adsabs/SciX_UAT_keywords huggingface dataset:
Near-infrared Methanol Bands Probe Energetic Processing of Icy Outer Solar System Objects

Frozen methanol was detected in the outer solar system on the surfaces of the Centaur 5145 Pholus, the Trans-Neptunian Object (55638) 2002 VE95, and more recently on (486958) Arrokoth. The icy surfaces of these objects are subjected to solar and cosmic ions that modify the physico-chemical properties of their surface. To study the effects of ion bombardment on methanol-rich surfaces, we performed experiments of ion irradiation of H2O:CH3OH mixtures and we monitored the evolution of the methanol near-infrared bands. We observed significant variations of the 2.34/2.27 μm methanol band ratios as a function of the irradiation dose. We then used the Arrokoth and Pholus spectra to test the 2.34/2.27 μm band ratio as a probe of irradiation of methanol-rich surfaces, and we estimated the timescales of processing by solar and cosmic ions. Our results indicate that solar energetic particles are the main drivers of changes in the near-infrared spectra of frozen surfaces in the outer solar system.

Keywords: laboratory astrophysics; small solar system bodies; surface composition; surface processes; solar energetic particles; cosmochemistry; spectroscopy
Detection of Flare-associated CME Candidates on Two M-dwarfs by GWAC and Fast, Time-resolved Spectroscopic Follow-ups

The flare-associated stellar coronal mass ejections (CMEs) of solar-like and late-type stars profoundly impact the habitability of any expolanets in the systems. In this paper, we report the detection of flare-associated CMEs for two M-dwarfs, thanks to a high-cadence survey carried out by the Ground Wide-angle Camera system and fast photometric and spectroscopic follow-ups. The flare energies in the R band are determined to be 1.6 × 1035 erg and 8.1 × 1033 erg based on modeling of their light curves. The time-resolved spectroscopic observations start at about 20 and 40 minutes after the trigger in both cases. The large projected maximum velocity of ~500-700 km s-1 suggests that the high-velocity wings of their Hα emission lines most likely result from CME events in both stars, after excluding the possibility of chromospheric evaporation and coronal rain. The masses of the CMEs are estimated to be 1.5-4.5 × 1019 g and 7.1 × 1018 g.

Keywords: stellar flares; optical flares; late-type dwarf stars; stellar coronal mass ejections; time domain astronomy; spectroscopy
Effects of General Relativistic Spin Precessions on the Habitability of Rogue Planets Orbiting Supermassive Black Holes

Recently, the possibility that several starless telluric planets may form around supermassive black holes (SMBHs) and receive energy input from the hole's accretion disk, which, under certain plausible circumstances, may make them habitable in a terrestrial sense, has gained increasing attention. In particular, an observer on a planet orbiting at distance r = 100 Schwarzschild radii from a maximally rotating Kerr SMBH with mass M• = 1 × 108 M⊙ in a plane slightly outside the equator of the latter, would see the gravitationally lensed accretion disk the same size as the Sun as seen from Earth. Moreover, the accretion rate might be imagined to be set in such a way that the apparent disk's temperature would be identical to that of the solar surface. We demonstrate that the post-Newtonian (pN) de Sitter and Lense-Thirring precessions of the spin axis of such a world would rapidly change, among other things, its tilt, ɛ, to its orbital plane by tens to hundreds of degrees over a time span of, say, just Δt = 400 yr, strongly depending on the obliquity η• of the SMBH's spin to the orbital plane. Thus, such relativistic features would have per se a relevant impact on the long-term habitability of the considered planet. Other scenarios are examined as well.

Keywords: black holes; exoplanets; celestial mechanics; astrobiology; gravitation; general relativity
Fallback Accretion Model for the Years-to-decades X-Ray Counterpart to GW170817

A new component was reported in the X-ray counterpart to the binary neutron star merger and gravitational-wave event GW170817, exceeding the afterglow emission from an off-axis structured jet. The afterglow emission from the kilonova/macronova ejecta may explain the X-ray excess but exceeds the radio observations if the spectrum is the same. We propose a fallback accretion model that a part of ejecta from the neutron star merger falls back and forms a disk around the central compact object. In the super-Eddington accretion phase, the X-ray luminosity stays near the Eddington limit of a few solar masses and the radio is weak, as observed. This will be followed by a power-law decay. The duration of the constant luminosity phase conveys the initial fallback timescale t0 in the past. The current multiyear duration requires t0 > 3-30 s, suggesting that the disk wind rather than the dynamical ejecta falls back after the jet launch. Future observations in the next decades will probe the timescale of t0 ~ 10-104 s, around the time of extended emission in short gamma-ray bursts. The fallback accretion has not been halted by the r-process heating, implying that fission is weak on the year scale. We predict that the X-ray counterpart will disappear in a few decades due to the r-process halting or the depletion of fallback matter.

Keywords: hydrodynamics; accretion; stellar accretion disks; gamma-ray bursts; astrophysical black holes; r-process; nucleosynthesis
Chandra Observations of Six Peter Pan Disks: Diversity of X-Ray-driven Internal Photoevaporation Rates Does Not Explain Their Rare Longevity

We present Chandra X-ray observations of six previously identified Peter Pan objects, rare ~40 Myr systems with evidence of primordial disk retention. We observe X-ray luminosities (0.8-3.0 keV) ranging from log L x ~ 27.7-29.1. We find that our Peter Pan sample exhibits X-ray properties similar to that of weak-lined T Tauri stars and do not exhibit evidence of stellar accretion induced X-ray suppression. Our observed Peter Pan X-ray luminosities are consistent with that measured for field dM stars of similar spectral type and age, implying their long primordial disk lifetimes are likely not a consequence of unusually faint X-ray host stars. Our derived X-ray photoevaporative mass-loss rates predict our systems have passed the point of rapid gas dispersal and call into question the impact of this internal mechanism for primordial disk dispersal around dM stars. Our qualitative assessment of the surrounding Peter Pan environments also does not predict unusually low levels of external photoevaporation relative to other respective moving group members. Overall, our results suggest Peter Pan disks may be a consequence of the low far-UV flux incident on the disk in low-mass dM stars given their relatively lower levels of accretion over the course of their pre-main-sequence evolution.

Keywords: x-ray astronomy; circumstellar disks; low mass stars
Substellar Hyades Candidates from the UKIRT Hemisphere Survey

We have used data from the UKIRT Hemisphere Survey to search for substellar members of the Hyades cluster. Our search recovered several known substellar Hyades members, and two known brown dwarfs that we suggest may be members based on a new kinematic analysis. We uncovered thirteen new substellar Hyades candidates, and obtained near-infrared follow-up spectroscopy of each with IRTF/SpeX. Six candidates with spectral types between M7 and L0 are ruled out as potential members based on their photometric distances (≳100 pc). The remaining seven candidates, with spectral types between L5 and T4, are all potential Hyades members, with five showing strong membership probabilities based on BANYAN Σ and a convergent point analysis. Distances and radial velocities are still needed to confirm Hyades membership. If confirmed, these would be some of the lowest mass free-floating members of the Hyades yet known, with masses as low as ~30 M Jup. An analysis of all known substellar Hyades candidates shows evidence that the full extent of the Hyades has yet to be probed for low-mass members, and more would likely be recovered with deeper photometric and astrometric investigations.

Keywords: low mass stars; open star clusters
VLA/Realfast Detection of a Burst from FRB 180916.J0158+65 and Tests for Periodic Activity

We report on the detection of a burst from FRB 180916 by realfast/Very Large Array and present software for interpreting fast radio bursts (FRB) periodicity. We demonstrate a range of periodicity analyses with bursts from FRB 180916, FRB 121102 and FRB 180814. Our results for FRB 180916 and FRB 121102 are consistent with published results. For FRB 180814, we did not detect any significant periodic episodes. The realfast-detected and other high-frequency bursts for FRB 180916 tend to lie at the beginning of the activity window, indicating a possible phase-frequency relation. The python package frbpa can be used to reproduce and expand on this analysis to test models for repeating FRBs.

Keywords: radio transient sources; radio bursts; high energy astrophysics
A Simplified Photodynamical Model for Planetary Mass Determination in Low-eccentricity Multitransiting Systems

Inferring planetary parameters from transit timing variations (TTVs) is challenging for small exoplanets because their transits may be so weak that determination of individual transit timing is difficult or impossible. We implement a useful combination of tools that together provide a numerically fast global photodynamical model. This is used to fit the TTV-bearing light curve, in order to constrain the masses of transiting exoplanets in low-eccentricity, multiplanet systems—and small planets in particular. We present inferred dynamical masses and orbital eccentricities in four multi-planet systems from Kepler's complete long-cadence data set. We test our model against Kepler-36/KOI-277, a system with some of the most precisely determined planetary masses through TTV inversion methods, and find masses of 5.56+0.41-0.45 and 9.76+0.79-0.89 ${m}_{\oplus }$ for Kepler-36 b and c, respectively—consistent with literature in both value and error. We then improve the mass determination of the four planets in Kepler-79/KOI-152, where literature values were physically problematic to 12.5+4.5-3.6, 9.5+2.3-2.1, 11.3+2.2-2.2 and 6.3+1.0-1.0 ${m}_{\oplus }$ for Kepler-79 b, c, d, and e, respectively. We provide new mass constraints where none existed before for two systems. These are 12.5+3.2-2.6 ${m}_{\oplus }$ for Kepler-450 c, and 3.3+1.7-1.0 and 17.4+7.1-3.8 ${m}_{\oplus }$ for Kepler-595 c (previously KOI-547.03) and b, respectively. The photodynamical code used here, called PyDynamicaLC, is made publicly available.

Keywords: exoplanets; exoplanet astronomy; super earths; mini neptunes
Gemini Near-Infrared Field Spectrograph Observations of the Seyfert 2 Galaxy Mrk 3: Feeding and Feedback on Galactic and Nuclear Scales

We explore the kinematics of the stars, ionized gas, and warm molecular gas in the Seyfert 2 galaxy Mrk 3 (UGC 3426) on nuclear and galactic scales with Gemini Near-Infrared Field Spectrograph observations, previous Hubble Space Telescope data, and new long-slit spectra from the Apache Point Observatory (APO) 3.5 m telescope. The APO spectra are consistent with our previous suggestion that a galactic-scale gas/dust disk at P.A. = 129°, offset from the major axis of the host S0 galaxy at P.A. = 28°, is responsible for the orientation of the extended narrow-line region. The disk is fed by an H I tidal stream from a gas-rich spiral galaxy (UGC 3422) ∼100 kpc to the NW of Mrk 3 and is ionized by the active galactic nucleus (AGN) to a distance of at least ∼20″ (∼5.4 kpc) from the central supermassive black hole (SMBH). The kinematics within at least 320 pc of the SMBH are dominated by outflows with radial (line-of-sight) velocities up to 1500 km s-1 in the ionized gas and 500 km s-1 in the warm molecular gas, consistent with in situ heating, ionization, and acceleration of ambient gas to produce the narrow-line region outflows. There is a disk of ionized and warm molecular gas within ∼400 pc of the SMBH that has reoriented close to the stellar major axis but is counterrotating, consistent with claims of external fueling of AGNs in S0 galaxies.

Keywords: seyfert galaxies; active galaxies; agn host galaxies; supermassive black holes; galaxy kinematics
An Asymmetric Double-degenerate Type Ia Supernova Explosion with a Surviving Companion Star

We present nebular spectroscopy of SN 2020hvf, a Type Ia supernova (SN Ia) with an early bump in its light curve. SN 2020hvf shares many spectroscopic and photometric similarities to the carbon-rich high-luminosity "03fg-like" SNe Ia. At >240 days after peak brightness, we detect unambiguous emission from [Ca II] λ λ7291, 7324, which is rarely observed in normal SNe Ia and only seen in peculiar subclasses. SN 2020hvf displays "sawtooth" emission profiles near 7300 Å that cannot be explained with single symmetric velocity components of [Fe II], [Ni II], and [Ca II], indicating an asymmetric explosion. The broad [Ca II] emission is best modeled by two velocity components offset by 1220 km s-1, which could be caused by ejecta associated with each star in the progenitor system, separated by their orbital velocity. For the first time in an SN Ia, we identify narrow (FWHM = 180 ± 40 km s-1) [Ca II] emission, which we associate with a wind from a surviving, puffed-up companion star. Few published spectra have sufficient resolution and the signal-to-noise ratio necessary to detect similar narrow [Ca II] emission; however, we have detected similar line profiles in other 03fg-like SNe Ia. The extremely narrow velocity width of [Ca II] has only otherwise been observed in SNe Iax at late times. Since this event likely had a double-degenerate "super-Chandrasekhar" mass progenitor system, we suggest that a single white dwarf (WD) was fully disrupted and a wind from a surviving companion WD is producing the observed narrow emission. It is unclear whether this unique progenitor and explosion scenario can explain the diversity of 03fg-like SNe Ia, potentially indicating that multiple progenitor channels contribute to this subclass.

Keywords: supernovae; observational astronomy; white dwarf stars; type ia supernovae
The AstroSat UV Deep Field North: The IRX–β Relation for the UV-selected Galaxies at z ∼ 0.5‑0.7

The relation between the observed UV continuum slope (β) and the infrared excess (IRX) is used as a powerful probe to understand the nature of dust attenuation law in high-redshift galaxies. We present a study of 83 UV-selected galaxies between a redshift of 0.5 and 0.7 from the AstroSat UV Deep Field north that encloses the GOODS-North field. Using empirical relation, we estimate the observed IRX of 52 galaxies that are detected in either one or both of the Herschel PACS 100 and 160 μm bands. We further utilize the multiband photometric data in 14–18 filters from the Ultra-Violet Imaging Telescope, KPNO, Hubble Space Telescope, Spitzer, and Herschel telescopes to perform spectral energy distribution (SED) modeling. Both the observed and model-derived IRX–β values show a large scatter within the span of previously known relations, signifying diversity in dust attenuation. We found a distinct relation between the best-fit power-law slope of the modified Calzetti relation (δ) in the IRX–β plane, where the steeper SMC-like attenuation law prefers lower δ values. Our SED model-based IRX–β relation shows a preference for steeper SMC-like attenuation, which we further confirm from the agreement between extinction-corrected star formation rates derived using the Hα emission line and the observed far-ultraviolet plus reprocessed far-IR fluxes. The current study reveals a strong positive correlation between IRX and the galaxy's stellar mass between 109.5 and 1011.0 M ⊙, signifying increased dust production in more massive star-forming galaxies.

Keywords: high-redshift galaxies; interstellar dust extinction; galaxy evolution; ultraviolet surveys
Photometric Biases in Modern Surveys

Many surveys use maximum-likelihood (ML) methods to fit models when extracting photometry from images. We show that these ML estimators systematically overestimate the flux as a function of the signal-to-noise ratio and the number of model parameters involved in the fit. This bias is substantially worse for resolved sources: while a 1% bias is expected for a 10σ point source, a 10σ resolved galaxy with a simplified Gaussian profile suffers a 2.5% bias. This bias also behaves differently depending how multiple bands are used in the fit: simultaneously fitting all bands leads the flux bias to become roughly evenly distributed between them, while fixing the position in "non-detection" bands (i.e., forced photometry) gives flux estimates in those bands that are biased low, compounding a bias in derived colors. We show that these effects are present in idealized simulations, outputs from the Hyper Suprime-Cam fake-object pipeline (SynPipe), and observations from Sloan Digital Sky Survey Stripe 82. Prescriptions to correct for the ML bias in flux, and its uncertainty, are provided.

Keywords: astrostatistics; astronomy data analysis; maximum likelihood estimation; fisher's information; astronomy data reduction; catalogs; surveys; ccd photometry
Modeling Stellar Abundance Patterns Resulting from the Addition of Earth-like Planetary Material

We model the observed precision differential abundance patterns of three G-type dwarfs, assuming a mass of planetary or disk material was added to or subtracted from the atmosphere of the star. The two-parameter model is fit by linear regression. The stellar abundance patterns are corrected for Galactic chemical evolution (GCE). The differential abundances can be highly correlated with the elemental condensation temperature. We show how it is possible to match not only the slope, but the quantitative abundance differences, assuming a composition for the added material equal to that of the bulk earth. We also model the wide pair HIP 34407 and HIP 34426, where GCE corrections are assumed unnecessary. An appendix discusses issues of volatility and condensation temperature.

Keywords: solar abundances; stellar abundances; cosmochemistry
First Observations of an Ion Vortex in a Magnetic Hole in the Solar Wind by MMS

The coronal heating region is able to generate mirror mode structures by ion mirror instabilities. Linear magnetic holes are believed to be the remnants of mirror mode structures, thus they are believed to be messengers from the coronal heating region. They can be convected to ∼9 au with the solar wind flow, indicating that a stabilizing mechanism is necessary to make the magnetic holes survive for such a long time. Here, we investigate a magnetic hole with a size of ∼6.7 ρi in the solar wind based on observations by the Magnetospheric Multiscale mission. The unprecedented high-resolution data enable us to reveal the existence of the ion vortex inside the structure for the first time. Such an ion vortex forms a ring-like current, which is consistent with the magnetic field depression. The self-consistent structure of the magnetic hole contributed by the ion vortex can help to further shed light on the mechanism of the long-term survival of magnetic holes in the astrophysical plasma.

Keywords: solar wind; planetary magnetospheres
The Structure and Stability of Massive Hot White Dwarfs

We investigate the structure and stability against radial oscillations, pycnonuclear reactions, and inverse β-decay of hot white dwarfs. We consider the fluid matter to be made up of nucleons and electrons confined in a Wigner-Seitz cell surrounded by free photons. It is considered that the temperature depends on the mass density considering the presence of an isothermal core. We find that the temperature produces remarkable effects on the equilibrium and radial stability of white dwarfs. The stable equilibrium configuration results are compared with those for white dwarfs estimated from the Extreme Ultraviolet Explorer survey and the Sloan Digital Sky Survey. We derive masses, radii, and central temperatures for the most massive white dwarfs according to the surface gravity and effective temperature reported by the surveys. We note that these massive stars are in the mass region where general relativity effects are important. These stars are near the threshold of instabilities due to radial oscillations, pycnonuclear reactions, and inverse β-decay. Regarding the radial stability of these stars as a function of the temperature, we find that it decreases with the increment of central temperature. We also find that the maximum-mass point and the zero eigenfrequencies of the fundamental mode are determined at the same central energy density. Regarding low-temperature stars, pycnonuclear reactions occur in similar central energy densities, and the central energy density threshold for inverse β-decay is not modified. For Tc ≥ 1.0 × 108 [K], the onset of radial instability is attained before pycnonuclear reaction and inverse β-decay.

Keywords: white dwarf stars; compact objects
PopSED: Population-level Inference for Galaxy Properties from Broadband Photometry with Neural Density Estimation

We present POPSED , a framework for the population-level inference of galaxy properties from photometric data. Unlike the traditional approach of first analyzing individual galaxies and then combining the results to determine the physical properties of the entire galaxy population, we directly make the population distribution the inference objective. We train normalizing flows to approximate the population distribution by minimizing the Wasserstein distance between the synthetic photometry of the galaxy population and the observed data. We validate our method using mock observations and apply it to galaxies from the GAMA survey. POPSED reliably recovers the redshift and stellar mass distribution of 105 galaxies using broadband photometry within <1 GPU hr, being 105-6 times faster than the traditional spectral energy distribution modeling method. From the population posterior, we also recover the star-forming main sequence for GAMA galaxies at z < 0.1. With the unprecedented number of galaxies in upcoming surveys, our method offers an efficient tool for studying galaxy evolution and deriving redshift distributions for cosmological analyses.

Keywords: stellar populations; galaxy photometry; galaxy evolution; neural networks; astrostatistics; sky surveys
Tidally-induced Magnetar Super Flare at the Eve of Coalescence with Its Compact Companion

In the late inspiral phase of a double neutron star (NS) or NS-black hole system in which one NS is a magnetar, the tidal force on the magnetar arisen from its companion will increase dramatically as the binary approaches. The tidal-induced deformation may surpass the maximum that the magnetar's crust can sustain just seconds or subseconds before the coalescence. A catastrophic global crust destruction may thus occur, and the magnetic energy stored in the magnetar's interior will have the opportunity to be released, which would be observed as a superflare with energy 100s of times larger than giant flares of magnetars. Such a mechanism can naturally explain the recently observed precursor of GRB 211211A, including its quasiperiodic oscillation. We predict that in the coming gravitational wave O4/O5 period, there could be a fraction of detected double NS mergers associated with such super flares. If observed, copious information on the structure and magnetic field in an NS interior can be obtained, which is hard to study elsewhere.

Keywords: stellar mergers; magnetars; neutron stars; compact objects; stellar mass black holes; gamma-ray bursts; gravitational wave sources