Sazuna/UAT_keywords huggingface dataset:
Dynamical Coupling between Anomalous Cosmic Rays and Solar Wind in Outer Heliosphere. Voyager 2 (V2) observed that pickup ions (PUIs) and anomalous cosmic rays (ACRs) have a significant influence on the solar wind structures in the outer heliosphere. In particular, the maxima in energetic particle intensities often lagged behind the shock front, while the flow velocity in some cases featured a precursor in front of the shock. These two effects are believed to be caused by the cease of ACR injection from PUIs at large heliocentric distances, and the backward diffusion of ACRs, respectively. This paper investigates the dynamical coupling between the ACRs and the solar wind in the outer heliosphere by means of a time-dependent numerical MHD simulation, in which the ACRs are treated as a massless fluid that only contributes its pressure to the system. Two types of inner boundary conditions were used, namely a synthetic short-term shock event and an extended period of data-driven solar wind variability based on the OMNI database. The lag of the ACR pressure maximum relative to the shock front, and the extended shock precursor were reproduced by the numerical results. The increase rate of the lag is related to the corresponding diffusion coefficient and the injection efficiency from PUIs to ACRs. The model was also applied to the termination shock, where simulations likewise showed that the peak in the ACR distribution can be located a short distance downstream of the shock front, indicating that the time-dependent diffusive shock acceleration mechanism is a candidate to interpret the lag between the ACR pressure peak and the shock front observed by V2.

Keywords: Pickup ions, Interplanetary shocks, Heliosphere, Cosmic rays
Modeling the Photometric Variability of Alpha<SUP>2</SUP> CVn with a Dynamical Magnetosphere. Alpha2 Canum Venaticorum (α 2 CVn) is a strongly magnetic star with peculiar chemical signatures and periodic variability that have been long attributed to the diffusion of magnetic elements through the photosphere, leading to chemical spots across the stellar surface. However, recent studies of other magnetic hot stars are consistent with magnetospheric clouds above the surface. Here we take a renewed approach to modeling α 2 CVn with a simplified dynamical magnetosphere and a tilted, offset magnetic dipole to reproduce its Transiting Exoplanet Survey Satellite variability. Our dipole model also reproduces well the magnetic surface map of α 2 CVn from Silvester et al. Its ultraviolet variability, from IUE archival spectra, is also consistent with traditional reddening models. However, other observable quantities from the system contradict the expectations of a magnetosphere, and we conclude that it is unlikely to be present in α 2 CVn.

Keywords: Magnetic stars
Recovering the Star Formation Histories of Recently Quenched Galaxies: The Impact of Model and Prior Choices. Accurate models of the star formation histories (SFHs) of recently quenched galaxies can provide constraints on when and how galaxies shut down their star formation. The recent development of nonparametric SFH models promises the flexibility required to make these measurements. However, model and prior choices significantly affect derived SFHs, particularly for post-starburst galaxies (PSBs), which have sharp changes in their recent SFH. In this paper, we create mock PSBs, then use the Prospector SED fitting software to test how well four different SFH models recover key properties. We find that a two-component parametric model performs well for our simple mock galaxies, but is sensitive to model mismatches. The fixed- and flexible-bin nonparametric models included in Prospector are able to rapidly quench a major burst of star formation, but systematically underestimate the post-burst age by up to 200 Myr. We develop a custom SFH model that allows for additional flexibility in the recent SFH. Our flexible nonparametric model is able to constrain post-burst ages with no significant offset and just ~90 Myr of scatter. Our results suggest that while standard nonparametric models are able to recover first-order quantities of the SFH (mass, SFR, average age), accurately recovering higher-order quantities (burst fraction, quenching time) requires careful consideration of model flexibility. These mock recovery tests are a critical part of future SFH studies. Finally, we show that our new, public SFH model is able to accurately recover the properties of mock star-forming and quiescent galaxies and is suitable for broader use in the SED fitting community. https://github.com/bd-j/prospector

Keywords: Galaxy formation, Galaxy ages, Galaxy evolution, Galaxy quenching, Post-starburst galaxies
A New Method of Fluxgate Magnetometer Offset Vector Determination in the Solar Wind Using Any Magnetic Field Variations. In-depth study of dynamic processes in the astrophysical plasma environment relies on high-precision measurement of the magnetic field. Fluxgate magnetometers (FGMs) are commonly used on spacecraft to measure the magnetic field. However, their zero offsets vary slowly with time, and therefore need regularly in-flight calibration. Traditional methods of calculating the zero offset are based on properties of Alfvén waves, mirror mode structures, or current sheets. Here, we develop a new method of calculating the zero offset using any interplanetary magnetic field (IMF) variations. We create an offset cube according to the possible range of the IMF strength. The average values of B L for the IMF variation events approximately obey the normal distribution if there are enough events, where B L is the magnetic field in the maximum variance direction. Any constant vector added to the natural magnetic field data of the events will make the standard deviation of the normal distribution larger. Thereby, the point is determined to be the zero offset so that the corresponding standard deviation at this point is the minimum in the offset cube. Our test results show that this method has a 95.5% probability of obtaining the zero offset with an error of less than 0.3 nT when 10-21 hr of data are used. Our method provides an option for the in-flight calibration of the spaceborne FGM in the solar wind when there are not enough Alfvén waves, mirror modes, or current sheets.

Keywords: Planetary magnetospheres, Solar wind, Interplanetary magnetic fields
Formation of CO through C (2s <SUP>2</SUP>2p <SUP>2</SUP> <SUP>3</SUP>P) and O (2s <SUP>2</SUP>2p <SUP>4</SUP> <SUP>3</SUP>P) Radiative Association. The formation of CO through the radiative association of the carbon (C, 2s 22p 2 3P) and oxygen (O, 2s 22p 4 3P) atoms is investigated. The corresponding cross sections and rate coefficients for temperatures T = 10-10,000 K are calculated using the quantum-mechanical approach based on ab initio potential energy curves, permanent dipole moments, and transition dipole moments, which are obtained by the internally contracted multi-reference configuration interaction method with the Davidson correction and aug-cc-pwCV5Z-DK basis set. All dipole-allowed transitions between singlet, triplet, and quintet states converging to the C (2s 22p 2 3P) + O (2s 22p 4 3P) dissociation limit are considered. Compared to the previous results that only contain the X1Σ+ → X1Σ+, A1Π → X1Σ+, and B1Σ+ → X1Σ+ transitions, our results suggest that the a'3Σ+ → a3Π and d3Δ → a3Π transitions make significant contributions to the radiative association for T = 10-30 K. The total rate coefficient at low temperatures is estimated to be about 10-18 cm3 s-1, which shows significant deviation from the previous results, where only three transitions were considered. New rate coefficients may improve the chemical modeling of CO in the low-density region of the interstellar medium.

Keywords: Interstellar molecules, Radiative processes, Astrochemistry
Kinematic Structure of the Large Magellanic Cloud Globular Cluster System from Gaia eDR3 and Hubble Space Telescope Proper Motions. We have determined bulk proper motions (PMs) for 31 LMC GCs from Gaia eDR3 and Hubble Space Telescope data using multiple independent analysis techniques. Combined with literature values for distances, line-of-sight velocities, and existing bulk PMs, we extract full 6D phase-space information for 32 clusters, allowing us to examine the kinematics of the LMC GC system in detail. Except for two GCs (NGC 2159 and NGC 2210) whose high velocities suggest they are not long-term members of the LMC system, the data are consistent with a flattened configuration that rotates like the stellar disk. The one-dimensional velocity dispersions are on the order of 30 km s-1, similar to that of old stellar populations in the LMC disk. Similarly to the case for Milky Way disk clusters, the velocity anisotropy is such that the dispersion is smallest in the azimuthal direction; however, alternative anisotropies cannot be ruled out, due to distance uncertainties. The data are consistent with a single multidimensional Gaussian velocity distribution. Given the non-collisional nature of the LMC disk, this suggests that most, if not all, of the LMC GCs are formed by a single formation mechanism in the stellar disk, despite a significant spread in age and metallicity. Any accreted halo GC population is absent or far smaller in the LMC compared to the Milky Way.

Keywords: Globular star clusters, Proper motions, Large Magellanic Cloud
Properties of the Lowest-metallicity Galaxies over the Redshift Range z = 0.2 to z = 1. Low-metallicity galaxies may provide key insights into the evolutionary history of galaxies. Galaxies with strong emission lines and high equivalent widths (rest-frame EW(Hβ) ≳ 30 Å) are ideal candidates for the lowest-metallicity galaxies to z ~ 1. Using a Keck/DEIMOS spectral database of about 18,000 galaxies between z = 0.2 and z = 1, we search for such extreme emission-line galaxies with the goal of determining their metallicities. Using the robust direct T  e  method, we identify eight new extremely metal-poor galaxies (XMPGs) with $12+\mathrm{log}$ O/H ≤7.65, including one at 6.949 ± 0.091, making it the lowest-metallicity galaxy reported to date at these redshifts. We also improve upon the metallicities for two other XMPGs from previous work. We investigate the evolution of Hβ using both instantaneous and continuous starburst models, finding that XMPGs are best characterized by continuous starburst models. Finally, we study the dependence on age of the buildup of metals and the emission-line strength.

Keywords: Starburst galaxies, Observational cosmology, Galaxy evolution, Galaxy abundances
Luminous Optical and X-Ray Flaring of the Putative Redback Millisecond Pulsar 1FGL J0523.5-2529. Several redback and black widow millisecond pulsar binaries have episodes of flaring in X-rays and optical. We initially detected such behavior from the Fermi selected redback candidate 1FGL J0523.5-2529 during optical time-series monitoring. Triggered observations with the Neil Gehrels Swift Observatory over the next ≈100 days showed episodic flaring in X-rays with luminosity up to 8 × 1033 erg s-1 (~100 times the minimum), and a comparable luminosity in the optical/UV, with similar power-law spectra of f  ν  ∝ ν -0.7. These are the most luminous flares seen in any nonaccreting "spider" pulsar system, which may be related to the large size of the companion through the fraction of the pulsar wind that it or its ablated wind intercepts. Simultaneously with an optical flare, we see Balmer line and He I emission, not previously known in this object, which is evidence of a stellar wind that may also inhibit detection of radio pulsations. The quiescent optical light curves, while dominated by ellipsoidal modulation, show evidence of variable nonuniform temperature that could be due either to large starspots or asymmetric heating of the companion by the pulsar. This may explain a previous measurement of unusual nonzero orbital eccentricity as, alternatively, distortion of the radial-velocity curve by the surface temperature distribution of the large companion.

Keywords: Gamma-ray sources, Millisecond pulsars
A Spatially Resolved Study of Hard X-Ray Emission in Kepler's Supernova Remnant: Indications of Different Regimes of Particle Acceleration. Synchrotron X-ray emission in young supernova remnants (SNRs) is a powerful diagnostic tool to study the population of high-energy electrons accelerated at the shock front and the acceleration process. We performed a spatially resolved spectral analysis of NuSTAR and XMM-Newton observations of the young Kepler's SNR, aiming to study in detail its nonthermal emission in hard X-rays. We selected a set of regions all around the rim of the shell and extracted the corresponding spectra. The spectra were analyzed by adopting a model of synchrotron radiation in the loss-limited regime, to constrain the dependence of the cutoff energy of the synchrotron radiation on the shock velocity. We identify two different regimes of particle acceleration, characterized by different Bohm factors. In the north, where the shock interacts with a dense circumstellar medium (CSM), we found a more efficient acceleration than in the south, where the shock velocity is higher and there are no signs of shock interaction with the dense CSM. Our results suggest an enhanced efficiency of the acceleration process in regions where the shock-CSM interaction generates an amplified and turbulent magnetic field. By combining hard X-ray spectra with radio and γ-ray observations of Kepler's SNR, we modeled the spectral energy distribution. In the light of our results we propose that the observed γ-ray emission is mainly hadronic and originates in the northern part of the shell.

Keywords: Supernova remnants, Cosmic ray sources
Neutral Stellar Winds toward the High-mass Star-forming Region G176.51+00.20. We observed the high-mass star-forming region G176.51+00.20 using the Five-hundred-meter Aperture Spherical radio Telescope with the 19 beam tracking observational mode. This is a pilot work of searching for neutral stellar winds traced by atomic hydrogen (i.e., H I winds) using the high-sensitivity H I line toward high-mass star-forming regions where bipolar molecular outflows have been detected with high sensitivity by Liu et al. H I wind was detected in this work only in Beam 1. We find here that, similar to low-mass star formation, no matter how large the inclination is, the H I wind is likely sufficiently strong to drive a molecular outflow. We also find that the abundance of H I in the H I wind is consistent with that of the H I narrow-line self-absorption (HINSA) in the same beam (i.e., Beam 1). This implies that there is probably an internal relationship between H I winds and HINSA. This result also reinforces the assertion that H I winds and detected molecular outflows are associated with each other.

Keywords: Interstellar molecules, Jets, Interstellar dynamics, Interstellar atomic gas, Interstellar abundances, Star formation
Burst-Disk Interaction in 4U 1636-536 as Observed by NICER. We present the detection of 51 thermonuclear X-ray bursts observed from 4U 1636-536 by the Neutron Star Interior Composition Explorer (NICER) over the course of a 3 yr monitoring campaign. We perform time-resolved spectroscopy for 40 of these bursts and show the existence of a strong soft excess in all the burst spectra. The excess emission can be characterized by the use of a scaling factor (the f  a  method) to the persistent emission of the source, which is attributed to the increased mass accretion rate onto the neutron star due to Poynting-Robertson drag. The soft excess emission can also be characterized by the use of a model taking into account the reflection of the burst emission off the accretion disk. We also present time-resolved spectral analysis of five X-ray bursts simultaneously observed by NICER and AstroSat, which confirm the main results with even greater precision. Finally, we present evidence for Compton cooling using seven X-ray bursts observed contemporaneously with NuSTAR, by means of a correlated decrease in the hard X-ray lightcurve of 4U 1636-536 as the bursts start.

Keywords: Stellar accretion disks, Neutron stars, X-ray bursts
AGN-driven Cold Gas Outflow of NGC 1068 Characterized by Dissociation-sensitive Molecules. Recent developments in (sub)millimeter facilities have drastically changed the amount of information obtained from extragalactic spectral scans. In this paper, we present a feature extraction technique using principal component analysis (PCA) applied to arcsecond-resolution (1.″0-2.″0 = 72-144 pc) spectral scan data sets for the nearby type-2 Seyfert galaxy NGC 1068, using Band 3 of the Atacama Large Millimeter/submillimeter Array. We apply PCA to 16 well-detected molecular line intensity maps convolved to a common 150 pc resolution. In addition, we include the [S III]/[S II] line ratio and [C I] 3 P 1-3 P 0 maps in the literature, both of whose distributions show a remarkable resemblance to that of a kiloparsec-scale biconical outflow from the central active galactic nucleus. We identify two prominent features: (1) central concentration at the circumnuclear disk (CND) and (2) two peaks across the center that coincide with the biconical outflow peaks. The concentrated molecular lines in the CND are mostly high-dipole molecules (e.g., H13CN, HC3N, and HCN). Line emissions from molecules known to be enhanced in an irradiated interstellar medium, CN, C2H, and HNC, show similar concentrations and extended components along the bicone, suggesting that molecule dissociation is a dominant chemical effect of the cold molecular outflow of this galaxy. Although further investigation should be made, this scenario is consistent with the faintness or absence of emission lines from CO isotopologues, CH3OH, and N2H+ in the outflow, which are easily destroyed by dissociating photons and electrons.

Keywords: Molecular gas, Interstellar phases, Galaxy nuclei, Multivariate analysis, Seyfert galaxies, Active galactic nuclei, Galaxy winds
An Exploration of an Early Gravity Transition in Light of Cosmological Tensions. We study a step-like transition in the value of the effective Planck mass (or effective gravitational constant) on cosmological scales prior to recombination. We employ cosmic microwave background, baryon acoustic oscillations, and Type Ia supernova data and find they are sufficient to strongly constrain our implementation of the effective field theory of dark energy and modified gravity, used to model the transition, to a limited parameter space. The data prefer a ~5% shift in the value of the effective Planck mass (&lt;10% at 2σ) prior to recombination. This Transitional Planck Mass (TPM) model is free to undergo its transition at any point over multiple decades of scale factor prior to recombination, ${\mathrm{log}}_{10}(a)=-{5.32}_{-0.72}^{+0.96}$ (68% confidence level). This lowers the sound horizon at last scattering, which increases the Hubble constant to 71.09 ± 0.75 km s-1 Mpc-1 with a combination of local measurements as prior and to ${69.22}_{-0.86}^{+0.67}$ km s-1 Mpc-1 when the prior is excluded. The TPM model improves χ 2 with respect to ΛCDM by Δχ 2 = -23.72 with the H 0 prior and Δχ 2 = -4.8 without the prior. The model allows for both H 0 &gt; 70 kms-1 Mpc-1 and S 8 &lt; 0.80 simultaneously with lower values of S 8 due to a reduction in the matter density Ω m  to offset the increase in H 0 relative to ΛCDM. While this is a particular modified gravity model, studying other variants of modified gravity may be a productive path for potentially resolving cosmological tensions while avoiding the need for a cosmological constant.

Keywords: Cosmology, Cosmological parameters, Dark energy
Neutrino Emission from Luminous Fast Blue Optical Transients. Mounting evidence suggests that luminous fast blue optical transients (LFBOTs) are powered by a compact object, launching an asymmetric and fast outflow responsible for the radiation observed in the ultraviolet, optical, infrared, radio, and X-ray bands. Proposed scenarios aiming to explain the electromagnetic emission include an inflated cocoon, surrounding a jet choked in the extended stellar envelope. Alternatively, the observed radiation may arise from the disk formed by the delayed merger of a black hole with a Wolf-Rayet star. We explore the neutrino production in these scenarios, i.e., internal shocks in a choked jet and interaction between the outflow and the circumstellar medium (CSM). If observed on axis, the choked jet provides the dominant contribution to the neutrino fluence. Intriguingly, the IceCube upper limit on the neutrino emission inferred from the closest LFBOT, AT2018cow, excludes a region of the parameter space otherwise allowed by electromagnetic observations. After correcting for the Eddington bias on the observation of cosmic neutrinos, we conclude that the emission from an on-axis choked jet and CSM interaction is compatible with the detection of two track-like neutrino events observed by the IceCube Neutrino Observatory in coincidence with AT2018cow, and otherwise considered to be of atmospheric origin. While the neutrino emission from LFBOTs does not constitute the bulk of the diffuse background of neutrinos observed by IceCube, the detection prospects of nearby LFBOTs with IceCube and the upcoming IceCube-Gen2 are encouraging. Follow-up neutrino searches will be crucial for unraveling the mechanism powering this emergent transient class.

Keywords: Neutrino astronomy, Transient sources, Particle astrophysics
Exploring Refractory Organics in Extraterrestrial Particles. The origin of organic compounds detected in meteorites and comets, some of which could have served as precursors of life on Earth, remains an open question. The aim of the present study is to make one more step in revealing the nature and composition of organic materials of extraterrestrial particles by comparing infrared spectra of laboratory-made refractory organic residues to spectra of cometary particles returned by the Stardust mission, interplanetary dust particles, and meteorites. Our results reinforce the idea of a pathway for the formation of refractory organics through energetic and thermal processing of molecular ices in the solar nebula. There is also the possibility that some of the organic material had formed already in the parental molecular cloud before it entered the solar nebula. The majority of the IR "organic" bands of the studied extraterrestrial particles can be reproduced in the spectra of the laboratory organic residues. We confirm the detection of water, nitriles, hydrocarbons, and carbonates in extraterrestrial particles and link it to the formation location of the particles in the outer regions of the solar nebula. To clarify the genesis of the species, high-sensitivity observations in combination with laboratory measurements like those presented in this paper are needed. Thus, this study presents one more piece of the puzzle of the origin of water and organic compounds on Earth and motivation for future collaborative laboratory and observational projects.

Keywords: Meteorite composition, Laboratory astrophysics, Solar system, Astrochemistry, Comet origins