adsabs/SciX_UAT_keywords huggingface dataset:
Exploring the Atmospheric Dynamics of the Extreme Ultrahot Jupiter KELT-9b Using TESS Photometry

We carry out a phase-curve analysis of the KELT-9 system using photometric observations from NASA's Transiting Exoplanet Survey Satellite (TESS). The measured secondary eclipse depth and peak-to-peak atmospheric brightness modulation are ${650}_{-15}^{+14}$ and 566 ± 16 ppm, respectively. The planet's brightness variation reaches maximum 31 ± 5 minutes before the midpoint of the secondary eclipse, indicating a 5°2 ± 0°9 eastward shift in the dayside hot spot from the substellar point. We also detect stellar pulsations on KELT-9 with a period of 7.58695 ± 0.00091 hr. The dayside emission of KELT-9b in the TESS bandpass is consistent with a blackbody brightness temperature of 4600 ± 100 K. The corresponding nightside brightness temperature is 3040 ± 100 K, comparable to the dayside temperatures of the hottest known exoplanets. In addition, we detect a significant phase-curve signal at the first harmonic of the orbital frequency and a marginal signal at the second harmonic. While the amplitude of the first harmonic component is consistent with the predicted ellipsoidal distortion modulation assuming equilibrium tides, the phase of this photometric variation is shifted relative to the expectation. Placing KELT-9b in the context of other exoplanets with phase-curve observations, we find that the elevated nightside temperature and relatively low day-night temperature contrast agree with the predictions of atmospheric models that include H2 dissociation and recombination. The nightside temperature of KELT-9b implies an atmospheric composition containing about 50% molecular and 50% atomic hydrogen at 0.1 bar, a nightside emission spectrum that deviates significantly from a blackbody, and a 0.5-2.0 μm transmission spectrum that is featureless at low resolution.

Keywords: hot jupiters; photometry; exoplanet astronomy
An X-Ray Census of Active Galactic Nuclei in the Virgo and Fornax Clusters of Galaxies with SRG/eROSITA

We present a uniform and sensitive X-ray census of active galactic nuclei (AGNs) in the two nearest galaxy clusters, Virgo and Fornax, utilizing the newly released X-ray source catalogs from the first all-sky scan of Spectrum-Roentgen-Gamma/eROSITA. A total of 50 and 10 X-ray sources are found positionally coincident with the nuclei of member galaxies in Virgo and Fornax, respectively, down to a 0.2–2.3 keV luminosity of ∼1039 erg s‑1 and reaching out to a projected distance well beyond the virial radius of both clusters. The majority of the nuclear X-ray sources are newly identified. There is weak evidence that the nuclear X-ray sources are preferentially found in late-type hosts. Several hosts are dwarf galaxies with a stellar mass below ∼109 M ⊙. We find that contamination by nonnuclear X-ray emission can be neglected in most cases, indicating the dominance of a genuine AGN. In the meantime, no nuclear X-ray source exhibits a luminosity higher than a few times 1041 erg s‑1, which might be owing to a steep intrinsic luminosity function. The X-ray AGN occupation rate is only ∼3% in both clusters, apparently much lower than that in field galaxies inferred from previous X-ray studies. Both aspects suggest that the cluster environment effectively suppresses AGN activity. The findings of this census have important implications for the interplay between galaxies and their central massive black holes in cluster environments.

Keywords: virgo cluster; galaxy clusters; x-ray astronomy; x-ray active galactic nuclei
GRB 230911A: The First Discovery of a Fermi GRB Optical Counterpart with the Gravitational-wave Optical Transient Observer (GOTO)

We report on the detection of candidate optical counterpart GOTO23akf/AT2023shv to the GRB 230911A with the Gravitational-wave Optical Transient Observer (GOTO) instruments located at La Palma, Canary Islands, and Siding Spring Observatory, Australia. The Fermi Gamma-ray Burst Monitor, which finds gamma-ray bursts (GRBs) nearly every two days, detected GRB 230911A with a statistical uncertainty of 4.°1. However, the large (~10-100 deg2) localization areas mostly impede the rapid identification of an optical counterpart. GOTO facilities fully covered 90% localization area of the GRB 230911A. We proposed GOTO23akf as the optical afterglow of GRB 230911A, subsequently confirmed through Swift-X-Ray Telescope observations in which an uncatalogued X-ray source spatially coincident with the GOTO candidate was detected. This is the first optical afterglow discovery for a Fermi GRB with the newly expanded GOTO network.

Keywords: gamma-ray bursts; optical observation
Intriguing Revelations from Lithium, Beryllium, and Boron

This is a report on some highlights of research on the rare light elements, lithium (Li), beryllium (Be), and boron (B), that were presented at my Henry Norris Russell Lecture in 2020 January. It is not a comprehensive review of work on these light elements, but contains sections on Big Bang nucleosynthesis of Li and the rarity of these light elements. It includes information on how they are observed, both historically and currently, and the difficulties entailed in determining their abundances. The production of Li, Be, and B is ongoing, so the youngest stars contain the most Li in their atmospheres and they have had less time to destroy it. All three elements are readily destroyed in stellar interiors, but have differing degrees of susceptibility to the particular nuclear fusion reactions which deplete their surface content. This feature makes them remarkably good probes into the otherwise unobservable interiors of stars and provides insights into internal-mixing processes. It also enhances the use of two or more of the three in sorting out the various processes at work in the insides of stars.

Keywords: stellar atmospheres; stellar evolution; stellar abundances
Variability from Thermoresistive Instability in the Atmospheres of Hot Jupiters

The atmosphere of a hot Jupiter may be subject to a thermoresistive instability, in which the increasing electrical conductivity with temperature leads to runaway ohmic heating. We introduce a simplified model of the local dynamics in the equatorial region of a hot Jupiter that incorporates the back reaction on the atmospheric flow as the increasing electrical conductivity leads to flux freezing, which in turn quenches the flow and therefore the ohmic heating. We demonstrate a new time-dependent solution that emerges for a temperature-dependent electrical conductivity (whereas a temperature-independent conductivity always evolves to a steady state). The periodic cycle consists of bursts of Alfvén oscillations separated by quiescent intervals, with the magnetic Reynolds number alternating between values smaller than and larger than unity, maintaining the oscillation. We investigate the regions of pressure and temperature in which the instability operates. For the typical equatorial accelerations seen in atmospheric models, we find instability at pressures ~0.1-1 bar and temperatures ≈1300-1800 K for magnetic fields ~10 G. Unlike previous studies based on a constant wind velocity, we find that the instability is stronger for weaker magnetic fields. Our results add support to the idea that variability should be a feature of magnetized hot Jupiter atmospheres, particularly at intermediate temperatures. The temperature dependence of the electrical conductivity is an important ingredient that should be included in MHD models of hot Jupiter atmospheric dynamics.

Keywords: astrophysical fluid dynamics; magnetohydrodynamics; exoplanet atmospheric variability; exoplanet atmospheric dynamics
The Baltimore Oriole's Nest: Cool Winds from the Inner and Outer Parts of a Star-forming Galaxy at z = 1.3

Strong galactic winds are ubiquitous at z ≳ 1. However, it is not well-known where inside galaxies these winds are launched from. We study the cool winds (~104 K) in two spatial regions of a massive galaxy at z = 1.3, which we nickname the "Baltimore Oriole's Nest." The galaxy has a stellar mass of 1010.3±0.3 M ⊙, is located on the star-forming main sequence, and has a morphology indicative of a recent merger. Gas kinematics indicate a dynamically complex system with velocity gradients ranging from 0 to 60 km s-1. The two regions studied are: a dust-reddened center (Central region), and a blue arc at 7 kpc from the center (Arc region). We measure the Fe II and Mg II absorption line profiles from deep Keck/DEIMOS spectra. Blueshifted wings up to 450 km s-1 are found for both regions. The Fe II column densities of winds are 1014.7±0.2 cm-2 and 1014.6±0.2 cm-2 toward the Central and Arc regions, respectively. Our measurements suggest that the winds are most likely launched from both regions. The winds may be driven by the spatially extended star formation, the surface density of which is around 0.2 M ⊙ yr-1 · kpc-2 in both regions. The mass outflow rates are estimated to be 4 M ⊙ yr-1 and 3 M ⊙ yr-1 for the Central and Arc regions, with uncertainties of one order of magnitude or more. The findings of this work and a few previous studies suggest that the cool galactic winds at z ≳ 1 might be commonly launched from the entire spatial extents of their host galaxies, due to extended galaxy star formation.

Keywords: galaxy formation; stellar feedback; galactic winds
The Stellar Content of the Young Open Cluster Berkeley 50 (IC 1310)

We observed the Galactic open cluster Berkeley 50 in order to determine its stellar content, distance, and age. We obtained UBV photometry of 1145 stars in a 12.'3 × 12.'3 field, and used Gaia proper motions and parallaxes to identify 64 members, of which we obtained spectra of the 17 brightest members. The majority of the observed population we classified as B dwarfs, with the exception of a newly identified red supergiant star, which our spectroscopy shows has a B-type companion. Our study establishes the distance as 3.8 kpc, with an average color-excess E(B ‑ V) = 0.9. Comparison of the physical properties of the cluster with the Geneva evolutionary tracks places the age of the cluster as 50–60 Myr, with its most massive members being ∼7M ⊙

Keywords: open star clusters; red supergiant stars; b stars
Probing the Cold Deep Depths of the California Molecular Cloud: The Icy Relationship between CO and Dust

We study the relationship between molecular gas and dust in the California Molecular Cloud over an unprecedented dynamic range of cloud depth (AV = 3-60 mag). We compare deep Herschel-based measurements of dust extinction with observations of the 12CO, 13CO, and C18O J = 2 - 1 lines on sub-parsec scales across the cloud. We directly measure the ratio of CO integrated intensity to dust extinction to derive the CO X-factor at over 105 independent locations in the cloud. Confirming an earlier study, we find that no single 12CO X-factor can characterize the molecular gas in the cold (Tdust ≤ 20) regions of the cloud that account for most of its mass. We are able to derive a single-valued X-factor for all three CO isotopologues in the warm (Tdust > 25 K) material that is spatially coincident with an H II region surrounding the star LkHα 101. We derive the LTE CO column densities for 13CO and C18O since we find both lines are relatively optically thin. In the warm cloud material, CO is completely in the gas phase and we are able to recover the total 13CO and C18O abundances. Using CO abundances and deep Herschel observations, we measure lower bounds to the freeze-out of CO onto dust across the whole cloud, finding some regions having CO depleted by a factor of >20. We construct the first maps of depletion that span the extent of a giant molecular cloud. Using these maps we identify 75 depletion-defined cores and discuss their physical nature.

Keywords: interstellar medium; giant molecular clouds; h ii regions; galactic and extragalactic astronomy; chemical abundances
Multiple X-line Reconnection Observed in Mercury's Magnetotail Driven by an Interplanetary Coronal Mass Ejection

How magnetic reconnection drives Mercury's magnetospheric dynamics under extreme solar wind conditions is not well understood. Here we report MESSENGER observations of an active reconnection event in Mercury's magnetotail driven by an interplanetary coronal mass ejection on 2011 November 23. The primary Hall magnetic field, sequential passage of X-lines with Hall field perturbations, and flux ropes (FRs) provide unambiguous evidence of multiple X-line reconnection in an unstable ion diffusion region. In addition, large FRs consisting of multiple successive small-scale FRs are ejected tailward at quasi-periodic intervals of ∼1 minute, which is comparable to the Dungey cycle time. We propose that these large FRs are generated by the interaction and coalescence of multiple ion-scale FRs. This is distinct from the commonly accepted Earth-like substorm process where plasmoids are created by widely separated X-lines in the magnetotail. These observations suggest that during extreme solar wind conditions multiple X-line reconnection may dominate the tail reconnection process and control the global dynamics of Mercury's magnetosphere.

Keywords: solar magnetic reconnection; mercury (planet); space plasmas; planetary magnetospheres; solar coronal mass ejections; solar-planetary interactions
A Size Estimate for Galaxy GN-z11

GN-z11 is the highest redshift galaxy spectroscopically confirmed with the Hubble Space Telescope (HST). Previous measurements of the effective radius of GN-z11 utilized GALFIT, which is not optimized to measure structural parameters for such a faint, distant object. Using new software called FORCEPHO, we derive a size from images in the F160W band obtained both from the complete CANDELS survey and additional midcycle observations in order to contribute to the knowledge base on the size evolution, size–luminosity, and size–mass relation of early galaxies. We find a half-light radius mean of 0.″036 ± 0.″006 corresponding to a physical size of 0.15 ± 0.025 kpc. This size, smaller than the point-spread function, is dramatically smaller than previous estimates with shallower HST data using galfit but consistent with recent measurements using forcepho on new JWST data. Such a small size suggests that GN-z11's high luminosity is dominated by an active galactic nucleus.

Keywords: agn host galaxies; active galactic nuclei; galaxy evolution
An ALMA 1.3 millimeter Search for Debris Disks around Solar-type Stars in the Pleiades

Millimeter emission from debris disks around stars of different ages provides constraints on the collisional evolution of planetesimals. We present ALMA 1.3 millimeter observations of a sample of 76 Solar-type stars in the ~115 Myr old Pleiades star cluster. These ALMA observations complement previous infrared observations of this sample by providing sensitivity to emission from circumstellar dust at lower temperatures, corresponding to debris at radii comparable to the Kuiper Belt and beyond. The observations obtain a beam size of 1.″5 (200 au) and a median rms noise of 54 μJy beam-1, which corresponds to a fractional luminosity L dust/L star ~ 10-4 for 40 K dust for a typical star in the sample. The ALMA images show no significant detections of the targeted stars. We interpret these limits in the context of a steady-state collisional cascade model for debris disk evolution that provides a good description of observations of the field population near the Sun but is not well-calibrated on younger populations. The ALMA nondetections of the Pleiades systems are compatible with the disk flux predictions of this model. We find no high fractional luminosity outliers from these ALMA data that could be associated with enhanced collisions resulting from activity not accounted for by steady-state evolution. However, we note that two systems (H II 1132 and HD 22680) show 24 μm excess much higher than the predictions of this model, perhaps due to unusually high dust production from dynamical events involving planets.

Keywords: debris disks; open star clusters
MASTER Optical Observation of LIGO/VIRGO S200224ca Error-box

We present the results of MASTER Global Robotic Net optical observations of LIGO/Virgo S200224ca error-box (O3 set). We observed 380 square degrees inside the 3σ error box during 1 month. We present optical transients found by MASTER auto-detection system during this inspection. They are not the optical counterparts, but the result of MASTER observation strategy, that is is briefly discussed. Also we present short analysis of Swift-UVOT, -XRT transients in MASTER database since 2010.

Keywords: ligo; automated telescopes; sky surveys; x-ray transient sources; transient sources; gravitational wave sources; gravitational wave astronomy; stellar mass black holes
Cosmic-Ray Transport in Simulations of Star-forming Galactic Disks

Cosmic-ray transport on galactic scales depends on the detailed properties of the magnetized, multiphase interstellar medium (ISM). In this work, we postprocess a high-resolution TIGRESS magnetohydrodynamic simulation modeling a local galactic disk patch with a two-moment fluid algorithm for cosmic-ray transport. We consider a variety of prescriptions for the cosmic rays, from a simple, purely diffusive formalism with constant scattering coefficient, to a physically motivated model in which the scattering coefficient is set by the critical balance between streaming-driven Alfvén wave excitation and damping mediated by local gas properties. We separately focus on cosmic rays with kinetic energies of ~1 GeV (high-energy) and ~30 MeV (low energy), respectively important for ISM dynamics and chemistry. We find that simultaneously accounting for advection, streaming, and diffusion of cosmic rays is crucial for properly modeling their transport. Advection dominates in the high-velocity, low-density hot phase, while diffusion and streaming are more important in higher-density, cooler phases. Our physically motivated model shows that there is no single diffusivity for cosmic-ray transport: the scattering coefficient varies by four or more orders of magnitude, maximal at density nH ~ 0.01 cm-3. The ion-neutral damping of Alfvén waves results in strong diffusion and nearly uniform cosmic-ray pressure within most of the mass of the ISM. However, cosmic rays are trapped near the disk midplane by the higher scattering rate in the surrounding lower-density, higher-ionization gas. The transport of high-energy cosmic rays differs from that of low-energy cosmic rays, with less effective diffusion and greater energy losses for the latter.

Keywords: cosmic rays; magnetohydrodynamics; interstellar medium
On Averaging Eccentric Orbits: Implications for the Long-term Thermal Evolution of Comets

One of the common approximations in long-term evolution studies of small bodies is the use of circular orbits averaging the actual eccentric ones, facilitating the coupling of processes with very different timescales, such as the orbital changes and the thermal processing. Here we test a number of averaging schemes for elliptic orbits in the context of the long-term evolution of comets, aiming to identify the one that best reproduces the elliptic orbits' heating patterns and the surface and subsurface temperature distributions. We use a simplified thermal evolution model applied on simulated comets both on elliptic and on their equivalent averaged circular orbits, in a range of orbital parameter space relevant to the inner solar system. We find that time-averaging schemes are more adequate than spatial-averaging ones. Circular orbits created by means of a time average of the equilibrium temperature approximate efficiently the subsurface temperature distributions of elliptic orbits in a large area of the orbital parameter space, rendering them a powerful tool for averaging elliptic orbits.

Keywords: comets; comet nuclei; comet interiors; computational methods
A Shallow-water Model Exploration of Atmospheric Circulation on Sub-Neptunes: Effects of Radiative Forcing and Rotation Period

Sub-Neptune-type exoplanets are abundant in our Galaxy yet have no solar system analogs. They exist in a broad range of stellar forcing and rotational regimes that are distinctly different from solar system planets and more commonly studied hot Jupiters. Here we present simulations that explore global atmospheric circulation of sub-Neptunes generated with a two-dimensional shallow-water model, SWAMPE. We explore the circulation regimes of synchronously rotating sub-Neptunes with a focus on the interaction of planetary rotation rate and radiative timescale in a variety of stellar insolations. In highly irradiated, short-timescale regimes, our models exhibit high day-night geopotential contrasts. As the timescales become longer, the geopotential contrasts and longitudinal variability decrease, while temporal variability increases. The transition from day-to-night flow to jet-dominated flow is primarily driven by the radiative timescale. Strong- and medium-forcing regimes exhibit transitions between day-to-night flow and jet-dominated flow at similar points in the parameter space. The weak-forcing regime differs owing to comparatively stronger rotational effects. Planetary rotation period dominates in determining equator-to-pole geopotential contrast. Our simulations exhibit higher time variability when either radiative timescale or rotation period is long.

Keywords: exoplanet atmospheres; mini neptunes; atmospheric circulation
A First Look with JWST Aperture Masking Interferometry: Resolving Circumstellar Dust around the Wolf–Rayet Binary WR 137 beyond the Rayleigh Limit

We present infrared aperture-masking interferometry (AMI) observations of newly formed dust from the colliding winds of the massive binary Wolf–Rayet system WR 137 with JWST using the Near Infrared Imager and Slitless Spectrograph (NIRISS). NIRISS AMI observations of WR 137 and a point-spread function calibrator star, HD 228337, were taken using the F380M and F480M filters in 2022 July and August as part of the Director's Discretionary Early Release Science program #1349. Interferometric observables (squared visibilities and closure phases) from the WR 137 "interferogram" were extracted and calibrated using three independent software tools: ImPlaneIA, AMICAL, and SAMpip. The analysis of the calibrated observables yielded consistent values except for slightly discrepant closure phases measured by ImPlaneIA. Based on all three sets of calibrated observables, images were reconstructed using three independent software tools: BSMEM, IRBis, and SQUEEZE. All reconstructed image combinations generated consistent images in both F380M and F480M filters. The reconstructed images of WR 137 reveal a bright central core with a ∼300 mas linear filament extending to the northwest. A geometric colliding-wind model with dust production constrained to the orbital plane of the binary system and enhanced as the system approaches periapsis provided a general agreement with the interferometric observables and reconstructed images. Based on a colliding-wind dust condensation analysis, we suggest that dust formation within the orbital plane of WR 137 is induced by enhanced equatorial mass loss from the rapidly rotating O9 companion star, whose axis of rotation is aligned with that of the orbit.

Keywords: circumstellar dust; wc stars; high contrast techniques; james webb space telescope; massive stars