Sazuna/UAT_keywords huggingface dataset:
Polarization Properties of 28 Repeating Fast Radio Burst Sources with CHIME/FRB. As part of the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) project, we report 41 new rotation measures (RMs) from 20 repeating fast radio bursts (FRBs) obtained between 2019 and 2023 for which no previous RM was determined. We also report 22 additional RM measurements for eight further repeating FRBs. We observe temporal RM variations in practically all repeating FRBs. Repeaters appear to be separated into two categories: those with dynamic and those with stable RM environments, differentiated by the ratios of RM standard deviations to the averaged RM magnitudes. Sources from stable RM environments likely have small RM contributions from the interstellar medium of their host galaxies, whereas sources from dynamic RM environments share some similarities with Galactic pulsars in eclipsing binaries but appear distinct from solitary pulsars in the Galactic centre. We observe a new stochastic, secular, and again stochastic trend in the temporal RM variation of FRB 20180916B, which does not support binary orbit modulation being its cause. We highlight two more repeaters that show RM sign change, namely FRBs 20290929C and 20190303A. We perform an updated comparison of polarization properties between repeating and nonrepeating FRBs, which show a marginal dichotomy in their distribution of electron-density-weighted parallel-component line-of-sight magnetic fields.

Keywords: Radio bursts, Polarimetry, Radio transient sources
Tracking the Chemical Evolution of Hydrocarbons Through Carbon Grain Supply in Protoplanetary Disks. The gas present in planet-forming disks typically exhibits strong emission features of abundant carbon and oxygen molecular carriers. In some instances, protoplanetary disks show an elevated C/O ratio above interstellar values, which leads to a rich hydrocarbon chemistry evidenced in the mid-infrared spectra. The origin of this strengthened C/O ratio may stem from the release of less complex hydrocarbons from the chemical processing of carbonaceous grains. We have explored a set of 42 single-cell models in which we match the physical conditions to the inner regions of planet-forming disks, while varying the C/O ratio by exploring different levels of CH4, C, H2O, and CO to the gas-phase chemistry, which we evaluate in both the cosmic/X-ray- and UV-driven limit. We find that the carbon-bearing species in our models exhibit high dependencies on the driver of the chemistry, where both CO and long chain hydrocarbons act as carbon sinks in the cosmic/X-ray-driven chemistry limit, while the vast majority ends up in atomic carbon and CO in the UV-driven limit. We also find moderate dependencies upon the C/O ratio, where this and the ionization rate/UV field determines the point of peak production of a species, as well as its equilibrium abundance. We also find that the production of several hydrocarbons, specifically C2H2, is strongly dependent up to an order of magnitude on the initial water abundance. We finally find that in the X-ray-driven limit, both CH4 and C serve as highly transient donor species to the carbon chemistry.

Keywords: Protoplanetary disks, Chemical abundances, Astrochemistry
Unraveling Visible Spectra of S-type Stars: The f<SUP>3</SUP>Δ–a<SUP>3</SUP>Δ (α System) and e<SUP>3</SUP>Π–a<SUP>3</SUP>Δ (β System) Band Systems of ZrO. ZrO has many low-lying states, and its spectra are essential for the characterization of S-type stars. A high-resolution emission spectrum recorded with a Fourier transform spectrometer at the National Solar Observatory is used for the analysis. The 0–0 and 1–0 bands of the f3Δ–a3Δ system (α system) and the 0–0 band of the e3Π–a3Δ system (β system) have been rotationally analyzed using the modern spectral fitting program PGOPHER. New ab initio calculations of transition dipole moments have been performed to determine the band strengths. These band strengths are used to produce line lists that are suitable for the simulation of stellar spectra.

Keywords: Spectral line lists, Molecular spectroscopy, Rotational spectroscopy
Extracting the Temperature Analytically in Hydrodynamics Simulations with Gas and Radiation Pressure. Numerical hydrodynamics simulations of gases dominated by ideal, nondegenerate matter pressure and thermal radiation pressure in equilibrium entail finding the temperature as part of the evolution. Since the temperature is not typically a variable that is evolved independently, it must be extracted from the evolved variables (e.g., the rest-mass density and specific internal energy). This extraction requires solving a quartic equation, which, in many applications, is done numerically using an iterative root-finding method. Here we show instead how the equation can be solved analytically and provide explicit expressions for the solution. We also derive Taylor expansions in limiting regimes and discuss the respective advantages and disadvantages of the iterative versus analytic approaches to solving the quartic.

Keywords: Analytical mathematics, Hydrodynamical simulations
Bias-corrected Fast Radio Burst Population and Spectra Using CHIME Injection Data. Fast radio bursts (FRBs), a class of millisecond-scale, highly energetic phenomena with unknown progenitors and radiation mechanisms, require proper statistical analysis as a key method for uncovering their mysteries. In this research, we build on the bias correction method using pulse injections for the first Canadian Hydrogen Intensity Mapping Experiment/FRB catalog, to include correlations between properties and to analyze the FRB population spectrum. This model includes six FRB properties: dispersion measure (DM), pulse width, scattering timescale, spectral index, spectral running, and fluence. By applying the multidimensional weight function calculated by the model, we update the corrected distributions, suggesting that more low-DM, short- and long-width, and short-scattering timescale events may exist. Using one-off events and the first bursts from repeaters, the derived intrinsic population spectrum has a best-fit power law of F(ν) ∝ να, where α = ‑2.29 ± 0.29. This confirms previous indications that FRBs are brighter or more numerous at low frequencies. Analyzing nonrepeaters only, we find α = ‑2.50 ± 0.43, while including all bursts from repeaters produces α = ‑1.91 ± 0.20. This hints that active repeaters, low-rate repeaters, and nonrepeaters may have different progenitors, mechanisms, or evolutionary stages.

Keywords: Radio bursts, Astrostatistics, Radio transient sources
Thermal Phase Curves in Hot Gas Giant Exoplanets Exhibit a Complex Dependence on Planetary Properties. We present a catalog of uniformly processed 3.6 μm and 4.5 μm band exoplanet thermal phase curves based on Infrared Array Camera observations obtained from the Spitzer Heritage Archive. The catalog includes phase curve measurements for 34 planets, 16 of which contain full orbit coverage and have detectable secondary eclipses in both channels. The data are processed in the EXCALIBUR pipeline using a uniform analysis consisting of aperture photometry and modeling of instrument effects along with the exoplanet signal. Nearest-neighbor regression with a Gaussian kernel is used to correct for instrumental systematics correlated to the star's centroid position and shape in conjunction with a novel test to avoid overfitting. These methods may have utility in addressing subpixel gain variations present in modern infrared detectors. We analyze the 3.6 μm and 4.5 μm phase curve properties and find a strong wavelength-dependent difference in how the properties correlate with physical parameters as well as evidence that the phase curve properties are determined by multiple physical parameters. We suggest that differences between the 3.6 μm and 4.5 μm phase curve properties are due to 3.6 μm observations probing regions of the atmosphere which could include a cloud layer. Taken together, the observed phase curve behavior suggests that different physical processes are responsible for establishing the thermal phase curve at different pressures, which are probed by different wavelengths, and that further 3D Global Circulation Model modeling is required to investigate the reason for this complex dependence on planetary properties.

Keywords: Exoplanet atmospheres
The Radial Variation of Suprathermal Particles in Stream Interaction Regions: Comparisons between Solar Orbiter, ACE, and STEREO-A. With the launch of Solar Orbiter, the intensity and composition of suprathermal particles have been sampled within the inner heliosphere at distances between ∼0.3 and 1 au. This includes a multitude of observations of suprathermal ions associated with stream interaction regions (SIRs) measured by the Solar Orbiter Energetic Particle Detector, with corresponding observations at 1 au from the Ultra-Low-Energy Isotope Spectrometer on the Advanced Composition Explorer mission and the Suprathermal Ion Telescope on the Solar-Terrestrial Relations Observatory-Ahead spacecraft. Comparing observations between these spacecraft enables a statistical view of the radial variations of SIR-associated suprathermal particles, allowing for greater insight into energetic particle transport within the inner heliosphere. The observed radial trends agree well with that found by M. A. I. Van Hollebeke et al. but indicate a smaller modulation of particle spectra due to transport than predicted by L. A. Fisk &amp; M. A. Lee. This possible difference between the observed empirical relationship and theoretical formulation may arise from either sub-Parker spiral topology in the rarefaction region and/or a velocity-dependent, rather than rigidity or explicit species-dependent, diffusion treatment in L. A. Fisk &amp; M. A. Lee.

Keywords: Corotating streams, Interplanetary physics
A High-accuracy Alignment Approach for Solar Images of Different Wavelengths. Image alignment plays a crucial role in solar physics research, primarily involving translation, rotation, and scaling. The different wavelength images of the chromosphere and transition region have structural complexity and differences in similarity, which poses a challenge to their alignment. Therefore, a novel alignment approach based on dense optical flow (OF) and the RANSAC algorithm is proposed in this paper. It takes the OF vectors of similar regions between images to be used as feature points for matching. Then, it calculates scaling, rotation, and translation. The study selects three wavelengths for two groups of alignment experiments: the 304 Å of the Atmospheric Imaging Assembly (AIA), the 1216 Å of the Solar Disk Imager (SDI), and the 465 Å of the Solar Upper Transition Region Imager (SUTRI). Two methods are used to evaluate alignment accuracy: Monte Carlo simulation and Uncertainty Analysis Based on the Jacobian Matrix. The evaluation results indicate that this approach achieves subpixel accuracy in the alignment of AIA 304 Å and SDI 1216 Å, while demonstrating higher accuracy in the alignment of AIA 304 Å and SUTRI 465 Å, which have greater similarity.

Keywords: Astronomy data analysis, Astronomical methods, Solar transition region
Laboratory Detection of the Methoxymethyl Radical, CH<SUB>3</SUB>OCH<SUB>2</SUB>, Using Faraday Rotation and Chirped-pulse Techniques in the (Sub)millimeter Wave Range. Modeling the abundance of interstellar complex organic molecules in space is a major challenge for astrophysicists. The relative roles of gas-phase and grain-surface processes in the formation and destruction of such large molecules remain unclear. Methyl formate (CH3OCHO, MF) and dimethyl ether (CH3OCH3, DME) species have been detected at relatively high abundances in both warm and cold objects of the interstellar medium (ISM), challenging an initial hypothesis favoring grain-surface processes for their formation. In this context, the methoxymethyl radical (CH3OCH2, RDME) has been proposed as a key species linking the abundances of MF and DME in the gas phase. Its detection may provide crucial information to disentangle and quantify the different processes involved in the formation and destruction of MF and DME. To support the search for RDME in space, we present the laboratory detection of its pure rotational spectrum in the vibronic ground state. Special care was taken to measure the frequencies of transitions expected to be intense under cold interstellar conditions. In total, we assigned and fitted 1007 transitions of the RDME with   and   values up to 34 and 5, respectively. A reliable spectral catalog has been generated using the spectroscopic parameters derived from the fit and can be used confidently for future searches of the RDME radical in the ISM.

Keywords: High resolution spectroscopy, Spectral line lists, Rotational spectroscopy, Laboratory astrophysics, Millimeter-wave spectroscopy, Molecular physics, Chirped-pulse Fourier-transform
VLASS Tidal Disruption Events with Optical Flares. I. The Sample and a Comparison to Optically Selected TDEs. In this work, we use the Jansky Very Large Array Sky Survey to compile the first sample of six radio-selected tidal disruption events (TDEs) with transient optical counterparts. While we still lack the statistics to do detailed population studies of radio-selected TDEs, we use these events to suggest trends in host galaxy and optical light-curve properties that may correlate with the presence of radio emission and hence can inform optically selected TDE radio follow-up campaigns. We find tentative trends that radio-selected TDEs tend to have faint and cool optical flares, as well as host galaxies with low supermassive black hole masses, although larger samples are required to establish these trends as statistically significant. Our radio-selected TDEs also tend to have more energetic, larger radio-emitting regions than radio-detected, optically selected TDEs. We consider possible explanations for these trends, including by invoking super-Eddington accretion and enhanced circumnuclear media. Finally, we constrain the radio-emitting TDE rate to be ≳10 Gpc‑3 yr‑1.

Keywords: Supermassive black holes, Tidal disruption, Radio transient sources
Hyperneutron Stars from an Ab Initio Calculation. The equation of state (EOS) of neutron matter plays a decisive role in understanding the neutron star properties and the gravitational waves from neutron star mergers. At sufficient densities, the appearance of hyperons generally softens the EOS, leading to a reduction in the maximum mass of neutron stars well below the observed values of about 2 M⊙. Even though repulsive three-body forces are known to solve this so-called "hyperon puzzle," so far performing ab initio calculations with a substantial number of hyperons for neutron star properties has remained elusive. Starting from the newly developed auxiliary field quantum Monte Carlo algorithm to simulate hyperneutron matter without any sign oscillations, we derive three distinct EOSs by employing the state-of-the-art nuclear lattice effective field theory. We include NΛ, ΛΛ two-body forces, NNΛ, and NΛΛ three-body forces. Consequently, we determine essential astrophysical quantities such as the neutron star mass, radius, tidal deformability, and universal I–Love–Q relation. The maximum mass, radius, and tidal deformability of a 1.4 M⊙ neutron star are predicted to be 2.17(1)(1) M⊙, R1.4M⊙ = 13.10(1)(7) km, and  , respectively, based on our most realistic EOS. These predictions are in good agreement with the latest astrophysical constraints derived from observations of massive neutron stars, gravitational waves, and joint mass–radius measurements. In addition, for the first time in ab initio calculations, we investigate both nonrotating and rotating neutron star configurations. The results indicate that the impact of rotational dynamics on the maximum mass is small, regardless of whether hyperons are present in the EOS or not.

Keywords: Nuclear physics
The Gaia Parallax Discrepancy for the Cluster Pismis 19 and Separating δ Scutis from Cepheids. Pre-Gaia distances for the open cluster Pismis 19 disagree with Gaia parallaxes. A Two Micron All Sky Survey (2MASS) JKs red clump distance was therefore established for Pismis 19 (2.90 ± 0.15 kpc), which reaffirms that zero-point corrections for Gaia are required. OGLE GD-CEP-1864 is confirmed as a member of Pismis 19 on the basis of DR3 proper motions and its 2MASS+Vista Variables in the Vía Láctea color─magnitude position near the tip of the turnoff. That 0.3 day variable star is likely a δ Scuti rather than a classical Cepheid. The case revealed a pertinent criterion to segregate those two populations in tandem with the break in the Wesenheit Leavitt Law (≃0.5 day). Just shortward of that period discontinuity are δ Scutis, whereas beyond the break lie first overtone classical Cepheids mostly observed beyond the first crossing of the instability strip.

Keywords: Variable stars, Star clusters
Velocity Structure of Circumstellar Environment around Class 0/I Protostars: Uncertainty in the Protostellar Mass Estimation Using Circumstellar Velocities. Recent high-resolution observations have enabled detailed investigations of the circumstellar environments around Class 0/I protostars. Several studies have reported that the infall velocity of the envelope is a few times smaller than the freefall velocity inferred from protostellar masses estimated via the observed rotational velocity of their Keplerian disks. To explore the physical origins of the slow infall, we perform a set of three-dimensional resistive magnetohydrodynamic simulations of the star formation process, extending to 105 yr after protostar formation. Our simulations show that the infall velocity decreases markedly at the outer edge of the pseudodisk (at radii of ∼100–1000 au) and is much slower than the expected freefall velocity. The degree of this reduction depends on (1) the initial magnetic field strength, (2) the alignment between the initial field and the rotation axis, and (3) the evolutionary stage of the system. Across our parameter space, the ratio of the infall velocity to the freefall velocity is as small as 0.2–0.5, which is consistent with the observations. We further examine the reliability of protostellar mass estimates derived from infall and rotational velocities. While the mass derived from disk rotation closely matches the true value, deviation by a factor of 0.3–2 is found for the estimates using the infall velocity; it is underestimated due to slow infall, but could also be overestimated due to the contribution of disk mass. These findings underscore the critical role of magnetic fields in shaping star formation dynamics and highlight the uncertainties associated with protostellar mass estimates.

Keywords: Circumstellar envelopes, Star formation, Protoplanetary disks, Circumstellar disks, Protostars, Magnetohydrodynamical simulations
Disentangling γ − β: The Fourth-order Velocity Moments Based on Spherical Jeans Analysis. Distinguishing a core and a cusp within dark matter halos is complexified by the existence of mass-anisotropy degeneracy, where various combinations of velocity anisotropy (β) and inner density slope (γ) yield similar observational signatures. We construct a dynamical model that incorporates the fourth-order velocity moments to alleviate this challenge. The inclusion of the fourth-order velocity moments enables a star's line-of-sight velocity distribution (LOSVD) to be flexible. This flexible LOSVD can range from a thin-tailed to a heavy-tailed distribution that is inaccessible if only the second-order moments are considered. We test the model on four mock galaxies having isotropic orbits, β = 0: two resembling dwarf spheroidal (dSph) galaxies and two resembling ultrafaint dwarfs (UFDs) in terms of velocity dispersion. Each category includes one galaxy with a cuspy Navarro─Frenk─White (NFW) profile and one with a cored density profile. The results show that a ratio of the global velocity dispersion to velocity error, σlos,global/δvlos ≳ 4, is crucial to avoid systematic biases arising from the strong sensitivity of fourth-order moments to the LOSVD tails. In cases where this velocity ratio condition is met, our model reliably recovers γ in dSph mock galaxies, with the true value recovered within ∼1σ, and strongly excludes a cuspy NFW profile for the cored dSph mock galaxy. However, recovering the density profiles of UFDs remains challenging due to their intrinsically low velocity dispersions.

Keywords: Stellar kinematics, Dark matter, Dwarf spheroidal galaxies
Exploring Unusual High-frequency Eclipses in MSP J1908+2105. This paper presents a comprehensive study of the eclipse properties of the spider millisecond pulsar (MSP) J1908+2105, using wide-band observations from the uGMRT and Parkes UWL. For the first time, we observed that this pulsar exhibits extended eclipses up to 4 GHz, the highest frequency band of the Parkes Ultra-Wideband, making it one of only three MSPs known to have such high-frequency eclipses. This study reveals synchrotron absorption as the primary eclipse mechanism for J1908+2105. We present modeling of synchrotron optical depth with various possible combinations of the parameters to explain the observed eclipsing in this as well as other spider MSPs. Observed eclipses at unusually high frequencies for J1908+2105 significantly aided in constraining the magnetic field and electron column density in the eclipse medium while modeling the synchrotron optical depth. Combining our findings with data from other MSPs in the literature, for the first time we note that a higher cutoff frequency of eclipsing, particularly above 1 GHz, is consistently associated with a higher electron column density (&gt;1017 cm‑2) in the eclipse medium. Additionally, we present the first evidence of lensing effects near eclipse boundaries in this MSP, leading to significant magnification of radio emissions. The orbital-phase-resolved polarization analysis presented in this paper further indicates variation in rotation measure and consequently stronger magnetic fields in the eclipse region.

Keywords: Binary pulsars, Millisecond pulsars
What Defines Stationarity in Space Plasmas. Starting from the concept of entropy defect in thermodynamics, we construct the entropy formulation of space plasmas, and then use it to develop a measure of their stationarity. In particular, we show that the statistics of this entropy results in two findings that improve our understanding of stationary and nonstationary systems: (i) variations of Boltzmann‑Gibbs (BG) entropy do not exceed twice the value of the thermodynamic kappa, the parameter that provides a measure of the entropy defect in both stationary and nonstationary states, while becoming the shape parameter that labels the kappa distributions in stationary states; and (ii) the ratio of the deviation of the BG entropy with kappa scales with the kappa deviation via a power law, while the respective exponent provides the stationarity deviation index (SDI), which measures the natural tendency of the system to depart from stationarity. We confirm the validity of these findings in three different heliospheric plasma data sets observed from three missions: (1) a solar energetic particle event, recorded by the Integrated Science Investigation of the Sun instrument on board the Parker Solar Probe; (2) near-Earth solar wind protons recorded by the Solar Wind Experiment instrument on board Wind; and (3) plasma protons in the heliosheath, the source of energetic neutral atoms recorded by Interstellar Boundary Explorer. The full strength and capability of the entropic deviation ratio and SDI can now be used by the space physics community for analyzing and characterizing the stationarity of space plasmas, as well as other researchers for analyzing any other correlated systems.

Keywords: Space plasmas, Solar wind, Heliosheath, Heliosphere