial velocities and additional TESS photometry, we aim to provide the first measurement of their masses, improve the measure of their size and orbital parameters, and study the evolution of the atmospheric mass-loss rate due to photoevaporation. We tested state-of-the-art analysis techniques and different models to mitigate the dominant signals due to stellar activity that are detected in the radial velocity time series. We used a hydro-based analytical description of the atmospheric mass-loss rate, coupled with a core-envelope model and stellar evolutionary tracks, to study the past and future evolution of the planetary masses and radii. We derived new measurements of the planetary orbital periods and radii ($P_b=7.10794\pm0.000009$ d, $r_b=2.02^{+0.06}{-0.05}$ $R{\oplus}$; $P_c=20.54379\pm0.00002$ d, $r_c=2.44\pm0.07$ $R_{\oplus}$), and determined mass upper limits ($m_b\lesssim$11 $M_{\oplus}$; $m_c\lesssim$31 $M_{\oplus}$; 95$\%$ confidence level), with evidence at a 2.1–2.7$\sigma$ significance level that HD\,63433\,c might be a dense mini-Neptune with a Neptune-like mass. For a grid of test masses below our derived dynamical upper limits, we found that HD\,63433\,b has very likely lost any gaseous H-He envelope, supporting HST-based observations that are indicative of there being no ongoing atmospheric evaporation. HD\,63433\,c will keep evaporating over the next $\sim$5 Gyr if its current mass is $m_c\lesssim$15 $M_{\oplus}$, while it should be hydrodynamically stable for higher masses.

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M. Damasso, D. Locci, S. Benatti, et. al.
Tue, 28 Mar 23
42/81

Comments: 22 pages, accepted for publication on Astronomy & Astrophysics

Science opportunities with solar sailing smallsats [EPA]

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http://arxiv.org/abs/2303.14917


Recently, we witnessed how the synergy of small satellite technology and solar sailing propulsion enables new missions. Together, small satellites with lightweight instruments and solar sails offer affordable access to deep regions of the solar system, also making it possible to realize hard-to-reach trajectories that are not constrained to the ecliptic plane. Combining these two technologies can drastically reduce travel times within the solar system, while delivering robust science. With solar sailing propulsion capable of reaching the velocities of ~5-10 AU/yr, missions using a rideshare launch may reach the Jovian system in two years, Saturn in three. The same technologies could allow reaching solar polar orbits in less than two years. Fast, cost-effective, and maneuverable sailcraft that may travel outside the ecliptic plane open new opportunities for affordable solar system exploration, with great promise for heliophysics, planetary science, and astrophysics. Such missions could be modularized to reach different destinations with different sets of instruments. Benefiting from this progress, we present the “Sundiver” concept, offering novel possibilities for the science community. We discuss some of the key technologies, the current design of the Sundiver sailcraft vehicle and innovative instruments, along with unique science opportunities that these technologies enable, especially as this exploration paradigm evolves. We formulate policy recommendations to allow national space agencies, industry, and other stakeholders to establish a strong scientific, programmatic, and commercial focus, enrich and deepen the space enterprise and broaden its advocacy base by including the Sundiver paradigm as a part of broader space exploration efforts.

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S. Turyshev, D. Garber, L. Friedman, et. al.
Tue, 28 Mar 23
43/81

Comments: 34 pages, 12 figures, 2 tables

Stability and detectability of exomoons orbiting HIP 41378 f, a temperate Jovian planet with an anomalously low apparent density [EPA]

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http://arxiv.org/abs/2303.14294


Moons orbiting exoplanets (“exomoons”) may hold clues about planet formation, migration, and habitability. We investigate the plausibility of exomoons orbiting the temperate ($T_\text{eq}=294$ K) giant ($R = 9.2$ $\text{R}_\oplus$) planet HIP 41378 f. Previous studies have suggested that HIP 41378 f has a low apparent bulk density of $0.09\,\text{g}\,\text{cm}^{-3}$ and a flat near-infrared transmission spectrum, suggesting that it may possess circumplanetary rings. Given the planet’s long orbital period ($P\approx1.5$ yr), it may also host a large exomoon. Here, we consider a hypothetical exomoon orbiting HIP 41378 f with the same satellite-to-planet mass ratio as the Moon-Earth system and assess its orbital stability using a suite of N-body and tidal migration simulations. We find that satellites up to this size are largely stable against Hill sphere escape and collisions with the host planet, consistent with theoretical stability limits determined by previous studies. We then simulate the expected transit signal from the exomoon and show that current transit observations likely cannot constrain the presence of exomoons orbiting HIP 41378 f, though future observations may be capable of detecting exomoons in other systems. Finally, we simulate the combined transmission spectrum of HIP 41378 f and an exomoon with a low-metallicity atmosphere, and show that the total effective spectrum is contaminated at the $\sim$10 ppm level. Our work not only demonstrates the feasibility of exomoons orbiting HIP 41378 f, but also shows that large exomoons may be a source of uncertainty in future high-precision measurements of exoplanet systems.

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C. Harada, C. Dressing, M. Alam, et. al.
Tue, 28 Mar 23
44/81

Comments: 24 pages, 9 figures, 2 tables; submitted to AJ

The evolution of catastrophically evaporating rocky planets [EPA]

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http://arxiv.org/abs/2303.15200


Catastrophically evaporating planets are observed through their dusty tails, formed through rocky material evaporated from their highly irradiated molten surfaces. The composition of these tails offers an avenue for studying the composition of rocky exoplanets, but only if the evolution of the underlying interior is understood. This is because it is the interior evolution that sets the composition at the base of the mass outflow. In this work, we present a model of the evolution of the interiors of catastrophically evaporating planets. Its basis is a one-dimensional code that takes into account energy flow through conduction and convection as well as melting. We find that these planets are likely to be entirely solid when significant mass loss occurs, other than a thin magma pool on the day side. Consequently, the outflows from the planets, and thus the dust tails, sample material only from the surface of the planet. We also use our model to investigate the occurrence rate of planets that can catastrophically evaporate, and find that, on average, a star in the Kepler sample has approximately one such planet. Our value is above, but within an order of magnitude of, the occurrence rate inferred from the Kepler statistics for Super-Earths, implying that exotic mechanisms to produce the catastrophically evaporating planet population may not be required. We also find that the range of substellar temperatures of the observed systems are well explained by recent theoretical models which only produce dust in a limited temperature region.

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A. Curry, R. Booth, J. Owen, et. al.
Tue, 28 Mar 23
48/81

Comments: Submitted to MNRAS

Day 'N' Nite: Habitability of Tidally Locked Planets with Sporadic Rotation [EPA]

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http://arxiv.org/abs/2303.14546


Tidally locked worlds provide a unique opportunity for constraining the probable climates of certain exoplanets. They are unique in that few exoplanet spin and obliquity states are known or will be determined in the near future: both of which are critical in modeling climate. A recent study shows the dynamical conditions present in the TRAPPIST-1 system make rotation and large librations of the substellar point possible for these planets, which are usually assumed to be tidally locked. We independently confirm the tendency for planets in TRAPPIST-1-like systems to sporadically transition from tidally locked libration to slow rotation using N-body simulations. We examine the nature and frequency of these spin states to best inform energy balance models which predict the temperature profile of the planet’s surface. Our findings show that tidally locked planets with sporadic rotation are able to be in both long-term persistent states and chaotic states: where rapid transitions between behaviors are present. Quasi-stable spin regimes, where the planet exhibits one spin behavior for up to hundreds of millennia, are likely able to form stable climate systems while the spin behavior is constant. 1D energy balance models show that tidally locked planets with sporadic rotation around M-dwarfs will experience a relatively small change in substellar temperature due to the lower albedo of ice in an infrared dominant stellar spectrum. The exact effects of large changes in temperature profiles on these planets as they rotate require more robust climate models, like 3D global circulation models, to better examine.

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C. Shakespeare and J. Steffen
Tue, 28 Mar 23
68/81

Comments: N/A

Secondary cratering from Rheasilvia as the possible origin of Vesta's equatorial troughs [EPA]

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http://arxiv.org/abs/2303.14955


Asteroid 4 Vesta has a set of parallel troughs aligned with its equator. Although previous evaluations suggest that it is of shock fracturing tectonic origin, we propose that the equatorial troughs can be created by secondary cratering from the largest impact basin, Rheasilvia. We calculated the trajectories of ejecta particles from Rheasilvia by considering Vesta’s rapid rotation. As a result, we found that secondary craters should be parallel to the latitude. In particular, if we assume that ejecta particles are launched at an initial launch velocity of approximately 350-380 m/s and a launch angle of 25 degree, the parallel equatorial troughs, the Divalia Fossae, can be suitably explained by secondary cratering. This model works well on objects, such as Haumea, Salacia, and Chariklo, but not on Mercury, the Moon, and regular satellites.

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N. Hirata
Tue, 28 Mar 23
70/81

Comments: 35 pages, 13 figures, 3 tables

A Large Double-ring Disk around the Taurus M Dwarf J04124068+2438157 [EPA]

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http://arxiv.org/abs/2303.14586


Planet formation imprints signatures on the physical structures of disks. In this paper, we present high-resolution ($\sim$50 mas, 8 au) Atacama Large Millimeter/submillimeter Array (ALMA) observations of 1.3 mm dust continuum and CO line emission toward the disk around the M3.5 star 2MASS J04124068+2438157. The dust disk consists only of two narrow rings at radial distances of 0.47 and 0.78 arcsec ($\sim$70 and 116 au), with Gaussian $\sigma$ widths of 5.6 and 8.5 au, respectively. The width of the outer ring is smaller than the estimated pressure scale height by $\sim25\%$, suggesting dust trapping in a radial pressure bump. The dust disk size, set by the location of the outermost ring, is significantly larger (by $3\sigma$) than other disks with similar millimeter luminosity, which can be explained by an early formation of local pressure bump to stop radial drift of millimeter dust grains. After considering the disk’s physical structure and accretion properties, we prefer planet–disk interaction over dead zone or photoevaporation models to explain the observed dust disk morphology. We carry out high-contrast imaging at $L’$ band using Keck/NIRC2 to search for potential young planets, but do not identify any source above $5\sigma$. Within the dust gap between the two rings, we reach a contrast level of $\sim$7 mag, constraining the possible planet below $\sim$2–4 $M_{\rm Jup}$. Analyses of the gap/ring properties suggest a $\sim$Saturn mass planet at $\sim$90 au is likely responsible for the formation of the outer ring, which can be potentially revealed with JWST.

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F. Long, B. Ren, N. Wallack, et. al.
Tue, 28 Mar 23
71/81

Comments: 15 pages, 5 figures. Accepted for publication in ApJ

Planet formation via pebble accretion in externally photoevaporating discs [EPA]

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http://arxiv.org/abs/2303.15177


We demonstrate that planet formation via pebble accretion is sensitive to external photoevaporation of the outer disc. In pebble accretion, planets grow by accreting from a flux of solids (pebbles) that radially drift inwards from the pebble production front. If external photoevaporation truncates the outer disc fast enough, it can shorten the time before the pebble production front reaches the disc outer edge, cutting off the supply of pebble flux for accretion, hence limiting the pebble mass reservoir for planet growth. Conversely, cloud shielding can protect the disc from strong external photoevaporation and preserve the pebble reservoir. Because grain growth and drift can occur quickly, shielding even on a short time-scale (<1 Myr) can have a non-linear impact on the properties of planets growing by pebble accretion. For example a $10^{-3} M_\oplus$ planetary seed at 25 au stays at 25 au with a lunar mass if the disc is immediately irradiated by a $10^3$ G$_0$ field, but grows and migrates to be approximately Earth-like in both mass and orbital radius if the disc is shielded for just 1 Myr. In NGC 2024, external photoevaporation is thought to happen to discs that are <0.5 Myr old, which coupled with the results here suggests that the exact planetary parameters can be very sensitive to the star forming environment. Universal shielding for time-scales of at least $\sim1.5$ Myr would be required to completely nullify the environmental impact on planetary architectures.

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L. Qiao, G. Coleman and T. Haworth
Tue, 28 Mar 23
73/81

Comments: Accepted for publication in mnras, 12 pages, 8 figures

Thermal emission from the Earth-sized exoplanet TRAPPIST-1 b using JWST [EPA]

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http://arxiv.org/abs/2303.14849


The TRAPPIST-1 system is remarkable for its seven planets that are similar in size, mass, density, and stellar heating to the rocky planets Venus, Earth, and Mars in our own Solar System (Gillon et al. 2017). All TRAPPIST-1 planets have been observed with the transmission spectroscopy technique using the Hubble or Spitzer Space Telescopes, but no atmospheric features have been detected or strongly constrained (Ducrot et al. 2018; de Wit et al. 2018; Zhang et al. 2018; Garcia et al. 2022). TRAPPIST-1 b is the closest planet to the system’s M dwarf star, and it receives 4 times as much irradiation as Earth receives from the Sun. This relatively large amount of stellar heating suggests that its thermal emission may be measurable. Here we present photometric secondary eclipse observations of the Earth-sized TRAPPIST-1 b exoplanet using the F1500W filter of the MIRI instrument on JWST. We detect the secondary eclipse in each of five separate observations with 8.7-sigma confidence when all data are combined. These measurements are most consistent with the re-radiation of the TRAPPIST-1 star’s incident flux from only the dayside hemisphere of the planet. The most straightforward interpretation is that there is little or no planetary atmosphere redistributing radiation from the host star and also no detectable atmospheric absorption from carbon dioxide (CO$_2$) or other species.

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T. Greene, T. Bell, E. Ducrot, et. al.
Tue, 28 Mar 23
76/81

Comments: Submitted to Nature

Dynamical masses of two young transiting sub-Neptunes orbiting HD 63433 [EPA]

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http://arxiv.org/abs/2303.15411


Although the number of exoplanets reported in the literature exceeds 5000 so far, only a few dozen of them are young planets ($\le$900 Myr). However, a complete characterization of these young planets is key to understanding the current properties of the entire population. Hence, it is necessary to constrain the planetary formation processes and the timescales of dynamical evolution by measuring the masses of exoplanets transiting young stars. We characterize and measure the masses of two transiting planets orbiting the 400 Myr old solar-type star HD\,63433, which is a member of the Ursa Major moving group. We analysed precise photometric light curves of five sectors of the TESS mission with a baseline of $\sim$750 days and obtained $\sim$150 precise radial velocity measurements with the visible and infrared arms of the CARMENES instrument at the Calar Alto 3.5 m telescope in two different campaigns of $\sim$500 days. We performed a combined photometric and spectroscopic analysis to retrieve the planetary properties of two young planets. The strong stellar activity signal was modelled by Gaussian regression processes. We have updated the transit parameters of HD\,63433\,b and c and obtained planet radii of R$p^b$\,=\,2.140\,$\pm$\,0.087 R$\oplus$ and R$p^c$\,=\,2.692\,$\pm$\,0.108 R$\oplus$. Our analysis allowed us to determine the dynamical mass of the outer planet with a 4$\sigma$ significance ($M_p^c$\,=\,15.54\,$\pm$\,3.86 M$\oplus$) and set an upper limit on the mass of the inner planet at 3$\sigma$ ($M_p^b$\,$<$\,21.76 M$\oplus$). According to theoretical models, both planets are expected to be sub-Neptunes, whose interiors mostly consist of silicates and water with no dominant composition of iron, and whose gas envelopes are lower than 2\% in the case of HD\,63433\,c. The envelope is unconstrained in HD\,63433\,b.

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M. Mallorquín, V. Béjar, N. Lodieu, et. al.
Tue, 28 Mar 23
79/81

Comments: N/A

Analytic understanding of the resonant nature of Kozai Lidov Cycles with a precessing quadruple potential [HEAP]

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http://arxiv.org/abs/2303.13579


The very long-term evolution of the hierarchical restricted three-body problem with a precessing quadruple potential is studied analytically. This problem describes the evolution of a star and a planet which are perturbed either by a (circular and not too inclined) binary star system or by one other star and a second more distant star, as well as a perturbation by one distant star and the host galaxy or a compact-object binary system orbiting a massive black hole in non-spherical nuclear star clusters \citep{arXiv:1705.02334v2, arXiv:1705.05848v2}. Previous numerical experiments have shown that when the precession frequency is comparable to the Kozai-Lidov time scale, long term evolution emerges that involves extremely high eccentricities with potential applications for a broad scope of astrophysical phenomena including systems with merging black holes, neutron stars or white dwarfs. We show that a central ingredient of the dynamics is a resonance between the perturbation frequency and the precession frequency of the eccentricity vector in the regime where the eccentricity vector, the precession axis and the quadruple direction are closely aligned. By averaging the secular equations of motion over the Kozai-Lidov Cycles we solve the problem analytically in this regime.

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Y. Klein and B. Katz
Mon, 27 Mar 23
9/59

Comments: 5 pages, 2 figures

Implicit electric field Conjugation: Data-driven focal plane control [IMA]

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http://arxiv.org/abs/2303.13719


Direct imaging of Earth-like planets is one of the main science cases for the next generation of extremely large telescopes. This is very challenging due to the star-planet contrast that must be overcome. Most current high-contrast imaging instruments are limited in sensitivity at small angular separations due to non-common path aberrations (NCPA). The NCPA leak through the coronagraph and create bright speckles that limit the on-sky contrast and therefore also the post-processed contrast. We aim to remove the NCPA by active focal plane wavefront control using a data-driven approach. We developed a new approach to dark hole creation and maintenance that does not require an instrument model. This new approach is called implicit Electric Field Conjugation (iEFC) and it can be empirically calibrated. This makes it robust for complex instruments where optical models might be difficult to realize. Numerical simulations have been used to explore the performance of iEFC for different coronagraphs. The method was validated on the internal source of the Magellan Adaptive Optics eXtreme (MagAO-X) instrument to demonstrate iEFC’s performance on a real instrument. Numerical experiments demonstrate that iEFC can achieve deep contrast below $10^{-9}$ with several coronagraphs. The method is easily extended to broadband measurements and the simulations show that a bandwidth up to 40% can be handled without problems. Experiments with MagAO-X showed a contrast gain of a factor 10 in a broadband light and a factor 20 to 200 in narrowband light. A contrast of $5\cdot10^{-8}$ was achieved with the Phase Apodized Pupil Lyot Coronagraph at 7.5 $\lambda/D$. The new iEFC method has been demonstrated to work in numerical and lab experiments. It is a method that can be empirically calibrated and it can achieve deep contrast. This makes it a valuable approach for complex ground-based high-contrast imaging systems.

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S. Haffert, J. Males, K. Ahn, et. al.
Mon, 27 Mar 23
13/59

Comments: 13 pages, 12 figures accepted by A&A

Compton-Getting effect due to terrestrial orbital motion observed on cosmic ray flow from Mexico-city Neutron Monitor [HEAP]

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http://arxiv.org/abs/2303.14101


We look for a diurnal anisotropy in the cosmic ray flow, using the Mexico-City Neutron Monitor (NM) detector, due to the Earth’s orbital motion and predicted by Compton-Getting (C-G) in 1935, as a first-order relativistic effect. The Mexico-City NM’s geographic latitude is not very high ($19.33^{\circ}$N), and it has a high cutoff geomagnetic rigidity (8.2 GV) and mountain altitude (2274 m asl) favoring the observation of the C-G effect. Furthermore, during the solar cycle minima, the galactic cosmic ray flux is maxima, and the solar magnetic field gets weakened, with a dipolar pattern. Its influence on cosmic rays reaching Earth is the smallest. Analysis of the combined counting rate during two solar minima, 2008 and 2019, from Mexico-city NM’s data yields the C-G effect with an amplitude variation of (0.043$\pm$ 0.019)\%, and phase of (6.15$\pm$ 1.71) LT. The expected amplitude variation is 0.044\%, and the phase of 6.00 LT.

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C. Navia, M. Oliveira and A. Nepomuceno
Mon, 27 Mar 23
15/59

Comments: 8 pages, 6 figures

Magnetohydrodynamic Model of Late Accretion onto a Protoplanetary Disk: Cloudlet Encounter Event [SSA]

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http://arxiv.org/abs/2303.14010


Recent observations suggest late accretion, which is generally nonaxisymmetric, onto protoplanetary disks. We investigated nonaxisymmetric late accretion considering the effects of magnetic fields. Our model assumes a cloudlet encounter event at a few hundred au scale, where a magnetized gas clump (cloudlet) encounters a protoplanetary disk. We studied how the cloudlet size and the magnetic field strength affect the rotational velocity profile in the disk after the cloudlet encounter. The results show that a magnetic field can either decelerate or accelerate the rotational motion of the cloudlet material, primarily depending on the relative size of the cloudlet to the disk thickness. When the cloudlet size is comparable to or smaller than the disk thickness, magnetic fields only decelerate the rotation of the colliding cloudlet material. However, if the cloudlet size is larger than the disk thickness, the colliding cloudlet material can be super-Keplerian as a result of magnetic acceleration. We found that the vertical velocity shear of the cloudlet produces a magnetic tension force that increases the rotational velocity. The acceleration mechanism operates when the initial plasma $\beta$ is $ \beta \lesssim 2\times 10^1 $. Our study shows that magnetic fields modify the properties of spirals formed by tidal effects. These findings may be important for interpreting observations of late accretion.

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M. Unno, T. Hanawa and S. Takasao
Mon, 27 Mar 23
21/59

Comments: 18 pages, 15 figures, 1 table, published in The Astrophysical Journal

Mutual gravitational energy of homogeneous prolate spheroids. Collinear case [EPA]

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http://arxiv.org/abs/2303.13892


The problem of mutual gravitational energy $W_{mut}$ for a system of two homogeneous prolate spheroids, whose symmetry axes are on the same line, is set and solved. The method of equigravitating elements is applied, where the external potentials of three-dimensional spheroids are represented by the potentials of one-dimensional inhomogeneous focal rods. The solution of the problem is reduced to the integration of the potential of one rod over the segment of the second rod. As a result, the expression $W_{mut}$ for two prolate spheroids can be obtained in a finite analytic form through elementary functions. The force of attraction between the spheroids is found. The function $W_{mut}$ is also represented by a power series in eccentricity of the spheroids. Possible applications of the obtained results are discussed.

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B. Kondratyev, V. Kornoukhov and E. Kireeva
Mon, 27 Mar 23
25/59

Comments: 8 pages, 4 figures

Thermal Emission from the Hot Jupiter WASP-103b in $J$ and $K_{\rm s}$ Bands [EPA]

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http://arxiv.org/abs/2303.13732


Hot Jupiters, particularly those with temperature higher than 2000\,K are the best sample of planets that allow in-depth characterization of their atmospheres. We present here a thermal emission study of the ultra hot Jupiter WASP\mbox{-}103\,b observed in two secondary eclipses with CFHT/WIRCam in $J$ and $K_{\rm s}$ bands. By means of high precision differential photometry, we determine eclipse depths in $J$ and $K_{\rm s}$ to an accuracy of 220 and 270\,ppm, which are combined with the published HST/WFC3 and Spitzer data to retrieve a joint constraints on the properties of WASP-103\,b dayside atmosphere. We find that the atmosphere is best fit with a thermal inversion layer included. The equilibrium chemistry retrieval indicates an enhanced C/O (1.35$^{+0.14}{-0.17}$) and a super metallicity with [Fe/H]$=2.19^{+0.51}{-0.63}$ composition. Given the near-solar metallicity of WASP-103 of [Fe/H]=0.06, this planet seems to be $\sim$100 more abundant than its host star. The free chemistry retrieval analysis yields a large abundance of FeH, H$^{-}$, CO$_2$ and CH$_4$. Additional data of better accuracy from future observations of JWST should provide better constraint of the atmospheric properties of WASP-103b.

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Y. Shi, W. Wang, G. Zhao, et. al.
Mon, 27 Mar 23
26/59

Comments: N/A

Acceleration of 1I/`Oumuamua from radiolytically produced H2 in H2O ice [EPA]

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http://arxiv.org/abs/2303.13698


In 2017, 1I/Oumuamua was identified as the first known interstellar object in the Solar System. Although typical cometary activity tracers were not detected,Oumuamua exhibited a significant non-gravitational acceleration. To date there is no explanation that can reconcile these constraints. Due to energetic considerations, outgassing of hyper-volatile molecules is favored over heavier volatiles like H2O and CO2. However, there are are theoretical and/or observational inconsistencies with existing models invoking the sublimation of pure H2 , N2, and CO. Non-outgassing explanations require fine-tuned formation mechanisms and/or unrealistic progenitor production rates. Here we report that the acceleration of Oumuamua is due to the release of entrapped molecular hydrogen which formed through energetic processing of an H2O-rich icy body. In this model,Oumuamua began as an icy planetesimal that was irradiated at low temperatures by cosmic rays during its interstellar journey, and experienced warming during its passage through the Solar System. This explanation is supported by a large body of experimental work showing that H2 is efficiently and generically produced from H2O ice processing, and that the entrapped H2 is released over a broad range of temperatures during annealing of the amorphous water matrix. We show that this mechanism can explain many of Oumuamua's peculiar properties without fine-tuning. This provides further support thatOumuamua originated as a planetesimal relic broadly similar to Solar System comets.

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J. Bergner and D. Seligman
Mon, 27 Mar 23
27/59

Comments: Author’s version; 23 pages, 3 figures

The clumpy structure of $ε$ Eridani's debris disc revisited by ALMA [EPA]

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http://arxiv.org/abs/2303.13584


$\epsilon$ Eridani is the closest star to our Sun known to host a debris disc. Prior observations in the (sub-)millimetre regime have potentially detected clumpy structure in the disc and attributed this to interactions with an (as yet) undetected planet. However, the prior observations were unable to distinguish between structure in the disc and background confusion. Here we present the first ALMA image of the entire disc, which has a resolution of 1.6″$\times$1.2″. We clearly detect the star, the main belt and two point sources. The resolution and sensitivity of this data allow us to clearly distinguish background galaxies (that show up as point sources) from the disc emission. We show that the two point sources are consistent with background galaxies. After taking account of these, we find that resolved residuals are still present in the main belt, including two clumps with a $>3\sigma$ significance — one to the east of the star and the other to the northwest. We perform $n$-body simulations to demonstrate that a migrating planet can form structures similar to those observed by trapping planetesimals in resonances. We find that the observed features can be reproduced by a migrating planet trapping planetesimals in the 2:1 mean motion resonance and the symmetry of the most prominent clumps means that the planet should have a position angle of either ${\sim10^\circ}$ or ${\sim190^\circ}$. Observations over multiple epochs are necessary to test whether the observed features rotate around the star.

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M. Booth, T. Pearce, A. Krivov, et. al.
Mon, 27 Mar 23
29/59

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

Tentative detection of titanium oxide in the atmosphere of WASP-69 b with a 4m ground-based telescope [EPA]

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http://arxiv.org/abs/2303.13202


Transiting planets provide unique opportunities for the atmospheric characterization of exoplanets as they can reveal composition and the temperature structures at the day-night terminator regions in planetary atmospheres, and help understand the atmospheric process and formation environments of exoplanets. Here, we present the optical transmission spectroscopic study of an inflated Saturn-mass planet WASP-69 b, obtained by the 4-meter ground-based telescope Southern Astrophysical Research Telescope (SOAR). We obtain spectroscopic transit light curves in 20 passbands from 502 to 890 nm, and fit them using Gaussian Processes and an analytical transit model to obtain independent transit depths for each. The derived transmission spectrum of WASP-69 b shows a slope with absorption depth increasing towards blue wavelengths, indicating a Rayleigh scattering in the atmosphere consistent with previous works. The retrieval analysis yields a tentative detection of TiO absorption feature in the transmission spectrum. We present the first results from the SOAR telescope to characterize exoplanetary atmospheres proving its capability and precision for hot Jupiters around bright stars in an area dominated by results from large ground-based telescopes or space telescopes.

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Q. Ouyang, W. Wang, M. Zhai, et. al.
Fri, 24 Mar 23
5/56

Comments: 21 pages, 17 figures, 9 tables, Accepted for publication in MNRAS

Three-dimensional, Time-dependent MHD Simulation of Disk-Magnetosphere-Stellar Wind Interaction in a T Tauri, Protoplanetary System [SSA]

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http://arxiv.org/abs/2303.13238


We present a three-dimensional, time-dependent, MHD simulation of the short-term interaction between a protoplanetary disk and the stellar corona in a T Tauri system. The simulation includes the stellar magnetic field, self-consistent coronal heating and stellar wind acceleration, and a disk rotating at sub-Keplerian velocity to induce accretion. We find that initially, as the system relaxes from the assumed initial conditions, the inner part of the disk winds around and moves inward and close to the star as expected. However, the self-consistent coronal heating and stellar wind acceleration build up the original state after some time, significantly pushing the disk out beyond $10R_\star$. After this initial relaxation period, we do not find clear evidence of a strong, steady accretion flow funneled along coronal field lines, but only weak, sporadic accretion. We produce synthetic coronal X-ray line emission light curves which show flare-like increases that are not correlated with accretion events nor with heating events. These variations in the line emission flux are the result of compression and expansion due to disk-corona pressure variations. Vertical disk evaporation evolves above and below the disk. However, the disk – stellar wind boundary stays quite stable, and any disk material that reaches the stellar wind region is advected out by the stellar wind.

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O. Cohen, C. Garraffo, J. Drake, et. al.
Fri, 24 Mar 23
7/56

Comments: Accepted to ApJ, 12 pages, 11 figures

Coronal X-Ray Emission from Nearby, Low-Mass, Exoplanet Host Stars Observed by the MUSCLES and Mega-MUSCLES HST Treasury Survey Projects [SSA]

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http://arxiv.org/abs/2303.12929


The high energy X-ray and ultraviolet (UV) radiation fields of exoplanet host stars play a crucial role in controlling the atmospheric conditions and the potential habitability of exoplanets. Major surveys of the X-ray/UV emissions from late-type (K and M spectral type) exoplanet hosts have been conducted by the MUSCLES and Mega-MUSCLES Hubble Space Telescope (HST) Treasury programs. These samples primarily consist of relatively old, “inactive”, low mass stars. In this paper we present results from X-ray observations of the coronal emission from these stars obtained using the Chandra X-ray Observatory, the XMM-Newton Observatory, and the Neil Gehrels Swift Observatory. The stars effectively sample the coronal activity of low-mass stars at a wide range of masses and ages. The vast majority (21 of 23) of the stars are detected and their X-ray luminosities measured. Short-term flaring variability is detected for most of the fully-convective (M $\leq$ 0.35 M${\odot}$) stars but not for the more massive M dwarfs during these observations. Despite this difference, the mean X-ray luminosities for these two sets of M dwarfs are similar with more massive (0.35 M${\odot}$ $\leq$ M $\leq$ 0.6 M$_{\odot}$) M dwarfs at $\sim$5 $\times$ 10$^{26}$ erg s$^{-1}$ compared to $\sim$2 $\times$ 10$^{26}$ erg s$^{-1}$ for fully-convective stars older than 1 Gyr. Younger, fully-convective M dwarfs have X-ray luminosities between 3 and 6 $\times$ 10$^{27}$ erg s$^{-1}$.The coronal X-ray spectra have been characterized and provide important information that is vital for the modeling of the stellar EUV spectra.

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A. Brown, P. Schneider, K. France, et. al.
Fri, 24 Mar 23
8/56

Comments: 39 pages, 15 figures. Accepted for publication in The Astronomical Journal

A spectacular jet from the bright 244-440 Orion proplyd: the MUSE NFM view [GA]

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http://arxiv.org/abs/2303.13205


In this work we present the highest spatial and spectral resolution integral field observations to date of the bipolar jet from the Orion proplyd 244-440 using MUSE NFM) observations on the VLT. We observed a previously unreported chain of six distinct knots in a roughly S-shaped pattern, and by comparing them with HST images we estimated proper motions in the redshifted knots of 9.5 mas yr$^{-1}$ with an inclination angle of $73^{\circ}$, though these quantities could not be measured for the blueshifted lobe. Analysis of the [FeII] and [NiII] lines suggests jet densities on the order of $\sim 10^5$ cm$^{-3}$. We propose that the observed S-shaped morphology originates from a jet launched by a smaller source with $M_\star < 0.2$ M${\odot}$ in orbital motion around a larger companion of $M\star \simeq 0.5$ M${\odot}$ at a separation of 30-40 au. The measured luminosities of the knots using the [OI]$\lambda6300$ and [SII]$\lambda6731$ lines were used to estimate a lower limit to the mass-loss rate in the jet of $1.3 \times 10^{-11}$ M${\odot}$ yr$^{-1}$ and an upper limit of $10^{-9}$ M$_{\odot}$ yr$^{-1}$, which is typical for low-mass driving sources. While the brightness asymmetry between the redshifted and blueshifted lobes is consistent with external irradiation, further analysis of the [NiII] and [FeII] lines suggests that photoionization of the jet is not likely to be a dominant factor, and that the emission is dominated by collisional excitation. The dynamical age of the jet compared to the anticipated survival time of the proplyd demonstrates that photoevaporation of the proplyd occurred prior to jet launching, and that this is still an active source. These two points suggest that the envelope of the proplyd may shield the jet from the majority of external radiation, and that photoionization of the proplyd does not appear to impact the ability of a star to launch a jet.

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A. Kirwan, C. Manara, E. Whelan, et. al.
Fri, 24 Mar 23
24/56

Comments: 30 pages, 20 figures

A Catalogue of Exoplanet Atmospheric Retrieval Codes [EPA]

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http://arxiv.org/abs/2303.12925


Exoplanet atmospheric retrieval is a computational technique widely used to infer properties of planetary atmospheres from remote spectroscopic observations. Retrieval codes typically employ Bayesian sampling algorithms or machine learning approaches to explore the range of atmospheric properties (e.g., chemical composition, temperature structure, aerosols) compatible with an observed spectrum. However, despite the wide adoption of exoplanet retrieval techniques, there is currently no systematic summary of exoplanet retrieval codes in the literature. Here, we provide a catalogue of the atmospheric retrieval codes published to date, alongside links to their respective code repositories where available. Our catalogue will be continuously updated via a Zenodo archive.

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R. MacDonald and N. Batalha
Fri, 24 Mar 23
25/56

Comments: 5 pages, 1 giant Table. Published in RNAAS. Live catalogue will be updated at this https URL

Synchronous rotation in the (136199) Eris-Dysnomia system [EPA]

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http://arxiv.org/abs/2303.13445


We combine photometry of Eris from a 6-month campaign on the Palomar 60-inch telescope in 2015, a 1-month Hubble Space Telescope WFC3 campaign in 2018, and Dark Energy Survey data spanning 2013–2018 to determine a light curve of definitive period $15.771\pm 0.008$~days (1-$\sigma$ formal uncertainties), with nearly sinusoidal shape and peak-to-peak flux variation of 3\%. This is consistent at part-per-thousand precision with the $P=15.78590\pm0.00005$~day period of Dysnomia’s orbit around Eris, strengthening the recent detection of synchronous rotation of Eris by Szakats et al (2022) with independent data. Photometry from Gaia is consistent with the same light curve. We detect a slope of $0.05\pm0.01$~mag per degree of Eris’ brightness with respect to illumination phase, intermediate between Pluto’s and Charon’s values. Variations of $0.3$~mag are detected in Dysnomia’s brightness, plausibly consistent with a double-peaked light curve at the synchronous period. The synchronous rotation of Eris is consistent with simple tidal models initiated with a giant-impact origin of the binary, but is difficult to reconcile with gravitational capture of Dysnomia by Eris.

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G. Bernstein, B. Holler, R. Navarro-Escamilla, et. al.
Fri, 24 Mar 23
37/56

Comments: Submitted to Planetary Science Journal

An extreme test case for planet formation: a close-in Neptune orbiting an ultracool star [EPA]

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http://arxiv.org/abs/2303.13321


In current theories of planet formation, close-orbiting planets as massive as Neptune are expected to be very rare around low-mass stars. We report the discovery of a Neptune-mass planet orbiting the `ultracool’ star LHS 3154, which is nine times less massive than the Sun. The planet’s orbital period is 3.7 days and its minimum mass is 13.2 Earth masses, giving it the largest known planet-to-star mass ratio among short-period planets ($<$\,100 days) orbiting ultracool stars. Both the core accretion and gravitational instability theories for planet formation struggle to account for this system. In the core-accretion scenario, in particular, the dust mass of the protoplanetary disk would need to be an order of magnitude higher than typically seen in protoplanetary disk observations of ultracool stars.

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G. Stefansson, S. Mahadevan, Y. Miguel, et. al.
Fri, 24 Mar 23
47/56

Comments: Original Manuscript as submitted to Science on Oct 17, 2022. In review

Implications for the Formation of 2005 UD from a New Convex Shape Model [EPA]

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http://arxiv.org/abs/2303.12991


(155140) 2005 UD has a similar orbit to (3200) Phaethon, an active asteroid in a highly eccentric orbit thought to be the source of the Geminid meteor shower. Evidence points to a genetic relationship between these two objects, but we have yet to fully understand how 2005 UD and Phaethon could have separated into this associated pair. Presented herein are new observations of 2005 UD from five observatories that were carried out during the 2018, 2019, and 2021 apparitions. We implemented light curve inversion using our new data, as well as dense and sparse archival data from epochs in 2005–2021 to better constrain the rotational period and derive a convex shape model of 2005 UD. We discuss two equally well-fitting pole solutions ($\lambda = 116.6^{\circ}$, $\beta = -53.6^{\circ}$) and ($\lambda = 300.3^{\circ}$, $\beta = -55.4^{\circ}$), the former largely in agreement with previous thermophysical analyses and the latter interesting due to its proximity to Phaethon’s pole orientation. We also present a refined sidereal period of $P_{\text{sid}} = 5.234246 \pm 0.000097$ hr. A search for surface color heterogeneity showed no significant rotational variation. An activity search using the deepest stacked image available of 2005 UD near aphelion did not reveal a coma or tail but allowed modeling of an upper limit of 0.04 to 0.37~kg s$^{-1}$ for dust production. We then leveraged our spin solutions to help limit the range of formation scenarios and the link to Phaethon in the context of nongravitational forces and timescales associated with the physical evolution of the system.

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J. Kueny, C. Chandler, M. Devogèle, et. al.
Fri, 24 Mar 23
49/56

Comments: 22 pages, 7 figure, 7 tables

On the origin of extreme trans-Neptunian objects within Modified Newtonian Dynamics [EPA]

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http://arxiv.org/abs/2303.13339


In this work, we investigate the dynamical origin of extreme trans-Neptunian objects (ETNOs) under the action of the External Field Effect (EFE), which is a consequence of Modified Newtonian Dynamics (MOND) applied to gravity around the Sun embedded in the gravitational field of the Galaxy. We perform N-body integrations of known ETNOs treated as massless particles and perturbed by four giant planets and EFE. Backward integrations show that these objects originated in the giant planet region, from where they were scattered and then evolved to their current orbits. A striking example of such evolution is Sedna, which may have been temporarily in a horseshoe orbit with Jupiter and Saturn only $30$~Myr ago. Another interesting example is the newly discovered retrograde ETNOs, whose dynamical connection with prograde ETNOs and Centaurs is shown. The EFE is considered as an alternative to Planet Nine in explaining the anomalous distribution of ETNO orbits, namely the orbital plane clustering and apsidal confinement. We also analyse the effect of MOND on the obliquity of the solar spin with respect to the invariant plane of the solar system. Finally, we discuss the significance of trans-Neptunian solar system in the context of the dark matter hypothesis.

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C. Migaszewski
Fri, 24 Mar 23
56/56

Comments: submitted to MNRAS