adsabs/SciX_UAT_keywords huggingface dataset:
CHANDRA X-Ray Observations of A119: Cold Fronts and a Shock in an Evolved Off-axis Merger

We present Chandra X-ray observations of the dynamically complex galaxy cluster A119 (z = 0.044). A119 is host to two narrow-angle-tail (NAT) radio sources (0053-015 and 0053-016), whose tails are oriented parallel to each other, despite orthogonally oriented jet axes. Imaging and spectral analysis reveal X-ray emission elongated along the NE-SW axis, along with the presence of complex structures, including surface brightness discontinuities, which suggest possible merger activity along this axis. From radial profiles of the X-ray surface brightness, temperature, pressure, and density, we identify two surface brightness edges that are found to be cold fronts, possibly associated with large-scale sloshing of intracluster medium gas. We also identify a brightness edge to the S that is found to be a shock front with Mach number M = 1.21 ± 0.11, consistent with a merger shock. In addition, previous optical studies show the alignment of optical substructures along the N-S direction. The elongated X-ray emission, orientations of the NAT tails, and alignment of the optical substructure all suggest recent or ongoing merger activity in the NE-SW direction.

Keywords: galaxy clusters; intracluster medium
Detectability of Rotational Modulation in Kepler Sun-like Stars as a Function of Age

We examine how the fraction f of stars for which rotational modulation has been detected in Kepler light curves depends on the stellar mass M ⋆ and age t ⋆. Our sample consists of ≈850 FGK stars hosting transiting planet candidates detected from the prime Kepler mission. For these stars, atmospheric parameters have been derived using high-resolution spectra from the California-Kepler survey, and rotational modulation has been searched in Kepler light curves homogeneously. We fit stellar models to the atmospheric parameters, Gaia parallax, and Two Micron All Sky Survey magnitude of these stars and obtain samples drawn from the posterior probability distributions for their masses and ages under a given, uninformative prior. We combine them with the result of rotational modulation search to simultaneously infer the mass-age distribution of the sample as well as f(M ⋆, t ⋆), in a manner that fully takes into account mass and age uncertainties of individual stars. We find that f remains near unity up to t ⋆ ~ 3 Gyr and drops to almost zero by t ⋆ ~ 5 Gyr, although the trend is less clearly detected for stars with ≲0.9 M ⊙ due to weaker age constraints. This finding is consistent with a view that the detection of rotational modulation is limited by photometric precision to younger stars that exhibit higher-amplitude modulation, and suggests that the detectability of rotational modulation in Kepler light curves is insensitive to metallicity and activity cycles for stars younger than the Sun.

Keywords: light curves; starspots; stellar activity; stellar magnetic fields; stellar rotation
Planet Eclipse Mapping with Long-term Baseline Drifts

High-precision lightcurves combined with eclipse-mapping techniques can reveal the horizontal and vertical structure of a planet's thermal emission and the dynamics of hot Jupiters. Someday, they even may reveal the surface maps of rocky planets. However, inverting lightcurves into maps requires an understanding of the planet, star, and instrumental trends because they can resemble the gradual flux variations as the planet rotates (i.e., partial phase curves). In this work, we simulate lightcurves with baseline trends and assess the impact on planet maps. Baseline trends can be erroneously modeled by incorrect astrophysical planet map features, but there are clues to avoid this pitfall in both the residuals of the lightcurve during eclipse and sharp features at the terminator of the planet. Models that use a Gaussian process or polynomial to account for a baseline trend successfully recover the input map even in the presence of systematics but with worse precision for the m = 1 spherical harmonic terms. This is also confirmed with the ThERESA eigencurve method where fewer lightcurve terms can model the planet without correlations between the components. These conclusions help aid the decision on how to schedule observations to improve map precision. If the m = 1 components are critical, such as measuring the east/west hot-spot shift on a hot Jupiter, better characterization of baseline trends can improve the m = 1 terms' precision. For latitudinal north/south information from m ≠ 1 mapping terms, it is preferable to obtain high signal to noise at ingress/egress with more eclipses.

Keywords: eclipses; hot jupiters; exoplanet atmospheres; planetary atmospheres; gaussian processes regression; astronomical techniques
Observations of the Orion Source I Disk and Outflow Interface

We imaged the continuum and molecular line emission from Orion Source I (SrcI) with up to 30 mas (12 au) resolution at 43, 99, 223, and 340 GHz in an attempt to probe the structure and chemistry of the circumstellar disk and bipolar outflow associated with this high-mass protostar. The continuum spectral index ranges from ∼2 along the midplane of the disk to ∼3 along the edges, consistent with dust that is optically thick in the midplane but becomes optically thin at the periphery. Salt (NaCl) emission is visible where the dust is optically thin; it provides a unique tracer of the velocity field within the disk. All other molecules that we have mapped—H2O, AlO, SiO, SiS, SO, and SO2—appear to originate primarily in the bipolar outflow. The base of the outflow is corotating with the disk. SiS shows a filamentary structure that is most prominent along the edges of the outflow. The molecular distributions suggest that Si and Al released from dust grains in the disk react with oxygen derived from H2O to form SiO and AlO, and with SO and SO2 to form SiS.

Keywords: protostars; circumstellar disks; molecular gas; astrochemistry
QLP Data Release Notes 001: K2 + TESS Analysis

TESS will target the ecliptic plane in Sectors 42-46. These sectors overlap with campaigns from the K2 mission, providing a unique opportunity for multi-mission light curve analysis. This data release note describes the combined analysis of K2 and TESS light curves as part of the Quick-Look Pipeline procedure, which processes light curves for all targets in TESS Full-Frame Images down to TESS magnitude T = 13.5. We describe updates to our codebase, and the planet transit search, candidate triage, and report generation that are affected by this combined analysis.

Keywords: exoplanets; exoplanet detection methods; transit photometry; time series analysis
A Word of Caution About Exoplanet Archival Data

In addition to original results from observations, exoplanet archives such as exoplanets.org and exoplanet.eu contain auxiliary products (unpublished semimajor axes and/or stellar parameters taken from supplementary studies) that are not sufficiently documented and/or not up-to-date, even for famous extrasolar systems. The NASA Exoplanet Archive does not publish auxiliary products, but a number of its entries are outdated; researchers should be encouraged to submit their results upon publication. In this note, we describe our recent experience with auxiliary products in three such systems, Kepler-223, Kepler-11, and GJ 876. We summarize the (in)compatible dynamical data that we obtained so that others may not have to go through the same trouble, even if this means relying on the original publications and private communications with the authors. At the same time, large statistical surveys utilizing only archival data are bound to be inaccurate to a certain extent.

Keywords: exoplanet catalogs
Surfaces of (Nearly) Dormant Comets and the Recent History of the Quadrantid Meteor Shower

The parent of the Quadrantid meteor shower is the inactive solar system small body (196256) 2003 EH1. EH1 has likely only gone dormant in the past few hundred years, and may be related to the bright comet C/1490 Y1. Compared with the other best-studied inactive meteor shower parent (3200) Phaethon, EH1 has received comparatively minimal characterization of its surface properties. We present the first reflectance spectrum and additional photometry of EH1, as well as new spectra of the nuclei of three nearly dormant comets P/2006 HR30 (Siding Spring), 364P/Pan-STARRS, and 249P/LINEAR for comparison. We also present new short-term high-resolution orbital integrations of these bodies for context. EH1s spectrum is red in color below 0.8 μm in between C and D types, consistent with previous photometric measurements, but is blue beyond 0.8 μm until at least 1.02 μm. 249P and 364P have both red slopes consistent with C taxonomic types and HR30 has a classic comet nucleus D-type slope. If the downturn in EH1's spectrum is due to an absorption feature, magnetite and olivine are plausible candidates, but more data are needed. 249P and 364P have similar recent and historical dynamical evolutions in addition to their similar surface properties. We discuss the interrelation between the dynamical histories and modern surfaces of these four objects and suggest avenues for further study to better constrain how the Quadrantids and Geminids were created.

Keywords: comet nuclei; comet surfaces; meteor showers; meteor streams; spectroscopy; spectrophotometry; orbital evolution
Visible and Near-infrared Spectral Properties of Martian Slope Streaks

Martian slope streaks are large surface features with lower albedo than their surroundings that are one of the few active geologic processes occurring on Mars today. We investigated the slope streaks' spectral properties using images from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) at nine sites, including three sites with observations over multiple years to enable time-series analysis. For each individual slope streak within each image, we determined the average spectra of each streak and of the slope immediately adjacent to account for changes in geology across a CRISM image or within slopes containing streaks. We find a trend where the visible spectral continuum (0.4-0.6 μm) is strongly negative for the darkest slope streaks, and the spectral continuum increases as the slope streaks fade, consistent across all sites and over multiple observations of the same site. We do not find absorption at 1.4 or 1.9 μm associated with hydration. In some slope streaks, we see evidence of Fe-bearing minerals, but these signatures are also found in the streak-free slope directly adjacent, suggesting that the streaks have a similar mineralogy to their surroundings. The spectral changes that we see are most consistent with changes in the fine dust component and support a dry flow mechanism whereby slope streaks are formed by processes that trigger dust removal from the slope in particular locations, with the streaks slowly fading as dust resettles on the surface.

Keywords: mars; surface processes; infrared spectroscopy; remote sensing
Simulating the Collapse of Rotating Primordial Gas Clouds to Study the Possibility of the Survival of Population III Protostars

It has been argued that the low-mass primordial stars (m Pop III ≤ 0.8 M ⊙) are likely to enter the main sequence and hence may possibly be found in present-day galaxies. However, due to limitations in existing numerical capabilities, current three-dimensional (3D) simulations of disk fragmentation are only capable of following a few thousand years of evolution after the formation of the first protostar. In this work, we use a modified version of the GADGET-2 smoothed particle hydrodynamics code to present the results of the nonlinear collapse of the gas clouds associated with various degrees of initial solid body rotation (parameterized by β) using a piecewise polytropic equation of state. The 3D simulations are followed until the epoch that occurs when 50M ⊙ of mass has been accreted in protostellar objects, which is adequate enough to investigate the dynamics of the protostars with the surrounding gaseous medium and to determine the mass function, accretion rate, and possibility of the survival of these protostellar objects to the present epoch. We found that evolving protostars that stay within slow-rotating parent clouds can become massive enough to survive, due to accretion in the absence of radiative feedback, whereas 10%-12% of those formed within fast-rotating clouds (β ≥ 0.1) could possibly be ejected from the gravitational bound cluster as low-mass stars.

Keywords: population iii stars; cosmology; stellar accretion; hydrodynamical simulations; protostars; initial mass function; low mass stars
Hidden Worlds: Dynamical Architecture Predictions of Undetected Planets in Multi-planet Systems and Applications to TESS Systems

Multi-planet systems produce a wealth of information for exoplanet science, but our understanding of planetary architectures is incomplete. Probing these systems further will provide insight into orbital architectures and formation pathways. Here we present a model to predict previously undetected planets in these systems via population statistics. The model considers both transiting and non-transiting planets, and can test the addition of more than one planet. Our tests show the model's orbital period predictions are robust to perturbations in system architectures on the order of a few percent, much larger than current uncertainties. Applying it to the multi-planet systems from the Transiting Exoplanet Survey Satellite (TESS) provides a prioritized list of targets, based on predicted transit depth and probability, for archival searches and for guiding ground-based follow-up observations hunting for hidden planets.

Keywords: exoplanets; astrostatistics
Turbulence in Particle-laden Midplane Layers of Planet-forming Disks

We examine the settled particle layers of planet-forming disks in which the streaming instability (SI) is thought to be either weak or inactive. A suite of low-to-moderate-resolution 3D simulations in a 0.2H-sized box, where H is the pressure scale height, are performed using PENCIL for two Stokes numbers, St = 0.04 and 0.2, at 1% disk metallicity. We find that a complex of Ekman-layer jet flows emerge subject to three co-acting linearly growing processes: (1) the Kelvin-Helmholtz instability (KHI), (2) the planet-forming disk analog of the baroclinic Symmetric Instability (SymI), and (3) a later-time weakly acting secondary transition process, possibly a manifestation of the SI, producing a radially propagating pattern state. For St = 0.2 KHI is dominant and manifests as off-midplane axisymmetric rolls, while for St = 0.04 the axisymmetric SymI mainly drives turbulence. SymI is analytically developed in a model disk flow, predicting that it becomes strongly active when the Richardson number (Ri) of the particle-gas midplane layer transitions below 1, exhibiting growth rates $\leqslant \sqrt{2/\mathrm{Ri}-2}\cdot {\rm{\Omega }}$ , where Ω is the local disk rotation rate. For fairly general situations absent external sources of turbulence it is conjectured that the SI, when and if initiated, emerges out of a turbulent state primarily driven and shaped by at least SymI and/or KHI. We also find that turbulence produced in 2563 resolution simulations are not statistically converged and that corresponding 5123 simulations may be converged for St = 0.2. Furthermore, we report that our numerical simulations significantly dissipate turbulent kinetic energy on scales less than six to eight grid points.

Keywords: astrophysical fluid dynamics; planetesimals; protoplanetary disks; hydrodynamical simulations
Fallback Rates from Partial Tidal Disruption Events

A tidal disruption event (TDE) occurs when a star plunges through a supermassive black hole's tidal radius, at which point the star's self-gravity is overwhelmed by the tidal gravity of the black hole. In a partial TDE, where the star does not reach the full disruption radius, only a fraction of the star's mass is tidally stripped while the rest remains intact in the form of a surviving core. Analytical arguments have recently suggested that the temporal scaling of the fallback rate of debris to the black hole asymptotes to t-9/4 for partial disruptions, effectively independently of the mass of the intact core. We present hydrodynamical simulations that verify the existence of this predicted, t-9/4 scaling. We also define a break timescale—the time at which the fallback rate transitions from a t-5/3 scaling to the characteristic t-9/4 scaling—and measure this break timescale as a function of the impact parameter and the surviving core mass. These results deepen our understanding of the properties and breadth of possible fallback curves expected from TDEs and will therefore facilitate more accurate interpretation of data from wide-field surveys.

Keywords: black hole physics; hydrodynamics; galaxy nuclei
Toward General Relativistic Magnetohydrodynamics Simulations in Stationary Nonvacuum Spacetimes

Accretion of magnetized gas on compact astrophysical objects such as black holes (BHs) has been successfully modeled using general relativistic magnetohydrodynamic (GRMHD) simulations. These simulations have largely been performed in the Kerr metric, which describes the spacetime of a vacuum and stationary spinning BH in general relativity (GR). The simulations have revealed important clues to the physics of accretion flows and jets near the BH event horizon and have been used to interpret recent Event Horizon Telescope images of the supermassive BHs M87* and Sgr A*. The GRMHD simulations require the spacetime metric to be given in horizon-penetrating coordinates such that all metric coefficients are regular at the event horizon. Only a few metrics, notably the Kerr metric and its electrically charged spinning analog, the Kerr-Newman metric, are currently available in such coordinates. We report here horizon-penetrating forms of a large class of stationary, axisymmetric, spinning metrics. These can be used to carry out GRMHD simulations of accretion on spinning, nonvacuum BHs and non-BHs within GR, as well as accretion on spinning objects described by non-GR metric theories of gravity.

Keywords: astrophysical black holes; supermassive black holes; accretion; relativistic jets; non-standard theories of gravity; gravastars; magnetohydrodynamical simulations; general relativity; wormholes; naked singularities
Powering Luminous Core Collapse Supernovae with Jets

I examine recent fittings of luminous supernovae (LSNe) with extra energy sources of magnetar and helium burning and find that in about half of these LSNe the fitting parameters have some problems. In some LSNe the total energy of these two energy sources is larger than the kinetic energy of the ejecta that the fitting yields. In some other LSNe the total energy of the delayed neutrino explosion mechanism and these two extra sources combined is smaller than the kinetic energy that the fitting yields. These difficulties suggest that, like earlier claims that jets power superluminous supernovae (SLSNe), jets also power the less luminous LSNe. A magnetar might also supply energy. However, in most cases jets supply more energy than the magnetar, during the explosion and possibly at late times. I strengthen an earlier claim that jets launched at magnetar birth cannot be ignored. I explain the trend of maximum rise time for a given luminosity of hydrogen deficient core collapse supernovae, in particular LSNe and SLSNe, with a toy model of jets that are active for a long time after explosion.

Keywords: supernovae; type ib supernovae; type ic supernovae; stellar jets
Constraining the X-Ray-Infrared Spectral Index of Second-timescale Flares from SGR 1935+2154 with Palomar Gattini-IR

The Galactic magnetar SGR 1935+2154 has been reported to produce the first example of a bright millisecond-duration radio burst (FRB 200428) similar to the cosmological population of fast radio bursts (FRBs). The detection of a coincident bright X-ray burst represents the first observed multiwavelength counterpart of an FRB. However, the search for similar emission at optical wavelengths has been hampered by the high inferred extinction on the line of sight. Here, we present results from the first search for second-timescale emission from the source at near-infrared (NIR) wavelengths using the Palomar Gattini-IR observing system in the J band, enabled by a novel detector readout mode that allows short exposure times of ≈0.84 s with 99.9% observing efficiency. With a total observing time of ≈12 hr (≈47,728 images) during its 2020 outburst, we place median 3σ limits on the second-timescale NIR fluence of ≲18 Jy ms (13.1 AB mag). The corresponding extinction-corrected limit is ≲125 Jy ms for an estimated extinction of AJ = 2.0 mag. Our observations were sensitive enough to easily detect an NIR counterpart of FRB 200428 if the NIR emission falls on the same power law as observed across its radio to X-ray spectrum. We report nondetection limits from epochs of four simultaneous X-ray bursts detected by the Insight-HXMT and NuSTAR telescopes during our observations. These limits provide the most stringent constraints to date on fluence of flares at ∼1014 Hz, and constrain the fluence ratio of the NIR emission to coincident X-ray bursts to RNIR ≲ 0.025 (fluence index ≳0.35).

Keywords: radio transient sources; magnetars; soft gamma-ray repeaters
The PHLEK Survey: A New Determination of the Primordial Helium Abundance

We present Keck NIRSPEC and Keck NIRES spectroscopy of sixteen metal-poor galaxies that have pre-existing optical observations. The near-infrared (NIR) spectroscopy specifically targets the He I λ10830 Å emission line, due to its sensitivity to the physical conditions of the gas in H II regions. We use these NIR observations, combined with optical spectroscopy, to determine the helium abundance of sixteen galaxies across a metallicity range $12+{{\rm{log}}}_{10}({\rm{O}}/{\rm{H}})$ = 7.13-8.00. This data set is combined with two other samples where metallicity and helium abundance measurements can be secured: star-forming galaxies selected from the Sloan Digital Sky Survey spectroscopic database, and existing low-metallicity systems in the literature. We calculate a linear fit to these measurements, accounting for intrinsic scatter, and report a new determination of the primordial helium number abundance, ${y}_{{\rm{P}}}={0.0805}_{-0.0017}^{+0.0017}$, which corresponds to a primordial helium mass fraction ${Y}_{{\rm{P}}}={0.2436}_{-0.0040}^{+0.0039}$ . Using our determination of the primordial helium abundance in combination with the latest primordial deuterium measurement, ${({\rm{D}}/{\rm{H}})}_{{\rm{P}}}\times {10}^{5}=2.527\pm 0.030$, we place a bound on the baryon density ${{\rm{\Omega }}}_{{\rm{b}}}{h}^{2}={0.0215}_{-0.0005}^{+0.0005}$ and the effective number of neutrino species ${N}_{\mathrm{eff}}={2.85}_{-0.25}^{+0.28}$ . These values are in 1.3σ agreement with those deduced from the Planck satellite observations of the temperature fluctuations imprinted on the cosmic microwave background.

Keywords: dwarf galaxies; galaxy abundances; galaxy chemical evolution; big bang nucleosynthesis