Sazuna/UAT_keywords huggingface dataset:
The Potential of the Wavelength-integrated Scattering Polarization of the Hydrogen Lyα Line for Probing the Solar Chromosphere. The intensity and the linear scattering polarization profiles of the hydrogen Lyα line encode valuable information on the thermodynamic and magnetic structure of the upper layers of the solar chromosphere. The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) sounding rocket experiment provided unprecedented spectropolarimetric data of this line, as well as two-dimensional broadband images in intensity and linear polarization. We theoretically investigate the potential of the Lyα broadband polarimetric signals for probing the solar chromosphere and its magnetic fields. We analyze the synthetic Stokes profiles obtained from a series of radiative transfer (RT) calculations out of local thermodynamic equilibrium, considering semi-empirical one-dimensional models of the solar atmosphere. The wavelength-integrated linear polarization signal is found to be dominated by the contribution from the wings when considering a Gaussian weighting function with a FWHM that corresponds to the CLASP slit-jaw broadband filter. These broadband linear polarization signals are strongly sensitive to magnetic fields of strengths on the order of 50 G, via the action of magneto-optical (MO) effects, and are expected to encode information on the middle-upper chromosphere. The two-dimensional broadband intensity and linear polarization images observed by CLASP can be suitably mimicked using synthetic wavelength-integrated signals obtained considering atmospheric models and magnetic fields that are representative of solar regions with different levels of activity, provided that the impact of MO effects is taken into account. Despite the limitations of a one-dimensional RT modeling, this work illustrates the diagnostic potential of filter-polarimetric Lyα signals for probing the solar chromosphere and its magnetism.

Keywords: Solar chromosphere, Spectropolarimetry, Solar magnetic fields, Radiative transfer
Unfolding Drift Effects for Cosmic Rays over the Period of the Sun's Magnetic Field Reversal. A well-established, comprehensive 3D numerical modulation model is applied to simulate galactic protons, electrons, and positrons from 2011 May to 2015 May, including the solar magnetic polarity reversal of Solar Cycle 24. The objective is to evaluate how simulations compare with corresponding Alpha Magnetic Spectrometer observations for 1.0-3.0 GV and what underlying physics follows from this comparison to improve our understanding of how the major physical modulation processes change, especially particle drift, from a negative to a positive magnetic polarity cycle. Apart from their local interstellar spectra, electrons and positrons differ only in their drift patterns, but they differ with protons in other ways such as adiabatic energy changes at lower rigidity. In order to complete the simulations for oppositely charged particles, antiproton modeling results are also obtained. Together, observations and corresponding modeling indicate the difference in the drift pattern before and after the recent polarity reversal and clarify to a large extent the phenomenon of charge-sign dependence during this period. The effect of global particle drift became negligible during this period of no well-defined magnetic polarity. The resulting low values of particles' mean free paths (MFPs) during the polarity reversal contrast their large values during solar minimum activity and as such expose the relative contributions and effects of the different modulation processes from solar minimum to maximum activity. We find that the drift scale starts recovering just after the polarity reversal, but the MFPs keep decreasing or remain unchanged for some time after the polarity reversal.

Keywords: Galactic cosmic rays, Heliosphere
Whistler Wave Observations by Parker Solar Probe During Encounter 1: Counter-propagating Whistlers Collocated with Magnetic Field Inhomogeneities and their Application to Electric Field Measurement Calibration. Observations of the young solar wind by the Parker Solar Probe (PSP) mission reveal the existence of intense plasma wave bursts with frequencies between 0.05 and 0.20f ce (tens of hertz up to ~300 Hz) in the spacecraft frame. The wave bursts are often collocated with inhomogeneities in the solar wind magnetic field, such as local dips in magnitude or sudden directional changes. The observed waves are identified as electromagnetic whistler waves that propagate either sunward, anti-sunward, or in counter-propagating configurations during different burst events. Being generated in the solar wind flow, the waves experience significant Doppler downshift and upshift of wave frequency in the spacecraft frame for sunward and anti-sunward waves, respectively. Their peak amplitudes can be larger than 2 nT, where such values represent up to 10% of the background magnetic field during the interval of study. The amplitude is maximum for propagation parallel to the background magnetic field. We (i) evaluate the properties of these waves by reconstructing their parameters in the plasma frame, (ii) estimate the effective length of the PSP electric field antennas at whistler frequencies, and (iii) discuss the generation mechanism of these waves.

Keywords: Solar wind
Probing the Cold Neutral Medium through H I Emission Morphology with the Scattering Transform. Neutral hydrogen (H I) emission exhibits complex morphology that encodes rich information about the physics of the interstellar medium. We apply the scattering transform (ST) to characterize the H I emission structure via a set of compact and interpretable coefficients, and find a connection between the H I emission morphology and H I cold neutral medium (CNM) phase content. Where H I absorption measurements are unavailable, the H I phase structure is typically estimated from the emission via spectral line decomposition. Here, we present a new probe of the CNM content using measures that are solely derived from H I emission spatial information. We apply the ST to GALFA-H I data at high Galactic latitudes ( $\left|b\right|\gt 30^\circ $ ), and compare the resulting coefficients to CNM fraction measurements derived from archival H I emission and absorption spectra. We quantify the correlation between the ST coefficients and the measured CNM fraction (f CNM), finding that the H I emission morphology encodes substantial f CNM-correlating information and that ST-based metrics for small-scale linearity are particularly predictive of f CNM. This is further corroborated by the enhancement of the I 857/N HI ratio with larger ST measures of small-scale linearity. These results are consistent with the picture of regions with higher CNM content being more populated by small-scale filamentary H I structures. Our work illustrates a physical connection between the H I morphology and phase content, and suggests that future phase decomposition methods can be improved by making use of both H I spectral and spatial information.

Keywords: Astrostatistics, H I line emission, Cold neutral medium, Wavelet analysis, Interstellar medium
UV and Lyα Halos of Lyα Emitters across Environments at z = 2.84. We present UV and Lyα radial surface brightness (SB) profiles of Lyα emitters (LAEs) at z = 2.84 detected with the Hyper Suprime-Cam on the Subaru Telescope. The depth of our data, together with the wide-field coverage including a protocluster, enable us to study the dependence of Lyα halos (LAHs) on various galaxy properties, including Mpc scale environments. UV and Lyα images of 3490 LAEs are extracted, and stacking the images yields SB sensitivity of $\sim 1\times {10}^{-20}\,\mathrm{erg}\,{{\rm{s}}}^{-1}\,{\mathrm{cm}}^{-2}\,{\mathrm{arcsec}}^{-2}$ in Lyα, reaching the expected level of optically thick gas illuminated by the UV background at z ~ 3. Fitting of the two-component exponential function gives the scale-lengths of 1.56 ± 0.01 and 10.4 ± 0.3 pkpc. Dividing the sample according to their photometric properties, we find that, while the dependence of halo scale-length on environment outside of the protocluster core is not clear, LAEs in the central regions of protoclusters appear to have very large LAHs, which could be caused by combined effects of source overlapping and diffuse Lyα emission from cool intergalactic gas permeating the forming protocluster core irradiated by active members. For the first time, we identify UV halos around bright LAEs that are probably due to a few lower-mass satellite galaxies. Through comparison with recent numerical simulations, we conclude that, while scattered Lyα photons from the host galaxies are dominant, star formation in satellites evidently contributes to LAHs, and that fluorescent Lyα emission may be boosted within protocluster cores at cosmic noon and/or near bright QSOs. * This research is based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Keywords: Galaxy formation, Galaxy environments, Intergalactic medium, Protoclusters, Circumgalactic medium, Lyman-alpha galaxies
Back to the Starting Point: On the Simulation of the Initial Magnetic Fields and Spin Periods of Nonaccreting Pulsars. Neutron stars (NSs) play essential roles in modern astrophysics. The magnetic fields and spin periods of newborn (zero-age) NSs have a large impact on the further evolution of NSs, which are, however, poorly explored in observations due to the difficulty of finding newborn NSs. In this work, we aim to infer the magnetic fields and spin periods (B i and P i) of zero-age NSs from the observed properties of the NS population. We select nonaccreting NSs whose evolution is solely determined by magnetic dipole radiation. We find that both B i and P i can be described by lognormal distribution, and the fitting sensitively depends on our parameters.

Keywords: Neutron stars, Accretion, Stellar rotation, Magnetic fields
Constraints on the Binarity of the WN3/O3 Class of Wolf-Rayet Stars. The WN3/O3 Wolf-Rayet (WR) stars were discovered as part of our survey for WRs in the Magellanic Clouds. The WN3/O3s show the emission lines of a high-excitation WN star and the absorption lines of a hot O-type star, but our prior work has shown that the absorption spectrum is intrinsic to the WR star. Their place in the evolution of massive stars remains unclear. Here we investigate the possibility that they are the products of binary evolution. Although these are not WN3+O3 V binaries, they could still harbor unseen companions. To address this possibility, we have conducted a multiyear radial velocity study of six of the nine known WN3/O3s. Our study finds no evidence of statistically significant radial velocity variations, and allows us to set stringent upper limits on the mass of any hypothetical companion star: for probable orbital inclinations, any companion with a period less than 100 days must have a mass &lt;2M ⊙. For periods less than 10 days, any companion would have to have a mass &lt;1M ⊙. We argue that scenarios where any such companion is a compact object are unlikely. The absorption lines indicate a normal projected rotational velocity, making it unlikely that these stars evolved with the aid of a companion star that has since merged. The modest rotation also suggests that these stars are not the result of homogenous evolution. Thus it is likely that these stars are a normal but short-lived stage in the evolution of massive stars. * This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: Wolf-Rayet stars, Massive stars, Stellar evolution
Observation of the Hall Magnetic Reconnection As Close As 56 Solar Radii from the Sun. A few thin current layers were detected in the rear boundary of an interplanetary coronal mass ejection (ICME) observed at 56 solar radii from the Sun as the Parker Solar Probe spacecraft approached the perihelion for the first time, and were caused by the interaction between the background solar wind and the rear boundary of the ICME. Among two of the current layers, the ion diffusion region of the Hall magnetic reconnection was directly detected, based on opposite ion jets, low-speed inflows, and the Hall effect. Both reconnection events were fast and occurred in the current layer with a small magnetic field shear angle and with significantly asymmetric magnetic field intensity as well as plasma between their two sides, i.e., an asymmetric magnetic reconnection with a strong guide field. A magnetic flux rope was detected inside one of the diffusion regions, indicating bursty reconnection. Additionally, multiple reconnection jets were detected inside the ICME and its rear boundary. Thus, we speculate that more ongoing reconnection events were occurring inside the ICME and its boundary. The observations suggested that fast Hall magnetic reconnection can occur as close as 56 solar radii from the Sun and plays a crucial role in ICME evolution.

Keywords: Solar wind, Heliosphere
Distorted-toroidal Flux Rope Model for Heliospheric Flux Ropes. The 3D characterization of magnetic flux ropes observed in the heliosphere has been a challenging task for decades. This is mainly due to the limitations on inferring the 3D global topology and physical properties from the 1D time series from any spacecraft. To advance our understanding of magnetic flux ropes whose configuration departs from the typical stiff geometries, here we present an analytical solution for a 3D flux rope model with an arbitrary cross section and a toroidal global shape. This constitutes the next level of complexity following the elliptic-cylindrical (EC) geometry. The mathematical framework was established by Nieves-Chinchilla et al. with the EC flux rope model, which describes a magnetic topology with an elliptical cross section as a first approach to changes in the cross section. In the distorted-toroidal flux rope model, the cross section is described by a general function. The model is completely described by a nonorthogonal geometry and the Maxwell equations can be consistently solved to obtain the magnetic field and relevant physical quantities. As a proof of concept, this model is generalized in terms of the radial dependence of current density components. The last part of this paper is dedicated to a specific function, $F(\varphi )=\delta (1-\lambda \cos \varphi )$ , to illustrate possibilities of the model. This model paves the way toward the investigation of complex distortions of magnetic structures in the solar wind. Future investigations will explore these distortions in depth by analyzing specific events; studying implications for physical quantities, such as magnetic fluxes, helicity, or energy; and evaluating the force balance with the ambient solar wind that allows such distortions.

Keywords: Solar wind, Solar coronal mass ejections, Solar evolution
The Rapid Onset of Stellar Bars in the Baryon-dominated Centers of Disk Galaxies. Recent observations of high-redshift galactic disks (z ≈ 1-3) show a strong negative trend in the dark-matter (DM) fraction f DM with increasing baryon surface density. For this to be true, the inner baryons must dominate over DM in early massive galaxies, as observed in the Milky Way today. If disks are dominant at early times, we show that stellar bars form promptly within these disks, leading to a high bar fraction. New James Webb Space Telescope observations provide the best evidence for mature stellar bars in this redshift range. The disk mass fraction f disk within R  s  = 2.2 R disk is the dominant factor determining how rapidly a bar forms. Using 3D hydro simulations of halo-bulge-disk galaxies, we confirm the "Fujii relation" for the exponential dependence of the bar formation time τ bar as a function of f disk. For f disk &gt; 0.3, the bar formation time declines exponentially fast with increasing f disk. Instead of Fujii's arbitrary threshold for when a bar appears, for the first time, we exploit the exponential growth timescale associated with the positive feedback cycle as the bar emerges from the underlying disk. A modified, mass-dependent trend is observed for halos relevant to systems at cosmic noon ( $10.5\lt \mathrm{log}{M}_{\mathrm{halo}}\lt 12$ ), where the bar onset is slower for higher-mass halos at a fixed f disk. If baryons dominate over DM within R ≈ R  s , we predict that a high fraction of bars will be found in high-redshift disks long before z = 1.

Keywords: Milky Way dark matter halo, Gravitational instability, Milky Way formation, Galaxy bars, Disk galaxies, Milky Way dynamics, Milky Way rotation, Milky Way Galaxy physics, Milky Way evolution, Milky Way mass
Revealing the Spectral State Transition of the Clocked Burster, GS 1826-238, with NuSTAR StrayCats. We present the long-term analysis of GS 1826-238, a neutron star X-ray binary known as the Clocked Burster, using data from NuSTAR StrayCats. StrayCats, a catalog of NuSTAR stray light data, contains data from bright, off-axis X-ray sources that have not been focused by the NuSTAR optics. We obtained stray light observations of the source from 2014-2021, reduced and analyzed the data using nustar-gen-utils Python tools, demonstrating the transition of the source from the island atoll state to a banana branch. We also present the light-curve analysis of Type I X-ray bursts from the Clocked Burster and show that the bursts from the banana/soft state are systematically shorter in duration than those from the island/hard state and have a higher burst fluence. From our analysis, we note an increase in the mass accretion rate of the source, and a decrease in burst frequency with the transition.

Keywords: Neutron stars, Low-mass x-ray binary stars, X-ray astronomy, Compact objects
GTC/CanariCam Mid-infrared Polarimetry of Magnetic Fields in Star-forming Region W51 IRS2. We present 0.″4 resolution imaging polarimetry at 8.7, 10.3, and 12.5 μm, obtained with CanariCam at the Gran Telescopio Canarias, of the central 0.11 pc × 0.28 pc (4.″2 × 10.″8) region of W51 IRS2. The polarization, as high as ~14%, arises from silicate particles aligned by the interstellar magnetic field (B-field). We separate, or unfold, the polarization of each sightline into emission and absorption components, from which we infer the morphologies of the corresponding projected B-fields that thread the emitting- and foreground-absorbing regions. We conclude that the projected B-field in the foreground material is part of the larger-scale ambient field. The morphology of the projected B-field in the mid-infrared (mid-IR) emitting region spanning the cometary H II region W51 IRS2W is similar to that in the absorbing region. Elsewhere, the two B-fields differ significantly with no clear relationship between them. The B-field across the W51 IRS2W cometary core appears to be an integral part of a champagne outflow of gas originating in the core and dominating the energetics there. The bipolar outflow, W51north jet, that appears to originate at or near SMA1/N1 coincides almost exactly with a clearly demarcated north-south swath of lower polarization. While speculative, comparison of mid-IR and submillimeter polarimetry on two different scales may support a picture in which SMA1/N1 plays a major role in the B-field structure across W51 IRS2.

Keywords: Star formation, Stellar jets, Magnetic fields
CHIME/FRB Discovery of 25 Repeating Fast Radio Burst Sources. We present the discovery of 25 new repeating fast radio burst (FRB) sources found among CHIME/FRB events detected between 2019 September 30 and 2021 May 1. The sources were found using a new clustering algorithm that looks for multiple events colocated on the sky having similar dispersion measures (DMs). The new repeaters have DMs ranging from ~220 to ~1700 pc cm-3, and include sources having exhibited as few as two bursts to as many as twelve. We report a statistically significant difference in both the DM and extragalactic DM (eDM) distributions between repeating and apparently nonrepeating sources, with repeaters having a lower mean DM and eDM, and we discuss the implications. We find no clear bimodality between the repetition rates of repeaters and upper limits on repetition from apparently nonrepeating sources after correcting for sensitivity and exposure effects, although some active repeating sources stand out as anomalous. We measure the repeater fraction over time and find that it tends to an equilibrium of ${2.6}_{-2.6}^{+2.9}$ % over our total time-on-sky thus far. We also report on 14 more sources, which are promising repeating FRB candidates and which merit follow-up observations for confirmation.

Keywords: High energy astrophysics, Radio transient sources
Hard TeV Gamma-Ray Afterglows of Nearby GRB 190829A as a Tentative Signature of Ultra-high-energy Cosmic Rays Accelerated in Gamma-Ray Burst Jets. The observed hard TeV gamma-ray spectrum of the nearby gamma-ray burst (GRB) 190829A may challenge the conventional leptonic GRB afterglow model. It has been proposed that an ultra-high-energy (UHE; ${\varepsilon }_{{\rm{p}}}^{{\prime} }\sim {10}^{20}$ eV) proton population can be pre-accelerated by internal shocks in GRB jets. We study the possible signatures of the UHE protons embedded in the TeV afterglows when they escape the afterglow fireball. We show that the leptonic model can represent the observed multiwavelength lightcurves and spectral energy distributions of GRB 190829A by considering the uncertainties of the model parameters. Attributing the TeV gamma-ray afterglows to the emission of both the electron self-Compton scattering process and the UHE proton synchrotron radiations in the afterglow fireball, we obtain tentative upper limits of ${\mathrm{log}}_{10}{\varepsilon }_{{\rm{p}}}^{{\prime} }/\mathrm{eV}\sim 20.46$ and ${\mathrm{log}}_{10}{E}_{{\rm{p}},\mathrm{total}}/\mathrm{erg}\leqslant 50.75$ , where E p,total is the total energy of the proton population. The synchrotron radiations of the UHE protons should dominate the early TeV gamma-ray afterglows, implying that early observations are critical for revealing the UHE proton population.

Keywords: Gamma-ray bursts, Cosmic rays
On the Anticorrelation between Duration and Redshift in Gamma-Ray Bursts. For gamma-ray bursts (GRBs) with durations greater than two seconds (so-called long GRBs), the intrinsic prompt gamma-ray emission appears, on average, to last longer for bursts at lower redshifts. We explore the nature of this duration-redshift anticorrelation, describing systems and conditions in which this cosmological evolution could arise. In particular, we explore its dependence on the metallicity of a massive star progenitor, because we can securely count on the average stellar metallicity to increase with decreasing redshift. Although stars with higher metallicity/lower redshift lose mass and angular momentum through line-driven winds, in some cases these stars are able to form more extended accretion disks when they collapse, potentially leading to longer-duration GRBs. We also examine how this duration-redshift trend may show up in interacting binary models composed of a massive star and compact object companion, recently suggested to be the progenitors of radio-bright GRBs. Under certain conditions, mass loss and equation-of-state effects from massive stars with higher metallicity and lower redshift can decrease the binary separation. This can then lead to spin-up of the massive star and allow for a longer-duration GRB upon the massive star's collapse. Finally, the duration-redshift trend may also be supported by a relatively larger population of small-separation binaries born in situ at low redshift.

Keywords: Close binary stars, Massive stars, Gamma-ray bursts