Sazuna/UAT_keywords huggingface dataset:
Data-constrained Magnetohydrodynamic Simulation of an Intermediate Solar Filament Eruption. Solar eruptive activities could occur in weak magnetic field environments and over large spatial scales, which are especially relevant to eruptions involving intermediate or quiescent solar filaments. To handle the large scales, we implement and apply a flux rope embedding method using regularized Biot-Savart laws in the spherical coordinate system. Combined with a potential field source surface model and a magneto-frictional method, a nonlinear force-free field comprising a flux rope embedded in a potential field is constructed. Using the combined nonlinear force-free field as the initial condition, we then perform a zero-β data-constrained magnetohydrodynamic (MHD) simulation for an M8.7 flare at 03:38 UT on 2012 January 23. The MHD model reproduces the eruption process, flare ribbon evolution (represented by the quasi-separatrix layer evolution), and kinematics of the flux rope. This approach could potentially model global-scale eruptions from weak field regions.

Keywords: Solar magnetic fields, Magnetohydrodynamics, Solar prominences, Solar corona
Constraining the Binarity of Black Hole Candidates: A Proof-of-concept Study of Gaia BH1 and Gaia BH2. Nearly a hundred binary black holes (BBHs) have been discovered with gravitational-wave signals emitted at their merging events. Thus, it is quite natural to expect that significantly more abundant BBHs with wider separations remain undetected in the Universe or even in our Galaxy. We consider a possibility that star─BH binary candidates may indeed host an inner BBH instead of a single BH. We present a detailed feasibility study of constraining the binarity of the currently available two targets, Gaia BH1 and Gaia BH2. Specifically, we examine three types of radial velocity (RV) modulations of a tertiary star in star─BBH triple systems; short-term RV modulations induced by the inner BBH, long-term RV modulations induced by the nodal precession, and long-term RV modulations induced by the von Zeipel-Kozai─Lidov oscillations. Direct three-body simulations combined with approximate analytic models reveal that the Gaia BH1 system may exhibit observable signatures of the hidden inner BBH if it exists at all. The methodology that we examine here is quite generic and is expected to be readily applicable to future star─BH binary candidates in a straightforward manner.

Keywords: Multiple stars, Black holes, Compact binary stars, Celestial mechanics, Three-body problem, Radial velocity
Calibrating VLBI Polarization Data Using GPCAL. I. Frequency-dependent Calibration. In this series of papers, we present new methods of frequency- and time-dependent instrumental polarization calibration for very long baseline interferometry (VLBI). In most existing calibration tools and pipelines, it has been assumed that instrumental polarization is constant over frequency within the instrument bandwidth and over time. The assumption is not always true and may prevent an accurate calibration, which can result in degradation of the quality of linear polarization images. In this paper, we present a method of frequency-dependent instrumental polarization calibration that is implemented in GPCAL, a recently developed polarization calibration pipeline. The method is tested using simulated data sets generated from real Very Long Baseline Array (VLBA) data. We present the results of applying the method to real VLBA data sets observed at 15 and 43 GHz. We were able to eliminate significant variability in cross-hand visibilities over frequency that is caused by frequency-dependent instrumental polarization. As a result of the calibration, linear polarization images were slightly to modestly improved as compared to those obtained without frequency-dependent instrumental polarization calibration. We discuss the reason for the minor impact of frequency-dependent instrumental polarization calibration on existing VLBA data sets and prospects for applying the method to future VLBI data sets, which are expected to provide very large bandwidths.

Keywords: Supermassive black holes, Astronomy software, Very long baseline interferometry, Relativistic jets, Astronomy data analysis, Polarimetry, High angular resolution
Calibrating VLBI Polarization Data Using GPCAL. II. Time-dependent Calibration. We present a new method of time-dependent instrumental polarization calibration for very long baseline interferometry (VLBI). This method has been implemented in the recently developed polarization calibration pipeline GPCAL. Instrumental polarization, also known as polarimetric leakage, is a direction-dependent effect, and it is not constant across the beam of a telescope. Antenna pointing model accuracy is usually dependent on time, resulting in off-axis polarimetric leakages that can vary with time. The method is designed to correct for the off-axis leakages with large amplitudes that can severely degrade linear polarization images. Using synthetic data generated based on real Very Long Baseline Array (VLBA) data observed at 43 GHz, we evaluate the performance of the method. It was able to reproduce the off-axis leakages assumed in the synthetic data, particularly those with large amplitudes. The method has been applied to two sets of real VLBA data, and the derived off-axis leakages show very similar trends over time for pairs of nearby sources. Furthermore, the amplitudes of the off-axis leakages are strongly correlated with the antenna gain correction factors. The results demonstrate that the method is capable of correcting for the off-axis leakages present in VLBI data. By calibrating time-dependent instrumental polarization, the rms noise levels of the updated linear polarization images have been significantly reduced. The method is expected to substantially enhance the quality of linear polarization images obtained from existing and future VLBI observations.

Keywords: Supermassive black holes, Astronomy software, Very long baseline interferometry, Relativistic jets, Astronomy data analysis, Polarimetry, High angular resolution
Varstrometry for Off-nucleus and Dual Sub-kiloparsec Active Galactic Nuclei (VODKA): Very Long Baseline Array Searches for Dual or Off-nucleus Quasars and Small-scale Jets. Dual and off-nucleus active supermassive black holes are expected to be common in the hierarchical structure formation paradigm, but their identification at parsec scales remains a challenge due to strict angular resolution requirements. We conducted a systematic study using the Very Long Baseline Array (VLBA) to examine 23 radio-bright candidate dual and off-nucleus quasars. The targets are selected by a novel astrometric technique (varstrometry) from Gaia, aiming to identify dual or off-nucleus quasars at (sub)kiloparsec scales. Among these quasars, eight exhibit either multiple radio components or significant (&gt;3σ) positional offsets between the VLBA and Gaia positions. The radio emission from the three candidates, which exhibit multiple radio components, is likely to originate from small-scale jets based on their morphology. Among the remaining five candidates with significant VLBA-Gaia offsets, three are identified as potential dual quasars at parsec scales, one is likely attributed to small-scale jets, and the origin of the last candidate remains unclear. We explore alternative explanations for the observed VLBA-Gaia offsets. We find no evidence for optical jets at kiloparsec scales, nor any contamination to Gaia astrometric noise from the host galaxy; misaligned coordinate systems are unlikely to account for our offsets. Our study highlights the promise of the varstrometry technique in discovering candidate dual or off-nucleus quasars and emphasizes the need for further confirmation and investigation to validate and understand these intriguing candidates.

Keywords: Double quasars, Radio jets, Quasars, Very long baseline interferometers, Radio loud quasars, Astronomical techniques, Active galactic nuclei, Astrometry, Gaia
Global Deceleration and Inward Movements of X-Ray Knots and Rims of RCW 103. The kinematics of shocks, ejecta knots, and the compact remnant of a supernova remnant give insights into the nature of the progenitor and the surrounding environment. We report on a measurement of the proper motion of X-ray knots and rims of the magnetar-hosting supernova remnant RCW 103. Chandra data obtained in three epochs, 1999, 2010, and 2016, are used. We find a global deceleration of 12 knots and rims in both northern and southern regions within the last ~24 yr, even though the age of the remnant is thought to be greater than 2 kyr. Some of them even changed their directions of motion from outward (~1000 km s-1) to inward (~-2000 km s-1). Our findings can be explained by a collision with a high-density medium at both the northern and southern edges of the remnant, although the remnant may still be expanding in the windblown cavity. The proper motion of the associated magnetar 1E 161348-5055 is possibly detected with a velocity of ≈500 km s-1.

Keywords: Magnetars, Supernova remnants, Circumstellar matter, X-ray sources, Shocks
The Metallicity Variations Along the Chromosome Maps: The Globular Cluster 47 Tucanae. The "chromosome maps" (ChMs) of globular clusters (GCs) have revealed that these ancient structures are inhomogeneous in metallicity in various ways and in different natures. Type II GCs generally display larger variations, sometimes coupled with slow neutron-capture (s) element enrichments on the ChMs redder sequences, which have been interpreted as due to multiple generations of stars. On the other hand, most GCs have inhomogeneous first populations (1P) in the form of large ranges in the ∆F275W,F814W values, pointing toward a not fully mixed pristine molecular cloud. We analyze the chemical composition of GC 47 Tucanae, which shows both inhomogeneous 1P stars and, although not formally a Type II GC, hosts a small number of stars distributed on the red side of the main stream of ChM stars. Our results suggest that 1P stars are inhomogeneous in the overall metallicity, with variations on the order of ~0.10 dex in all the chemical species. The anomalous stars distributed on a redder sequence of the ChM are further enriched in metals but have no evidence for a significant enrichment in the s elements. Our three second population stars located on the normal component of the map have metallicities similar to those of the metal-richer 1P oup, suggesting that this population formed from these stars. Although three stars is a too-small sample to draw strong conclusions, the low spread in metals of these objects might point toward formation in a fully mixed medium, possibly after a cooling flow phase. *Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO program 105.20NB, and on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

Keywords: Population II stars, Chemical abundances, Star clusters
Nonextensive Behavior of Stellar Rotation in the Galactic Disk Components. The solar neighborhood is a unique stellar astrophysical laboratory formed by a variety of stars from different origins. In particular, two of the most notable populations known are the thick and thin disk stars, each characterized by distinct chemical compositions, ages, kinematics, and origins. Based on Tsallis nonextensive statistics, we investigate the observed distribution of the projected rotational velocity of the thin and thick disk component stars. Through Bayesian inference, our results show that the $v\sin i$ distributions of the Galactic disk populations selected from both kinematic and chemical criteria follow a nonextensive behavior, where non-Gaussian statistics provide a more accurate representation. We also observed an anticorrelation between the entropic index q and the age of disk components confirming the interpretation of initial angular momentum memory loss scaled by the parameter q. In contrast, a subextensivity case with q &gt; 1 was found for the old high-α metal-rich subgroup hαmr, and due to their distinguished rotational behavior and atypical subextensive regime, we infer that thick disk and hαmr stars are, in fact, distinct objects. Our results also suggest that the rotational velocities of stars are defined not only by their evolutionary spin-down processes but also by their birth sites.

Keywords: Stellar kinematics, Stellar abundances, Galaxy disks, Galaxy evolution, Stellar rotation
Near-IR Weak-lensing (NIRWL) Measurements in the CANDELS Fields. I. Point-spread Function Modeling and Systematics. We have undertaken a near-IR weak-lensing (NIRWL) analysis of the CANDELS HST/WFC3-IR F160W observations. With the Gaia proper motion–corrected catalog as an astrometric reference, we updated the astrometry of the five CANDELS mosaics and achieved an absolute alignment within 0.″02 ± 0.″02, on average, which is a factor of several superior to existing mosaics. These mosaics are available to download (https://drive.google.com/drive/folders/1k9WEV3tBOuRKBlcaTJ0-wTZnUCisS__r). We investigated the systematic effects that need to be corrected for weak-lensing measurements. We find that the largest contributing systematic effect is caused by undersampling. We find a subpixel centroid dependence on the PSF shape that causes the PSF ellipticity and size to vary by up to 0.02 and 3%, respectively. Using the UDS as an example field, we show that undersampling induces a multiplicative shear bias of ‑0.025. We find that the brighter-fatter effect causes a 2% increase in the size of the PSF and discover a brighter-rounder effect that changes the ellipticity by 0.006. Based on the small range of slopes in a galaxy's spectral energy distribution (SED) within the WFC3-IR bandpasses, we suggest that the impact of the galaxy SED on the PSF is minor. Finally, we model the PSF of WFC3-IR F160W for weak lensing using a principal component analysis. The PSF models account for temporal and spatial variations of the PSF. The PSF corrections result in residual ellipticities and sizes, ∣de 1∣ &lt; 0.0005 ± 0.0003, ∣de 2∣ &lt; 0.0005 ± 0.0003, and ∣dR∣ &lt; 0.0005 ± 0.0001, that are sufficient for the upcoming NIRWL search for massive overdensities in the five CANDELS fields.

Keywords: Weak gravitational lensing, Galaxy clusters, Hubble Space Telescope, Infrared astronomy, Astrometry, Galaxy groups
Linking the Metallicity Enrichment History to the Star Formation History: An SFH-regulated Chemical Evolution Model and Its Implications for the Gas Cycling Process. The metallicity enrichment history (MEH) of a galaxy is determined by its star formation history (SFH) and the gas cycling process. In this paper, we construct a chemical evolution model that is regulated by the SFH of the system. In this SFH-regulated model, the evolution of all other variables, including the MEH, can be determined by the SFH. We test this model on six locally isolated dwarf galaxies covering three dwarf types that were observed by the Local Cosmology from Isolated Dwarfs (LCID) project. The SFHs and MEHs of these LCID galaxies are relatively reliable because they have been measured from deep color-magnitude diagrams that reach the main-sequence turnoff stars with good photometric accuracy. With simple assumptions of the star formation law and the mass-dependent outflows, our SFH-regulated model successfully reproduces the MEHs of all six LCID galaxies from their SFHs, with only one free parameter, the wind efficiency η ~ 1.0, for all six galaxies. This model provides a physically motivated link that directly connects the SFH and MEH of a galaxy, which will be useful to accommodate into the state-of-the-art stellar population synthesis models to help relieve the nuisance of the heavy degeneracy between the ages and metallicities of the stellar populations.

Keywords: Galaxy formation, Dwarf galaxies, Galaxy evolution
Coherent Cherenkov Radiation by Bunches in Fast Radio Bursts. Fast radio bursts (FRBs) are extragalactic radio transients with extremely high brightness temperature, which strongly suggests the presence of coherent emission mechanisms. In this study, we introduce a novel radiation mechanism for FRBs involving coherent Cherenkov radiation (ChR) emitted by bunched particles that may originate within the magnetosphere of a magnetar. We assume that some relativistic particles are emitted from the polar cap of a magnetar and move along magnetic field lines through a charge-separated magnetic plasma, emitting coherent ChR along their trajectory. The crucial condition for ChR to occur is that the refractive index of the plasma medium, denoted as n  r , must satisfy the condition ${n}_{r}^{2}\gt 1$ . We conduct comprehensive calculations to determine various characteristics of ChR, including its characteristic frequency, emission power, required parallel electric field, and coherence factor. Notably, our proposed bunched coherent ChR mechanism has the remarkable advantage of generating a narrower-band spectrum. Furthermore, a frequency downward-drifting pattern and ~100% linearly polarized emission can be predicted within the framework of this emission mechanism.

Keywords: Magnetars, Radio bursts, Radiative processes, Radio transient sources
Hidden Giants in JWST's PEARLS: An Ultramassive z = 4.26 Submillimeter Galaxy that Is Invisible to HST. We present a multiwavelength analysis using the Submillimeter Array (SMA), James Clerk Maxwell Telescope, NOEMA, JWST, the Hubble Space Telescope (HST), and the Spitzer Space Telescope of two dusty strongly star-forming galaxies, 850.1 and 850.2, seen through the massive cluster lens A 1489. These SMA-located sources both lie at z = 4.26 and have bright dust continuum emission, but 850.2 is a UV-detected Lyman-break galaxy, while 850.1 is undetected at ≲ 2 μm, even with deep JWST/NIRCam observations. We investigate their stellar, interstellar medium, and dynamical properties, including a pixel-level spectral energy distribution analysis to derive subkiloparsec-resolution stellar-mass and A  V  maps. We find that 850.1 is one of the most massive and highly obscured, A  V  ~ 5, galaxies known at z &gt; 4 with M * ~1011.8 M ⊙ (likely forming at z &gt; 6), and 850.2 is one of the least massive and least obscured, A  V  ~ 1, members of the z &gt; 4 dusty star-forming population. The diversity of these two dust-mass-selected galaxies illustrates the incompleteness of galaxy surveys at z ≳ 3-4 based on imaging at ≲ 2 μm, the longest wavelengths feasible from HST or the ground. The resolved mass map of 850.1 shows a compact stellar-mass distribution, ${R}_{{\rm{e}}}^{\mathrm{mass}}$ ~1 kpc, but its expected evolution means that it matches both the properties of massive, quiescent galaxies at z ~ 1.5 and ultramassive early-type galaxies at z ~ 0. We suggest that 850.1 is the central galaxy of a group in which 850.2 is a satellite that will likely merge in the near future. The stellar morphology of 850.1 shows arms and a linear bar feature that we link to the active dynamical environment it resides within.

Keywords: Ultraluminous infrared galaxies, Galaxy evolution, Submillimeter astronomy, Lyman-break galaxies, High-redshift galaxies
The Origin of Low-redshift Event Rate Excess as Revealed by the Low-luminosity Gamma-Ray Bursts. The relation between the event rate of long gamma-ray bursts and the star formation rate is still controversial, especially at the low-redshift end. Dong et al. confirmed that the gamma-ray burst rate always exceeds the star formation rate at a low redshift of z &lt; 1 in spite of the sample completeness. However, the reason for low-redshift excess is still unclear. Since low-luminosity bursts are at smaller redshifts generally, we choose three Swift long burst samples and classify them into low- and high-luminosity bursts in order to check whether the low-redshift excess is existent and if the excess is biased by the sample size and completeness. To degenerate the redshift evolution from luminosity, we adopt the nonparametric method to study the event rate of the two types of long bursts in each sample. It is found that the high-luminosity burst rate is consistent with the star formation rate within the whole redshift range, while the event rate of low-luminosity bursts exceeds the star formation rate at a low redshift of z &lt; 1. Consequently, we conclude that the low-redshift excess is contributed by the low-luminosity bursts with possibly new origins unconnected with the star formation, which is also independent of the sample size and the sample completeness.

Keywords: Gamma-ray bursts
The Impact of Angle-dependent Partial Frequency Redistribution on the Scattering Polarization of the Solar Na I D Lines. The long-standing paradox of the linear polarization signal of the Na I D1 line was recently resolved by accounting for the atom's hyperfine structure and the detailed spectral structure of the incident radiation field. That modeling relied on the simplifying angle-averaged (AA) approximation for partial frequency redistribution (PRD) in scattering, which potentially neglects important angle-frequency couplings. This work aims at evaluating the suitability of a PRD-AA modeling for the D1 and D2 lines through comparisons with general angle-dependent (AD) PRD calculations in both the absence and presence of magnetic fields. We solved the radiative transfer problem for polarized radiation in a 1D semiempirical atmospheric model with microturbulent and isotropic magnetic fields, accounting for PRD effects and comparing PRD-AA and PRD-AD modelings. The D1 and D2 lines are modeled separately as a two-level atomic system with hyperfine structure. The numerical results confirm that a spectrally structured radiation field induces linear polarization in the D1 line. However, the PRD-AA approximation greatly impacts the Q/I shape, producing an antisymmetric pattern instead of the more symmetric PRD-AD one while presenting a similar sensitivity to magnetic fields between 10 and 200 G. Under the PRD-AA approximation, the Q/I profile of the D2 line presents an artificial dip in its core, which is not found for the PRD-AD case. We conclude that accounting for PRD-AD effects is essential to suitably model the scattering polarization of the Na I D lines. These results bring us closer to exploiting the full diagnostic potential of these lines for the elusive chromospheric magnetic fields.

Keywords: Solar atmosphere, Solar physics, Spectropolarimetry, Radiative transfer
Are Quasi-periodic Pulsations Independent of Loop Oscillations in Solar Flare?. We investigated oscillations in an M8.7 solar flare (SOL2014-10-22), including quasi-periodic pulsations (QPPs) in light curves and Doppler shift oscillations in the flare loops. Using Bayesian-based Markov Chain Monte Carlo, Fast Fourier Transform, and wavelet analysis method, QPPs were identified at microwave and hard X-ray wave bands during the impulsive phase, and the dominant period is 40-50 s. They should be associated with a repetitive energy release process, which accelerates nonthermal electrons periodically. On the other hand, we cannot rule out the possibility of the modulation of external waves because of the lower temporal resolution of spectroscopic observation. However, almost immediately after QPPs, a minority of flare loops display their Doppler velocity oscillations with a significant period of ~4 minutes, which are observed by the Interface Region Imaging Spectrograph at the coronal line Fe XXI 1354.08 Å (T ~ 107 K), while its intensity and width show no similar oscillation. Our observations suggest that flare loop oscillations are most likely the fast kink mode waves with a phase speed of ~840 km s-1. The magnetic field strength in flare loops was estimated to be 54-69 G via the coronal seismology. The QPPs and loop oscillation could be independent of each other in this event.

Keywords: Solar oscillations, Solar flares, Solar coronal lines, Solar electromagnetic emission