Sazuna/UAT_keywords huggingface dataset:
The Stochastic X-Ray Variability of the Accreting Millisecond Pulsar IGR J17062-6143. This work presents an investigation of the stochastic X-ray variability from the 164 Hz accreting millisecond pulsar IGR J17062-6143, based on regular observations collected with the Neutron Star Interior Composition Explorer between 2017 July and 2020 August. Over this period, the power-density spectrum showed a stable morphology, with broad ~25% rms band-limited noise below 16 Hz. Quasi-periodic oscillations (QPOs) were occasionally observed, with the most notable detections including a low-frequency QPO centered at 2.7 Hz and a sharp QPO centered at 115 Hz that may be a 2:3 resonance with the spin frequency. Further, the energy dependence of the band-limited noise is studied through a spectroscopic analysis of the complex covariance in two frequency intervals. It is found that the power-law continuum is the primary driver for the observed variability, although the thermal (blackbody) emission also appears to be intrinsically variable in area (5% rms) and temperature (1% rms). Notably, the 1 keV emission feature seen in all X-ray spectra of IGR J17062-6143 varies with the same amplitude as the power-law emission, but systematically lags behind that continuum emission. These results appear consistent with a scenario in which a time-variable Compton scattering corona is the primary source for the observed stochastic variability, with the variability observed in the emission feature and at the lowest photon energies being due to the disk reflection of the power-law continuum.

Keywords: Low-mass x-ray binary stars, Millisecond pulsars
Physically Motivated Fit to Mass Surface Density Profiles Observed in Galaxies. Polytropes have gained renewed interest because they account for several seemingly disconnected observational properties of galaxies. Here we study whether polytropes are also able to explain the stellar mass distribution within galaxies. We develop a code to fit surface density profiles using polytropes projected in the plane of the sky (propols). Sérsic profiles are known to be good proxies for the global shapes of galaxies and we find that, ignoring central cores, propols, and Sérsic profiles are indistinguishable within observational errors (within 5% over five orders of magnitude in surface density). The range of physically meaningful polytropes yields Sérsic indexes between 0.4 and 6. The code has been systematically applied to ~750 galaxies with carefully measured mass density profiles and including all morphological types and stellar masses ( $7\lt {\rm{log}}[{M}_{\star }/{{\rm{M}}}_{\odot }]\lt 12$ ). The propol fits are systematically better than Sérsic profiles when ${\rm{log}}({M}_{\star }/{{\rm{M}}}_{\odot })\lesssim 9$ and systematically worse when ${\rm{log}}({M}_{\star }/{{\rm{M}}}_{\odot })\gtrsim 10$ . Although with large scatter, the observed polytropic indexes increase with increasing mass and tend to cluster around m = 5. For the most massive galaxies, propols are very good at reproducing their central parts, but they do not handle well cores and outskirts overall. Polytropes are self-gravitating systems in thermal meta-equilibrium as defined by the Tsallis entropy. Thus, the above results are compatible with the principle of maximum Tsallis entropy dictating the internal structure in dwarf galaxies and in the central region of massive galaxies.

Keywords: Gravitational equilibrium, Galaxy dark matter halos, Milky Way formation, Galaxy properties, Galaxy structure, Galaxy physics, Galaxy stellar halos
Supernova-driven Mechanism of Cusp-core Transformation: an Appraisal. We present and test an effective model for N-body simulations that aims at mimicking the impact of supernova (SN) feedback on the dark matter (DM) distribution of isolated halos hosting dwarf galaxies. Although the model is physically decoupled from the cosmological history of both the DM halo and the dwarf galaxy, it allows us to study the impact of different macroscopic parameters such as galaxy concentration, feedback energy, and energy injection time in the process of SN-driven core formation in a physically clear way. Using our effective model in a suite of N-body simulations of an isolated halo with different SN feedback parameters, we find that whether or not a DM core forms is determined by the total amount of SN feedback energy that is transferred to the DM particles. At a fixed injected energy, transfer of energy to the DM is more efficient the faster the energy is injected and the more compact the galaxy is, leading to an increased size of the formed DM core as a result. Analyzing the orbital evolution of kinematic tracers, we demonstrate that a core forms through SN feedback only if the energy injection is impulsive relative to the dynamical timescale of particles in the inner halo. However, there is no fundamental link between the total amount of injected energy and the injection rate. Consequently, the presence of signatures of impulsive changes of the gravitational potential is not a sufficient condition for dwarf-sized halos to have cored density profiles.

Keywords: Dwarf galaxies, Stellar dynamics, Stellar feedback
Ion Cloud Expansion after Hyper-velocity Dust Impacts Detected by the Magnetospheric Multiscale Mission Electric Probes in the Dipole Configuration. Dust impact detection by electric field instruments is a well-established technique. On the other hand, not all aspects of signal generation by dust impacts are completely understood. We present a study of events related to dust impacts on the spacecraft body detected by electric field probes operating simultaneously in the monopole (probe-to-spacecraft potential measurement) and dipole (probe-to-probe potential measurement) configurations by the Earth-orbiting Magnetospheric Multiscale mission spacecraft. This unique measurement allows us to investigate connections between monopole and dipole data. Our analysis shows that the signal detected by the electric field instrument in a dipole configuration is generated by an ion cloud expanding along the electric probes. In this case, expanding ions affect not only the potential of the spacecraft body but also one or more electric probes at the end of antenna booms. Electric probes located far from the spacecraft body can be influenced by an ion cloud only when the spacecraft is located in tenuous ambient plasma inside of the Earth's magnetosphere. Derived velocities of the expanding ions on the order of tens of kilometers per second are in the range of values measured experimentally in the laboratory.

Keywords: Interstellar dust, Very small grains, Plasma clouds, Meteoroid dust clouds, Interplanetary dust
Extragalactic Magnetism with SOFIA (Legacy Program). I. The Magnetic Field in the Multiphase Interstellar Medium of M51. The recent availability of high-resolution far-infrared (FIR) polarization observations of galaxies using HAWC+/SOFIA has facilitated studies of extragalactic magnetic fields in the cold and dense molecular disks. We investigate whether any significant structural differences are detectable in the kiloparsec-scale magnetic field of the grand design face-on spiral galaxy M51 when traced within the diffuse (radio) and the dense and cold (FIR) interstellar medium (ISM). Our analysis reveals a complex scenario where radio and FIR polarization observations do not necessarily trace the same magnetic field structure. We find that the magnetic field in the arms is wrapped tighter at 154 μm than at 3 and 6 cm; statistically significant lower values for the magnetic pitch angle are measured at FIR in the outskirts (R ≥ 7 kpc) of the galaxy. This difference is not detected in the interarm region. We find strong correlations of the polarization fraction and total intensity at FIR and radio with the gas column density and 12CO(1-0) velocity dispersion. We conclude that the arms show a relative increase of small-scale turbulent B-fields at regions with increasing column density and dispersion velocities of the molecular gas. No correlations are found with H I neutral gas. The star formation rate shows a clear correlation with the radio polarized intensity, which is not found in FIR, pointing to a small-scale dynamo-driven B-field amplification scenario. This work shows that multiwavelength polarization observations are key to disentangling the interlocked relation between star formation, magnetic fields, and gas kinematics in the multiphase ISM. * The SOFIA Legacy Group for Magnetic Fields in Galaxies software repository is available at https://github.com/galmagfields/hawc via the official project website, http://galmagfields.com/, and Zenodo/GitHub, https://doi.org/10.5281/zenodo.5116134.

Keywords: Radio astronomy, Spiral galaxies, Molecular clouds, Polarimetry, Far infrared astronomy, Star formation, Magnetic fields, Extragalactic magnetic fields
AGN-Host Interaction in IC 5063. I. Large-scale X-Ray Morphology and Spectral Analysis. We report the analysis of the deep (~270 ks) X-ray Chandra data of one of the most radio-loud, Seyfert 2 galaxies in the nearby universe (z = 0.01135), IC 5063. The alignment of the radio structure with the galactic disk and ionized bicone, enables us to study the effects of both radio jet and nuclear irradiation on the interstellar medium (ISM). The nuclear and bicone spectra suggest a low photoionization phase mixed with a more ionized or thermal gas component, while the cross-cone spectrum is dominated by shocked and collisionally ionized gas emission. The clumpy morphology of the soft (&lt;3 keV) X-ray emission along the jet trails, and the large (≃2.4 kpc) filamentary structure perpendicular to the radio jets at softer energies (&lt;1.5 keV), suggest a large contribution of the jet-ISM interaction to the circumnuclear gas emission. The hard X-ray continuum (&gt;3 keV) and the Fe Kα 6.4 keV emission are both extended to kpc size along the bicone direction, suggesting an interaction of nuclear photons with dense clouds in the galaxy disk, as observed in other Compton Thick (CT) active nuclei. The northwest cone spectrum also exhibits an Fe XXV emission line, which appears spatially extended and spatially correlated with the most intense radio hot-spot, suggesting jet-ISM interaction.

Keywords: X-ray active galactic nuclei, Active galactic nuclei
Local Analogs to High-redshift Galaxies. I. Characterization of Dust Emission and Star Formation History. Star-forming dwarf galaxies have properties similar to those expected in high-redshift galaxies. Hence, these local galaxies may provide insights into the evolution of the first galaxies and the physical processes at work. We present a sample of 11 potential local analogs to high-z (LAHz) galaxies. The sample consists of blue compact dwarf galaxies, selected to have spectral energy distributions that fit galaxies at 1.5 &lt; z &lt; 4. We use SOFIA-HAWC+ observations combined with optical and near-infrared data to characterize the dust properties, star formation rate (SFR), and star formation histories (SFHs) of the sample of LAHz galaxies. We employ Bayesian analysis to characterize the dust using two-component blackbody models. Using the LIGHTNING package, we fit the spectral energy distribution of the LAHz galaxies over the far-UV-far-infrared wavelength range and derive the SFH in five time steps up to a look-back time of 13.3 Gyr. Of the 11 LAHz candidates, six galaxies have SFH consistent with no star formation activity at look-back times beyond 1 Gyr. The remaining galaxies show residual levels of star formation at ages ≳1 Gyr, making them less suitable as local analogs. The six young galaxies stand out in our sample by having the lowest gas-phase metallicities. They are characterized by warmer dust, having the highest specific SFR and the highest gas mass fractions. The young age of these six galaxies suggests that merging is less important as a driver of the star formation activity. The six LAHz candidates are promising candidates for studies of the gasdynamics role in driving star formation.

Keywords: Interstellar medium, Blue compact dwarf galaxies, Star formation, Dust continuum emission
The Observed Mass Distribution of Galactic Black Hole LMXBs Is Biased against Massive Black Holes. The discovery of gravitational-wave radiation from merging black holes (BHs) also uncovered BHs with masses in the range of ≈20-160 M⊙. In contrast, the most massive Galactic stellar-mass BH currently known has a mass of ≈21 M⊙. While low-mass X-ray binaries (LMXBs) will never independently evolve into a binary BH system, and binary evolution effects can play an important role in explaining the different BH masses found through studies of X-ray binaries and gravitational-wave events, (electromagnetic) selection effects may also play a role in this discrepancy. Assuming BH LMXBs originate in the Galactic plane, we show that the spatial distributions of the current samples of confirmed and candidate BH LMXBs are both biased to sources that lie at a large distance from the plane. Specifically, most of the confirmed and candidate BH LMXBs are found at a Galactic height larger than three times the scale height for massive star formation. In addition, the confirmed BH LMXBs are found at larger distances to the Galactic center than the candidate BH LMXBs. Interstellar absorption makes candidate BH LMXBs in the plane and bulge too faint for a dynamical mass measurement using current instrumentation. Given the observed and theoretical evidence for BH natal and/or Blaauw kicks, their relation with BH mass and binary orbital period, and the relation between outburst recurrence time and BH mass, the observational selection effects imply that the current sample of confirmed BH LMXBs is biased against the most massive BHs.

Keywords: Stellar mass black holes
The Formation of Astromolecule Ethynyl Cyclopropenylidene (c-C<SUB>3</SUB>HCCH) from C<SUB>2</SUB>H and c-C<SUB>3</SUB>H<SUB>2</SUB>. Reaction schema for the formation of the recently detected ethynyl cyclopropenylidene (c-C3HCCH) molecule are currently lacking in the literature. The present quantum chemical study shows that the reaction of the abundant ethynyl (C2H) and cyclopropenylidene (c-C3H2) molecules proceeds barrierlessly through the formation of a 1 2A c-HC3HCCH intermediate at 71.2 kcal mol-1 below the reactants. The uphill exit channel climb for the C-H bond dissociation will compete with a transition state 45.9 kcal mol-1 below the reactants to form another, lower-energy intermediate ( $1{\ }^{2}A^{\prime} $ c-C3H2CCH) 84.3 kcal mol-1 below the reactants. The direct dissociation from the first intermediate is likely the dominant pathway under astrophysical conditions because the hydrogen leaving group can dissipate the energy kinetically. In either case of direct dissociation or crossing the transition state, the hydrogen atom dissociation to the final products lying 27.2 kcal mol-1 below the starting materials requires a crossover of electronic states with the singly occupied molecular orbital moving from the π cloud of the cyclopropenyl group onto the leaving H atom. As a result, this C2H + c-C3H2 → c-C3HCCH + H reaction should be as fast as theorized in astrophysical media such as TMC-1, where the titular molecule has now been observed.

Keywords: Polycyclic aromatic hydrocarbons, Molecular clouds, Astrochemistry
Eclipsing Binaries in the Open Cluster Ruprecht 147. IV: The Active Triple System EPIC 219511354. We report follow-up spectroscopic observations of the 1.62 day, K-type, detached, active, near-circular, double-lined eclipsing binary EPIC 219511354 in the open cluster Ruprecht 147, identified previously on the basis of photometric observations from the Kepler/K2 mission. This is the fourth eclipsing system analyzed in this cluster. A combined analysis of the light curve and radial velocities yields accurate masses of MAa = 0.912 ± 0.013 M⊙ and MAb = 0.822 ± 0.010 M⊙ for the primary (star Aa) and secondary (Ab), along with radii of RAa = 0.920 ±0.016 R⊙ and RAb = 0.851 ± 0.016 R⊙, and effective temperatures of 5035 ± 150 and 4690 ± 130 K, respectively. Comparison with current models of stellar evolution for the known age and metallicity of the cluster reveals that both radii are larger (by 10%-14%) and both temperatures cooler (by ~6%) than theoretically predicted, as is often seen in M dwarfs. This is likely caused by the significant stellar activity in the system, manifested here by 6% peak-to-peak out-of-eclipse variability, a filled-in Hα line, and its detection as an X-ray source. We also find EPIC 219511354 to be a hierarchical triple system, with a low-mass tertiary in an eccentric 220 day orbit.

Keywords: Stellar photometry, Binary stars, Stellar evolutionary models, Radial velocity, Stellar activity, Eclipsing binary stars, Open star clusters
Estimating the Contribution of Foreground Halos to the FRB 180924 Dispersion Measure. Fast radio burst (FRB) dispersion measures (DMs) record the presence of ionized baryons that are otherwise invisible to other techniques enabling resolution of the matter distribution in the cosmic web. In this work, we aim to estimate the contribution to FRB 180924 DM from foreground galactic halos. Localized by ASKAP to a massive galaxy, this sightline is notable for an estimated cosmic web contribution to the DM (DMcosmic =220 pc cm-3), which is less than the average value at the host redshift (z = 0.3216) estimated from the Macquart relation (280 pc cm-3). In the favored models of the cosmic web, this suggests few intersections with foreground halos at small impact parameters (≲100 kpc). To test this hypothesis, we carried out spectroscopic observations of the field galaxies within ~1' of the sightline with VLT/MUSE and Keck/LRIS. Furthermore, we developed a probabilistic methodology that leverages photometric redshifts derived from wide-field DES and WISE imaging. We conclude that there is no galactic halo that closely intersects the sightline and also that the net DM contribution from halos DMhalos &lt; 45 pc cm-3 (95% c.l.). This value is lower than the DMhalos estimated from an "average" sightline (121 pc cm-3) using the Planck ΛCDM model and the Aemulus halo mass function and reasonably explains its low DMcosmic value. We conclude that FRB 180924 represents the predicted majority of sightlines in the universe with no proximate foreground galactic halos. Our framework lays the foundation for a comprehensive analysis of FRB fields in the near future.

Keywords: Cosmology, Galaxy dark matter halos, Quasar absorption line spectroscopy, Extragalactic astronomy, Radio transient sources
Ion Acceleration and the Development of a Power-law Energy Spectrum in Magnetic Reconnection. How charged particles are accelerated efficiently and form a power-law energy spectrum in magnetic reconnection is a problem that is not well understood. In a previous paper, it was shown that the electron Kelvin-Helmholtz instability (EKHI) in force-free magnetic reconnection generates fast-expanding vortices that can accelerate electrons in a few tens of ion gyroperiods (less than 1 ms in the solar corona) to form a power-law energy distribution. In this paper, we present a particle-in-cell (PIC) simulation study of ion acceleration in force-free magnetic reconnection in the presence of the EKHI-induced turbulence. We find that ions are not significantly accelerated by the EKHI-induced stochastic electric field until the magnetic vortices expand to sizes comparable to the ion gyroradius. The Alfvén waves generated by the EKHI couple with the magnetic vortices, leading to resonance between the ions inside the magnetic vortices and Alfvén waves and enhanced ion heating. The induced Alfvén wave resonance results in a broken power-law energy spectrum with a breakpoint at $\sim {m}_{i}{v}_{A}^{2}$ , where vA is the Alfvén velocity. We show that the process that forms the nonthermal tail is a second-order Fermi mechanism and the mean spectral index is α = (1 + 4a2D/R)/2, where D is the spatial scale of the inductive electric field, R is that of vortices, and a = Bg/B0, with ratio of guide field Bg and asymptotic B0.

Keywords: Solar energetic particles, Solar radio flares, Spectral energy distribution, Solar magnetic reconnection
Modeling Radio Recombination in MWC 349A. I. Saturation Properties. Strong nonlocal thermodynamic equilibrium recombination line emission from the envelope of MWC 349A has been studied observationally and theoretically and has been used to derive information about the physical and kinematic properties of the circumstellar environment around this object. In this paper, we construct a detailed model of radiative transfer of the commonly observed maser lines H26α and H30α in MWC 349A, specifically taking into account the effect of maser saturation. The envelope is modeled as a combination of an ionized Keplerian rotating disk and a disk wind expanding at a velocity of 60 km s-1. Our modeling results show that millimeter-line H26α is significantly affected by the saturation effect. The line intensity is predicted to be greatly reduced in comparison with previous models which ignore the saturation effect. The H30α maser is predicted to be unsaturated. Our model shows that the predicted intensity and line shape are in agreement with observations. The predicted position-velocity diagrams are also consistent with observations and the interpretation that the H26α maser appears at smaller radii in comparison to the H30α maser. We also emphasize that the wind component is important in shaping the line profiles of the recombination masers.

Keywords: Astrophysical masers
The Nonrelaxation of Magnetic Field Lines in Solar Wind Magnetic Reconnection Exhausts. We present a case study using data from multiple spacecraft and statistics from the ACE spacecraft to investigate the relaxation of reconnected magnetic field lines in solar wind magnetic reconnection exhausts, which constitute one of the two outflow regions resulting from magnetic reconnection, and which are often characterized by a plasma jet, magnetic strength depletion, and density and temperature enhancements. The normal magnetic fractions (∣Bn/B∣) of the reconnection exhausts are used to indicate the degrees of relaxation of the magnetic field lines. 97 out of 98 reconnection exhausts have a relatively small ∣Bn/B∣ (&lt;0.3), while only one exhaust associated with a relatively small interplanetary coronal mass ejection has a large ∣Bn/B∣ of 0.85. This result demonstrates the nonrelaxed nature of reconnected magnetic field lines in solar wind, due to the open boundary condition. As a consequence, the magnetic tension of such nonrelaxed magnetic field lines can accelerate the local plasma to produce the observed jet within the reconnection exhaust. Our results support the understanding that most solar wind reconnection exhausts are probably initiated near the Sun, where the plasma beta is low, and that they are not ongoing when they are observed at 1 au, because of the solar wind expansion from near the Sun to 1 au.

Keywords: Solar wind, Interplanetary magnetic fields, Solar magnetic reconnection