Sazuna/UAT_keywords huggingface dataset:
Upper Limit on Brackett-γ Emission from the Immediate Accretion Flow onto the Galactic Black Hole. We present the first observational constraint on the Brackett-γ (Brγ) recombination line emission associated with the supermassive black hole at the center of our Galaxy, known as Sgr A*. By combining 13 yr of data with the adaptive optics fed integral field spectrograph OSIRIS at the W. M. Keck Observatory obtained as part of the Galactic Center Orbits Initiative, we extract the near-infrared spectrum within ∼0.2″ of the black hole and we derive an upper limit on the Brγ flux. The aperture was set to match the size of the disk-like structure that was recently reported based on millimeter-wave Atacama Large Millimeter/submillimeter Array (ALMA) observations of the hydrogen recombination line, H30α. Our stringent upper limit is at least a factor of 80 (and up to a factor of 245) below what would be expected from the ALMA measurements and strongly constrains possible interpretation of emission from this highly underluminous supermassive black hole.

Keywords: Accretion, Supermassive black holes, Galactic center, Interstellar atomic gas, Bondi accretion, Near infrared astronomy
The Peculiar X-Ray Transient Swift J0840.7-3516: An Unusual Low-mass X-Ray Binary or a Tidal Disruption Event?. We report on the X-ray properties of the new transient Swift J0840.7-3516, discovered with Swift/BAT in 2020 February, using extensive data from Swift, MAXI, NICER, and NuSTAR. The source flux increased for ∼103 s after the discovery, decayed rapidly over ∼5 orders of magnitude in five days, and then remained almost constant over nine months. Large-amplitude short-term variations on timescales of 1-104 s were observed throughout the decay. In the initial flux rise, the source showed a hard power-law-shaped spectrum with a photon index of ∼1.0 extending up to ∼30 keV, above which an exponential cutoff was present. The photon index increased in the following rapid decay and became ∼2 at the end of the decay. A spectral absorption feature at 3-4 keV was detected in the decay. It is not straightforward to explain all the observed properties by any known class of X-ray sources. We discuss the possible nature of the source, including a Galactic low-mass X-ray binary with multiple extreme properties and a tidal disruption event by a supermassive black hole or a Galactic neutron star.

Keywords: Low-mass x-ray binary stars, X-ray transient sources, Tidal disruption
Probing Elastic Quark Phases in Hybrid Stars with Radius Measurements. The internal composition of neutron stars is currently largely unknown. Due to the possibility of phase transitions in quantum chromodynamics, stars could be hybrid and have quark cores. We investigate some imprints of elastic quark phases (only when perturbed) on the dynamical stability of hybrid stars. We show that they increase the dynamical stability window of hybrid stars in the sense that the onset of instabilities happens at larger central densities than the ones for maximum masses. In particular, when the shear modulus of a crystalline quark phase is taken at face value, the relative radius differences between elastic and perfect-fluid hybrid stars with null radial frequencies (onset of instability) would be up to 1%-2%. Roughly, this would imply a maximum relative radius dispersion (on top of the perfect-fluid predictions) of 2%-4% for stars in a given mass range exclusively due to the elasticity of the quark phase. In the more agnostic approach where the estimates for the quark shear modulus only suggest its possible order of magnitude (due to the many approximations taken in its calculation), the relative radius dispersion uniquely due to a quark phase elasticity might be as large as 5%-10%. Finally, we discuss possible implications of the above dispersion of radii for the constraint of the elasticity of a quark phase with electromagnetic missions such as NICER, eXTP, and ATHENA.

Keywords: Neutron stars, Stellar oscillations, General relativity
Core Mass Estimates in Strong Lensing Galaxy Clusters Using a Single-halo Lens Model. The core mass of galaxy clusters is an important probe of structure formation. Here we evaluate the use of a single-halo model (SHM) as an efficient method to estimate the strong lensing cluster core mass, testing it with ray-traced images from the Outer Rim simulation. Unlike detailed lens models, the SHM represents the cluster mass distribution with a single halo and can be automatically generated from the measured lensing constraints. We find that the projected core mass estimated with this method, MSHM, has a scatter of 8.52% and a bias of 0.90% compared to the "true" mass within the same aperture. Our analysis shows no systematic correlation between the scatter or bias and the lens-source system properties. The bias and scatter can be reduced to 3.26% and 0.34%, respectively, by excluding models that fail a visual inspection test. We find that the SHM success depends on the lensing geometry, with single giant arc configurations accounting for most of the failed cases due to their limiting constraining power. When excluding such cases, we measure a scatter and bias of 3.88% and 0.84%, respectively. Finally, we find that when the source redshift is unknown, the model-predicted redshifts are overestimated, and the MSHM is underestimated by a few percent, highlighting the importance of securing spectroscopic redshifts of background sources. Our analysis provides a quantitative characterization of MSHM, enabling its efficient use as a tool to estimate the strong lensing cluster core masses in the large samples, expected from current and future surveys.

Keywords: Galaxy clusters, Strong gravitational lensing
An Analysis Pipeline for CHIME/FRB Full-array Baseband Data. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has become a leading facility for detecting fast radio bursts (FRBs) through the CHIME/FRB backend. CHIME/FRB searches for fast transients in polarization-summed intensity data streams that have 24 kHz spectral and 1 ms temporal resolution. The intensity beams are pointed to predetermined locations in the sky. A triggered baseband system records the coherent electric field measured by each antenna in the CHIME array at the time of FRB detections. Here we describe the analysis techniques and automated pipeline developed to process these full-array baseband data recordings. Whereas the real-time FRB detection pipeline has a localization limit of several arcminutes, offline analysis of baseband data yields source localizations with subarcminute precision, as characterized by using a sample of pulsars and one repeating FRB with known positions. The baseband pipeline also enables resolving temporal substructure on a microsecond scale and the study of polarization including detections of Faraday rotation.

Keywords: Pointing accuracy, Extragalactic radio sources, Radio astrometry, High time resolution astrophysics, Radio bursts, Radio telescopes, Radio interferometers, Radio interferometry, Algorithms, Radio transient sources
Revealing a Centrally Condensed Structure in OMC-3/MMS 3 with ALMA High-resolution Observations. Using the Atacama Large Millimeter/submillimeter Array (ALMA), we investigated the peculiar millimeter source MMS 3 located in the Orion Molecular Cloud 3 (OMC-3) region in the 1.3 mm continuum, CO (J = 2-1), SiO (J = 5-4), C18O (J = 2-1), N2D+ (J = 3-2), and DCN (J = 3-2) emissions. With the ALMA high angular resolution (∼0"2), we detected a very compact and highly centrally condensed continuum emission with a size of 0"45 × 0"32 (P.A. = 0°22). The peak position coincides with the locations of previously reported Spitzer/IRAC and X-ray sources within their positional uncertainties. We also detected an envelope with a diameter of ∼6800 au (P.A. = 75°) in the C18O (J = 2-1) emission. Moreover, a bipolar outflow was detected in the CO (J = 2-1) emission for the first time. The outflow is elongated roughly perpendicular to the long axis of the envelope detected in the C18O (J = 2-1) emission. Compact high-velocity CO gas in the (redshifted) velocity range of 22-30 km s-1, presumably tracing a jet, was detected near the 1.3 mm continuum peak. A compact and faint redshifted SiO emission was marginally detected in the CO outflow lobe. The physical quantities of the outflow in MMS 3 are somewhat smaller than those in other sources in the OMC-3 region. The centrally condensed object associated with the near-infrared and X-ray sources, the flattened envelope, and the faint outflow indicate that MMS 3 harbors a low-mass protostar with an age of ∼103 yr.

Keywords: Protostars, Star formation
Continuous Jets and Backflow Models for the Formation of W50/SS 433 in Magnetohydrodynamics Simulations. The formation mechanism of the W50/SS 433 complex has long been a mystery. We propose a new scenario in which the SS 433 jets themselves form the W50/SS 433 system. We carry out magnetohydrodynamics simulations of the propagation of two side jets using the public code CANS+. As found in previous jet studies, when the propagating jet is lighter than the surrounding medium, the shocked plasma flows back from the jet tip to the core. We find that the morphology of light jets is spheroidal at early times; afterward, the shell and wings are developed by the broadening spherical cocoon. The morphology depends strongly on the density ratio of the injected jet to the surrounding medium. Meanwhile, the ratio of the lengths of the two side jets depends only on the density profile of the surrounding medium. We also find that most of the jet kinetic energy is dissipated at the oblique shock formed by the interaction between the backflow and beam flow, rather than at the jet terminal shock. The position of the oblique shock is spatially consistent with the X-ray and TeV gamma-ray hotspots of W50.

Keywords: Magnetohydrodynamical simulations
Detecting the Figure Rotation of Dark Matter Halos with Tidal Streams. The dark matter halos that surround Milky Way-like galaxies in cosmological simulations are, to first order, triaxial. Nearly 30 yr ago it was predicted that such triaxial dark matter halos should exhibit steady figure rotation or tumbling motions for durations of several gigayears. The angular frequency of figure rotation predicted by cosmological simulations is described by a log-normal distribution of pattern speed Ωp with a median value 0.15 h km s-1 kpc-1 (∼0.15 h rad Gyr-1 ∼ 9° h Gyr-1) and a width of 0.83h km s-1 kpc-1. These pattern speeds are so small that they have generally been considered both unimportant and undetectable. In this work we show that even extremely slow figure rotation can significantly alter the structure of extended stellar streams produced by the tidal disruption of satellites in the Milky Way halo. We simulate the behavior of a Sagittarius-like polar tidal stream in triaxial dark matter halos with different shapes, when the halos are rotated about the three principal axes. For pattern speeds typical of cosmological halos, we demonstrate, for the first time, that a Sagittarius-like tidal stream would be altered to a degree that is detectable even with current observations. This discovery will potentially allow for a future measurement of figure rotation of the Milky Way's dark matter halo, perhaps enabling the first evidence of this relatively unexplored prediction of cold dark matter.

Keywords: Galaxy dark matter halos, Milky Way dark matter halo, Tidal disruption, Galaxy dynamics, Milky Way dynamics, Sagittarius dwarf spheroidal galaxy, Dark matter
Rapidly Declining Hostless Type Ia Supernova KSP-OT-201509b from the KMTNet Supernova Program: Transitional Nature and Constraint on <SUP>56</SUP>Ni Distribution and Progenitor Type. We report the early discovery and multicolor (BVI) high-cadence light-curve analyses of the rapidly declining sub-Chandrasekhar Type Ia supernova KSP-OT-201509b (= AT 2015cx) from the KMTNet Supernova Program. The Phillips and color stretch parameters of KSP-OT-201509b are ΔMB,15 ≃ 1.62 mag and sBV ≃ 0.54, respectively, at an inferred redshift of 0.072. These, together with other measured parameters (such as the strength of the secondary I-band peak, colors, and luminosity), identify the source to be a rapidly declining Type Ia of a transitional nature that is closer to Branch-normal than 91bg-like. Its early light-curve evolution and bolometric luminosity are consistent with those of homologously expanding ejecta powered by radioactive decay and a Type Ia SN explosion with 0.32 ± 0.01 M⊙ of synthesized 56Ni mass, 0.84 ± 0.12 M⊙ of ejecta mass, and (0.61 ± 0.14) × 1051 erg of ejecta kinetic energy. While its B - V and V - I colors evolve largely synchronously with the changes in the I-band light curve, as found in other supernovae, we also find the presence of an early redward evolution in V - I prior to -10 days since peak. The bolometric light curve of the source is compatible with a stratified 56Ni distribution extended to shallow layers of the exploding progenitor. Comparisons between the observed light curves and those predicted from ejecta-companion interactions clearly disfavor Roche lobe-filling companion stars at large separation distances, thus supporting a double-degenerate scenario for its origin. The lack of any apparent host galaxy in our deep stack images reaching a sensitivity limit of ∼28 mag arcsec-2 makes KSP-OT-201509b a hostless Type Ia supernova and offers new insights into supernova host galaxy environments.

Keywords: Type Ia supernovae, Supernovae
One Channel to Rule Them All? Constraining the Origins of Binary Black Holes Using Multiple Formation Pathways. The second LIGO-Virgo catalog of gravitational-wave (GW) transients has more than quadrupled the observational sample of binary black holes. We analyze this catalog using a suite of five state-of-the-art binary black hole population models covering a range of isolated and dynamical formation channels and infer branching fractions between channels as well as constraints on uncertain physical processes that impact the observational properties of mergers. Given our set of formation models, we find significant differences between the branching fractions of the underlying and detectable populations, and the diversity of detections suggests that multiple formation channels are at play. A mixture of channels is strongly preferred over any single channel dominating the detected population: an individual channel does not contribute to more than ≃70% of the observational sample of binary black holes. We calculate the preference between the natal spin assumptions and common-envelope efficiencies in our models, favoring natal spins of isolated black holes of ≲0.1 and marginally preferring common-envelope efficiencies of ≳2.0 while strongly disfavoring highly inefficient common envelopes. We show that it is essential to consider multiple channels when interpreting GW catalogs, as inference on branching fractions and physical prescriptions becomes biased when contributing formation scenarios are not considered or incorrect physical prescriptions are assumed. Although our quantitative results can be affected by uncertain assumptions in model predictions, our methodology is capable of including models with updated theoretical considerations and additional formation channels.

Keywords: Bayesian statistics, Stellar mass black holes, Gravitational wave sources, Gravitational wave astronomy, Compact objects, LIGO, Stellar evolution
Gravitoviscous Protoplanetary Disks with a Dust Component. V. The Dynamic Model for Freeze-out and Sublimation of Volatiles. The snowlines of various volatile species in protoplanetary disks are associated with abrupt changes in gas composition and dust physical properties. Volatiles may affect dust growth, as they cover grains with icy mantles that can change the fragmentation velocity of the grains. In turn, dust coagulation, fragmentation, and drift through the gas disk can contribute to the redistribution of volatiles between the ice and gas phases. Here we present the hydrodynamic model FEOSAD for protoplanetary disks with two dust populations and volatile dynamics. We compute the spatial distributions of major volatile molecules (H2O, CO2, CH4, and CO) in the gas, on small and grown dust, and analyze the composition of icy mantles over the initial 0.5 Myr of disk evolution. We show that most of the ice arrives to the surface of the grown dust through coagulation with small grains. Spiral structures and dust rings forming in the disk, as well as photodissociation in the outer regions, lead to the formation of complex snowline shapes and multiple snowlines for each volatile species. During the considered disk evolution, the snowlines shift closer to the star, with their final position being a factor of 4-5 smaller than that at the disk formation epoch. We demonstrate that volatiles tend to collect in the vicinity of their snowlines, both in the ice and gas phases, leading to the formation of thick icy mantles potentially important for dust dynamics. The dust size is affected by a lower fragmentation velocity of bare grains in the model with a higher turbulent viscosity.

Keywords: Protostars, Circumstellar dust, Protoplanetary disks
Radiation Belt Response to Fast Reverse Shock at Geosynchronous Orbit. Fast reverse shocks (FRSs) cause the magnetosphere to expand, by contrast to the well-known compressions caused by the impact of fast forward shocks (FFS). Usually, FFSs are more geoeffective than FRSs, and consequently the inner magnetosphere dynamic responses to both shock types can be quite different. In this study, we investigate for the first time the radiation belt response to an FRS impact using multi-satellite observations and numerical simulations. Spacecraft on the dayside observed decreases in magnetic field strength and energetic (∼40-475 keV) particle fluxes. Timing analysis shows that the magnetic field signature propagated from the dayside to the nightside magnetosphere. Particles with different energies vary simultaneously at each spacecraft, implying a non-dispersive particle response to the shock. Spacecraft located at lower L-shells did not record any significant signatures. The observations indicate a local time dependence of the response associated with the shock inclination, with the clearest signatures being observed in the dusk-midnight sector. Simulations underestimate the amplitude of the magnetic field variations observed on the nightside. The observed decreases in the electron intensities result from a combination of radial gradient and adiabatic effects. The radial gradients in the spectral index appear to be the dominant contributor to the observed variations of electrons seen on the dayside (near noon and dusk) and on the nightside (near midnight). This study shows that even an FRS can affect the radiation belts significantly and provides an opportunity to understand their dynamic response to a sudden expansion of the magnetosphere.

Keywords: Fast solar wind, Van Allen radiation belts, Interplanetary discontinuities, Solar wind, Solar-planetary interactions, Interplanetary particle acceleration, Interplanetary magnetic fields, Solar-terrestrial interactions, Solar activity, Planetary magnetospheres, Magnetohydrodynamical simulations
Experimental Study on CH<SUP>+</SUP> Formation from Doubly Charged Carbon and Molecular Hydrogen. We studied the reaction of doubly charged carbon C2+ (C III) with molecular hydrogen, a possible source of the high, unexplained abundances of interstellar CH+. The experiment was carried out using the cryogenic linear 22-pole radio frequency ion trap. The measured reaction rate coefficient amounts to (1.5 ± 0.2) × 10-10 cm3 s-1, nearly independently of the covered temperature range from 15 to 300 K. In the product distribution study, the C+ ion was identified as the dominant product of the reaction. For the CH+ production, we determine an upper limit for the reaction rate coefficient at 2 × 10-12 cm3 s-1.

Keywords: Interstellar molecules, Molecular physics, Laboratory astrophysics, Astrochemistry
Analyzing Supergranular Power Spectra Using Helioseismic Normal-mode Coupling. Normal-mode coupling is a technique applied to probe the solar interior using surface observations of oscillations. The technique, which is straightforward to implement, makes more use of the seismic information in the wave field than other comparable local imaging techniques and therefore has the potential to significantly improve current capabilities. Here, we examine supergranulation power spectra using mode-coupling analyses of intermediate-to-high-degree modes by invoking a Cartesian-geometric description of wave propagation under the assumption that the localized patches are much smaller in size than the solar radius. We extract the supergranular power spectrum and compare the results with prior helioseismic studies. Measurements of the dispersion relation and lifetimes of supergranulation, obtained using near surface modes (f and p1), are in accord with the literature. We show that the cross-coupling between the p2 and p3 acoustic modes, which are capable of probing greater depths, are also sensitive to supergranulation.

Keywords: Helioseismology, Solar physics, Supergranulation
Pristine PSP/WISPR Observations of the Circumsolar Dust Ring near Venus's Orbit. The Parker Solar Probe mission (PSP) has completed seven orbits around the Sun. The Wide-field Imager for Solar Probe (WISPR) on PSP consists of two visible light heliospheric imagers, which together image the interplanetary medium between 13°5 and 108° elongation. The PSP/WISPR nominal science observing window occurs during the solar encounters, which take place when the spacecraft (S/C) is within 0.25 au from the Sun. During Orbit 3, an extended science campaign took place while PSP transited between 0.5 and 0.25 au (during both inbound and outbound orbit segments). PSP mission operations implemented a variety of 180° S/C rolls about the S/C-Sun pointing axis during the extended science window. The vantage of the PSP location, combined with the different S/C roll orientations, allowed us to unveil a circumsolar dust density enhancement associated with Venus's orbit. Specifically, we observed an excess brightness band of about 1% at its center over the brightness of the background zodiacal light in all PSP/WISPR images obtained during the extended campaign. We explain this brightness band as due to an increase in the density of the circumsolar dust orbiting the Sun close to the Venusian orbit. The projected latitudinal extent of the ring is estimated at about 0.043 au ± 0.004 au, exhibiting an average density enhancement of the order of 10%. Here, we report and characterize the first comprehensive, pristine observations of the plane-of-sky projection of the dust ring in almost its full 360° longitudinal extension.

Keywords: Interplanetary dust, Solar F corona, Circumstellar dust