adsabs/SciX_UAT_keywords huggingface dataset:
Young Black Hole and Neutron Star Systems in the Nearby Star-forming Galaxy M33: The NuSTAR View

We can learn about the formation and evolution of compact objects, such as neutron stars and black holes (BHs), by studying the X-ray emission from accreting systems in nearby star-forming galaxies. The hard (E > 10 keV) X-ray emission in particular allows strong discrimination among the accretion states and compact object types. We conducted a NuSTAR survey (~600 ks) of the Local Group spiral galaxy M33 to study the distribution of X-ray binary (XRB) accretors in an actively star-forming environment. We constructed color-intensity and color-color diagrams to infer XRB accretion states. Using these diagrams, we have classified 28 X-ray sources in M33 by comparing their hard X-ray colors to those of known systems. Four sources lie in the parameter space occupied by X-ray pulsars, while 8, 10, and 4 sources lie in the parameter space occupied by BHs in the hard, intermediate, and soft states, respectively. The known ultraluminous X-ray source M33 X-8 is also found to be consistent with that source type. Some sources overlap within the Z/Atoll sources due to the overlap of the two categories of BHs and Z/Atoll sources. In contrast to a similar NuSTAR survey of M31 (with a low-mass XRB-dominant population), the source population in M33 is dominated by high-mass XRBs (HMXBs), allowing the study of a very different population with similar sensitivity due to the galaxy's similar distance. This characterization of a population of HMXB accretion states will provide valuable constraints for theoretical XRB population synthesis studies to their formation and evolution.

Keywords: neutron stars; compact objects; black holes; triangulum galaxy; accretion; stellar accretion; classification; ultraluminous x-ray sources; high mass x-ray binary stars; x-ray binary stars; stellar classification
Supervised Convolutional Neural Networks for Classification of Flaring and Nonflaring Active Regions Using Line-of-sight Magnetograms

Solar flares are explosions in the solar atmosphere that release intense bursts of short-wavelength radiation and are capable of producing severe space-weather. Flares release free energy built up in coronal fields, which are rooted in active regions (ARs) on the photosphere, via magnetic reconnection. The exact processes that lead to reconnection are not fully known and therefore reliable forecasting of flares is challenging. Recently, photospheric magnetic-field data has been extensively analyzed using machine learning (ML) and these studies suggest that flare-forecasting accuracy does not strongly depend on how long in advance flares are predicted. Here, we use ML to understand the evolution of AR magnetic fields before and after flares. We explicitly train convolutional neural networks (CNNs) to classify Solar Dynamics Observatory/Helioseismic and Magnetic Imager line-of-sight magnetograms into ARs producing at least one M- or X-class flare or as nonflaring. We find that flaring ARs remain in flare-productive states—marked by recall > 60% with a peak of ∼80%—days before and after flares. We use occlusion maps and statistical analysis to show that the CNN pays attention to regions between the opposite polarities from ARs and the CNN output is dominantly decided by the total unsigned line-of-sight flux of ARs. Using synthetic bipole magnetograms, we find spurious dependencies of the CNN output on magnetogram dimensions for a given bipole size. Our results suggest that it is important to use CNN designs that eliminate such artifacts in CNN applications for processing magnetograms and, in general, solar image data.

Keywords: convolutional neural networks; solar flares; astronomy data analysis
The Principal Component Analysis Filtering Method for an Unbiased Spectral Survey of Complex Organic Molecules

A variety of interstellar complex organic molecules (COMs) have been detected in various physical conditions. However, in the protostellar and protoplanetary environments, their complex kinematics make line profiles blend together and the line strength of weak lines weaker. In this paper, we utilize the principal component analysis technique to develop a filtering method that can extract COM spectra from the main kinematic component associated with COM emission and increase the signal-to-noise ratio (S/N) of spectra. This filtering method corrects non-Gaussian line profiles caused by the kinematics. For this development, we adopt the ALMA BAND 6 spectral survey data of V883 Ori, an eruptive young star with a Keplerian disk. A filter was, first, created using 34 strong and well-isolated COM lines and then applied to the entire spectral range of the data set. The first principal component (PC1) describes the most common emission structure of the selected lines, which is confined within the water sublimation radius (~0.″3) in the Keplerian disk of V883 Ori. Using this PC1 filter, we extracted high-S/N kinematics-corrected spectra of V883 Ori over the entire spectral coverage of ~50 GHz. The PC1-filtering method reduces the noise by a factor of ~2 compared to the average spectra over the COM emission region. One important advantage of this PC1-filtering method over the previously developed matched-filtering method is the ability to preserve the original integrated intensities of COM lines.

Keywords: star formation; astrochemistry
Origin of Sub-TeV Afterglow Emission from Gamma-Ray Bursts GRB 190114C and GRB 180720B

The detection of GRB 180722B and GRB 190114C in sub-TeV gamma-rays has opened up a new window to study gamma-ray bursts in high-energy gamma-rays. Recently it has been shown that the synchrotron and inverse Compton processes are responsible for the production of these high-energy gamma-rays during the afterglow. Here, for the first time we demonstrate that the photohadronic scenario that is successful in explaining the multi-TeV flaring in high-energy blazars is also applicable for gamma-ray bursts. We show that the sub-TeV spectra of GRB 190114C and GRB 180720B are due to the interaction of high-energy protons with the background photons in the synchrotron self-Compton region and synchrotron region, respectively. The nature of the background photon distributions help us to constrain their bulk Lorentz factors.

Keywords: particle astrophysics; blazars; gamma-ray bursts; relativistic jets
Reconfiguration and Eruption of a Solar Filament by Magnetic Reconnection with an Emerging Magnetic Field

Both observations and simulations suggest that the solar filament eruption is closely related to magnetic flux emergence. It is thought that the eruption is triggered by magnetic reconnection between the filament and the emerging flux. However, the details of such a reconnection are rarely presented. In this study, we report the detailed reconnection between a filament and its nearby emerging fields, which led to the reconfiguration and subsequent partial eruption of the filament located over the polarity inversion line of active region 12816. Before the reconnection, we observed repeated brightenings in the filament at a location that overlies a site of magnetic flux cancellation. Plasmoids form at this brightening region, and propagate bidirectionally along the filament. These indicate the tether-cutting reconnection that results in the formation and eruption of a flux rope. To the northwest of the filament, magnetic fields emerge, and reconnect with the context ones, resulting in repeated jets. Afterwards, other magnetic fields emerge near the northwestern filament endpoints, and reconnect with the filament, forming the newly reconnected filament and loops. A current sheet repeatedly occurs at the interface, with the mean temperature and emission measure of 1.7 MK and 1.1×1028 cm-5. Plasmoids form in the current sheet, and propagate along it and further along the newly reconnected filament and loops. The newly reconnected filament then erupts, while the unreconnected filament remains stable. We propose that besides the orientation of emerging fields, some other parameters, such as the position, distance, strength, and area, are also crucial for triggering the filament eruption.

Keywords: solar magnetic reconnection; solar filaments; solar magnetic fields; solar ultraviolet emission; plasma physics
The Second Radio Synchrotron Background Workshop: Conference Summary and Report

We summarize the second radio synchrotron background workshop, which took place on 2022 June 15-17 in Barolo, Italy. This meeting was convened because available measurements of the diffuse radio zero level continue to suggest that it is several times higher than can be attributed to known Galactic and extragalactic sources and processes, rendering it the least well-understood electromagnetic background at present and a major outstanding question in astrophysics. The workshop agreed on the next priorities for investigations of this phenomenon, which include searching for evidence of the radio Sunyaev-Zel'dovich effect, carrying out cross-correlation analyses of radio emission with other tracers, and supporting the completion of the 310 MHz absolutely calibrated sky map project.

Keywords: radio continuum emission; galactic radio sources; extragalactic radio sources; radio astronomy
Orbital Dynamics in a Triaxial Barred Galaxy Model. I. The 2D System

We present the planar orbital dynamics of a realistic barred galaxy model, containing a nucleus (bulge), a triaxial bar, and a disk. After conducting a systematic and exhaustive orbit classification, we manage to determine how the dynamical parameters associated with the bar (mass, semiaxes, and angular velocity) affect the nature of the trajectories of the test particle. In our analysis, we distinguish not only between ordered, chaotic, and escaping motions but also between different types of regular orbits. More specifically, we reveal how the main types of regular orbits are influenced by the changes in the parameters of the galactic bar. Of particular interest is the phenomenon of trapped chaos that occurs in this galaxy model.

Keywords: galaxy structure; galaxy physics; galactic bulge
The SOFIA Massive (SOMA) Star Formation Survey. III. From Intermediate- to High-mass Protostars

We present $\sim 10\mbox{--}40\,\mu {\rm{m}}$ SOFIA-FORCAST images of 14 intermediate-mass protostar candidates as part of the SOFIA Massive (SOMA) Star Formation Survey. We build spectral energy distributions, also using archival Spitzer, Herschel, and IRAS data. We then fit the spectral energy distributions with radiative transfer models of Zhang & Tan, based on turbulent core accretion theory, to estimate key protostellar properties. With the addition of these intermediate-mass sources, based on average properties derived from SED fitting, SOMA protostars span luminosities from $\sim {10}^{2}\,\mathrm{to}\,{10}^{6}\ {L}_{\odot }$, current protostellar masses from $\sim 0.5\,{\rm{t}}{\rm{o}}\,35\,{M}_{\odot }$, and ambient clump mass surface densities, ${{\rm{\Sigma }}}_{\mathrm{cl}}$ , from $0.1\,\mathrm{to}\,{\rm{g}}\,{\mathrm{cm}}^{-2}$. A wide range of evolutionary states of the individual protostars and of the protocluster environments is also probed. We have also considered about 50 protostars identified in infrared dark clouds that are expected to be at the earliest stages of their evolution. With this global sample, most of the evolutionary stages of high- and intermediate-mass protostars are probed. The best-fitting models show no evidence that a threshold value of the protocluster clump mass surface density is required to form protostars up to $\sim 25\ {M}_{\odot }$. However, to form more massive protostars, there is tentative evidence that ${{\rm{\Sigma }}}_{\mathrm{cl}}$ needs to be $\gtrsim 1\,{\rm{g}}\,{\mathrm{cm}}^{-2}$. We discuss how this is consistent with expectations from core accretion models that include internal feedback from the forming massive star.

Keywords: massive stars; star formation; interstellar medium; jets; infrared sources
Alfvén Speed Transition Zone in the Solar Corona

The Alfvén radius, rA, at which solar wind radial outflow speed exceeds the Alfvén wave speed, is an important parameter in understanding solar wind evolution in the extended corona. The mean solar wind angular momentum scales with ${r}_{A}^{2}$ in the axisymmetric steady-state approximation, so the Alfvén radius is often referenced in the study of solar wind corotation and dynamics. Alfvén wave speed is derived from the magnetic-field intensity and plasma mass density. In the inner coronal regions, these parameters were previously estimated using empirical models based on remote sensing observations or from inverse-square scaling of measurements at 1 au. Parker Solar Probe (PSP) orbital encounters now provide in situ coronal plasma measurements to determine Alfvén speeds within 30 solar radii of the heliocenter. We combined the PSP solar-wind speed measurements and calculated Alfvén speeds with an inner corona wind speed profile from remote sensing studies. The zone of super-Alfvénic speed cross over is estimated to occur at mean heliocentric distance of 17.9 ± 2.1 R⊙ for slow solar winds of the low heliolatitude corona in a near-minimum solar activity state. Our rA values constrain the angular momentum flux to a mean of 3.5 ± 1.01 × 1022 N m sr-1, reinforcing the recent PSP results by direct measurements of particle flows.

Keywords: solar wind; solar corona
Grain Growth in the Dust Ring with a Crescent around the Very Low-mass Star ZZ Tau IRS with JVLA

The azimuthal asymmetries of dust rings in protoplanetary disks such as a crescent around young stars are often interpreted as dust traps, and thus as ideal locations for planetesimal and planet formations. Whether such dust traps effectively promote planetesimal formation in disks around very low-mass stars (VLM; a mass of ≲0.2 M ☉) is debatable, as the dynamical and grain growth timescales in such systems are long. To investigate grain growth in such systems, we studied the dust ring with a crescent around the VLM star ZZ Tau IRS using the Karl G. Jansky Very Large Array at centimeter wavelengths. Significant signals were detected around ZZ Tau IRS. To estimate the maximum grain size ( ${a}_{\max }$ ) in the crescent, we compared the observed spectral energy distribution (SED) with SEDs for various ${a}_{\max }$ values predicted by radiative transfer calculations. We found ${a}_{\max }\,\gtrsim $ 1 mm and ≲60 μm in the crescent and ring, respectively, though our modeling efforts rely on uncertain dust properties. Our results suggest that grain growth occurred in the ZZ Tau IRS disk, relative to the sub-micron-sized interstellar medium. Planet formation in a crescent with millimeter-sized pebbles might proceed more efficiently than in other regions with submillimeter-sized pebbles via pebble accretion scenarios.

Keywords: protoplanetary disks
Recipes for Jet Feedback and Spin Evolution of Black Holes with Strongly Magnetized Super-Eddington Accretion Disks

A spinning black hole (BH) accreting from a disk of strongly magnetized plasma via a magnetically arrested disk is known to produce an efficient electromagnetic jet powered by the BH's spin energy. We present general relativistic radiative magnetohydrodynamic simulations of magnetically arrested systems covering a range of sub- to super-Eddington accretion rates. Using the numerical results from these simulations, we develop formulae to describe the magnetization, jet efficiency, and spin evolution of an accreting BH as a function of its spin and accretion rate. A BH with near-Eddington accretion experiences a mild degree of spin-down because of angular momentum loss through the jet, leading to an equilibrium spin of 0.8 rather than 1.0 at the Eddington limit. As the accretion rate increases above Eddington, the spin-down effect becomes progressively stronger, ultimately converging on previous predictions based on nonradiative simulations. In particular, spin evolution drives highly super-Eddington systems toward a BH spin near zero. The formulae developed in this letter may be applied to galaxy- and cosmological-scale simulations that include BHs. If magnetically arrested disk accretion is common among supermassive BHs, the present results have broad implications for active galactic nucleus feedback and cosmological spin evolution.

Keywords: accretion; active galactic nuclei; magnetohydrodynamics; relativistic disks; relativistic jets; black hole physics
Investigating Possible Binarity for GJ 229B

GJ 229B, the first type-T brown dwarf to be discovered, has presented a tension between comparisons with evolutionary models and the larger-than-expected mass and radius values derived from spectroscopic and astrometric observations. We examine the hypothesis that GJ 229B is actually a binary substellar object by using two grid-based fits using evolutionary models to explore the range of mass ratios of the possible binary components. We find that the best-fit component values are most consistent with a roughly 2:1 binary mass ratio and an age range of 2-6 Gyr. The observed temperatures, masses, and apparent radii match expected values from evolutionary models for a binary much better than a single-object model, but more detailed observations and modeling are needed to definitively confirm the binary hypothesis.

Keywords: brown dwarfs; t dwarfs; binary stars; stellar atmospheres
Further Development of Event-based Analysis of X-Ray Polarization Data

An event-based maximum likelihood method for handling X-ray polarimetry data is extended to include the effects of background and nonuniform sampling of the possible position angle space. While nonuniform sampling in position angle space generally introduces cross terms in the uncertainties of polarization parameters that could create degeneracies, there are interesting cases that engender no bias or parameter covariance. When including background in Poisson-based likelihood formulation, the formula for the minimum detectable polarization has nearly the same form as for the case of Gaussian statistics derived by Elsner et al. in the limiting case of an unpolarized signal. A polarized background is also considered, which demonstrably increases uncertainties in source polarization measurements. In addition, a Kolmogorov-style test of the event position angle distribution is proposed that can provide an unbinned test of models where the polarization angle in Stokes space depends on event characteristics such as time or energy.

Keywords: polarimetry; x-ray astronomy; astronomical methods; analytical mathematics
Periodic and Phase-locked Modulation in PSR B1929+10 Observed with FAST

We present a detailed single-pulse analysis for PSR B1929+10 based on observations with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The main pulse (MP) and interpulse (IP) are found to be modulated with a periodicity of ∼12 times the pulsar's rotational period (P). The ∼12P modulation is confirmed as a periodic amplitude modulation instead of systematic drifting. The periodic amplitude modulation in the IP is found to be anti-correlated with that in the weak preceding component of the MP (MP_I), but correlated with that in the first two components of the MP (MP_II), which implies that the modulation patterns in the IP and the MP are phase-locked. What is more interesting is that the modulation in MP_II is delayed from that in the IP by about 1P. Furthermore, high-sensitivity observations by FAST reveal that weak emission exists between the MP and the IP. In addition, we confirm that the separation between the IP and the MP is independent of radio frequency. The above results are a conundrum for pulsar theories and cannot be satisfactorily explained by the current pulsar models. Therefore, our results observed with FAST provide an opportunity to probe the structure of pulsar emission and the neutron star's magnetosphere.

Keywords: pulsars; radio pulsars; neutron stars; magnetospheric radio emissions; observational astronomy
Gravitational Waves from Neutrino Emission Asymmetries in Core-collapse Supernovae

We present a broadband spectrum of gravitational waves (GWs) from core-collapse supernovae (CCSNe) sourced by neutrino emission asymmetries for a series of full 3D simulations. The associated GW strain probes the long-term secular evolution of CCSNe and small-scale turbulent activity and provides insight into the geometry of the explosion. For nonexploding models, both the neutrino luminosity and the neutrino gravitational waveform will encode information about the spiral SASI. The neutrino memory will be detectable for a wide range of progenitor masses for a galactic event. Our results can be used to guide near-future decihertz and long-baseline GW detection programs, including aLIGO, the Einstein Telescope, and DECIGO.

Keywords: gravitational waves; core-collapse supernovae; supernova neutrinos
Figure Rotation of IllustrisTNG Halos

We use the TNG50 and TNG50 dark matter (DM)-only simulations from the IllustrisTNG simulation suite to conduct an updated survey of halo figure rotation in the presence of baryons. We develop a novel methodology to detect coherent figure rotation about an arbitrary axis and for arbitrary durations, and we apply it to a catalog of 1577 DM halos from the DM-only run and 1396 DM halos from the DM+baryons (DM+B) run that are free of major mergers. Figure rotation was detected in 94% of DM-only halos and 82% of the DM+B halos. The pattern speeds of rotations lasting ≳1h -1 Gyr were log-normally distributed with medians of 0.25 h km s-1 kpc-1 for DM-only in agreement with past results, but 14% higher at 0.29 h km s-1 kpc-1 in the DM+B halos. We find that rotation axes are typically aligned with the halo minor or major axis in 57% of DM-only halos and in 62% of DM+B halos. The remaining rotation axes were not strongly aligned with any principal axis but typically lie in the plane containing the halo minor and major axes. Longer-lived rotations showed greater alignment with the halo minor axis in both simulations. Our results show that, in the presence of baryons, figure rotation is marginally less common, shorter-lived, faster, and better aligned with the minor axis than in DM-only halos. This updated understanding will be consequential for future efforts to constrain figure rotation in the Milky Way dark halo using the morphology and kinematics of tidal streams.

Keywords: dark matter distribution; galaxy dark matter halos; milky way dark matter halo; galaxy evolution; milky way evolution
Anisotropy of Solar Wind Turbulence in the Inner Heliosphere at Kinetic Scales: PSP Observations

The anisotropy of solar wind turbulence is a critical issue in understanding the physics of energy transfer between scales and energy conversion between fields and particles in the heliosphere. Using the measurement of Parker Solar Probe (PSP), we present an observation of the anisotropy at kinetic scales in the slow, Alfvénic, solar wind in the inner heliosphere. The magnetic compressibility behaves as expected for kinetic Alfvénic turbulence below the ion scale. A steepened transition range is found between the inertial and kinetic ranges in all directions with respect to the local background magnetic field direction. The anisotropy of k⊥ ≫ k∥ is found evident in both transition and kinetic ranges, with the power anisotropy P⊥/P∥ > 10 in the kinetic range leading over that in the transition range and being stronger than that at 1 au. The spectral index varies from αt∥ = -5.7 ± 1.0 to αt⊥ = -3.7 ± 0.3 in the transition range and αk∥ = -3.12 ± 0.22 to αk⊥ = -2.57 ± 0.09 in the kinetic range. The corresponding wavevector anisotropy has the scaling of ${k}_{\parallel }\sim {k}_{\perp }^{0.71\pm 0.17}$ in the transition range, and changes to ${k}_{\parallel }\sim {k}_{\perp }^{0.38\pm 0.09}$ in the kinetic range, consistent with the kinetic Alfvénic turbulence at sub-ion scales.

Keywords: solar wind; interplanetary turbulence; alfven waves