Sazuna/UAT_keywords huggingface dataset:
Discovery of the Elusive Carbonic Acid (HOCOOH) in Space. A quarter century after the detection of the last interstellar carboxylic acid, acetic acid (CH3COOH), we report the discovery of a new one, the cis-trans form of carbonic acid (HOCOOH), toward the Galactic center molecular cloud G+0.693-0.027. HOCOOH stands as the first interstellar molecule containing three oxygen atoms and the third carboxylic acid detected so far in the interstellar medium. Albeit the limited available laboratory measurements (up to 65 GHz), we have also directly identified several pairs of unblended lines in the astronomical data (between 75 and 120 GHz), which allowed us to slightly improve the set of spectroscopic constants. We derive a column density for cis-trans HOCOOH of N = (6.4 ± 0.4) × 1012 cm-2, which yields an abundance with respect to molecular H2 of 4.7 × 10-11. Meanwhile, the extremely low dipole moment (about 15 times lower) of the lower-energy conformer, cis-cis HOCOOH, precludes its detection. We obtain an upper limit to its abundance with respect to H2 of ≤1.2 × 10-9, which suggests that cis-cis HOCOOH might be fairly abundant in interstellar space, although it is nearly undetectable by radio astronomical observations. We derive a cis-cis/cis-trans ratio of ≤25, consistent with the smaller energy difference between both conformers compared with the relative stability of trans- and cis-formic acid. Finally, we compare the abundance of these acids in different astronomical environments, further suggesting a relationship between the chemical content found in the interstellar medium and the chemical composition of the minor bodies of the solar system, which could be inherited during the star formation process.

Keywords: Interstellar molecules, Galactic center, Spectral line identification, Astrochemistry, Interstellar clouds
White Dwarfs Revealed in Gaia's Candidate Compact Object Binaries. Discovery and characterization of black holes (BHs), neutron stars (NSs), and white dwarfs (WDs) with detached luminous companions (LCs) in wide orbits are exciting because they are important test beds for dark remnant (DR) formation physics as well as binary stellar evolution models. Recently, 187 candidates have been identified from Gaia's non-single star catalog as wide orbit (P orb/day &gt; 45), detached binaries hosting DRs. We identify UV counterparts for 49 of these sources in the archival GALEX data. Modeling the observed spectral energy distribution (SED) spanning from the FUV-NUV to IR for these sources and stellar evolution models, we constrain the LC properties including mass, bolometric luminosity, and effective temperature for these 49 sources. Using the LC masses, and the astrometric mass function constrained by Gaia, we constrain the DR masses for these sources. We find that nine have masses clearly in the NS or BH mass range. Fifteen sources exhibit significant NUV excess and four show excess both in the FUV and NUV. The simplest explanation for these excess UV fluxes is that the DRs in these sources are WDs. Using SED modeling we constrain the effective temperature and bolometric luminosity for these 15 sources. Our estimated DR masses for all of these 15 sources are lower than the Chandrasekhar mass limit for WDs. Interestingly, five of these sources had been wrongly identified as NSs in the literature.

Keywords: Neutron stars, Black holes, White dwarf stars, Compact binary stars, Ultraviolet astronomy, Spectral energy distribution, Detached binary stars, Compact objects
Disk Wind-Driven Expanding Radio-emitting Shell in Tidal Disruption Events. We study the evolution of a nonrelativistically expanding thin shell in radio-emitting tidal disruption events (TDEs) based on a one-dimensional spherically symmetric model considering the effect of both a time-dependent mass-loss rate of the disk wind and the ambient mass distribution. The analytical solutions are derived in two extreme limits; one is the approximate solution near the origin in the form of the Taylor series, and the other is the asymptotic solution in which the ambient matter is dominant far away from the origin. Our numerical solutions are confirmed to agree with the respective analytical solutions. We find that no simple power law of the time solution exists in early to middle times because the mass-loss rate varies over time, affecting the shell dynamics. We also discuss the application of our model to the observed radio-emitting TDE, AT 2019dsg.

Keywords: High energy astrophysics, Tidal disruption, Transient sources, Radio astronomy, Astrophysical black holes, Radio transient sources
First Impressions: Early-time Classification of Supernovae Using Host-galaxy Information and Shallow Learning. Substantial effort has been devoted to the characterization of transient phenomena from photometric information. Automated approaches to this problem have taken advantage of complete phase coverage of an event, limiting their use for triggering rapid follow-up of ongoing phenomena. In this work, we introduce a neural network with a single recurrent layer designed explicitly for early photometric classification of supernovae (SNe). Our algorithm leverages transfer learning to account for model misspecification, host-galaxy photometry to solve the data-scarcity problem soon after discovery, and a custom weighted loss to prioritize accurate early classification. We first train our algorithm using state-of-the-art transient and host-galaxy simulations, then adapt its weights and validate it on the spectroscopically confirmed SNe Ia, SNe II, and SNe Ib/c from the Zwicky Transient Facility Bright Transient Survey. On observed data, our method achieves an overall accuracy of 82% ± 2% within 3 days of an event's discovery, and an accuracy of 87% ± 5% within 30 days of discovery. At both early and late phases, our method achieves comparable or superior results to the leading classification algorithms with a simpler network architecture. These results help pave the way for rapid photometric and spectroscopic follow-up of scientifically valuable transients discovered in massive synoptic surveys.

Keywords: Light curve classification , Supernovae, Classification, Neural networks
Observational Signatures of Electron-driven Chromospheric Evaporation in a White-light Flare. We investigate observational signatures of explosive chromospheric evaporation during a white-light flare (WLF) that occurred on 2022 August 27. Using the moment analysis, bisector techniques, and the Gaussian fitting method, redshifted velocities of less than 20 km s‑1 are detected in low-temperature spectral lines of Hα, C I, and Si IV at the conjugated flare kernels, which could be regarded as downflows caused by chromospheric condensation. Blueshifted velocities of ∼30‑40 km s‑1 are found in the high-temperature line of Fe XXI, which can be interpreted as upflows driven by chromospheric evaporation. A nonthermal hard X-ray (HXR) source is cospatial with one of the flare kernels, and the Doppler velocities are temporally correlated with the HXR fluxes. The nonthermal energy flux is estimated to be at least (1.3 ± 0.2) × 1010 erg s‑1 cm‑2. The radiation enhancement at Fe I 6569.2 Å and 6173 Å suggests that the flare is a WLF. Moreover, the while-light emission at Fe I 6569.2 Å is temporally and spatially correlated with the blueshift of the Fe XXI line, suggesting that both the white-light enhancement and the chromospheric evaporation are triggered and driven by nonthermal electrons. All of our observations support the scenario of an electron-driven explosive chromospheric evaporation in the WLF.

Keywords: Solar flares, Solar ultraviolet emission, Solar x-ray emission, Solar white-light flares, Solar chromosphere
Hard X-Ray Observation and Multiwavelength Study of the PeVatron Candidate Pulsar Wind Nebula "Dragonfly". We studied the PeVatron nature of the pulsar wind nebula (PWN) G75.2+0.1 ("Dragonfly") as part of our NuSTAR observational campaign of energetic PWNe. The Dragonfly is spatially coincident with LHAASO J2018+3651, whose maximum photon energy is 0.27 PeV. We detected a compact (radius $1^{\prime} $ ) inner nebula of the Dragonfly without a spectral break in 3-20 keV using NuSTAR. A joint analysis of the inner nebula with archival Chandra and XMM-Newton (XMM) observations yields a power-law spectrum with Γ = 1.49 ± 0.03. Synchrotron burnoff is observed from the shrinkage of the NuSTAR nebula at higher energies, from which we infer the magnetic field in the inner nebula of 24 μG at 3.5 kpc. Our analysis of archival XMM data and 13 yr of Fermi-LAT data confirms the detection of an extended ( $\sim 10^{\prime} $ ) outer nebula in 2-6 keV (Γ = 1.82 ± 0.03) and the nondetection of a GeV nebula, respectively. Using the VLA, XMM, and HAWC data, we modeled a multiwavelength spectral energy distribution of the Dragonfly as a leptonic PeVatron. The maximum injected particle energy of 1.4 PeV from our model suggests that the Dragonfly is likely a PeVatron. Our model prediction of the low magnetic field (2.7 μG) in the outer nebula and recent interaction with the host supernova remnant's reverse shock (4 kyr ago) align with common features of PeVatron PWNe. The origin of its highly asymmetric morphology, pulsar proper motion, PWN-supernova remnant (SNR) interaction, and source distance will require further investigations in the future, including a multiwavelength study using radio, X-ray, and gamma-ray observations.

Keywords: Rotation powered pulsars, High energy astrophysics, Gamma-ray sources, Spectral energy distribution, X-ray sources, Pulsar wind nebulae
Evidence for Misalignment between Debris Disks and Their Host Stars. We place lower limits on the obliquities between debris disks and their host stars for 31 systems by comparing their disk and stellar inclinations. While previous studies did not find evidence for misalignment, we identify six systems with minimum obliquities falling between ~30°and 60°, indicating that debris disks can be significantly misaligned with their stars. These high-obliquity systems span a wide range of stellar parameters with spectral types K through A. Previous works have argued that stars with masses below 1.2 M ☉ (spectral types of ~F6) have magnetic fields strong enough to realign their rotation axes with the surrounding disk via magnetic warping; given that we observe high obliquities for relatively low-mass stars, magnetic warping alone is likely not responsible for the observed misalignments. Yet, chaotic accretion is expected to result in misalignments of ~20° at most and cannot explain the larger obliquities found in this work. While it remains unclear how primordial misalignment might occur and what role it plays in determining the spin-orbit alignment of planets, future work expanding this sample is critical toward understanding the mechanisms that shape these high-obliquity systems.

Keywords: Planetary alignment, Circumstellar disks, Stellar rotation, Debris disks, Planet formation
Constraining Cosmology with Machine Learning and Galaxy Clustering: The CAMELS-SAM Suite. As the next generation of large galaxy surveys come online, it is becoming increasingly important to develop and understand the machine-learning tools that analyze big astronomical data. Neural networks are powerful and capable of probing deep patterns in data, but they must be trained carefully on large and representative data sets. We present a new "hump" of the Cosmology and Astrophysics with MachinE Learning Simulations (CAMELS) project: CAMELS-SAM, encompassing one thousand dark-matter-only simulations of (100 h -1 cMpc)3 with different cosmological parameters (Ω m  and σ 8) and run through the Santa Cruz semi-analytic model for galaxy formation over a broad range of astrophysical parameters. As a proof of concept for the power of this vast suite of simulated galaxies in a large volume and broad parameter space, we probe the power of simple clustering summary statistics to marginalize over astrophysics and constrain cosmology using neural networks. We use the two-point correlation, count-in-cells, and void probability functions, and we probe nonlinear and linear scales across 0.68 &lt; R &lt;27 h -1 cMpc. We find our neural networks can both marginalize over the uncertainties in astrophysics to constrain cosmology to 3%-8% error across various types of galaxy selections, while simultaneously learning about the SC-SAM astrophysical parameters. This work encompasses vital first steps toward creating algorithms able to marginalize over the uncertainties in our galaxy formation models and measure the underlying cosmology of our Universe. CAMELS-SAM has been publicly released alongside the rest of CAMELS, and it offers great potential to many applications of machine learning in astrophysics: https://camels-sam.readthedocs.io.

Keywords: Galaxy formation, Neural networks, Large-scale structure of the universe, Cosmological parameters from large-scale structure, N-body simulations
Galactic Bar Resonances with Diffusion: An Analytic Model with Implications for Bar-Dark Matter Halo Dynamical Friction. The secular evolution of disk galaxies is largely driven by resonances between the orbits of "particles" (stars or dark matter) and the rotation of non-axisymmetric features (spiral arms or a bar). Such resonances may also explain kinematic and photometric features observed in the Milky Way and external galaxies. In simplified cases, these resonant interactions are well understood: for instance, the dynamics of a test particle trapped near a resonance of a steadily rotating bar is easily analyzed using the angle-action tools pioneered by Binney, Monari, and others. However, such treatments do not address the stochasticity and messiness inherent to real galaxies-effects that have, with few exceptions, been previously explored only with complex N-body simulations. In this paper, we propose a simple kinetic equation describing the distribution function of particles near an orbital resonance with a rigidly rotating bar, allowing for diffusion of the particles' slow actions. We solve this equation for various values of the dimensionless diffusion strength Δ, and then apply our theory to the calculation of bar-halo dynamical friction. For Δ = 0, we recover the classic result of Tremaine and Weinberg that friction ultimately vanishes, owing to the phase mixing of resonant orbits. However, for Δ &gt; 0, we find that diffusion suppresses phase mixing, leading to a finite torque. Our results suggest that stochasticity-be it physical or numerical-tends to increase bar-halo friction, and that bars in cosmological simulations might experience significant artificial slowdown, even if the numerical two-body relaxation time is much longer than a Hubble time.

Keywords: Galaxy dark matter halos, Plasma physics, Stellar kinematics, Orbital resonances, Barred spiral galaxies, Dynamical friction, Galactic bar
Long-term Evolution of Warps in Debris Disks-Application to the Gyr-old System HD 202628. We present the results of N-body simulations meant to reproduce the long-term effects of mutually inclined exoplanets on debris disks, using the HD 202628 system as a proxy. HD 202628 is a Gyr-old solar-type star that possesses a directly observable, narrow debris ring with a clearly defined inner edge and nonzero eccentricity, hinting at the existence of a sculpting exoplanet. The eccentric nature of the disk leads us to examine the effect on it over Gyr timescales from an eccentric and inclined planet, placed on its orbit through scattering processes. We find that, in systems with dynamical timescales akin to that of HD 202628, a planetary companion is capable of completely tilting the debris disk. This tilt is preserved over the Gyr age of the system. Simulated observations of our models show that an exoplanet around HD 202628 with an inclination misalignment ≳10° would cause the disk to be observably diffuse and broad, which is inconsistent with Atacama Large Millimeter Array (ALMA) observations. With these observations, we conclude that, if there is an exoplanet shaping this disk, it likely had a mutual inclination of less than 5° with the primordial disk. The conclusions of this work can be applied either to debris disks appearing as narrow rings (e.g., Fomalhaut and HR 4796) or to disks that are vertically thick at ALMA wavelengths (e.g., HD 110058).

Keywords: Celestial mechanics, Debris disks, Planetary-disk interactions, N-body simulations
Avalanches and the Distribution of Reconnection Events in Magnetized Circumstellar Disks. Cosmic rays produced by young stellar objects can potentially alter the ionization structure, heating budget, chemical composition, and accretion activity in circumstellar disks. The inner edges of these disks are truncated by strong magnetic fields, which can reconnect and produce flaring activity that accelerates cosmic radiation. The resulting cosmic rays can provide a source of ionization and produce spallation reactions that alter the composition of planetesimals. These reconnection and particle acceleration processes are analogous to the physical processes that produce flaring in and the heating of stellar coronae. Flaring events on the surface of the Sun exhibit a power-law distribution of energy, reminiscent of those measured for earthquakes and avalanches. Numerical lattice reconnection models are capable of reproducing the observed power-law behavior of solar flares under the paradigm of self-organized criticality. One interpretation of these experiments is that the solar corona maintains a nonlinear attractor-or "critical"-state by balancing energy input via braided magnetic fields and output via reconnection events. Motivated by these results, we generalize the lattice reconnection formalism for applications in the truncation region of magnetized disks. Our numerical experiments demonstrate that these nonlinear dynamical systems are capable of both attaining and maintaining criticality in the presence of Keplerian shear and other complications. The resulting power-law spectrum of flare energies in the equilibrium attractor state is found to be nearly universal in magnetized disks. This finding indicates that magnetic reconnection and flaring in the inner regions of circumstellar disks occur in a manner similar to the activity on stellar surfaces. These results, in turn, have ramifications for the spallation-driven injection of radionuclides in planetesimals, disk ionization, and the subsequent planetary formation process.

Keywords: Solar magnetic reconnection, Nucleosynthesis, Cosmic ray nucleosynthesis, Circumstellar disks, Exoplanet formation, Planet formation
Choked Jets in Expanding Envelope as the Origin of the Neutrino Emission Associated with Tidal Disruption Events. Three tidal disruption event (TDE) candidates (AT2019dsg, AT2019fdr, AT2019aalc) have been found to be coincident with high-energy astrophysical neutrinos in multimessenger follow-ups. Recent studies suggest the presence of a quasi-spherical, optically thick envelope around the supermassive black holes in TDEs, resulted from stellar debris after the disruption. The envelope may expand outwardly with a velocity of ~104 km s-1, as indicated by the emission line widths. We study whether the neutrino signal can be explained by choked relativistic jets inside the expanding envelope. While powerful jets, such as that in Swift J1644+57, can successfully break out from the envelope, those with relatively weak power could be choked by the envelope. Choked jets can still accelerate cosmic rays and produce high-energy neutrinos via interaction with the thermal photons in the envelope. We explore the parameter space of the jets that can produce detectable neutrino flux while being choked in the expanding envelope. We find that the cumulative neutrino numbers of AT2019fdr and AT2019aalc are consistent with the expected range imposed by observations, while the allowed parameter space for AT2019dsg is small. The neutrino time delay relative to the optical peak time of TDEs can be explained as the jet propagation time in the envelope before being choked. The discovery of TDE-associated neutrino events may suggest that jets might have been commonly formed in TDEs, as expected from super-Eddington accretion, but most of them are too weak to break out from the expanding envelopes.

Keywords: Neutrino astronomy, Relativistic jets, Tidal disruption, Cosmic rays
Particle Energization at a High Mach Number Perpendicular Shock: 1D Particle-in-cell Simulations. In this paper, we use a 1D particle-in-cell simulation code to study particle preaccelerations at a high Mach number perpendicular shock. Our simulation results show that almost all of the injected particles can be reflected at the shock front, and then they immediately gyrate back to upstream for a long distance. That facilitates the formation of a large-scale shock foot where they dominate the average velocity of particles and the formation of resultant electric fields with several subareas, unlike a low Mach number shock with fewer reflected particles. In the large-scale shock foot with subareas, these reflected particles can be energized by the motional electric fields and unexpected electrostatic fields, which means they may undergo multiple stages of preacceleration processes when gyrating just before the high Mach number perpendicular shock front with high-intensity particle reflection.

Keywords: Solar coronal mass ejection shocks, Shocks, Planetary bow shocks
Analysis of Solar-like X-class Flare on Wolf 359 Observed Simultaneously with TESS and XMM-Newton. We present an analysis of a flare on the Wolf 359 star based on simultaneous observations of Transiting Exoplanet Survey Satellite and XMM-Newton. A stellar flare with energy comparable to an X-class solar flare is analyzed on this star for the first time. The main goal of the study was to determine whether the same physical processes drive and occur in stellar flares as in solar flares. We tried to estimate the flare class by various direct and indirect methods. Light curves and spectra in different energy ranges were used to determine the parameters and profiles of the flare. From the XMM-Newton EPIC-pn X-ray data, we estimated the temperature and emission measure during the flare. The thermodynamical timescale and the loop semi-length were also determined with two different methods. The RGS spectra enabled us to calculate the differential emission measure (DEM) distributions. The obtained DEM distributions have three components at temperature values of 3, 7, and 16-17 MK. The analysis of the line ratio in helium-like triplets allowed us to determine the plasma electron density. Our results for the flare loop on Wolf 359 were compared to typical parameters for solar flares observed with GOES and RHESSI. This supports our conclusion that the processes taking place in stellar flares are like those in solar flares. The determined geometrical parameters of the phenomenon do not differ from the values of analogs occurring on the Sun.

Keywords: X-ray astronomy, Stellar magnetic fields, Stellar flares, Stellar activity