Sazuna/UAT_keywords huggingface dataset:
INTEGRAL Limits on Past High-energy Activity from FRB 20200120E in M81. The repeating fast radio burst FRB 20200120E is located in a globular cluster belonging to the nearby M81 galaxy. Its small distance (3.6 Mpc) and accurate localization make it an interesting target to search for bursting activity at high energies. From 2003 November to 2021 September, the INTEGRAL satellite has obtained an exposure time of 18 Ms on the M81 sky region. We used these data to search for hard X-ray bursts from FRB 20200120E using the IBIS/ISGRI instrument, without finding any significant candidate, down to an average fluence limit of ~10-8 erg cm-2 (20-200 keV). The corresponding limit on the isotropic luminosity for a burst of duration Δt is $\sim {10}^{45}\left(\tfrac{10\,\mathrm{ms}}{{\rm{\Delta }}t}\right)$ erg s-1, the deepest limit obtained for an extragalactic FRB in the hard X-ray range. This rules out the emission of powerful flares at a rate higher than 0.1 yr-1 that could be expected in models invoking young hyperactive magnetars.

Keywords: Magnetars, Radio bursts
Retrieving Exoplanet Atmospheres Using Planetary Infrared Excess: Prospects for the Night Side of WASP-43 b and Other Hot Jupiters. To increase the sample size of future atmospheric characterization efforts, we build on the planetary infrared excess (PIE) technique that has been proposed as a means to detect and characterize the thermal spectra of transiting and non-transiting exoplanets using sufficiently broad wavelength coverage to uniquely constrain the stellar and planetary spectral components from spatially unresolved observations. We performed simultaneous retrievals of stellar and planetary spectra for the archetypal planet WASP-43b in its original configuration and a non-transiting configuration to determine the efficacy of the PIE technique for characterizing the planet's night-side atmospheric thermal structure and composition using typical out-of-transit JWST observations. We found that using PIE with JWST should enable the stellar and planetary spectra to be disentangled with no degeneracies seen between the two flux sources, thus allowing robust constraints on the planet's night-side thermal structure and water abundance to be retrieved. The broad wavelength coverage achieved by combining spectra from NIRISS, NIRSpec, and MIRI enables PIE retrievals that are within 10% of the precision attained using traditional secondary eclipse measurements, although mid-IR observations with MIRI alone may face up to 3.5× lower precision on the planet's irradiation temperature. For non-transiting planets with unconstrained radius priors, we were able to identify and break the degeneracy between planet radius and irradiation temperature using data that resolved the peak of both the stellar and planetary spectra, thus potentially increasing the number of planets amenable to atmospheric characterization with JWST and other future mission concepts.

Keywords: Infrared excess, Exoplanet atmospheric composition , Astronomical methods, Exoplanet atmospheres
Early Initiation of Inner Solar System Formation at the Dead-zone Inner Edge. The inner solar system possesses a unique orbital structure in which there are no planets inside the Mercury orbit and the mass is concentrated around the Venus and Earth orbits. The origins of these features still remain unclear. We propose a novel concept that the building blocks of the inner solar system formed at the dead-zone inner edge in the early phase of the protosolar disk evolution, where the disk is effectively heated by the disk accretion. First, we compute the dust evolution in a gas disk with a dead zone and obtain the spatial distribution of rocky planetesimals. The disk is allowed to evolve both by a viscous diffusion and magnetically driven winds. We find that the rocky planetesimals are formed in concentrations around ~1 au with a total mass comparable to the mass of the current inner solar system in the early phase of the disk evolution within ≲0.1 Myr. Based on the planetesimal distribution and the gas-disk structure, we subsequently perform N-body simulations of protoplanets to investigate the dynamical configuration of the planetary system. We find that the protoplanets can grow into planets without significant orbital migration because of the rapid clearing of the inner disk by the magnetically driven disk winds. Our model can explain the origins of the orbital structure of the inner solar system. Several other features such as the rocky composition can also be explained by the early formation of rocky planetesimals.

Keywords: Solar system formation, Protoplanetary disks, Solar system terrestrial planets
Faintest of Them All: ZTF 21aaoryiz/SN 2021fcg-Discovery of an Extremely Low Luminosity Type Iax Supernova. We present the discovery of ZTF 21aaoryiz/SN 2021fcg-an extremely low luminosity Type Iax supernova. SN 2021fcg was discovered by the Zwicky Transient Facility in the star-forming galaxy IC0512 at a distance of ≈27 Mpc. It reached a peak absolute magnitude of Mr = -12.66 ± 0.20 mag, making it the least luminous thermonuclear supernova discovered to date. The E(B - V) contribution from the underlying host galaxy is unconstrained. However, even if it were as large as 0.5 mag, the peak absolute magnitude would be Mr = -13.78 ± 0.20 mag-still consistent with being the lowest-luminosity SN. Optical spectra of SN 2021fcg taken at 37 and 65 days post-maximum show strong [Ca II], Ca II, and Na I D emission and several weak [Fe II] emission lines. The [Ca II] emission in the two spectra has extremely low velocities of ≈1300 and 1000 km s-1, respectively. The spectra very closely resemble those of the very low luminosity Type Iax supernovae SN 2008 ha, SN 2010ae, and SN 2019gsc taken at similar phases. The peak bolometric luminosity of SN 2021fcg is ≈ ${2.5}_{-0.3}^{+1.5}\times {10}^{40}$ erg s-1, which is a factor of 3 lower than that for SN 2008 ha. The bolometric lightcurve of SN 2021fcg is consistent with a very low ejected nickel mass (M ${}_{\mathrm{Ni}}\approx {0.8}_{-0.5}^{+0.4}\times {10}^{-3}$ M⊙). The low luminosity and nickel mass of SN 2021fcg pose a challenge to the picture that low-luminosity SNe Iax originate from deflagrations of near-Mch hybrid carbon-oxygen-neon white dwarfs. Instead, the merger of a carbon-oxygen and oxygen-neon white dwarf is a promising model to explain SN 2021fcg.

Keywords: White dwarf stars, Type Ia supernovae, Time domain astronomy
Gas-phase Synthesis of Silaformaldehyde (H<SUB>2</SUB>SiO) and Hydroxysilylene (HSiOH) in Outflows of Oxygen-rich Asymptotic Giant Branch Stars. Silicon- and oxygen-containing species such as silicon monoxide (SiO) and silicon dioxide (SiO2) represent basic molecular building blocks connected to the growth of silicate grains in outflows of oxygen-rich asymptotic giant branch (AGB) stars like R Doradus. Yet the fundamental mechanisms of the formation of silicate grains and the early processes that initiate the coupling of the silicon with the oxygen chemistries in circumstellar envelopes have remained obscure. Here, in a crossed molecular beams experiment combined with ab initio electronic structure calculations, we reveal that at least the d2-silaformaldehyde (D2SiO) and d2-hydroxysilylene (DSiOD) molecules-proxies for the astronomically elusive silaformaldehyde (H2SiO) and hydroxysilylene (HSiOH) molecules-can be synthesized via the reaction of the D1-silylidyne radical (SiD; X2Π) with D2-water (D2O) under single-collision conditions. This system represents a benchmark of a previously overlooked class of reactions, in which the silicon-oxygen bond coupling can be initiated by a reaction between the simplest silicon-bearing radical (silylidyne) and one of the most abundant species in the circumstellar envelopes of evolved oxygen-rich AGB stars (water). As supported by novel astrochemical modeling, considering that silicon- and oxygen-containing species like H2SiO and HSiOH might be photolyzed easily, they ultimately connect to simple molecular precursors such as SiO that drive a chain of reactions conceivably forming higher molecular weight silicon oxides and, ultimately, a population of silicates at high temperatures.

Keywords: Interstellar dust, Circumstellar envelopes, Laboratory astrophysics, Astrochemistry
Unveiling Shrouded Oceans on Temperate sub-Neptunes via Transit Signatures of Solubility Equilibria versus Gas Thermochemistry. The recent discovery and initial characterization of sub-Neptune-sized exoplanets that receive stellar irradiance of approximately Earth's raised the prospect of finding habitable planets in the coming decade, because some of these temperate planets may support liquid-water oceans if they do not have massive H2/He envelopes and are thus not too hot at the bottom of the envelopes. For planets larger than Earth, and especially planets in the 1.7-3.5 R⊕ population, the mass of the H2/He envelope is typically not sufficiently constrained to assess the potential habitability. Here we show that the solubility equilibria versus thermochemistry of carbon and nitrogen gases typically results in observable discriminators between small H2 atmospheres versus massive ones, because the condition to form a liquid-water ocean and that to achieve the thermochemical equilibrium are mutually exclusive. The dominant carbon and nitrogen gases are typically CH4 and NH3 due to thermochemical recycling in a massive atmosphere of a temperate planet, and those in a small atmosphere overlying a liquid-water ocean are most likely CO2 and N2, followed by CO and CH4 produced photochemically. NH3 is depleted in the small atmosphere by dissolution into the liquid-water ocean. These gases lead to distinctive features in the planet's transmission spectrum, and a moderate number of transit observations with the James Webb Space Telescope should tell apart a small atmosphere versus a massive one on planets like K2-18 b. This framework thus points to a way to use near-term facilities to constrain the atmospheric mass and habitability of temperate sub-Neptune exoplanets.

Keywords: Extrasolar rocky planets, Ocean planets, Extrasolar ice giants, Transmission spectroscopy, Habitable planets, Exoplanet atmospheres
The Tail of Late-forming Dwarf Galaxies in ΛCDM. We use a robust analytical model together with a high-resolution hydrodynamical cosmological simulation to demonstrate that in a Lambda cold dark matter (ΛCDM) universe, a small fraction of dwarf galaxies inhabiting dark matter (DM) halos in the mass range 3 × 109 ≲ M200/M⊙ ≲ 1010 form unusually late (z &lt; 3) compared to the bulk population of galaxies. These galaxies originate from the interplay between the stochastic growth of DM halos and the existence of a time-dependent DM halo mass below which galaxies do not form. The formation epoch of the simulated late-forming galaxies traces remarkably well the time when their host DM halos first exceeded a nontrivial (but well-understood) time-dependent critical mass, thus making late-forming dwarfs attractive cosmological probes with constraining power over the past growth history of their host halos. The agreement between our model and the simulation results demonstrates that the population of simulated late-forming dwarfs is a robust cosmological outcome and largely independent of the specific galaxy formation model included in the simulations provided: (1) the universe underwent cosmic reionization before ${z}_{\mathrm{re}}\sim 8;$ (2) star formation proceeds in gas that self-gravitates; and (3) galaxy formation is largely restricted to atomic-cooling halos before zre. The scarcity of massive late-forming dwarfs expected in ΛCDM implies that the great majority of bright, metal-poor, and actively star-forming dwarfs observed in our local universe-the most obvious candidates for these late-forming galaxies-cannot be undergoing their formation for the first time at the present day in a ΛCDM universe.

Keywords: Reionization, Galaxy formation, Dwarf galaxies, Compact dwarf galaxies
PeV Photon and Neutrino Flares from Galactic Gamma-Ray Binaries. The high-energy radiation from short period binaries containing a massive star with a compact relativistic companion was detected from radio to TeV γ-rays. We show here that PeV regime protons can be efficiently accelerated in the regions of collision of relativistic outflows of a compact object with stellar winds in these systems. The accelerated proton spectra in the presented Monte Carlo model have an upturn in the PeV regime and can provide very hard spectra of sub-PeV photons and neutrinos by photomeson processes in the stellar radiation field. The recent report of a possible sub-PeV γ-ray flare in coincidence with a high-energy neutrino can be understood in the frame of this model. The γ-ray binaries may contribute substantially to the Galactic component of the detected high-energy neutrino flux.

Keywords: Gamma-ray sources, High-energy cosmic radiation
Internal R-process Abundance Spread of M15 and a Single Stellar Population Model. The member stars in globular cluster M15 show a substantial spread in the abundances of r-process elements. We argue that a rare and prolific r-process event enriched the natal cloud of M15 in an inhomogeneous manner. To critically examine the possibility, we perform cosmological galaxy formation simulations and study the physical conditions for the inhomogeneous enrichment. We explore a large parameter space of the merger event time and the site. Our simulations reproduce the large r-process abundance spread if a neutron-star merger occurs at ~100 pc away from the formation site of the cluster and in a limited time range of a few tens of millions of years before the formation. Interestingly, a bimodal feature is found in the Eu abundance distribution in some cases, similarly to that inferred from recent observations. M15 member stars do not show the clear correlation between the abundances of Eu and light elements such as Na that is expected in models with two stellar populations. We thus argue that a majority of the stars in M15 are formed in a single burst. The ratio of heavy to light r-process element abundance [Eu/Y] ~ 1.0 is consistent with that of the so-called r-II stars, suggesting that a lanthanide-rich r-process event dominantly enriched M15.

Keywords: Globular star clusters, R-process, Star formation, Chemical abundances
On the Formation of an Eccentric Nuclear Disk following the Gravitational Recoil Kick of a Supermassive Black Hole. The anisotropic emission of gravitational waves during the merger of two supermassive black holes can result in a recoil kick of the merged remnant. We show here that eccentric nuclear disks-stellar disks of eccentric, apse-aligned orbits-can directly form as a result. An initially circular disk of stars will align orthogonal to the black hole kick direction with a distinctive "tick-mark" eccentricity distribution and a spiral pattern in mean anomaly.

Keywords: Astrodynamics, N-body problem, Gravitational waves, Galaxy nuclei
Efficient Formation Pathway of Methyl Formate: The Role of OH Radicals on Ice Dust. Three structural isomers of the C2H4O2 molecule, namely, methyl formate (MF; HCOOCH3), acetic acid (CH3COOH), and glycolaldehyde (HOCH2CHO), have attracted considerable attention as targets for understanding pathways toward molecular complexity in the interstellar medium (ISM). Among these isomers, MF is decisively abundant in various astronomical objects. For various formation pathways of MF, surface reactions on cosmic dust would play an important role. However, when compared to observations, the formation of MF has been found to be relatively inefficient in laboratory experiments in which methanol (CH3OH)-dominant ices were processed by ultraviolet photons and cosmic-ray analogs. Here, we show experimental results on the effective formation of MF by the photolysis of CH3OH on water ice at 10 K. We found that the key parameter leading to the efficient formation of MF is the supply of OH radicals by the photolysis of H2O, which significantly differs from CH3OH-rich experimental conditions. Moreover, using an ultrahigh-sensitivity surface analysis method, we succeeded in constraining the decisive formation pathway of MF via the photolysis of methoxymethanol (MM; CH3OCH2OH), which would improve our current understanding of chemical evolution in the ISM.

Keywords: Interstellar dust processes, Astrochemistry, Dense interstellar clouds
Nonthermal Particle Acceleration at Highly Oblique Nonrelativistic Shocks. The nonthermal acceleration of electrons and ions at an oblique, nonrelativistic shock is studied using large-scale particle-in-cell simulations in one spatial dimension. Physical parameters are selected to highlight the role of electron preheating in injection and subsequent acceleration of particles at high Mach number shocks. Simulation results show evidence for the early onset of the diffusive shock acceleration process for both electrons and ions at a highly oblique subluminal shock. Ion acceleration efficiencies of ≲5% are measured at late times, though this is not the saturated value.

Keywords: Galactic cosmic rays, Shocks, Plasma astrophysics
Building Better Spin Models for Merging Binary Black Holes: Evidence for Nonspinning and Rapidly Spinning Nearly Aligned Subpopulations. Recent work paints a conflicting portrait of the distribution of black hole spins in merging binaries measured with gravitational waves. Some analyses find that a significant fraction of merging binaries contain at least one black hole with a spin tilt &gt;90° with respect to the orbital angular momentum vector, which has been interpreted as a signature for dynamical assembly. Other analyses find that the data are consistent with a bimodal population in which some binaries contain black holes with negligible spin while the rest contain black holes with spin vectors preferentially aligned with the orbital angular momentum vector. In this work, we scrutinize models for the distribution of black hole spins to pinpoint possible failure modes in which the model yields a faulty conclusion. We reanalyze data from the second LIGO-Virgo gravitational-wave transient catalog (GWTC-2) using a revised spin model, which allows for a subpopulation of black holes with negligible spins. In agreement with recent results by Roulet et al., we show that the GWTC-2 detections are consistent with two distinct subpopulations. We estimate that 69%-90% (90% credible interval) of merging binaries contain black holes with negligible spin χ ≈ 0. The remaining binaries are part of a second subpopulation in which the spin vectors are preferentially (but not exactly) aligned to the orbital angular momentum. The black holes in this second subpopulation are characterized by spins of χ ~ 0.5. We suggest that the inferred spin distribution is consistent with the hypothesis that all merging binaries form via the field formation scenario.

Keywords: Gravitational wave astronomy, Astrophysical black holes
Fast Sausage Oscillations in Coronal Loops with Fine Structures. Fast sausage modes (FSMs) in flare loops have long been invoked to account for rapid quasi-periodic pulsations (QPPs) with periods of order seconds in flare lightcurves. However, most theories of FSMs in solar coronal cylinders assume a perfectly axisymmetric equilibrium, an idealized configuration apparently far from reality. In particular, it remains to be examined whether FSMs exist in coronal cylinders with fine structures. Working in the framework of ideal magnetohydrodynamics (MHD), we numerically follow the response to an axisymmetric perturbation of a coronal cylinder for which a considerable number of randomly distributed fine structures are superposed on an axisymmetric background. The parameters for the background component are largely motivated by the recent IRIS identification of a candidate FSM in Fe XXI 1354 Å observations. We find that the composite cylinder rapidly settles to an oscillatory behavior largely compatible with a canonical trapped FSM. This happens despite that kink-like motions develop in the fine structures. We further synthesize the Fe XXI 1354 Å emissions, finding that the transverse Alfvén time characterizes the periodicities in the intensity, Doppler shift, and Doppler width signals. Distinct from the case without fine structuring, a nonvanishing Doppler shift is seen even at the apex. We conclude that density-enhanced equilibria need not be strictly axisymmetric to host FSM-like motions in general, and FSMs remain a candidate interpretation for rapid QPPs in solar flares.

Keywords: Magnetohydrodynamics, Solar corona
Confirmation of Iron Emission Lines and Nondetection of TiO on the Dayside of KELT-9b with MAROON-X. We present dayside thermal emission observations of the hottest exoplanet KELT-9b using the new MAROON-X spectrograph. We detect atomic lines in emission with a signal-to-noise ratio of 10 using cross-correlation with binary masks. The detection of emission lines confirms the presence of a thermal inversion in KELT-9b's atmosphere. We also use M-dwarf stellar masks to search for TiO, which has recently been invoked to explain the unusual Hubble Space Telescope WFC3 spectrum of the planet. We find that the KELT-9b atmosphere is inconsistent with the M-dwarf masks. Furthermore, we use an atmospheric retrieval approach to place an upper limit on the TiO volume mixing ratio of 10-8.5 (at 99% confidence). This upper limit is inconsistent with the models used to match the WFC3 data, which require at least an order of magnitude more TiO, thus suggesting the need for an alternate explanation of the space-based data. Our retrieval results also strongly prefer an inverted temperature profile and atomic/ion abundances largely consistent with the expectations for a solar composition gas in thermochemical equilibrium. The exception is the retrieved abundance of Fe+, which is about 1-2 orders of magnitude greater than predictions. These results highlight the growing power of high-resolution spectrographs on large ground-based telescopes to characterize exoplanet atmospheres when used in combination with new retrieval techniques.

Keywords: Exoplanet atmospheres, Hot Jupiters
The Magnetic Origin of Solar Campfires. Solar campfires are fine-scale heating events, recently observed by Extreme Ultraviolet Imager (EUI) on board Solar Orbiter. Here we use EUI 174 Å images, together with EUV images from Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA), and line-of-sight magnetograms from SDO/Helioseismic and Magnetic Imager (HMI) to investigate the magnetic origin of 52 randomly selected campfires in the quiet solar corona. We find that (i) the campfires are rooted at the edges of photospheric magnetic network lanes; (ii) most of the campfires reside above the neutral line between majority-polarity magnetic flux patch and a merging minority-polarity flux patch, with a flux cancelation rate of ~1018 Mx hr-1; (iii) some of the campfires occur repeatedly from the same neutral line; (iv) in the large majority of instances, campfires are preceded by a cool-plasma structure, analogous to minifilaments in coronal jets; and (v) although many campfires have "complex" structure, most campfires resemble small-scale jets, dots, or loops. Thus, "campfire" is a general term that includes different types of small-scale solar dynamic features. They contain sufficient magnetic energy (~1026-1027 erg) to heat the solar atmosphere locally to 0.5-2.5 MK. Their lifetimes range from about 1 minute to over 1 hr, with most of the campfires having a lifetime of &lt;10 minutes. The average lengths and widths of the campfires are 5400 ± 2500 km and 1600 ± 640 km, respectively. Our observations suggest that (a) the presence of magnetic flux ropes may be ubiquitous in the solar atmosphere and not limited to coronal jets and larger-scale eruptions that make CMEs, and (b) magnetic flux cancelation is the fundamental process for the formation and triggering of most campfires.

Keywords: Solar coronal transients, Quiet sun, Solar coronal heating, Solar filaments, Solar magnetic fields