Sazuna/UAT_keywords huggingface dataset:
Constraining a Model of the Radio Sky below 6 MHz Using the Parker Solar Probe/FIELDS Instrument in Preparation for Upcoming Lunar-based Experiments. We present a Bayesian analysis of data from the FIELDS instrument on board the Parker Solar Probe (PSP) spacecraft with the aim of constraining low-frequency (≲6 MHz) sky in preparation for several upcoming lunar-based experiments. We utilize data recorded during PSP's coning roll maneuvers, in which the axis of the spacecraft is pointed 45° off of the Sun. The spacecraft then rotates about a line between the Sun and the spacecraft with a period of 24 minutes. We reduce the data into two formats: roll-averaged, in which the spectra are averaged over the roll, and phase-binned, in which the spectra are binned according to the phase of the roll. We construct a forward model of the FIELDS observations that includes numerical simulations of the antenna beam, an analytic emissivity function of the galaxy, and estimates of the absorption due to free electrons. Fitting 5 parameters, we find that the roll-averaged data can be fit well by this model, and we obtain posterior parameter constraints that are in general agreement with previous estimates. The model is not, however, able to fit the phase-binned data well, likely due to limitations such as the lack of nonsmooth emission structure at both small and large scales, enforced symmetry between the northern and southern galactic hemispheres, and large uncertainties in the free electron density. This suggests that significant improvement in the low-frequency sky model is needed in order to fully and accurately represent the sky at frequencies below 6 MHz.

Keywords: Cosmology, Bayesian statistics, Nested sampling, Astronomy data analysis, Interstellar absorption, Interstellar synchrotron emission, Radio astronomy
Revisiting the Parameter Space of Binary Neutron Star Merger Event GW170817. Since the gravitational wave event GW170817 and gamma-ray burst GW170817A, there have been numerous studies constraining the burst properties through analysis of the afterglow light curves. Most agree that the burst was viewed off-axis with a ratio of the observer angle to the jet angle (θ obs/θ  j ) between 4 and 6. We use a parameterized model and broadband synchrotron data up to ~800 days post-merger to constrain parameters of the burst. To reproduce the hydrodynamics of a gamma-ray burst outflow, we use a two-parameter "boosted fireball" model. The structure of a boosted fireball is determined by the specific internal energy, η 0, and the bulk Lorentz factor, γ  B ( ~ 1/θ  j ), with shapes varying smoothly from a quasi-spherical outflow for low values of γ  B  to a highly collimated jet for high values. We run simulations with γ  B  in the range 1-20 and η 0 in the range 2-15. To calculate light curves, we use a synchrotron radiation model characterized by F peak, ν  m , and ν  c , and calculate millions of spectra at different times and θ obs values using the boxfit radiation code. We can tabulate the spectral parameter values from our spectra and rapidly generate arbitrary light curves for comparison to data in MCMC analysis. We find that our model prefers a gamma-ray burst with jet energy E  j  ~ 1050 erg and with an observer angle of ${\theta }_{\mathrm{obs}}={0.65}_{-0.14}^{+0.13}$ radians and ratio to the jet opening angle of (θ obs/θ  j ) = ${5.4}_{-0.38}^{+0.53}$ .

Keywords: Neutron stars, Gamma-ray bursts, Jets, High energy astrophysics, Gravitational wave sources, Gravitational waves, Compact objects
Interplanetary Magnetic Field Effect on the Location of the Martian Bow Shock: MAVEN Observations. The Martian bow shock (BS) is generated with the mass-loading and magnetic pileup processes when the solar wind interacts with the Martian ionosphere. In this vein, the interplanetary magnetic field (IMF) frozen in the solar wind can affect the location of the Martian BS, which is less reported. Based on the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, we manually identify 10,283 BS crossings during a period of the gradually declining solar cycle phase (2014 October-2020 December) and investigate the effects of the intensity and orientation of the IMF on the Martian BS. In the Mars Solar Orbital coordinate system, our results show the following: (1) The Martian BS, including the subsolar and flank regions, linearly moves away from Mars when the IMF intensity increases, which confirms the theoretical and the MHD simulation results. (2) Under the radial IMF condition, we first demonstrate that the subsolar and flank regions of the Martian BS are situated closer to Mars compared to other IMF situations. This might be caused by the weaker magnetic pileup process and the "low-pressure magnetosheath" model under the radial IMF condition. (3) Moreover, the cross section of the Martian BS is elongated in the north-south direction when the Y component of the IMF is dominant, which is on account of the fast magnetosonic speed effect and verifies the elongation phenomenon of the terrestrial BS. The IMF intensity and orientation effects cannot be ignored and should be considered in future models of the Martian BS.

Keywords: Martian satellites, Mars, Planetary bow shocks, Interplanetary magnetic fields
Role of Magnetic Fields in the Formation of Direct Collapse Black Holes. Direct collapse black holes are the leading candidates for the origin of the first supermassive black holes. However, the role of magnetic fields during their formation is still unclear as none of the previous studies has been evolved long enough to assess their impact during the accretion phase. Here, we report the results from a suite of 3D cosmological magnetohydrodynamic (MHD) simulations which are evolved for 1.6 Myr comparable to the expected lifetime of supermassive stars (SMSs). Our findings suggest that magnetic fields are rapidly amplified by strong accretion shocks irrespective of the initial magnetic field strength and reach the saturation state. They stabilize the accretion disks and significantly reduce fragmentation by enhancing the Jeans mass in comparison with pure hydrodynamical runs. Although the initial clump masses are larger in MHD runs, the rapid coalescence of clumps in non-MHD cases due to the higher degree of fragmentation results in similar masses. Overall, the central clumps have masses of 105 M ⊙ and the mean mass accretion rates of ~0.1 M ⊙ yr-1 are similar in both MHD and non-MHD cases. The multiplicity of SMSs is significantly reduced in MHD simulations. Such strongly amplified magnetic fields are expected to launch jets and outflows which may be detected with upcoming radio telescopes.

Keywords: Early universe, Supermassive black holes, Population III stars, Primordial galaxies, Computational methods
Beam Pattern Evolution of Accreting X-Ray Pulsar 1A 0535+262 during Its 2020 Giant Outburst. We report on pulse profile decomposition analysis of bright transient X-ray pulsar 1A 0535+262 using broadband Insight-HXMT observations during a giant outburst of the source in 2020. We show that the observed pulse profile shape can be described in terms of a combination of two symmetric single-pole contributions for a wide range of energies and luminosities for a fixed geometry defining the basic geometry of the pulsar. This corresponds to a slightly distorted dipole magnetic field, i.e., one pole has to be offset by ~12° from the antipodal position of the other pole. We reconstruct the intrinsic beam patterns of the pulsar assuming that the geometry is recovered from the decomposition analysis, and we find evidence for a transition between "pencil" and "fan" beams in energy ranges above the cyclotron line energy, which can be interpreted as a transition from sub- to supercritical accretion regimes associated with the onset of an accretion column. At lower energies, however, the beam pattern appears to be more complex and contains a substantial "fan" beam and an additional "pencil" beam component at all luminosities. The latter is not related to the accretion rate and is stronger in the fading phase of the outburst. We finally discuss the results in the context of other observational and theoretical findings earlier reported for the source in the literature.

Keywords: X-ray binary stars
Formulating the r-mode Problem for Slowly Rotating Neutron Stars. We revisit the problem of inertial r-modes in stratified stars, drawing on a more precise description of the composition stratification in a mature neutron star. The results highlight issues with the traditional approach to the problem, leading us to rethink the computational strategy for the r-modes of nonbarotropic neutron stars. We outline two strategies for dealing with the problem. For moderate to slowly rotating neutron stars the only viable alternative may be to approach the problem numerically from the outset, while a meaningful slow-rotation calculation can be carried out for the fastest known spinning stars (which may be close to being driven unstable by the emission of gravitational waves). We demonstrate that the latter approach leads to a problem close, but not identical, to that for barotropic inertial modes. We also suggest that these reformulations of the problem likely resolve the long-standing problem of singular behavior associated with a corotation point in rotating relativistic neutron stars. This issue needs to be resolved in order to guide future gravitational-wave searches.

Keywords: Neutron stars, Asteroseismology, Astrophysical fluid dynamics
The Discovery of Blue-cored Dwarf Early-type Galaxies in Isolated Environments. The presence of blue-cored dwarf early-type galaxies (dE(bc)s) in high-density environments supports the scenario of the transformation of infalling late-type galaxies into quiescent dwarf early-type galaxies by environmental effects. While low-density environments lacking environmental processes could not be relevant to the formation of dE(bc)s, we discovered a large sample of rare dE(bc)s in isolated environments at z &lt; 0.01 using the NASA-Sloan Atlas catalog. Thirty-two isolated dE(bc)s were identified by visual inspection of the Sloan Digital Sky Survey images and g - r color profiles. We found that (1) isolated dE(bc)s exhibit similar structural parameters to dE(bc)s in the Virgo cluster; (2) based on the color-magnitude relation, color gradients, and optical emission lines of dE(bc)s, isolated dE(bc)s show more vigorous, centrally concentrated star formation (SF) compared to their counterparts in the Virgo cluster; (3) at a given stellar mass, isolated dE(bc)s tend to have a larger fraction of gas mass than their Virgo counterparts. We discuss a scenario of episodic SF sustained by gas accretion, suggested by Sánchez Almeida et al., in which the star-bursting blue compact dwarf galaxy (BCD)-quiescent BCD (QBCD) cycle can be repeated during the Hubble time. We suggest that, in this cadence, isolated dE(bc)s might be QBCDs at pre- or post-BCD stages. Our results imply that dE(bc)s comprise a mixture of objects with two types of origins, nature or nurture, depending on their environment.

Keywords: Blue compact dwarf galaxies, Galaxy environments, Dwarf galaxies, Dwarf elliptical galaxies, Star formation, Galaxy evolution, Field galaxies
Discovery of Two Polars from a Crossmatch of ZTF and the SRG/eFEDS X-Ray Catalog. Magnetic cataclysmic variables (CVs) are luminous Galactic X-ray sources, which have been difficult to find in purely optical surveys due to their lack of outburst behavior. The eROSITA telescope on board the Spektr-RG mission is conducting an all-sky X-ray survey and recently released the public eROSITA Final Equatorial Depth Survey (eFEDS) catalog. We crossmatched the eFEDS catalog with photometry from the Zwicky Transient Facility and discovered two new magnetic CVs. We obtained high-cadence optical photometry and phase-resolved spectroscopy for each magnetic CV candidate and found them both to be polars. Among the newly discovered magnetic CVs is eFEDS J085037.2+044359/ZTFJ0850+0443, an eclipsing polar with orbital period P orb = 1.72 hr and WD mass M WD = 0.81 ± 0.08M ⊙. We suggest that eFEDS J085037.2+044359/ZTFJ0850+0443 is a low magnetic field strength polar, with B WD ≲ 10 MG. We also discovered a non-eclipsing polar, eFEDS J092614.1+010558/ZTFJ0926+0105, with orbital period P orb = 1.47 hr and magnetic field strength B WD = 36-42 MG.

Keywords: X-ray astronomy, Cataclysmic variable stars, Binary stars, Time domain astronomy
A Candidate Relativistic Tidal Disruption Event at 340 Mpc. We present observations of an extreme radio flare, VT J024345.70-284040.08, hereafter VT J0243, from the nucleus of a galaxy with evidence for historic Seyfert activity at redshift z = 0.074. Between NRAO Very Large Array (VLA) Sky Survey observations in 1993 to VLA Sky Survey observations in 2018, VT J0243 rose from a ~ GHz radio luminosity of ν L  ν  ≲ 1038 erg s-1 to ν L  ν  ~ 1040 erg s-1, and still continues to brighten. The radio spectral energy distribution evolution is consistent with a nascent jet that has slowed over ~3000 days with an average 0.1 &lt;&lt;β&gt;&lt; 0.6. The jet is energetic (~1051-52 erg), and had a radius ~0.7 pc in 2021 December. X-ray observations suggest a persistent or evolving corona, possibly associated with an accretion disk, and IR and optical observations constrain any high-energy counterpart to be sub-Eddington. VT J0243 may be an example of a young, off-axis radio jet from a slowly evolving tidal disruption event. Other more mysterious triggers for the accretion enhancement and jet launching are possible. In either case, VT J0243 is a unique example of a nascent jet, highlighting the unknown connection between supermassive black holes, the properties of their accretion flows, and jet launching.

Keywords: High energy astrophysics, Tidal disruption, Relativistic jets, Transient sources, Active galactic nuclei, Radio transient sources
A Statistical Study of IRIS Observational Signatures of Nanoflares and Nonthermal Particles. Nanoflares are regarded as one of the major mechanisms of magnetic energy release and coronal heating in the solar outer atmosphere. We conduct a statistical study on the response of the chromosphere and transition region to nanoflares, as observed by the Interface Region Imaging Spectrograph (IRIS), by using an algorithm for the automatic detection of these events. The initial atmospheric response to these small heating events is observed, with IRIS, as transient brightening at the foot points of coronal loops heated to high temperatures (&gt;4 MK). For four active regions, observed over 143 hr, we detected 1082 footpoint brightenings under the IRIS slit, and for those we extracted physical parameters from the IRIS Mg II and Si IV spectra that are formed in the chromosphere and transition region, respectively. We investigate the distributions of the spectral parameters, and the relationships between the parameters, also comparing them with predictions from RADYN numerical simulations of nanoflare-heated loops. We find that these events, and the presence of nonthermal particles, tend to be more frequent in flare productive active regions, and where the hot 94 Å emission measured by the Atmospheric Imaging Assembly is higher. We find evidence for highly dynamic motions characterized by strong Si IV nonthermal velocities (not dependent on the heliocentric x-coordinate, i.e., on the angle between the magnetic field and the line of sight) and asymmetric Mg II spectra. These findings provide tight new constraints on the properties of nanoflares and nonthermal particles in active regions, and their effects on the lower atmosphere.

Keywords: Solar coronal heating, Solar active regions, Solar physics, Solar transition region, Solar chromosphere
Tomography of a Solar Plage with the Tenerife Inversion Code. We apply the Tenerife Inversion Code (TIC) to the plage spectropolarimetric observations obtained by the Chromospheric LAyer SpectroPolarimeter (CLASP2). These unprecedented data consist of full Stokes profiles in the spectral region around the Mg II h and k lines for a single slit position, with around two thirds of the 196″ slit crossing a plage region and the rest crossing an enhanced network. A previous analysis of these data had allowed us to infer the longitudinal component of the magnetic field by applying the weak-field approximation (WFA) to the circular polarization profiles, and to assign the inferred magnetic fields to different layers of the solar atmosphere based on the results of previous theoretical radiative transfer investigations. In this work, we apply the recently developed TIC to the same data. We obtain a stratified model atmosphere that fits the intensity and circular polarization profiles at each position along the spectrograph slit and we compare our results for the longitudinal component of the magnetic field with the previously obtained WFA results, highlighting the generally good agreement in spite of the fact that the WFA is known to produce an underestimation when applied to the outer lobes of the Mg II h and k circular polarization profiles. Finally, we use the inverted model atmospheres to give a rough estimation of the energy that could be carried by Alfvén waves propagating in the chromosphere in the plage and network regions, showing that it is sufficient to compensate for the estimated energy losses in the chromosphere of solar active regions.

Keywords: Solar chromosphere, Spectropolarimetry, Solar magnetic fields, Plages
Disentangling the AGN and Star formation Contributions to the Radio-X-Ray Emission of Radio-loud Quasars at 1 &lt; Z &lt; 2. We constrain the emission mechanisms responsible for the prodigious electromagnetic output generated by active galactic nuclei (AGNs) and their host galaxies with a novel state-of-the-art AGN radio-to-X-ray spectral energy distribution model fitting code (ARXSED). ARXSED combines multiple components to fit the spectral energy distributions (SEDs) of AGNs and their host galaxies. Emission components include radio structures such as lobes and jets, infrared emission from the AGN torus, visible-to-X-ray emission from the accretion disk, and radio-to-ultraviolet emission from the host galaxy. Applying ARXSED to the radio SEDs of 20 3CRR quasars at 1 &lt; z &lt; 2 verifies the need for more than a simple power law when compact radio structures are present. The nonthermal emission contributes 91%-57% of the observed-frame 1.25 mm to 850 μm flux, and this component must be accounted for when using these wavelengths to estimate star formation properties. We predict the presence of strong radio-linked X-ray emission in more than half the sample sources. ARXSED estimates median (and the associated first and third quartile ranges) BH mass of ${2.9}_{1.7}^{6.0}\times {10}^{9}\,{M}_{\odot }$ , logarithm of Eddington ratio of $-{1.0}_{-1.2}^{-0.6}$ , and spin of ${0.98}_{0.94}^{0.99}$ for our sample. The inferred AGN torus and accretion disk parameters agree with those estimated from spectroscopic analyses of similar samples in the literature. We present the median intrinsic SED of the luminous radio-loud quasars at 1 &lt; z ≲ 2; this SED represents a significant improvement in the way each component is modeled.

Keywords: AGN host galaxies, Quasars, Radio loud quasars, Radio galaxies, Active galactic nuclei, Spectral energy distribution
A Geometric Model to Interpret the γ-Ray Quasiperiodic Oscillation of PG 1553+113. We propose a jet helical motion model to explain the γ-ray quasiperiodic oscillation of PG 1553+113. In this model, we hypothesize that a relativistic jet with constant angular velocity rotates around the axis, causing the Doppler factor of the jet to vary over time, leading to periodic changes in flux. In addition, we consider that the parameters of the emission field vary slightly during the observation period and can be obtained by directly fitting their multiwavelength spectra. Then, we use the resulting emission field information and the model to reproduce the light curve. Our model successfully explains the 2.18 ± 0.08 yr γ quasiperiodic oscillation of PG 1553+113, which is consistent with previous studies. Most importantly, we notice an upward trend in the light curve, and we suggest that this upward trend is due to long-term variability with a timescale of ~42 yr.

Keywords: Non-thermal radiation sources, Active galaxies, BL Lacertae objects
Reconstructing the XUV Spectra of Active Sun-like Stars Using Solar Scaling Relations with Magnetic Flux. The Kepler space telescope and Transiting Exoplanet Survey Satellite unveiled that Sun-like stars frequently host exoplanets. These exoplanets are subject to fluxes of ionizing radiation in the form of X-ray and extreme-ultraviolet (EUV) radiation that may cause changes in their atmospheric dynamics and chemistry. While X-ray fluxes can be observed directly, EUV fluxes cannot be observed because of severe interstellar medium absorption. Here we present a new empirical method to estimate the whole stellar X-ray plus EUV (XUV) and far-UV (FUV) spectra as a function of total unsigned magnetic fluxes of stars. The response of the solar XUV and FUV spectrum (0.1-180 nm) to the solar total unsigned magnetic flux is investigated by using the long-term Sun-as-a-star data set over 10 yr, and the power-law relation is obtained for each wavelength with a spectral resolution of 0.1-1 nm. We applied the scaling relations to active young Sun-like stars (G dwarfs), EK Dra (G1.5V), π 1 Uma (G1.5V), and κ 1 Ceti (G5V) and found that the observed spectra (except for the unobservable longward EUV wavelength) are roughly consistent with the extension of the derived power-law relations with errors of an order of magnitude. This suggests that our model is a valuable method to derive the XUV/FUV fluxes of Sun-like stars, including the EUV band mostly absorbed at wavelengths longward of 36 nm. We also discuss differences between the solar extensions and stellar observations at wavelengths in the 2-30 nm band and conclude that simultaneous observations of magnetic and XUV/FUV fluxes are necessary for further validations.

Keywords: Solar active region magnetic fields, Starspots, Solar ultraviolet emission, Solar extreme ultraviolet emission, Stellar x-ray flares, Solar coronal heating, Extreme ultraviolet astronomy, Solar x-ray emission, Solar active regions, Magnetic variable stars, Stellar coronae, Magnetic fields
Bumblebee Black Holes in Light of Event Horizon Telescope Observations. We report the existence of novel static spherical black hole solutions in a vector-tensor gravitational theory called the bumblebee gravity model, which extends the Einstein-Maxwell theory by allowing the vector to nonminimally couple to the Ricci curvature tensor. A test of the solutions in the strong-field regime is performed for the first time using the recent observations of the supermassive black hole shadows in the galaxy M87 and the Milky Way from the Event Horizon Telescope Collaboration. The parameter space is found largely unexcluded and more experiments are needed to fully bind the theory.

Keywords: Black hole physics, Reissner-Nordström black holes, Scalar-tensor-vector gravity, Event horizons, Charged black holes