Sazuna/UAT_keywords huggingface dataset:
Estimating the Evolution of Sparks in the Partially Screened Gap of Pulsars from Subpulse Drifting. A novel scheme has been developed to show that the observed phase behavior associated with subpulse drifting from two pulsars, J1034-3224 and J1720-2933, can be used to obtain the magnetic field configuration in the partially screened gap (PSG). The outflowing plasma along the open magnetic field line region of pulsars is generated as a result of spark discharges in an inner acceleration region (IAR) above the polar cap. The IAR has been modeled as a PSG with a steady supply of positively charged ions emitted from the heated polar cap surface dominated by strong non-dipolar magnetic fields. In a PSG the sparks are tightly packed and constrained to be present along the polar cap boundary. The sparks lag behind the rotation of the star during their lifetimes. As a result, the sparking pattern evolves along two different directions in a clockwise and counterclockwise manner around a stationary central spark and can be associated with the observed phenomenon of subpulse drifting. PSR J1034-3224 has four prominent components and exhibits bi-drifting where alternate components show the opposite sense of drifting, while PSR J1720-2933 has a single component profile and shows systematically coherent drift bands. We show that the differences in their drifting behavior can be directly linked to different natures of the non-dipolar surface magnetic field configurations.

Keywords: Radio pulsars, Pulsars
The Formation of Hard Very High Energy Spectra from Gamma-ray Burst Afterglows via Two-zone Synchrotron Self-Compton Emission. Electron Compton scattering of target photons into the gamma-ray energy band (inverse Compton scattering; IC) is commonly expected to dominate the very high energy (VHE) spectra in gamma-ray bursts (GRBs) especially during the afterglow phase. For sufficiently large center-of-mass energies in these collisions, the effect of the electron recoil starts reducing the scattering cross-section (the Klein-Nishina regime). The IC spectra generated in the Klein-Nishina regime is softer and has a smaller flux level compared to the synchrotron spectra produced by the same electrons. The detection of afterglow emission from nearby GRB190829A in the VHE domain with H.E.S.S. has revealed an unexpected feature: the slope of the VHE spectrum matches well the slope of the X-ray spectra, despite expectations that, for the IC production process, the impact of the Klein-Nishina effect should be strong. The multi-wavelength spectral energy distribution appears to be inconsistent with predictions of one-zone synchrotron-self-Compton models. We study the possible impact of two-zone configuration on the properties of IC emission when the magnetic field strength differs considerably between the two zones. Synchrotron photons from the strong magnetic field zone provide the dominant target for cooling of the electrons in the weak magnetic field zone, which results in a formation of hard electron distribution and consequently of a hard IC emission. We show that the two-zone model can provide a good description of the Swift's X-ray Telescope and VHE H.E.S.S. data.

Keywords: Gamma-ray bursts, High energy astrophysics, Non-thermal radiation sources, X-ray sources, Gamma-ray astronomy, Gamma-ray transient sources, Particle astrophysics
The GMRT High Resolution Southern Sky Survey for Pulsars and Transients. V. Localization of Two Millisecond Pulsars. The timing follow-up of newly discovered millisecond pulsars (MSPs) is hindered by the larger positional uncertainty (a few tens of arcminutes) associated with the discovery. In this paper, we present the localization of two MSPs, discovered by the GMRT High Resolution Southern Sky survey, up to arcsecond accuracy using a 33 MHz offline coherently dedispersed gated correlator. This gated correlator is an upgraded version of the earlier 16 MHz design. This new development with a factor of 2 enhancement in the observing bandwidth offers better sensitivity in the image domain, leading to more precise localization. Aided by the precise position, we followed up these two MSPs with sensitive phased-array (PA) beams of upgraded GMRT from 300 to 1460 MHz. More sensitive observations in the PA mode for these two MSPs yield precise (~sub-μs) time-of-arrivals, with dispersion measure uncertainties in the range of 10-4-10-5 pc cm-3. We also report the profile evolution of the two MSPs over 300-1460 MHz. Finally, we discuss the suitability of these MSPs for the pulsar timing array experiments aimed to detect low-frequency gravitational waves.

Keywords: Millisecond pulsars, Astronomical techniques, Pulsars
A Heating Mechanism via Magnetic Pumping in the Intracluster Medium. Turbulence driven by active galactic nuclei activity, cluster mergers, and galaxy motion constitutes an attractive energy source for heating the intracluster medium (ICM). How this energy dissipates into the ICM plasma remains unclear, given its low collisionality and high magnetization (precluding viscous heating by Coulomb processes). Kunz et al. proposed a viable heating mechanism based on the anisotropy of the plasma pressure under ICM conditions. The present paper builds upon that work and shows that particles can be heated by large-scale turbulent fluctuations via magnetic pumping. We study how the anisotropy evolves under a range of forcing frequencies, what waves and instabilities are generated, and demonstrate that the particle distribution function acquires a high-energy tail. For this, we perform particle-in-cell simulations where we periodically vary the mean magnetic field B (t). When B (t) grows (dwindles), a pressure anisotropy P ⊥ &gt; P ∥(P ⊥ &lt; P ∥) builds up (P ⊥ and P ∥ are, respectively, the pressures perpendicular and parallel to B (t)). These pressure anisotropies excite mirror (P ⊥ &gt; P ∥) and oblique firehose (P ∥ &gt; P ⊥) instabilities, which trap and scatter the particles, limiting the anisotropy, and providing a channel to heat the plasma. The efficiency of this mechanism depends on the frequency of the large-scale turbulent fluctuations and the efficiency of the scattering the instabilities provide in their nonlinear stage. We provide a simplified analytical heating model that captures the phenomenology involved. Our results show that this process can be relevant in dissipating and distributing turbulent energy at kinetic scales in the ICM.

Keywords: Galaxy clusters, High energy astrophysics, Plasma astrophysics, Intracluster medium, Magnetic fields, Galaxies
A Possible Surviving Companion of the SN Ia in the Galactic SNR G272.2-3.2. We use the Gaia EDR3 to explore the Galactic supernova remnant (SNR) G272.2-3.2, produced by the explosion of a Type Ia supernova (SN Ia) about 7500 yr ago, to search for a surviving companion. From the abundances in the SNR ejecta, G272.2-3.2 is a normal SN Ia. The Gaia parallaxes allow us to select the stars located within the estimated distance range of the SNR, and the Gaia proper motions allow us to study their kinematics. From the Gaia EDR3 photometry, we construct the H-R diagram of the selected sample, which we compare with the theoretical predictions for the evolution of possible star companions of SNe Ia. We can discard several proposed types of companions by combining kinematics and photometry. We can also discard hypervelocity stars. We focus our study on the kinematically most peculiar star, Gaia EDR3 5323900215411075328 (hereafter MV-G272), an 8.9σ outlier in proper motion. It is of M1-M2 stellar type. Its trajectory on the sky locates it at the center of the SNR, 6000-8000 yr ago, a unique characteristic among the sample. Spectra allow a stellar parameter determination and a chemical abundance analysis. In conclusion, we have a candidate to be the surviving companion of the SN Ia that resulted in SNR G272.2-3.2. It is supported by its kinematical characteristics and its trajectory within the SNR. This opens the possibility of a single-degenerate scenario for an SN Ia with an M-type dwarf companion.

Keywords: Type Ia supernovae
Pointlike Sources among z &gt; 11 Galaxy Candidates: Contaminants due to Supernovae at High Redshifts?. The recent searches for z &gt; 11 galaxies using the James Webb Space Telescope have resulted in an unexpectedly high number of candidate objects, which imply at least 1 order of magnitude higher number density of z &gt; 11 galaxies than the previously favored predictions. A question has risen whether there are some new types of contaminants among these candidates. The candidate sample of Yan et al., totaling 87 dropouts, is the largest one, and we notice that a number of these candidates are pointlike. We hypothesize that the point-source dropouts could be supernovae at high redshifts. Further investigation shows that most of their spectral energy distributions indeed can be explained by supernovae at various redshifts from z ~ 1 to 15, which lends support to this hypothesis. Attributing such point-source dropouts to supernova contamination cannot eliminate the tension, however, because they only account for ~10% of the Yan et al. sample. On the other hand, the discovery of "contaminant" supernovae at z &gt; 3 will have a series of important implications. Ironically, the existence of supernovae at z &gt; 10 would still imply that the previously favored picture of early galaxy formation severely underestimates the global star formation rate density such redshifts. Multiple-epoch JWST imaging will be the simplest and yet the most efficient way to further test this hypothesis.

Keywords: Early universe, Galaxy formation, Core-collapse supernovae, Type Ia supernovae, Galaxy evolution, Supernovae
Unveiling the Mechanism for the Rapid Acceleration Phase in a Solar Eruption. Two major mechanisms have been proposed to drive the solar eruptions: the ideal magnetohydrodynamic instability and the resistive magnetic reconnection. Due to the close coupling and synchronicity of the two mechanisms, it is difficult to identify their respective contribution to solar eruptions, especially to the critical rapid acceleration phase. Here, to shed light on this problem, we conduct a data-driven numerical simulation for the flux rope eruption on 2011 August 4, and quantify the contributions of the upward exhaust of the magnetic reconnection along the flaring current sheet and the work done by the large-scale Lorentz force acting on the flux rope. Major simulation results of the eruption, such as the macroscopic morphology, early kinematics of the flux rope and flare ribbons, match well with the observations. We estimate the energy converted from the magnetic slingshot above the current sheet and the large-scale Lorentz force exerting on the flux rope during the rapid acceleration phase, and find that (1) the work done by the large-scale Lorentz force is about 4.6 times higher than the former, and (2) decreased strapping force generated by the overlying field facilitates the eruption. These results indicate that the large-scale Lorentz force plays a dominant role in the rapid acceleration phase for this eruption.

Keywords: Solar magnetic fields, Solar active region magnetic fields, Solar coronal mass ejections, Magnetohydrodynamical simulations
The Empirical Limits of Gyrochronology. The promise of gyrochronology is that, given a star's rotation period and mass, its age can be inferred. The reality of gyrochronology is complicated by effects other than ordinary magnetized braking that alter stellar rotation periods. In this work, we present an interpolation-based gyrochronology framework that reproduces the time- and mass-dependent spin-down rates implied by the latest open cluster data, while also matching the rate at which the dispersion in initial stellar rotation periods decreases as stars age. We validate our technique for stars with temperatures of 3800-6200 K and ages of 0.08-2.6 gigayears (Gyr), and use it to reexamine the empirical limits of gyrochronology. In line with previous work, we find that the uncertainty floor varies strongly with both stellar mass and age. For Sun-like stars (≈5800 K), the statistical age uncertainties improve monotonically from ±38% at 0.2 Gyr to ±12% at 2 Gyr, and are caused by the empirical scatter of the cluster rotation sequences combined with the rate of stellar spin-down. For low-mass K dwarfs (≈4200 K), the posteriors are highly asymmetric due to stalled spin-down, and ±1σ age uncertainties vary non-monotonically between 10% and 50% over the first few gigayears. High-mass K dwarfs (5000 K) older than ≈1.5 Gyr yield the most precise ages, with limiting uncertainties currently set by possible changes in the spin-down rate (12% systematic), the calibration of the absolute age scale (8% systematic), and the width of the slow sequence (4% statistical). An open-source implementation, gyro-interp, is available online at github.com/lgbouma/gyro-interp.

Keywords: Field stars, Stellar rotation, Bayesian statistics, Stellar ages
The Hot Main Kuiper Belt Size Distribution from OSSOS. Using the absolute detection calibration and abundant detections of the Outer Solar System Origins Survey project, we provide population measurements for the main Kuiper Belt. For absolute magnitude H  r  &lt; 8.3, there are 30,000 nonresonant main-belt objects, with twice as many hot-component objects than cold, and with total mass of 0.014 M ⊕, only one-seventh of which is in the cold belt (assuming a cold-object albedo about half that of hot-component objects). We show that trans-Neptunian objects with 5.5 &lt; H  r  &lt; 8.3 (rough diameters 400-100 km) have indistinguishable absolute magnitude (size) distributions, regardless of being in the cold classical Kuiper Belt (thought to be primordial) or the "hot" population (believed to be implanted after having been formed elsewhere). We discuss how this result was not apparent in previous examinations of the size distribution due to the complications of fitting assumed power-law functional forms to the detections at differing depths. This shared size distribution is surprising in light of the common paradigm that the hot-population planetesimals formed in a higher density environment much closer to the Sun, in an environment that also (probably later) formed larger (dwarf planet and bigger) objects. If this paradigm is correct, our result implies that planetesimal formation was relatively insensitive to the local disk conditions and that the subsequent planet-building process in the hot population did not modify the shape of the planetesimal size distribution in this 50-300 km range.

Keywords: Luminosity function, Sky surveys, Classical Kuiper belt objects
Polarization in the GG Tau Ring-Confronting Dust Self-scattering, Dust Mechanical and Magnetic Alignment, Spirals, and Dust Grain Drift. We report Atacama Large Millimeter/submillimeter Array (ALMA) polarization observations at 3 and 0.9 mm toward the GG Tau A system. In the ring, the percentage is relatively homogeneous at 3 mm, being 1.2%, while it exhibits a clear radial variation at 0.9 mm with a mean increasing from 0.6% to 2.8% toward larger radius (r). The polarization orientation at r &gt; 1.″85 appears nearly azimuthal at both wavelengths. At r &lt; 1.″85, the pattern remains azimuthal at 3 mm but becomes radial at 0.9 mm. The dust self-scattering model with ${a}_{\max }$ of 1 mm could reproduce the observed polarization orientation and percentage at 0.9 mm, but the expected polarization percentage at 3 mm would be 0.2%, much smaller than the detected 1.2%. Dust alignment with poloidal magnetic field could qualitatively reproduce the flip in polarization at r &lt; 1.″85 and also the detected polarization percentage. A closer inspection of the nearly azimuthal pattern reveals that polarization orientations are systematically deviating by -9.°0 ± 1.°2 from the tangent of the orbit ellipses. This deviation agrees with the direction of the spiral pattern observed in the near-infrared, but it is unclear how dust grains could be aligned along such spirals. For the scenario where the -9° deviation (-7.°3 after considering the inclination effect) measures the radial component of the dust drift motion, the expected inward drifting velocity would be ~12.8% of the Keplerian speed, a factor of 2.8 larger than the theoretical predictions. Possible additional interpretations of the polarization are discussed, but there is no single mechanism that could explain the detected polarization simultaneously.

Keywords: Interstellar medium, Circumstellar disks
MINDS. The Detection of <SUP>13</SUP>CO<SUB>2</SUB> with JWST-MIRI Indicates Abundant CO<SUB>2</SUB> in a Protoplanetary Disk. We present JWST-MIRI Medium Resolution Spectrometer (MRS) spectra of the protoplanetary disk around the low-mass T Tauri star GW Lup from the MIRI mid-INfrared Disk Survey Guaranteed Time Observations program. Emission from 12CO2, 13CO2, H2O, HCN, C2H2, and OH is identified with 13CO2 being detected for the first time in a protoplanetary disk. We characterize the chemical and physical conditions in the inner few astronomical units of the GW Lup disk using these molecules as probes. The spectral resolution of JWST-MIRI MRS paired with high signal-to-noise data is essential to identify these species and determine their column densities and temperatures. The Q branches of these molecules, including those of hot bands, are particularly sensitive to temperature and column density. We find that the 12CO2 emission in the GW Lup disk is coming from optically thick emission at a temperature of ~400 K. 13CO2 is optically thinner and based on a lower temperature of ~325 K, and thus may be tracing deeper into the disk and/or a larger emitting radius than 12CO2. The derived ${N}_{{\mathrm{CO}}_{2}}$ / ${N}_{{{\rm{H}}}_{2}{\rm{O}}}$ ratio is orders of magnitude higher than previously derived for GW Lup and other targets based on Spitzer-InfraRed-Spectrograph data. This high column density ratio may be due to an inner cavity with a radius in between the H2O and CO2 snowlines and/or an overall lower disk temperature. This paper demonstrates the unique ability of JWST to probe inner disk structures and chemistry through weak, previously unseen molecular features.

Keywords: Protoplanetary disks, Planet formation
The Image of the M87 Black Hole Reconstructed with PRIMO. We present a new reconstruction of the Event Horizon Telescope (EHT) image of the M87 black hole from the 2017 data set. We use PRIMO, a novel dictionary-learning-based algorithm that uses high-fidelity simulations of accreting black holes as a training set. By learning the correlations between the different regions of the space of interferometric data, this approach allows us to recover high-fidelity images even in the presence of sparse coverage and reach the nominal resolution of the EHT array. The black hole image comprises a thin bright ring with a diameter of 41.5 ± 0.6 μas and a fractional width that is at least a factor of 2 smaller than previously reported. This improvement has important implications for measuring the mass of the central black hole in M87 based on the EHT images.

Keywords: Black hole physics, Supermassive black holes, Black holes, Principal component analysis, Long baseline interferometry
Information Horizon of Solar Active Regions. Information theory is used to characterize the solar active region periodicities and memories from the Carrington map images 1974-2021. The active regions typically evolve and move from one map to the next. In order to track these active region structures in sequences of images, an innovative method based on information theory is developed. Image entropy provides a measure of the organization of structures in the images. The entropy can also be used as a filter to identify structures and partition the active regions, which are then registered for each image. The partitions are used to compute the mutual information and measure the information flow from the active regions from one image to the next. Finally, conditional mutual information is used to give a measure of the information flow from one image to another given the third image. The results suggest the following: (1) there is a long-term memory of two cycles or more; (2) the coherence time of the active regions is ~2 yr; and (3) the average active region structure scale size carrying the most information is approximately 118 × 103-236 × 103 Mm2. The study has implications to the short- and long-term predictability of active regions and sunspots as well as the nature of flux transport at the Sun. Finally, our innovative method can be similarly applied to stellar data to determine the dynamics of the active regions of stars.

Keywords: Solar cycle, Sunspots, Solar dynamo, Solar active regions, Magnetogram, Solar magnetic bright points
Global Dynamic Scaling Relations of H I-rich Ultra-diffuse Galaxies. The baryonic Tully-Fisher relation (BTFR), which connects the baryonic mass of galaxies with their circular velocities, has been validated across a wide range of galaxies, from dwarf galaxies to massive galaxies. Recent studies have found that several ultra-diffuse galaxies (UDGs) deviate significantly from the BTFR, indicating a galaxy population with abnormal dynamical properties. However, such studies were still confined within a small sample size. In this study, we used the 100% complete Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) to investigate the BTFR of 88 H I-rich UDGs (HUDGs), which is the largest UDG sample with dynamical information. We found that the HUDGs form a continuous distribution in the BTFR diagram, with high-velocity galaxies consistent with normal dwarf galaxies at a 1σ level, and low-velocity galaxies deviating from the BTFR, in line with that reported in the literature. We point out that the observed deviation may be subject to various selection effects or systemic biases. Nevertheless, we found that the significance of the deviation of HUDGs from the BTFR and TFR are different, i.e., they either deviate from the BTFR or from the TFR. Our result indicates that a high gas fraction may play an important role in explaining the deviation of HUDGs from BTFR.

Keywords: Galaxy formation, Galaxy dynamics, Dwarf galaxies, Galaxy evolution, Low surface brightness galaxies
Relativistic Collisionless Shocks in Inhomogeneous Magnetized Plasmas. Relativistic collisionless shocks are associated with efficient particle acceleration when propagating into weakly magnetized homogeneous media; as the magnetization increases, particle acceleration becomes suppressed. We demonstrate that this changes when the upstream carries kinetic-scale inhomogeneities, as is often the case in astrophysical environments. We use fully kinetic simulations to study relativistic perpendicular shocks in magnetized pair plasmas interacting with upstream density perturbations. For amplitudes of δ ρ/ρ ≳ 0.5, the upstream fluctuations are found to corrugate the shock front and generate large-scale turbulent shear motions in the downstream, which in turn are capable of accelerating particles. This can revive relativistic magnetized shocks as viable energization sites in astrophysical systems, such as jets and accretion disks. The generation of large-scale magnetic structures also has important implications for polarization signals from blazars.

Keywords: High energy astrophysics, Relativistic jets, Plasma astrophysics, Computational methods, Shocks