Sazuna/UAT_keywords huggingface dataset:
Dynamo Model for North-South Asymmetry of Solar Activity. Observations reveal a relatively small but statistically significant north-south (NS) asymmetry in sunspot activity varying on a timescale of several solar cycles. This paper proposes a dynamo model for the phenomenon of long-term NS asymmetry. The model separates dynamo equations for magnetic fields of dipolar and quadrupolar equatorial parity. The NS asymmetry results from the superposition of dipolar and quadrupolar fields. Model computations confirm the formerly proposed excitation of the quadrupolar dynamo mode by a dominant dipolar mode mediated by the equator-symmetric fluctuations in the α-effect as a mechanism for the long-term NS asymmetry. An analytically solvable example of oscillations excited by short-term random forcing is given to justify the numerical result of NS asymmetry coherent on a timescale of several (about six in the present model) solar cycles resulting from random variations in the α-effect on a timescale of one solar rotation. The model computations show the phase-locking phenomenon of dipolar and quadrupolar fields oscillating predominantly in phase (northern type asymmetry) or in antiphase (southern type asymmetry) with relatively short irregular transitions between these two states. Large asymmetry in the simulated Grand minima is found and explained by weak magnetic quenching of the α-effect during the minima. The possibility of polar field asymmetry in activity minima as a precursor of sunspot asymmetry in the following activity cycles is discussed based on the dynamo model and observations.

Keywords: Solar magnetic fields, Solar dynamo
How Temporal Symmetry Defines Morphology in BATSE Gamma-Ray Burst Pulse Light Curves. We present compelling evidence that most gamma-ray burst (GRB) pulse light curves can be characterized by a smooth single-peaked component coupled with a more complex emission structure that is temporally symmetric around the time of the pulse peak. The model successfully fits 86% of Burst and Transient Source Experiment GRB pulses bright enough for structural properties to be measured. Surprisingly, a GRB pulse's light-curve morphology can be accurately predicted by the pulse asymmetry and the stretching/compression needed to align the structural components preceding the temporal mirror with the time-reversed components following it. Such a prediction is only possible because GRB pulses exhibit temporal symmetry. Time-asymmetric pulses include fast rise exponential decays, rollercoaster pulses, and asymmetric u-pulses, while time-symmetric pulses include u-pulses and crowns. Each morphological type is characterized by specific asymmetries, stretching parameters, durations, and alignments between the smooth and structured components, and a delineation in the asymmetry/stretching distribution suggests that symmetric pulses and asymmetric pulses may belong to separate populations. Furthermore, pulses belonging to the short GRB class exhibit similar morphologies to the long GRB class, but appear to simply occur on shorter timescales.

Keywords: Astrostatistics techniques, Gamma-ray bursts, Light curve classification
Gravitational Lensing Formalism in a Curved Arc Basis: A Continuous Description of Observables and Degeneracies from the Weak to the Strong Lensing Regime. Gravitationally lensed curved arcs provide a wealth of information about the underlying lensing distortions. Extracting precise lensing information from extended sources is a key component in many studies aiming to answer fundamental questions about the universe. To maintain accuracy with increased precision, it is of vital importance to characterize and understand the impact of degeneracies inherent in lensing observables. In this work, we present a formalism to describe the gravitational lensing distortion effects resulting in curved extended arcs based on the eigenvectors and eigenvalues of the local lensing Jacobian and their directional differentials. We identify a nonlocal and nonlinear extended deflector basis that inherits these local properties. Our parameterization is tightly linked to observable features in extended sources and allows one to accurately extract the lensing information of extended images without imposing an explicit global deflector model. We quantify what degeneracies can be broken based on specific assumptions about the local lensing nature and assumed intrinsic source shape. Our formalism is applicable from the weak linear regime to the semi-linear regime and all the way up to the highly nonlinear regime of highly magnified arcs of multiple images. The methodology and implementation presented in this work provides a framework to assessing systematics, to guide inference efforts in the right choices in complexity based on the data at hand, and to quantify the lensing information extracted in a model-independent way (https://github.com/sibirrer/curved_arcs).

Keywords: Weak gravitational lensing, Strong gravitational lensing, Gravitational lensing
Data-constrained Magnetohydrodynamic Simulation of a Long-duration Eruptive Flare. We perform a zero-β magnetohydrodynamic simulation for the C7.7 class flare initiated at 01:18 UT on 2011 June 21 using the Message Passing Interface Adaptive Mesh Refinement Versatile Advection Code (MPI-AMRVAC). The initial condition for the simulation involves a flux rope, which we realize through the regularized Biot-Savart laws, whose parameters are constrained by observations from the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) and the Extreme Ultraviolet Imager (EUVI) on the twin Solar Terrestrial Relations Observatory (STEREO). This data-constrained initial state is then relaxed to a force-free state by the magnetofrictional module in MPI-AMRVAC. The further time-evolving simulation results reproduce the eruption characteristics obtained by SDO/AIA 94 Å, 304 Å, and STEREO/EUVI 304 Å observations fairly well. The simulated flux rope possesses similar eruption direction, height range, and velocity to the observations. In particular, the two phases of slow evolution and fast eruption are reproduced by varying the density distribution in the light of the draining process of the filament material. Our data-constrained simulations also show other advantages, such as a large field of view (about 0.76 R⊙). We study the twist of the magnetic flux rope and the decay index of the overlying field, and find that in this event, both the magnetic strapping force and the magnetic tension force are sufficiently weaker than the magnetic hoop force, thus allowing the successful eruption of the flux rope. We also find that the anomalous resistivity is necessary to keep the correct morphology of the erupting flux rope.

Keywords: Solar photosphere, Solar prominences, Solar filaments, Solar corona, Solar magnetic fields, Solar activity
The Highly Self-absorbed Blazar PKS 1351-018. PKS 1351-018 at a redshift of z = 3.71 is one of the most luminous, steady synchrotron sources with a luminosity &gt;1047 erg s-1. The synchrotron luminosity does not seem to have varied by more than ~25% over 35 yr. In order to appreciate this remarkable behavior, if it were at z = 0.5, it would have a flux density at 15 GHz in a range of 110-137 Jy over 11 yr. In spite of this steady behavior, two strong γ-ray flares ≲1049 erg s-1 were detected in 2011 and 2016. There is a blazar-like behavior coexisting with the steady behavior. This study is aimed at elucidating the dual nature of this source. We find that the radio source is extremely compact with a bright core and a steep spectrum secondary component, 12 mas away, that appears to be constant in position and flux density in six epochs from 1995-2018. We estimate that a jet with a time averaged power of (5.2 ± 3.2) × 1045 erg s-1 terminates in this lobe, which is advancing ≳0.9c at a deprojected distance of 1-3 kpc from the central engine. This is the rare case of a young (~6000 yr), very powerful radio source that is viewed a few degrees from the jet axis. We find evidence of a high velocity (4000 km s-1), high ionization wind emanating from a luminous quasar. The young radio jet appears to experience modest bending as it navigates through the intense quasar environment.

Keywords: Radio loud quasars
Gravitational Wave Backgrounds from Coalescing Black Hole Binaries at Cosmic Dawn: An Upper Bound. The successive discoveries of binary merger events by Advanced LIGO-Virgo have been revealing the statistical properties of binary black hole (BBH) populations. A stochastic gravitational wave background (GWB) is a useful tool to probe the cosmological evolution of those compact mergers. In this paper, we study the upper bound on a GWB produced by BBH mergers, whose stellar progenitors dominate the reionization process at the cosmic dawn. Since early reionization by those progenitors yields a high optical depth of the universe inconsistent with the Planck measurements, the cumulative mass density is limited to ρ⋆ ≲ 107 M⊙ Mpc-3. Even with this upper bound, the amplitude of a GWB owing to the high-z BBH mergers is expected to be as high as ${{\rm{\Omega }}}_{\mathrm{gw}}\simeq {1.48}_{-1.27}^{+1.80}\times {10}^{-9}$ at f ≃ 25 Hz, while their merger rate at the present day is consistent or lower than the observed GW event rate. This level of GWB is detectable at the design sensitivity of Advanced LIGO-Virgo and would indicate a major contribution of the high-z BBH population to the local GW events. The spectral index is expected to be substantially flatter than the canonical value of ≃2/3 generically produced by lower-redshift and less-massive BBHs. Moreover, if their mass function is more top heavy than in the local universe, the GWB spectrum is even more skewed toward lower frequencies, which would allow us to extract information on the mass function of merging BBHs at high redshifts.

Keywords: Gravitational wave astronomy
On the Role of Solar Wind Expansion as a Source of Whistler Waves: Scattering of Suprathermal Electrons and Heat Flux Regulation in the Inner Heliosphere. The role of solar wind expansion in generating whistler waves is investigated using the EB-iPic3D code, which models solar wind expansion self-consistently within a fully kinetic semi-implicit approach. The simulation is initialized with an electron velocity distribution function modeled after observations of the Parker Solar Probe during its first perihelion at 0.166 au, consisting of a dense core and an antisunward strahl. This distribution function is initially stable with respect to kinetic instabilities. Expansion drives the solar wind into successive regimes where whistler heat flux instabilities are triggered. These instabilities produce sunward whistler waves initially characterized by predominantly oblique propagation with respect to the interplanetary magnetic field. The excited waves interact with the electrons via resonant scattering processes. As a consequence, the strahl pitch angle distribution broadens and its drift velocity reduces. The strahl electrons are scattered in the direction perpendicular to the magnetic field, and an electron halo is formed. At a later stage, resonant electron firehose instability is triggered and further affects the electron temperature anisotropy as the solar wind expands. Wave-particle interaction processes are accompanied by a substantial reduction of the solar wind heat flux. The simulated whistler waves are in qualitative agreement with observations in terms of wave frequencies, amplitudes, and propagation angles. Our work proposes an explanation for the observations of oblique and parallel whistler waves in the solar wind. We conclude that solar wind expansion has to be factored in when trying to explain kinetic processes at different heliocentric distances.

Keywords: Space plasmas, Solar wind, Plasma astrophysics
Merger or Not: Accounting for Human Biases in Identifying Galactic Merger Signatures. Significant galaxy mergers throughout cosmic time play a fundamental role in theories of galaxy evolution. The widespread usage of human classifiers to visually assess whether galaxies are in merging systems remains a fundamental component of many morphology studies. Studies that employ human classifiers usually construct a control sample, and rely on the assumption that the bias introduced by using humans will be evenly applied to all samples. In this work, we test this assumption and develop methods to correct for it. Using the standard binomial statistical methods employed in many morphology studies, we find that the merger fraction, error, and the significance of the difference between two samples are dependent on the intrinsic merger fraction of any given sample. We propose a method of quantifying merger biases of individual human classifiers and incorporate these biases into a full probabilistic model to determine the merger fraction and the probability of an individual galaxy being in a merger. Using 14 simulated human responses and accuracies, we are able to correctly label a galaxy as merger or isolated to within 1% of the truth. Using 14 real human responses on a set of realistic mock galaxy simulation snapshots our model is able to recover the pre-coalesced merger fraction to within 10%. Our method can not only increase the accuracy of studies probing the merger state of galaxies at cosmic noon, but also can be used to construct more accurate training sets in machine-learning studies that use human classified data sets.

Keywords: Astronomical methods, Bayesian statistics, Galaxy mergers
Implications of Flat Optically Thick Microwave Spectra in Solar Flares for Source Size and Morphology. The study aims to examine the spectral dynamics of the low-frequency, optically thick gyrosynchrotron microwave emission in solar flares to determine the characteristics of the emitting source. We present the high-resolution spectra of a set of microwave bursts observed by the Expanded Owens Valley Solar Array (EOVSA) during its commissioning phase in the 2.5-18 GHz frequency range with 1 second time resolution. Out of the 12 events analyzed in this study, nine bursts exhibit a direct decrease with time in the optically thick spectral index αl, an indicator of source morphology. Particularly, five bursts display a "flat" spectrum (αl ≤ 1.0) compared to that expected for a homogeneous/uniform source (αl ≈ 2.9). These flat spectra at low frequencies (&lt;10 GHz) can be defined as the emission from a spatially inhomogeneous source with a large area and/or with multiple emission components. In a subset of six events with partial cross-correlation data, both the events with flat spectra show a source size of ~120″ at 2.6-3 GHz. Modeling based on inhomogeneity supports the conclusion that multiple discrete sources can only reproduce a flat spectrum. We report that these flat spectra appear predominantly in the decay phase and typically grow flatter over the duration in most of the bursts, which indicates an increasing inhomogeneity and complexity of the emitting volume as the flare progresses. This large volume of flare emission filled with the trapped energetic particles is often invisible in other wavelengths, like hard X-rays, presumably due to the collisionless conditions in these regions of low ambient density and magnetic field strength.

Keywords: Solar coronal radio emission, Solar flares, Solar flare spectra, Solar radio emission, Non-thermal radiation sources, Active solar corona, Solar radio flares
Ice Inheritance in Dynamical Disk Models. The compositions of planet-forming disks are set by a combination of material inherited from the interstellar medium and material reprocessed during disk formation and evolution. Indeed, comets and primitive meteorites exhibit interstellar-like isotopic ratios and/or volatile compositions, supporting that some pristine material was incorporated intact into icy planetesimals in the solar nebula. To date, the survival of volatile interstellar material in the disk stage has not been modeled using realistic disk physics. Here, we present a modeling framework to track the destruction of interstellar ices on dust grains undergoing transport processes within a disk, with a particular focus on explaining the incorporation of pristine material into icy planetesimals. We find that it is difficult to explain inheritance through the local assembly of comets, as ice destruction is rapid for small (&lt;10 μm) grains in the inner few tens of au. Instead, a plausible pathway to inheritance is to form pebbles at larger disk radii, which then drift inward to the comet-forming zone with their ices mostly preserved. Small grains beyond ~100 au can experience ice photodissociation at the tens of percent level; however, little of the ice is actually lost from the grain, likely making this a robust site for in situ ice chemistry. Our models also indicate that many complex organic species should survive passage through the disk intact. This raises the possibility that organics synthesized in the interstellar medium can be delivered to terrestrial planets by icy-body impact and thus potentially participate in origins of life chemistry.

Keywords: Comet origins, Protoplanetary disks, Astrochemistry
Detection of a Low-frequency Quasi-periodic Oscillation in the Soft State of Cygnus X-1 with Insight-HXMT. We report the detection of a short-lived narrow quasi-periodic oscillation (QPO) at ~88 mHz in an Insight-HXMT exposure during the soft state of the persistent black hole high-mass X-ray binary Cygnus X-1. This QPO is significantly detected in all three instruments of Insight-HXMT, so in the broad energy range 1-250 keV. The fractional rms of the QPO does not show significant variations above 3 keV (~5%) while it decreases at lower energy (~2%). We show that this QPO is different from the type-A, -B, and -C QPOs usually observed in black hole X-ray binaries. We compare QPOs at similar frequencies that have been previously detected in other persistent high-mass X-ray binaries in the soft state; we speculate that such QPOs might relate to some local inhomogeneity rarely formed in the accretion flow of wind-fed accretion systems.

Keywords: Accretion, Black hole physics, Black holes, High energy astrophysics, X-ray point sources, High mass x-ray binary stars, Stellar mass black holes, X-ray observatories
The Cross-sectional Shape and Height Expansion of Coronal Loops: High-resolution Coronal Imager (Hi-C) Analysis of AR 12712. Coronal loop observations have existed for many decades yet the precise shape of these fundamental coronal structures is still widely debated since the discovery that they appear to undergo negligible expansion between their footpoints and apex. In this work a selection of eight EUV loops and their 22 sub-element strands are studied from the second successful flight of NASA's High-resolution Coronal Imager (Hi-C 2.1). Four of the loops correspond to open fan structures with the other four considered to be magnetically closed loops. Width analysis is performed on the loops and their sub-resolution strands using our method of fitting multiple Gaussian profiles to cross-sectional intensity slices. It is found that while the magnetically closed loops and their sub-element strands do not expand along their observable length, open fan structures may expand an additional 150% of their initial width. Following recent work, the Pearson correlation coefficient between peak intensity and loop/strand width are found to be predominantly positively correlated for the loops (≈88%) and their sub-element strands (≈80%). These results align with the hypothesis of Klimchuk &amp; DeForest that loops and-for the first time-their sub-element strands have approximately circular cross-sectional profiles.

Keywords: Solar coronal loops, Solar active regions, Solar corona
The Einstein Ring GAL-CLUS-022058s: a Lensed Ultrabright Submillimeter Galaxy at z = 1.4796. We report an ultrabright lensed submillimeter galaxy at zspec = 1.4796, identified as a result of a full-sky cross-correlation of the AllWISE and Planck compact source catalogs aimed at searching for bright submillimeter galaxies at z ~ 1.5-2.8. Atacama Pathfinder Experiment (APEX)/LABOCA observations of the candidate galaxy reveal a source with flux S870μm = 54 ± 8 mJy. The position of the APEX source coincides with the position of the AllWISE mid-IR source and with the Einstein ring GAL-CLUS-022058s, observed with the Hubble Space Telescope. Archival VLT/FORS observations reveal the redshift of this Einstein ring, zspec = 1.4796, and the detection of the CO(5-4) line at zspec = 1.4802 with APEX/nFLASH230 confirms the redshift of the submillimeter emission. The lensed source appears to be gravitationally magnified by a massive foreground galaxy cluster lens at z = 0.36. We use Lenstool to model the gravitational lensing, which is close to a "fold arc" configuration for an elliptical mass distribution of the central halo, where four images of the lensed galaxy are seen; the mean magnification is μL = 18 ± 4. We have determined an intrinsic rest-frame infrared luminosity of LIR ≍1012L☉ and a likely star formation rate of ~70-170 M☉yr-1. The molecular gas mass is Mmol ~ 2.6 × 1010M☉ and the gas fraction is f = 0.34 ± 0.07. We also obtain a stellar mass log (M*/M☉) = 10.7 ± 0.1 and a specific star formation rate log (sSFR/Gyr-1) = 0.15 ± 0.03. This galaxy lies on the so-called main sequence of star-forming galaxies at this redshift.

Keywords: Galaxy clusters, Starburst galaxies, Strong gravitational lensing, Submillimeter astronomy, Ultraluminous infrared galaxies, High-redshift galaxies
SN 2017fgc: A Fast-expanding Type Ia Supernova Exploded in Massive Shell Galaxy NGC 474. We present extensive optical photometric and spectroscopic observations of the high-velocity (HV) Type Ia supernova (SN Ia) 2017fgc, covering the phase from ~12 days before to ~389 days after maximum brightness. SN 2017fgc is similar to normal SNe Ia, with an absolute peak magnitude of ${M}_{\max }^{B}\approx $ -19.32 ± 0.13 mag and a post-peak decline of ∆m15(B) = 1.05 ± 0.07 mag. Its peak bolometric luminosity is derived as (1.32 ± 0.13) × 1043 erg s-1, corresponding to a 56Ni mass of 0.51 ± 0.03 M☉. The light curves of SN 2017fgc are found to exhibit excess emission in the UBV bands in the early nebular phase and pronounced secondary shoulder/maximum features in the RrIi bands. Its spectral evolution is similar to that of HV SNe Ia, with a maximum-light Si II velocity of 15,000 ± 150 km s-1 and a post-peak velocity gradient of ~120 ± 10 km s-1 day-1. The Fe II and Mg II lines blended near 4300 Å and the Fe II, Si II, and Fe III lines blended near 4800 Å are obviously stronger than those of normal SNe Ia. Inspecting a large sample reveals that the strength of the two blends in the spectra, and the secondary peak in the i/r-band light curves, are found to be positively correlated with the maximum-light Si II velocity. Such correlations indicate that HV SNe Ia may experience more complete burning in the ejecta and/or that their progenitors have higher metallicity. Examining the birthplace environment of SN 2017fgc suggests that it likely arose from a stellar environment with young and high-metallicity populations.

Keywords: Type Ia supernovae, Supernovae
GRIT: A Package for Structure-Preserving Simulations of Gravitationally Interacting Rigid Bodies. The spin-orbit coupling of planetary systems plays an important role in the dynamics and habitability of planets. However, symplectic integrators that can accurately simulate not only how orbit affects spin but also how spin affects orbit have not been constructed for general systems. Thus, we develop symplectic Lie-group integrators to simulate systems consisting gravitationally interacting rigid bodies. A user friendly package (GRIT3 ) is provided and external forcings, such as tidal interactions, are also included. As a demonstration, this package is applied to Trappist-I. The results show that the differences in transit-timing variations due to spin-orbit coupling could reach a few min in 10-year measurements, and strong planetary perturbations can push Trappist-I f, g and h out of the synchronized states.

Keywords: Exoplanet dynamics, Black hole spin-flip, Oblateness, Celestial mechanics, Few-body systems, Planetary dynamics