Category Archives: Earth and Planetary Astrophysics

The Mantis Network III: Expanding the limits of chemical searches within ultra hot-Jupiters. New detections of Ca I, V I, Ti I, Cr I, Ni I, Sr II, Ba II, and Tb II in KELT-9 b [EPA]

Posted on by

http://arxiv.org/abs/2304.04285


Cross-correlation spectroscopy is an invaluable tool in the study of exoplanets. However, aliasing between spectral lines makes it vulnerable to systematic biases. This work strives to constrain the aliases of the cross-correlation function to provide increased confidence in the detections of elements in the atmospheres of ultra-hot Jupiters (UHJs) observed with high-resolution spectrographs. We use a combination of archival transit observations of the UHJ KELT-9 b obtained with the HARPS-N and CARMENES spectrographs and show that it is possible to leverage each instrument’s strengths to produce robust detections at substantially reduced signal-to-noise. Aliases that become present at low signal-to-noise regimes are constrained through a linear regression model. We confirm previous detections of H I, Na I, Mg I, Ca II, Sc II, Ti II, Cr II, Fe I, and Fe II, and detect eight new species Ca I, Cr I, Ni I, Sr II, Tb II at the 5$\sigma$ level and Ti I, V I, Ba II above the 3$\sigma$ level. Ionised terbium (Tb II) has never before been seen in an exoplanet atmosphere. We further conclude that a 5$\sigma$ threshold may not provide a reliable measure of confidence when used to claim detections, unless the systematics in the cross-correlation function caused by aliases are taken into account.

Read this paper on arXiv…

N. Borsato, H. Hoeijmakers, B. Prinoth, et. al.
Tue, 11 Apr 23
43/63

Comments: Accepted for publication on the 1st of April 2023

Characterisation of the upper atmospheres of HAT-P-32 b, WASP-69 b, GJ 1214 b, and WASP-76 b through their He I triplet absorption [EPA]

Posted on by

http://arxiv.org/abs/2304.03839


Characterisation of atmospheres undergoing photo-evaporation is key to understanding the formation, evolution, and diversity of planets. However, only a few upper atmospheres that experience this kind of hydrodynamic escape have been characterised. Our aim is to characterise the upper atmospheres of the hot Jupiters HAT-P-32 b and WASP-69 b, the warm sub-Neptune GJ 1214 b, and the ultra-hot Jupiter WASP-76 b through high-resolution observations of their HeI triplet absorption. In addition, we also reanalyse the warm Neptune GJ 3470 b and the hot Jupiter HD 189733 b. We used a spherically symmetric 1D hydrodynamic model coupled with a non-local thermodynamic equilibrium model. Comparing synthetic absorption spectra with observations, we constrained the main parameters of the upper atmosphere of these planets and classify them according to their hydrodynamic regime. Our results show that HAT-P-32 b photo-evaporates at (130$\pm$70)$\times$10$^{11}$ gs$^{-1}$ with a hot (12 400$\pm$2900 K) upper atmosphere; WASP-69 b loses its atmosphere at (0.9$\pm$0.5)$\times$10$^{11}$ gs$^{-1}$ and 5250$\pm$750 K; and GJ 1214 b, with a relatively cold outflow of 3750$\pm$750 K, photo-evaporates at (1.3$\pm$1.1)$\times$10$^{11}$ gs$^{-1}$. For WASP-76 b, its weak absorption prevents us from constraining its temperature and mass-loss rate significantly; we obtained ranges of 6000-17 000\,K and 23.5$\pm$21.5$\times$10$^{11}$ gs$^{-1}$. Our reanalysis of GJ 3470 b yields colder temperatures, 3400$\pm$350 K, but practically the same mass-loss rate as in our previous results. Our reanalysis of HD 189733 b yields a slightly higher mass-loss rate, (1.4$\pm$0.5)$\times$10$^{11}$ gs$^{-1}$, and temperature, 12 700$\pm$900 K compared to previous estimates. Our results support that photo-evaporated outflows tend to be very light.

Read this paper on arXiv…

M. Lampón, M. López-Puertas, J. Sanz-Forcada, et. al.
Tue, 11 Apr 23
45/63

Comments: N/A

Sublimation of ices during the early evolution of Kuiper belt objects [EPA]

Posted on by

http://arxiv.org/abs/2304.04482


Kuiper belt objects, such as Arrokoth, the probable progenitors of short-period comets, formed and evolved at large heliocentric distances, where the ambient temperatures appear to be sufficiently low for preserving volatile ices. By detailed numerical simulations, we follow the long-term evolution of small bodies, composed of amorphous water ice, dust, and ices of other volatile species that are commonly observed in comets. The heat sources are solar radiation and the decay of short-lived radionuclides. The bodies are highly porous and gases released in the interior flow through the porous medium. The most volatile ices, CO and CH$_4$ , are found to be depleted down to the center over a time scale on the order of 100 Myr. Sublimation fronts advance from the surface inward, and when the temperature in the inner part rises sufficiently, bulk sublimation throughout the interior reduces gradually the volatile ices content until they are completely lost. All the other ices survive, which is compatible with data collected by New Horizons on Arrokoth, showing the presence of methanol, and possibly, H$_2$O, CO$_2$, NH$_3$ and C$_2$H$_6$, but no hypervolatiles. The effect of short-lived radionuclides is to increase the sublimation equilibrium temperatures and reduce volatile depletion times. We consider the effect of the bulk density, abundance ratios and heliocentric distance. At 100~au, CO is depleted, but CH$_4$ survives to present time, except for a thin outer layer. Since CO is abundantly detected in comets, we conclude that the source of highly volatile species in active comets must be gas trapped in amorphous ice.

Read this paper on arXiv…

A. Parhi and D. Prialnik
Tue, 11 Apr 23
46/63

Comments: 8 pages, 7 figures

Jupiter's cloud-level variability triggered by torsional oscillations in the interior [EPA]

Posted on by

http://arxiv.org/abs/2304.04460


Jupiter’s weather layer exhibits long-term and quasi-periodic cycles of meteorological activity that can completely change the appearance of its belts and zones. There are cycles with intervals from 4 to 9 years, dependent on the latitude, which were detected in 5$\mu$m radiation, which provides a window into the cloud-forming regions of the troposphere; however, the origin of these cycles has been a mystery. Here we propose that magnetic torsional oscillations/waves arising from the dynamo region could modulate the heat transport and hence be ultimately responsible for the variability of the tropospheric banding. These axisymmetric waves are magnetohydrodynamic waves influenced by the rapid rotation, which have been detected in Earth’s core, and have been recently suggested to exist in Jupiter by the observation of magnetic secular variations by Juno. Using the magnetic field model JRM33, together with the density distribution model, we compute the expected speed of these waves. For the waves excited by variations in the zonal jet flows, their wavelength can be estimated from the width of the alternating jets, yielding waves with a half period of 3.2-4.7 years in 14-23$^\circ$N, consistent with the intervals with the cycles of variability of Jupiter’s North Equatorial Belt and North Temperate Belt identified in the visible and infrared observations. The nature of these waves, including the wave speed and the wavelength, is revealed by a data-driven technique, dynamic mode decomposition, applied to the spatio-temporal data for 5$\mu$m emission. Our results imply that exploration of these magnetohydrodynamic waves may provide a new window to the origins of quasi-periodic patterns in Jupiter’s tropospheric clouds and to the internal dynamics and the dynamo of Jupiter.

Read this paper on arXiv…

K. Hori, C. Jones, A. Antuñano, et. al.
Tue, 11 Apr 23
50/63

Comments: N/A

TOI-3785 b: A Low-Density Neptune Orbiting an M2-Dwarf Star [EPA]

Posted on by

http://arxiv.org/abs/2304.04730


Using both ground-based transit photometry and high-precision radial velocity (RV) spectroscopy, we confirm the planetary nature of TOI-3785 b. This transiting Neptune orbits an M2-Dwarf star with a period of ~4.67 days, a planetary radius of 5.14 +/- 0.16 Earth Radii, a mass of 14.95 +4.10, -3.92 Earth Masses, and a density of 0.61 +0.18, -0.17 g/cm^3. TOI-3785 b belongs to a rare population of Neptunes (4 Earth Radii < Rp < 7 Earth Radii) orbiting cooler, smaller M-dwarf host stars, of which only ~10 have been confirmed. By increasing the number of confirmed planets, TOI-3785 b offers an opportunity to compare similar planets across varying planetary and stellar parameter spaces. Moreover, with a high transmission spectroscopy metric (TSM) of ~150 combined with a relatively cool equilibrium temperature of 582 +/- 16 K and an inactive host star, TOI-3785 b is one of the more promising low-density M-dwarf Neptune targets for atmospheric follow-up. Future investigation into atmospheric mass loss rates of TOI-3785 b may yield new insights into the atmospheric evolution of these low-mass gas planets around M-dwarfs.

Read this paper on arXiv…

L. Powers, J. Libby-Roberts, A. Lin, et. al.
Tue, 11 Apr 23
59/63

Comments: 22 pages, 6 figures, 6 tables, Submitted to AJ

Molecules with ALMA at Planet-forming Scales (MAPS). Complex Kinematics in the AS 209 Disk Induced by a Forming Planet and Disk Winds [EPA]

Posted on by

http://arxiv.org/abs/2304.03665


We study the kinematics of the AS 209 disk using the J=2-1 transitions of $^{12}$CO, $^{13}$CO, and C$^{18}$O. We derive the radial, azimuthal, and vertical velocity of the gas, taking into account the lowered emission surface near the annular gap at ~1.7 (200 au) within which a candidate circumplanetary disk-hosting planet has been reported previously. In $^{12}$CO and $^{13}$CO, we find a coherent upward flow arising from the gap. The upward gas flow is as fast as $150~{\rm m~s}^{-1}$ in the regions traced by $^{12}$CO emission, which corresponds to about 50% of the local sound speed or $6\%$ of the local Keplerian speed. Such an upward gas flow is difficult to reconcile with an embedded planet alone. Instead, we propose that magnetically driven winds via ambipolar diffusion are triggered by the low gas density within the planet-carved gap, dominating the kinematics of the gap region. We estimate the ambipolar Elsasser number, Am, using the HCO$^+$ column density as a proxy for ion density and find that Am is ~0.1 at the radial location of the upward flow. This value is broadly consistent with the value at which numerical simulations find ambipolar diffusion drives strong winds. We hypothesize the activation of magnetically-driven winds in a planet-carved gap can control the growth of the embedded planet. We provide a scaling relationship which describes the wind-regulated terminal mass: adopting parameters relevant to 100 au from a solar-mass star, we find the wind-regulated terminal mass is about one Jupiter mass, which may help explain the dearth of directly imaged super-Jovian-mass planets.

Read this paper on arXiv…

M. Galloway-Sprietsma, J. Bae, R. Teague, et. al.
Mon, 10 Apr 23
8/36

Comments: N/A

The Disc Miner II: Revealing Gas substructures and Kinematic signatures from Planet-disc interaction through line profile analysis [EPA]

Posted on by

http://arxiv.org/abs/2304.03607


[Abridged] The aim of this work is to identify potential signatures from planet-disc interaction in the circumstellar discs around the young stars MWC 480, HD 163296, AS 209, IM Lup, and GM Aur, through the study of molecular lines observed as part of the ALMA large program MAPS. Extended and localised perturbations in velocity, line width, and intensity have been analysed jointly using the discminer framework, in three bright CO lines, 12CO, 13CO and C18O $J=2-1$, to provide a comprehensive summary of the kinematic and column density substructures that planets might be actively sculpting in these discs. We find convincing evidence for the presence of four giant planets located at wide orbits in three of the discs in the sample: two around HD 163296, one in MWC 480, and one in AS 209. One of the planet candidates in HD 163296, P94, originally proposed by Izquierdo et al. (2022) using lower velocity resolution 12CO data, is confirmed and linked to localised velocity and line width perturbations in 13CO and C18O too. We highlight that line widths are also powerful tracers of planet-forming sites as they are sensitive to turbulent motions triggered by planet-disc interactions. In MWC 480, we identified non-axisymmetric line width enhancements around the radial separation of candidate planet-driven buoyancy spirals proposed by Teague et al. (2021), which we used to narrow the location of the planet candidate to an orbital radius of $R=245$ au and $\rm{PA}=193^\circ$. In the disc of AS 209, we found excess 12CO line widths centred at $R=210$ au, $\rm{PA}=151^\circ$, spanning around the immediate vicinity of the circumplanetary disc candidate proposed by Bae et al. (2022), which further supports its presence. Our simultaneous analysis of multiple tracers and observables aims to lay the groundwork for robust studies of molecular line properties focused on the search for young planets in discs.

Read this paper on arXiv…

A. Izquierdo, L. Testi, S. Facchini, et. al.
Mon, 10 Apr 23
13/36

Comments: Accepted for publication in A&A

Water Production Rates from SOHO/SWAN Observations of Comets C/2020 S3 (Erasmus), C/2021 A1 (Leonard) and C/2021 O3 (PanSTARRS) [EPA]

Posted on by

http://arxiv.org/abs/2304.03333


In 2021 and 2022 the hydrogen comae of three long period comets, C/2020 S3 (Erasmus), C/2021 A1 (Leonard) and C/2021 O3 (PanSTARRS) were observed with the Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyman-alpha camera on the SOlar and Heliosphere Observer (SOHO) satellite. SWAN obtains nearly daily full-sky images of the hydrogen Lyman-alpha distribution of the interstellar hydrogen as it passes through the solar system yielding information about the solar wind and solar ultraviolet fluxes that eats away at it by ionization and charge exchange. The hydrogen comae of comets, when of sufficient brightness, are also observed. Water production rates have been calculated over time for each of these comets. Of particular interest are comet C/2021 O3 (PanSTARRS) which apparently disintegrated a few days before its perihelion at 0.28 au and C/2021 A1 (Leonard) which also disintegrated beginning about 20 days after its perihelion peak. The behavior of comet C/2020 S3 (Erasmus) was more typical without dramatic fading, but still was asymmetric about perihelion, with a more rapid turn on before perihelion and more extended activity well after perihelion.

Read this paper on arXiv…

M. Combi, T. Mäkinen, J. Bertaux, et. al.
Mon, 10 Apr 23
16/36

Comments: 20 pages, 4 Figures, 4 Tables

The PEPSI Exoplanet Transit Survey. III: The detection of FeI, CrI and TiI in the atmosphere of MASCARA-1 b through high-resolution emission spectroscopy [EPA]

Posted on by

http://arxiv.org/abs/2304.03328


Hot giant planets like MASCARA-1 b are expected to have thermally inverted atmospheres, that makes them perfect laboratory for the atmospheric characterization through high-resolution spectroscopy. Nonetheless, previous attempts of detecting the atmosphere of MASCARA-1 b in transmission have led to negative results.
In this paper we aim at the detection of the optical emission spectrum of MASCARA-1 b.
We used the high-resolution spectrograph PEPSI to observe MASCARA-1 (spectral type A8) near the secondary eclipse of the planet. We cross-correlated the spectra with synthetic templates computed for several atomic and molecular species.
We obtained the detection of FeI, CrI and TiI in the atmosphere of MASCARA-1 b with a S/N ~7, 4 and 5 respectively, and confirmed the expected systemic velocity of ~13 km/s and the radial velocity semi-amplitude of MASCARA-1 b of ~200 km/s. The detection of Ti is of particular importance in the context of the recently proposed Ti cold-trapping below a certain planetary equilibrium temperature.
We confirm the presence of an the atmosphere around MASCARA-1 b through emission spectroscopy. We conclude that the atmospheric non detection in transmission spectroscopy is due to the high gravity of the planet and/or to the overlap between the planetary track and its Doppler shadow.

Read this paper on arXiv…

G. Scandariato, F. Borsa, A. Bonomo, et. al.
Mon, 10 Apr 23
34/36

Comments: N/A

The Runaway Greenhouse Effect on Hycean Worlds [EPA]

Posted on by

http://arxiv.org/abs/2304.02698


Hycean worlds are a proposed subset of sub-Neptune exoplanets with substantial water inventories, liquid surface oceans and extended hydrogen-dominated atmospheres that could be favourable for habitability. In this work, we aim to quantitatively define the inner edge of the Hycean habitable zone using a 1D radiative-convective model. As a limiting case, we model a dry hydrogen-helium envelope above a surface ocean. We find that 10 to 20 bars of atmosphere produces enough greenhouse effect to drive a liquid surface ocean supercritical when forced with current Earth-like instellation. Introducing water vapour into the atmosphere, we show the runaway greenhouse instellation limit is greatly reduced due to the presence of superadiabatic layers where convection is inhibited. This moves the inner edge of the habitable zone from $\approx$ 1 AU for a G-star to 1.6 AU (3.85 AU) for a Hycean world with a H$_2$-He inventory of 1 bar (10 bar). For an M-star, the inner edge is equivalently moved from 0.17 AU to 0.28 AU (0.54 AU). Our results suggest that most of the current Hycean world observational targets are not likely to sustain a liquid water ocean. We present an analytical framework for interpreting our results, finding that the maximum possible OLR scales approximately inversely with the dry mass inventory of the atmosphere. We discuss the possible limitations of our 1D modelling and recommend the use of 3D convection-resolving models to explore the robustness of superadiabatic layers.

Read this paper on arXiv…

H. Innes, S. Tsai and R. Pierrehumbert
Fri, 7 Apr 23
4/50

Comments: Submitted to ApJ, comments welcome

Spectral Type and Geometric Albedo of (98943) 2001 CC21, the Hayabusa2# Mission Target [EPA]

Posted on by

http://arxiv.org/abs/2304.02917


We conducted optical polarimetry and near-infrared spectroscopy of JAXA’s Hayabusa2# mission target, (98943) 2001 CC21, in early 2023. Our new observations indicated that this asteroid has a polarimetric inversion angle of ~21 deg, absorption bands around 0.9 and 1.9 um, and a geometric albedo of 0.285 +- 0.083. All these features are consistent with those of S-type but inconsistent with L-type. Based on this evidence, we conclude that JAXA’s Hayabusa2# spacecraft will explore an S-type asteroid with albedo and size (0.42-0.56 km when we assume the absolute magnitude of 18.6) similar to (25143) Itokawa.

Read this paper on arXiv…

J. Geem, M. Ishiguro, M. Granvik, et. al.
Fri, 7 Apr 23
27/50

Comments: 5 pages, 3 figures, Submitted to MNRAS Letter on 2023 April 3

Hyades Member K2-136c: The Smallest Planet in an Open Cluster with a Precisely Measured Mass [EPA]

Posted on by

http://arxiv.org/abs/2304.02779


K2-136 is a late-K dwarf ($0.742\pm0.039$ M$\odot$) in the Hyades open cluster with three known, transiting planets and an age of $650\pm70$ Myr. Analyzing K2 photometry, we found that planets K2-136b, c, and d have periods of $8.0$, $17.3$, and $25.6$ days and radii of $1.014\pm0.050$ R$\oplus$, $3.00\pm0.13$ R$\oplus$, and $1.565\pm0.077$ R$\oplus$, respectively. We collected 93 radial velocity measurements (RVs) with the HARPS-N spectrograph (TNG) and 22 RVs with the ESPRESSO spectrograph (VLT). Analyzing HARPS-N and ESPRESSO data jointly, we found K2-136c induced a semi-amplitude of $5.49\pm0.53$ m s$^{-1}$, corresponding to a mass of $18.1\pm1.9$ M$\oplus$. We also placed $95$% upper mass limits on K2-136b and d of $4.3$ and $3.0$ M$\oplus$, respectively. Further, we analyzed HST and XMM-Newton observations to establish the planetary high-energy environment and investigate possible atmospheric loss. K2-136c is now the smallest planet to have a measured mass in an open cluster and one of the youngest planets ever with a mass measurement. K2-136c has $\sim$75% the radius of Neptune but is similar in mass, yielding a density of $3.69^{+0.67}_{-0.56}$ g cm$^{-3}$ ($\sim$2-3 times denser than Neptune). Mass estimates for K2-136b (and possibly d) may be feasible with more RV observations, and insights into all three planets’ atmospheres through transmission spectroscopy would be challenging but potentially fruitful. This research and future mass measurements of young planets are critical for investigating the compositions and characteristics of small exoplanets at very early stages of their lives and providing insights into how exoplanets evolve with time.

Read this paper on arXiv…

A. Mayo, C. Dressing, A. Vanderburg, et. al.
Fri, 7 Apr 23
29/50

Comments: Accepted in AJ, 25 pages, 10 figures, 5 tables

On Elusive Observations and a Sly Companion of Comet Wirtanen (C/1956 F1) [EPA]

Posted on by

http://arxiv.org/abs/2304.02872


Noting that the extensive astrometric observations of the double comet Wirtanen (C/1956 F1) made by E. Roemer have never been published, I replicate the contents of a fortuitously discovered copy of her measurement records of the companion’s offsets from the main mass in 1957-1959 and use with such data by others to refine the fragmentation solution. The sublimation-driven nongravitational acceleration is shown to essentially control the companion’s motion in the orbital plane. The fragmentation parameters derived by the author in 1978 have now been improved and strong disagreement with the independent results by Roemer is noted. The revised model is employed to predict the positions of the companion on the plates exposed by Roemer on 25 September 1960, which she reported to show the principal nucleus but not the companion. At my request, these plates have now been scanned and processed at the Lowell Observatory, and the companion is found to be located at the predicted position. The images of the main mass and the companion on one of the two plates are displayed.

Read this paper on arXiv…

Z. Sekanina
Fri, 7 Apr 23
40/50

Comments: 10 pages, 3 figures, 4 tables

High-resolution Emission Spectroscopy of the Ultrahot Jupiter KELT-9b: Little Variation in Day- and Nightside Emission Line Contrasts [EPA]

Posted on by

http://arxiv.org/abs/2304.03248


The transmission spectrum of the ultrahot Jupiter KELT-9b ($T_{eq}$ $\sim$ 4000 K) exhibits absorption by several metal species. We searched for atomic and molecular lines in its emission spectrum by observing partial phase curves with the CARMENES spectrograph ($R$ $\sim$ 80,000 $-$ 95,000). We find evidence for emission by Si I in the atmosphere of KELT-9b for the first time. Additionally we find evidence for emission by Mg I and Ca II, which were previously detected in transmission, and confirmed earlier detections of Fe I emission. Conversely, we find no evidence for dayside emission from Al I, Ca I, Cr I, FeH, Fe II, K I, Li I, Mg II, Na I, OH, Ti I, TiO, V I, V II, VO, and Y I. By employing likelihood mapping, we find indications of there being little variation in emission line contrast between the day- and nightsides $-$suggesting that KELT-9b may harbor iron emission on its nightside. Our results demonstrate that high-resolution ground-based emission spectroscopy can provide valuable insights into exoplanet atmospheres.

Read this paper on arXiv…

A. Ridden-Harper, E. Mooij, R. Jayawardhana, et. al.
Fri, 7 Apr 23
41/50

Comments: Accepted for publication in AJ

Photometry of outer Solar System objects from the Dark Energy Survey I: photometric methods, light curve distributions and trans-Neptunian binaries [EPA]

Posted on by

http://arxiv.org/abs/2304.03017


We report the methods of and initial scientific inferences from the extraction of precision photometric information for the $>800$ trans-Neptunian objects (TNOs) discovered in the images of the Dark Energy Survey (DES). Scene-modelling photometry is used to obtain shot-noise-limited flux measures for each exposure of each TNO, with background sources subtracted. Comparison of double-source fits to the pixel data with single-source fits are used to identify and characterize two binary TNO systems. A Markov Chain Monte Carlo method samples the joint likelihood of the intrinsic colors of each source as well as the amplitude of its flux variation, given the time series of multiband flux measurements and their uncertainties. A catalog of these colors and light curve amplitudes $A$ is included with this publication. We show how to assign a likelihood to the distribution $q(A)$ of light curve amplitudes in any subpopulation. Using this method, we find decisive evidence (i.e. evidence ratio $<0.01$) that cold classical (CC) TNOs with absolute magnitude $6<H_r<8.2$ are more variable than the hot classical (HC) population of the same $H_r$, reinforcing theories that the former form in situ and the latter arise from a different physical population. Resonant and scattering TNOs in this $H_r$ range have variability consistent with either the HC’s or CC’s. DES TNOs with $H_r<6$ are seen to be decisively less variable than higher-$H_r$ members of any dynamical group, as expected. More surprising is that detached TNOs are decisively less variable than scattering TNOs, which requires them to have distinct source regions or some subsequent differential processing.

Read this paper on arXiv…

P. Bernardinelli, G. Bernstein, N. Jindal, et. al.
Fri, 7 Apr 23
43/50

Comments: Submitted to AAS journals, data release forthcoming and will be included in journal version

MOA-2022-BLG-249Lb: Nearby microlensing super-Earth planet detected from high-cadence surveys [EPA]

Posted on by

http://arxiv.org/abs/2304.02815


We investigate the data collected by the high-cadence microlensing surveys during the 2022 season in search for planetary signals appearing in the light curves of microlensing events. From this search, we find that the lensing event MOA-2022-BLG-249 exhibits a brief positive anomaly that lasted for about 1 day with a maximum deviation of $\sim 0.2$~mag from a single-source single-lens model. We analyze the light curve under the two interpretations of the anomaly: one originated by a low-mass companion to the lens (planetary model) and the other originated by a faint companion to the source (binary-source model). It is found that the anomaly is better explained by the planetary model than the binary-source model. We identify two solutions rooted in the inner–outer degeneracy, for both of which the estimated planet-to-host mass ratio, $q\sim 8\times 10^{-5}$, is very small. With the constraints provided by the microlens parallax and the lower limit on the Einstein radius, as well as the blend-flux constraint, we find that the lens is a planetary system, in which a super-Earth planet, with a mass $(4.83\pm 1.44)~M_\oplus$, orbits a low-mass host star, with a mass $(0.18\pm 0.05)~M_\odot$, lying in the Galactic disk at a distance $(2.00\pm 0.42)$~kpc. The planet detection demonstrates the elevated microlensing sensitivity of the current high-cadence lensing surveys to low-mass planets.

Read this paper on arXiv…

C. Han, A. Gould, Y. Jung, et. al.
Fri, 7 Apr 23
46/50

Comments: 10 pages, 9 figures

Intra-system uniformity: a natural outcome of dynamical sculpting [EPA]

Posted on by

http://arxiv.org/abs/2304.02634


There is evidence that exoplanet systems display intra-system uniformity in mass, radius, and orbital spacing (like “peas in a pod”) when compared with the system-to-system variations of planetary systems. This has been interpreted as the outcome of the early stages of planet formation, indicative of a picture in which planets form at characteristic mass scales with uniform separations. In this paper, we argue instead that intra-system uniformity in planet sizes and orbital spacings likely arose from the long-term dynamical sculpting of initially-overly-packed planetary systems (in other words, the giant impact phase). With a suite of $N$-body simulations, we demonstrate that systems with random initial masses and compact planet spacings naturally develop intra-system uniformity, in quantitative agreement with observations, due to collisions between planets. Our results suggest that the pre-giant impact planet mass distribution is fairly wide and provide evidence for the prevalence of dynamical sculpting in shaping the observed population of exoplanets.

Read this paper on arXiv…

C. Lammers, N. Murray and S. Hadden
Thu, 6 Apr 23
4/76

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

Accretion of aerodynamically large pebbles [EPA]

Posted on by

http://arxiv.org/abs/2304.02044


Due to their aerodynamical coupling with gas, pebbles in protoplanetary discs can drift over large distances to support planet growth in the inner disc. In the past decade, this pebble accretion has been studied extensively for aerodynamically small pebbles (Stokes number St < 1). However, accretion can also operate in the St > 1 mode, e.g., when planetesimals collisionally fragment to smaller bodies or when the primordial gas disc disperses. This work aims to extend the study of pebble accretion to these aerodynamically loosely coupled particles. We integrate the pebble’s equation of motion, accounting for gas drag, stellar and planetary gravity, in the midplane of a laminar disc. The accretion probability ($\epsilon$) is calculated as function of Stokes number, disc pressure gradient index, planet mass and eccentricity. We find that for Stokes number above unity $\epsilon$(St) first rises, due to lower drift and aided by a large atmospheric capture radius, until it reaches a plateau where the efficiency approaches 100 per cent. At high St the plateau region terminates as particles become trapped in resonance. These results are well described by a semi-analytical “kick-and-drift” model and we also provide fully analytical prescriptions for $\epsilon$. We apply our model to the accretion of $\sim 30 \mu$m dust particles in a dispersing protoplanetary and secondary (CO-rich) debris disc. It shows that physically small particles are mainly accreted as aerodynamically large Stokes number pebbles during the debris disc phase. Earth-mass planets may obtain $\sim 25$ per cent of their heavy elements through this late accretion phase.

Read this paper on arXiv…

H. Huang and C. Ormel
Thu, 6 Apr 23
15/76

Comments: 19 pages, 16 figures, 5 tables. Accepted for publication in MNRAS

The influence of cold Jupiters in the formation of close-in planets. I. planetesimal transport [EPA]

Posted on by

http://arxiv.org/abs/2304.02045


The formation of a cold Jupiter (CJ) is expected to quench the influx of pebbles and the migration of cores interior to its orbit, thus limiting the efficiency of rocky planet formation either by pebble accretion and/or orbital migration. Observations, however, show that the presence of outer CJs ( >1 au and >0.3 Jupiter masses) correlates with the presence of inner Super Earths (at <1 au). This observation may simply be a result of an enhanced initial reservoir of solids in the nebula required to form a CJ or a yet-to-be-determined mechanism assisted by the presence of the CJ. In this work, we focus on the latter alternative and study the orbital transport of planetesimals interior to a CJ subject to the gravity and drag from a viscously-evolving gaseous disk. We find that a secular resonance sweeping inwards through the disk gradually transports rings of planetesimals when their drag-assisted orbital decay is faster than the speed of the resonance scanning. This snowplow-like process leads to large concentration (boosted by a factor of ~10-100) of size-segregated planetesimal rings with aligned apsidal lines, making their expected collisions less destructive due to their reduced velocity dispersion. This process is efficient for a wide range of alpha-disk models and Jovian masses, peaking for ~1-5 Jupiter masses, typical of observed CJs in radial velocity surveys. Overall, our work highlights the major role that the disk’s gravity may have on the orbital redistribution of planetesimals, depicting a novel avenue by which CJs may enhance the formation of inner planetary systems, including super-Earths and perhaps even warm and hot Jupiters.

Read this paper on arXiv…

S. Best, A. Sefilian and C. Petrovich
Thu, 6 Apr 23
34/76

Comments: 18 pages, 11 figures

Geometric Solution to the Angles-Only Initial Orbit Determination Problem [EPA]

Posted on by

http://arxiv.org/abs/2304.02157


Initial orbit determination (IOD) from line-of-sight (i.e., bearing) measurements is a classical problem in astrodynamics. Indeed, there are many well-established methods for performing the IOD task when given three line-of-sight observations at known times. Interestingly, and in contrast to these existing methods, concepts from algebraic geometry may be used to produce a purely geometric solution. This idea is based on the fact that bearings from observers in general position may be used to directly recover the shape and orientation of a three-dimensional conic (e.g., a Keplerian orbit) without any need for knowledge of time. In general, it is shown that five bearings at unknown times are sufficient to recover the orbit — without the use of any type of initial guess and without the need to propagate the orbit. Three bearings are sufficient for purely geometric IOD if the orbit is known to be (approximately) circular. The method has been tested over different scenarios, including one where extra observations make the system of equations over-determined.

Read this paper on arXiv…

M. Mancini, T. Duff, A. Leykin, et. al.
Thu, 6 Apr 23
42/76

Comments: 31 pages excluding back matter, 14 figures

Three long period transiting giant planets from TESS [EPA]

Posted on by

http://arxiv.org/abs/2304.02139


We report the discovery and orbital characterization of three new transiting warm giant planets. These systems were initially identified as presenting single transit events in the light curves generated from the full frame images of the Transiting Exoplanet Survey Satellite (TESS). Follow-up radial velocity measurements and additional light curves were used to determine the orbital periods and confirm the planetary nature of the candidates. The planets orbit slightly metal-rich late F- and early G-type stars. We find that TOI 4406b has a mass of $M_P$= 0.30 $\pm$ 0.04 $M_J$ , a radius of $R_P$= 1.00 $\pm$ 0.02 $R_J$ , and a low eccentricity orbit (e=0.15 $\pm$ 0.05) with a period of P= 30.08364 $\pm$ 0.00005 d . TOI 2338b has a mass of $M_P$= 5.98 $\pm$ 0.20 $M_J$ , a radius of $R_P$= 1.00 $\pm$ 0.01 $R_J$ , and a highly eccentric orbit (e= 0.676 $\pm$ 0.002 ) with a period of P= 22.65398 $\pm$ 0.00002 d . Finally, TOI 2589b has a mass of $M_P$= 3.50 $\pm$ 0.10 $M_J$ , a radius of $R_P$= 1.08 $\pm$ 0.03 $R_J$ , and an eccentric orbit (e = 0.522 $\pm$ 0.006 ) with a period of P= 61.6277 $\pm$ 0.0002 d . TOI 4406b and TOI 2338b are enriched in metals compared to their host stars, while the structure of TOI 2589b is consistent with having similar metal enrichment to its host star.

Read this paper on arXiv…

R. Brahm, S. Ulmer-Moll, M. Hobson, et. al.
Thu, 6 Apr 23
43/76

Comments: 24 pages, 16 figures, accepted in AJ

Modelling the optical energy profile of the 2021 October Jupiter impact flash [EPA]

Posted on by

http://arxiv.org/abs/2304.02184


We have conducted numerical simulations to reproduce the observed optical energy profile of the 15 October 2021 (UT) impact flash on Jupiter, which was the largest and the most well-observed flash event detected by ground-based movie observations. The observed long-duration ($\sim 5.5~{\rm s}$) optical emission can be reproduced by an impact of an object with an exceptionally small angle of entry relative to the horizontal. The apparent lack of the impact debris feature despite the large impact object was possibly due to the shallower angle of entry ($\le 12^\circ$), which resulted in the lower ablation per unit volume at altitudes higher than $50 \, {\rm km}$, and the volume densities of the ablated materials were too low to allow the debris particulates to coagulate. The absence of temporal methane absorption change in the observed flash spectrum is consistent with the best-fit results. The model better fits the observed optical energy profile for weaker material (cometary and stony) cases than for metallic ones. Based on the simulation results, prospects for future observations of impact flashes are discussed.

Read this paper on arXiv…

K. Arimatsu, K. Tsumura, F. Usui, et. al.
Thu, 6 Apr 23
63/76

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

The Hamiltonian for von Zeipel-Lidov-Kozai oscillations [EPA]

Posted on by

http://arxiv.org/abs/2304.01257


The Hamiltonian used in classical analyses of von Zeipel-Lidov-Kozai or ZLK oscillations in hierarchical triple systems is based on the quadrupole potential from a distant body on a fixed orbit, averaged over the orbits of both the inner and the outer bodies (“double-averaging”). This approximation can be misleading, because the corresponding Hamiltonian conserves the component of angular momentum of the inner binary normal to the orbit of the outer binary, thereby restricting the volume of phase space that the system can access. This defect is usually remedied by including the effects of the octopole potential, or by allowing the outer orbit to respond to variations in the inner orbit. However, in a wide variety of astrophysical systems nonlinear perturbations are comparable to or greater than these effects. The long-term effects of nonlinear perturbations are described by an additional Hamiltonian, which we call Brown’s Hamiltonian. At least three different forms of Brown’s Hamiltonian are found in the literature; we show that all three are related by a gauge freedom, although one is much simpler than the others. We argue that investigations of ZLK oscillations in triple systems should include Brown’s Hamiltonian.

Read this paper on arXiv…

S. Tremaine
Wed, 5 Apr 23
32/62

Comments: 11 pages, 3 figures. To be published in Monthly Notices of the Royal Astronomical Society

How to form compact & other longer-lived planet-induced vortices: VSI, planet migration, or re-triggers, but not feedback [EPA]

Posted on by

http://arxiv.org/abs/2304.01674


Past computational studies of planet-induced vortices have shown that the dust asymmetries associated with these vortices can be long-lived enough that they should be much more common in mm/sub-mm observations of protoplanetary discs, even though they are quite rare. Observed asymmetries also have a range of azimuthal extents from compact to elongated even though computational studies have shown planet-induced vortices should be preferentially elongated. In this study, we use 2-D and 3-D hydrodynamic simulations to test whether those dust asymmetries should really be so long-lived or so elongated. With higher resolution (29 cells per scale height) than our previous work, we find that vortices can be more compact by developing compact cores when higher-mass planets cause them to re-form, or if they are seeded by tiny compact vortices from the vertical shear instability (VSI), but not through dust feedback in 3-D as was previously expected in general. Any case with a compact vortex or core(s) also has a longer lifetime. Even elongated vortices can have longer lifetimes with higher-mass planets or if the associated planet is allowed to migrate, the latter of which can cause the dust asymmetry to stop decaying as the planet migrates away from the vortex. These longer dust asymmetry lifetimes are even more inconsistent with observations, perhaps suggesting that discs still have an intermediate amount of effective viscosity.

Read this paper on arXiv…

M. Hammer and M. Lin
Wed, 5 Apr 23
34/62

Comments: 24 pages, 21 figures; Submitted to MNRAS

LHS 475 b: A Venus-sized Planet Orbiting a Nearby M Dwarf [EPA]

Posted on by

http://arxiv.org/abs/2304.01920


Based on photometric observations by TESS, we present the discovery of a Venus-sized planet transiting LHS 475, an M3 dwarf located 12.5 pc from the Sun. The mass of the star is $0.274 \pm 0.015~\rm{M_{Sun}}$. The planet, originally reported as TOI 910.01, has an orbital period of $2.0291025 \pm 0.0000020$ days and an estimated radius of $0.955 \pm 0.053~\rm{R_{Earth}}$. We confirm the validity and source of the transit signal with MEarth ground-based follow-up photometry of five individual transits. We present radial velocity data from CHIRON that rule out massive companions. In accordance with the observed mass-radius distribution of exoplanets as well as planet formation theory, we expect this Venus-sized companion to be terrestrial, with an estimated RV semi-amplitude close to 1.0 m/s. LHS 475 b is likely too hot to be habitable but is a suitable candidate for emission and transmission spectroscopy.

Read this paper on arXiv…

K. Ment, D. Charbonneau, J. Irwin, et. al.
Wed, 5 Apr 23
35/62

Comments: 17 pages, 5 figures, submitted to AJ

Testing protoplanetary disc evolution with CO fluxes. A proof of concept in Lupus and Upper Sco [EPA]

Posted on by

http://arxiv.org/abs/2304.01760


The Atacama Large Millimeter/submillimeter Array (ALMA) revolutionised our understanding of protoplanetary discs. However, the available data have not given conclusive answers yet on the underlying disc evolution mechanisms (viscosity or MHD winds). Improving upon the current results, mostly based on the analysis of disc sizes, is difficult because larger, deeper and higher angular resolution surveys would be required, which could be prohibitive even for ALMA. In this Letter, we introduce an alternative method to study disc evolution based on $^{12}$CO fluxes. In fact, fluxes can be readily collected using less time-consuming, lower resolution observations, while tracing the same disc physico-chemical processes as sizes: assuming that $^{12}$CO is optically thick, fluxes scale with the disc surface area. We developed a semi-analytical model to compute $^{12}$CO fluxes and benchmarked it against the results of DALI thermochemical models, recovering an agreement within a factor of three. As a proof of concept we compared our models with Lupus and Upper Sco data, taking advantage of the increased samples, by a factor 1.3 (Lupus) and 3.6 (Upper Sco), when studying fluxes instead of sizes. Models and data agree well only if CO depletion is considered. However, the uncertainties on the initial conditions limited our interpretation of the observations. Our new method can be used to design future ad hoc observational strategies to collect better data and give conclusive answers on disc evolution.

Read this paper on arXiv…

F. Zagaria, S. Facchini, A. Miotello, et. al.
Wed, 5 Apr 23
43/62

Comments: 10 pages, 9 figures; accepted for publication in A&A Letters. Code and data available at this https URL

The orbit of Aegaeon and the 7:6 Mimas-Aegaeon resonance [EPA]

Posted on by

http://arxiv.org/abs/2304.01923


Aegaeon (S/2008 S 1) is the last satellite discovered by the Cassini spacecraft at the end of the 2000s. Like the satellites Methone and Anthe, it is involved in mean motion resonance with the mid-sized Mimas. In this work, we give a detailed analysis of the current orbit of Aegaeon identifying the resonant, secular and long-term perturbations due to Mimas and the oblateness of Saturn, and the effects of Tethys. For this task, we perform thousands of numerical simulations of full equations of motion of ensembles of small bodies representing clones of Aegaeon. We have mapped the domain of the 7:6 Mimas-Aegaeon resonance in the phase space of the semi-major axis and eccentricity. It displays a large area dominated by regular motions associated with the 7:6 corotation resonance surrounded by chaotic layers. Aegaeon is currently located very close to the periodic orbit of the resonance, which extends up to eccentricities $\sim0.025$ centered at semi-major axis $\sim168,028$ km. We show that the current orbit of Aegaeon has an important forced component in eccentricity due to the 7:6 resonance. The orbital inclination of Aegaeon has a non-negligible forced value due to long-term perturbations of Mimas. These two forced modes explain the complex perturbed orbit of Aegaeon without requiring the co-existence of multiple resonances.

Read this paper on arXiv…

N. Jr. and A. Rodríguez
Wed, 5 Apr 23
47/62

Comments: 24 pages, 8 figures

Approaches for Retrieving Sulfur Species Abundances from Dual X/Ka Band Radio Occultations of Venus with EnVision and VERITAS [EPA]

Posted on by

http://arxiv.org/abs/2304.02006


The EnVision and VERITAS missions to Venus will fly with X and Ka band telecommunications channels which can be used to conduct radio occultation studies of Venus’ atmosphere. While link attenuation measurements during prior S and X band occultation experiments have been used to determine vertical profiles of H$_2$SO$_4$ vapor abundance, the addition of the Ka band channel introduces greater sensitivity to the abundances of H$_2$SO$_4$ aerosols and SO$_2$ gas, permitting retrieval of their vertical profiles from dual band measurements. Such measurements would be valuable in the assessment of chemical and dynamical processes governing short and long-term variability in Venus’ atmosphere. This paper considers the sensitivity of the X/Ka band radio attenuation measurement to these atmospheric constituents, as well as uncertainties and regularization approaches for conducting retrievals of these atmospheric sulfur species from future occultation experiments. We introduce methods for seeding maximum likelihood estimation retrievals using shape models and simple atmospheric transport constraints. From simulated retrievals, we obtain mean errors of the order of 0.5 ppm, 20 ppm, and 10 mg/m$^3$ for H$_2$SO$_4$ vapor, SO$_2$, and H$_2$SO$_4$ aerosol abundances, respectively, for simultaneous retrieval.

Read this paper on arXiv…

A. Akins, T. Bocanegra-Bahamón, K. Wang, et. al.
Wed, 5 Apr 23
60/62

Comments: 29 pages, 11 figures, accepted to PSJ

Interstellar Objects [EPA]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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

Eight exoplanet candidates in SAO survey [EPA]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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

Comments: 20 pages

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

Posted on by

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.

Read this paper on arXiv…

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

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

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

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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

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

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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

Comments: 6 pages, 5 figures

Interstellar Objects and Exocomets [EPA]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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

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

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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

Comments: 28 pages, 11 figures, submitted to Icarus

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

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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

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

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

Posted on by

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.

Read this paper on arXiv…

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

Comments: 12 pages, 7 figures

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

Posted on by

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.

Read this paper on arXiv…

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

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

Saturn's Seismic Rotation Revisited [EPA]

Posted on by

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.

Read this paper on arXiv…

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

Comments: Accepted to PSJ

The ultraviolet habitable zone of exoplanets [EPA]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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

Comments: 36 pages, 10 figures, and 3 tables

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

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

M. Roman
Thu, 30 Mar 23
59/66

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

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

Posted on by

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.

Read this paper on arXiv…

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

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

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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 $10^{-4}$.

Read this paper on arXiv…

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

Comments: 23 pages, 17 figures; Submitted to ApJ

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

Posted on by

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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

Comments: 15 pages, 8 figures, 2 tables

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

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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

Comments: N/A

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

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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

A Catalogue of Exoplanet Atmospheric Retrieval Codes [EPA]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

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]

Posted on by

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.

Read this paper on arXiv…

C. Migaszewski
Fri, 24 Mar 23
56/56

Comments: submitted to MNRAS

The Masses of a Sample of Radial-Velocity Exoplanets with Astrometric Measurements [EPA]

Posted on by

http://arxiv.org/abs/2303.12409


Being one of the most fundamental physical parameter of astronomical objects, mass plays a vital role in the study of exoplanets, including their temperature structure, chemical composition, formation, and evolution. However, nearly a quarter of the known confirmed exoplanets lack measurements of their masses. This is particularly severe for those discovered via the radial-velocity (RV) technique, which alone could only yield the minimum mass of planets. In this study, we use published RV data combined with astrometric data from a cross-calibrated Hipparcos-Gaia Catalog of Accelerations (HGCA) to jointly constrain the masses of 115 RV-detected substellar companions, by conducting full orbital fits using the public tool \texttt{orvara}. Among them, 9 exoplanets with $M_{\rm p}\,{\rm sin}\,i<13.5\ M_{\rm Jup}$ are reclassified to the brown dwarf (BD) regime, and 16 BD candidates ($13.5\leqslant M_{\rm p}\,{\rm sin}\,i<80\,M_{\rm Jup}$) turn out to be low-mass M dwarfs. We point out the presence of a transition in the BD regime as seen in the distributions of host star metallicity and orbital eccentricity with respect to planet masses. We confirm the previous findings that companions with masses below $42.5\ M_{\rm Jup}$ might primarily form in the protoplanetary disc through core accretion or disc gravitational instability, while those with masses above $42.5\ M_{\rm Jup}$ formed through the gravitational instability of molecular cloud like stars. Selection effects and detection biases which may affect our analysis to some extent, are discussed.

Read this paper on arXiv…

G. Xiao, Y. Liu, H. Teng, et. al.
Thu, 23 Mar 23
8/67

Comments: 37 pages, 14 figures, accepted by Research in Astronomy and Astrophysics

New Recurrently Active Main-belt Comet 2010 LH15 [EPA]

Posted on by

http://arxiv.org/abs/2303.12102


We announce the discovery of a main-belt comet (MBC), 2010 LH15 (alternately designated 2010 TJ175). MBCs are a rare type of main-belt asteroid that display comet-like activity, such as tails or comae, caused by sublimation. Consequently, MBCs help us map the location of solar system volatiles, providing insight into the origins of material prerequisite for life as we know it. However, MBCs have proven elusive, with fewer than 20 found among the 1.1 million known main-belt asteroids. This finding derives from Active Asteroids, a NASA Partner Citizen Science program we designed to identify more of these important objects. After volunteers classified an image of 2010 LH15 as showing activity, we carried out a follow-up investigation which revealed evidence of activity from two epochs spanning nearly a decade. This discovery is timely, with 2010 LH15 inbound towards its 2024 March perihelion passage, with potential activity onset as early as late 2023.

Read this paper on arXiv…

C. Chandler, W. Oldroyd, H. Hsieh, et. al.
Thu, 23 Mar 23
25/67

Comments: 4 pages, 1 figure

Interpebble contact radius in a comet nucleus [EPA]

Posted on by

http://arxiv.org/abs/2303.12272


In recent years, the gravitational collapse of pebble clumps in the early Solar System has been regarded as a plausible scenario for the origin of comets. In this context, “pebbles” represent mm- to cm-sized dust aggregates composed of (sub)micron-sized dust particles, and the structure of km-sized comets is thought to be an agglomerate of pebbles. The contact radius for pebble-pebble contacts was modelled in an earlier study; however, the pressure dependence of the interpebble contact radius was not considered. Here, we revisit the interpebble contact radius in a comet nucleus. We calculated the interpebble contact radius based on JKR contact theory, and we took into consideration the effect of lithostatic pressure. We found that the interpebble contact radius varies with depth from the surface, and the earlier model underestimated it by one order of magnitude at the centre of the comet nucleus.

Read this paper on arXiv…

S. Arakawa, D. Nishiura and M. Furuichi
Thu, 23 Mar 23
36/67

Comments: 9 pages, 6 figures. Accepted for publication in MNRAS