Sazuna/UAT_keywords huggingface dataset:
Detection of a Radio Bubble around the Ultraluminous X-Ray Source Holmberg IX X-1. We present C- and X-band radio observations of the famous utraluminous X-ray source (ULX) Holmberg IX X-1, previously discovered to be associated with an optical emission line nebula several hundred parsecs in extent. Our recent infrared study of the ULX suggested that a jet could be responsible for the infrared excess detected at the ULX position. The new radio observations, performed using the Karl G. Jansky Very Large Array (VLA) in B-configuration, reveal the presence of a radio counterpart to the nebula with a spectral slope of -0.56 similar to other ULXs. Importantly, we find no evidence for an unresolved radio source associated with the ULX itself, and we set an upper limit on any 5 GHz radio core emission of 6.6 μJy (4.1 × 1032 erg s-1). This is 20 times fainter than what we expect if the bubble is energized by a jet. If a jet exists its core component is unlikely to be responsible for the infrared excess unless it is variable. Strong winds which are expected in super-Eddington sources could also play an important role in inflating the radio bubble. We discuss possible interpretations of the radio/optical bubble and we prefer the jet+winds-blown bubble scenario similar to the microquasar SS 433.

Keywords: X-ray binary stars, Radio jets, Black holes, Supernova remnants, Emission nebulae
Hot Plasma Effects on the Pitch-angle Scattering Rates of Radiation Belt Electrons Due to Plasmaspheric Hiss. Plasmaspheric hiss is known to be a major contributor to the dynamic losses of Earth's radiation belt electrons. While previous computation attempts of hiss-driven electron losses are limited to the cold plasma approximation, in this study we find that hot plasma effects will modify the hiss dispersion relation and result in changes in the electron bounce-averaged electron pitch angle diffusion coefficients. Cold plasma approximation tends to overestimate the diffusion coefficients of ≲100 keV electrons by orders of magnitude, while the scattering efficiency of higher energy electrons is not greatly affected. As the L-shell decreases or the parameter $\alpha * \,=\,{{\rm{\Omega }}}_{e}^{2}/{\omega }_{\mathrm{pe}}^{2}$ decreases (where ${{\rm{\Omega }}}_{e}$ is the electron gyrofrequency and ${\omega }_{\mathrm{pe}}$ is the plasma frequency), the decrease of diffusion coefficients of low energy electrons caused by hot plasma effects become more pronounced. It is also shown that both the increase of hot electron abundance and temperature anisotropy can weaken the scattering efficiency of ≲100 keV electrons at almost all pitch angles, while the diffusion coefficients of higher energy electrons decrease at large pitch angles. Our study confirms the importance of including hot plasma effects in evaluations of hiss-driven scattering loss of radiation belt electrons.

Keywords: Van Allen radiation belts, Planetary magnetospheres, Space plasmas
Solar Flare Prediction Using Magnetic Field Diagnostics above the Photosphere. In this article, we present the application of the weighted horizontal gradient of magnetic field (WGM) flare prediction method to three-dimensional (3D) extrapolated magnetic configurations of 13 flaring solar active regions (ARs). The main aim is to identify an optimal height range, if any, in the interface region between the photosphere and lower corona, where the flare onset time prediction capability of WGM is best exploited. The optimal height is where flare prediction, by means of the WGM method, is achieved earlier than at the photospheric level. 3D magnetic structures, based on potential and nonlinear force-free field extrapolations, are constructed to study a vertical range from the photosphere up to the low corona with a 45 km step size. The WGM method is applied as a function of height to all 13 flaring AR cases that are subject to certain selection criteria. We found that applying the WGM method between 1000 and 1800 km above the solar surface would improve the prediction of the flare onset time by around 2-8 hr. Certain caveats and an outlook for future work along these lines are also discussed.

Keywords: Solar active region magnetic fields, Solar flares, Solar photosphere, Space weather, The Sun, Sunspots, Solar active regions, Solar corona, Solar activity, Solar chromosphere, Solar magnetic bright points, Delta sunspots
Spectral Characteristics and Formation Height of Off-limb Flare Ribbons. Flare ribbons are bright manifestations of flare energy dissipation in the lower solar atmosphere. For the first time, we report on high-resolution imaging spectroscopy observations of flare ribbons situated off limb in the Hβ and Ca II 8542 Å lines and make a detailed comparison with radiative hydrodynamic simulations. Observations of the X8.2 class solar flare SOL 2017-09-10T16:06 UT obtained with the Swedish Solar Telescope reveal bright horizontal emission layers in Hβ line-wing images located near the footpoints of the flare loops. The apparent separation between the ribbon observed in the Hβ wing and the nominal photospheric limb is about 300-500 km. The Ca II 8542 Å line-wing images show much fainter ribbon emissions located right on the edge of the limb, without clear separation from the limb. RADYN models are used to investigate synthetic spectral line profiles for the flaring atmosphere, and good agreement is found with the observations. The simulations show that, toward the limb, where the line of sight is substantially oblique with respect to the vertical direction, the flaring atmosphere model reproduces the high contrast of the off-limb Hβ ribbons and their significant elevation above the photosphere. The ribbons in the Ca II 8542 Å line-wing images are located deeper in the lower solar atmosphere with a lower contrast. A comparison of the height deposition of electron beam energy and the intensity contribution function shows that the Hβ line-wing intensities can be a useful tracer of flare energy deposition in the lower solar atmosphere.

Keywords: High resolution spectroscopy, Solar flares, Solar flare spectra, Optical flares, Spectroscopy, Radiative transfer simulations, Solar chromosphere
Wolf-Rayet Galaxies in SDSS-IV MaNGA. I. Catalog Construction and Sample Properties. Wolf-Rayet (WR) galaxies are a rare galaxy type that hosts living high-mass stars during the WR phase (I.e., WR stars) and can thus provide constraints on the stellar initial mass function, massive star formation, stellar evolution models, etc. Spatially resolved spectroscopy should in principle identify WR galaxies more efficiently than single-fiber surveys of galactic centers, as WR stars should be more preferentially found in disks. Using integral field unit data from the ongoing SDSS-IV MaNGA survey, we have performed a thorough search for WR galaxies. We first identify H II regions in each datacube and carry out full spectral fitting to the stacked spectra. We then visually inspect the residual spectrum of each H II region and identify significant WR "blue bumps" at 4600-4750 Å. The WR catalog includes 267 WR regions of ∼500 pc (radius) sizes, distributed in 90 galaxies from MaNGA Product Launch-7. We find that WR regions are exclusively found in galaxies with the bluest colors and highest star formation rates. Most WR galaxies have late-type morphologies and show relatively large asymmetry in their images, implying WR regions exist more in interacting galaxies. We estimate the stellar mass function of WR galaxies and the mass-dependent detection rate (typically ∼2%). This rate is about 40 times higher than that in catalogs from SDSS single-fiber surveys and half that of the CALIFA-based catalog. The difference in detection rates can be explained mainly by three factors: spatial coverage, spectral signal-to-noise ratio, and redshift ranges of parent samples. We tabulate WR galaxy properties for future studies.

Keywords: Starburst galaxies, Star forming regions, Emission line galaxies, Galaxy mass distribution, Star formation, Galaxy evolution, Wolf-Rayet stars, Redshift surveys, Galaxies
The BAT AGN Spectroscopic Survey. XVIII. Searching for Supermassive Black Hole Binaries in X-Rays. Theory predicts that a supermassive black hole binary (SMBHB) could be observed as a luminous active galactic nucleus (AGN) that periodically varies on the order of its orbital timescale. In X-rays, periodic variations could be caused by mechanisms including relativistic Doppler boosting and shocks. Here we present the first systematic search for periodic AGNs using 941 hard X-ray light curves (14-195 keV) from the first 105 months of the Swift Burst Alert Telescope (BAT) survey (2004-2013). We do not find evidence for periodic AGNs in Swift-BAT, including the previously reported SMBHB candidate MCG+11-11-032. We find that the null detection is consistent with the combination of the upper-limit binary population in AGNs in our adopted model, their expected periodic variability amplitudes, and the BAT survey characteristics. We have also investigated the detectability of SMBHBs against normal AGN X-ray variability in the context of the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) survey. Under our assumptions of a binary population and the periodic signals they produce, which have long periods of hundreds of days, up to 13% true periodic binaries can be robustly distinguished from normal variable AGNs with the ideal uniform sampling. However, we demonstrate that realistic eROSITA sampling is likely to be insensitive to long-period binaries because longer observing gaps reduce their detectability. In contrast, large observing gaps do not diminish the prospect of detecting binaries of short, few-day periods, as 19% can be successfully recovered, the vast majority of which can be identified by the first half of the survey.

Keywords: Surveys, Active galaxies, X-ray sources
Alfvén-wave-driven Magnetic Rotator Winds from Low-mass Stars. I. Rotation Dependences of Magnetic Braking and Mass-loss Rate. Observations of stellar rotation show that low-mass stars lose angular momentum during the main sequence. We simulate the winds of sunlike stars with a range of rotation rates, covering the fast and slow magneto-rotator regimes, including the transition between the two. We generalize an Alfvén-wave-driven solar wind model that builds on previous works by including the magneto-centrifugal force explicitly. In this model, the surface-averaged open magnetic flux is assumed to scale as ${B}_{* }{f}_{* }^{\mathrm{open}}\propto {\mathrm{Ro}}^{-1.2}$ , where ${f}_{* }^{\mathrm{open}}$ and Ro are the surface open-flux filling factor and Rossby number, respectively. We find that, (1) the angular-momentum loss rate (torque) of the wind is described as ${\tau }_{{\rm{w}}}\approx 2.59\times {10}^{30}\ \mathrm{erg}\ {\left({{\rm{\Omega }}}_{* }/{{\rm{\Omega }}}_{\odot }\right)}^{2.82}$ , yielding a spin-down law ${{\rm{\Omega }}}_{* }\propto {t}^{-0.55}$ . (2) The mass-loss rate saturates at ${\dot{M}}_{{\rm{w}}}\sim 3.4\times {10}^{-14}{M}_{\odot }\ {\mathrm{yr}}^{-1}$ , due to the strong reflection and dissipation of Alfvén waves in the chromosphere. This indicates that the chromosphere has a strong impact in connecting the stellar surface and stellar wind. Meanwhile, the wind ram pressure scales as ${P}_{{\rm{w}}}\propto {{\rm{\Omega }}}_{* }^{0.57}$ , which is able to explain the lower envelope of the observed stellar winds by Wood et al. (3) The location of the Alfvén radius is shown to scale in a way that is consistent with one-dimensional analytic theory. Additionally, the precise scaling of the Alfvén radius matches previous works, which used thermally driven winds. Our results suggest that the Alfvén-wave-driven magnetic rotator wind plays a dominant role in the stellar spin-down during the main sequence.

Keywords: Magnetohydrodynamical simulations, Solar wind, Stellar evolution, Stellar mass loss, Stellar winds, Stellar rotation, Solar evolution
X-Ray Emission Evolution of the Galactic Ultraluminous X-Ray Pulsar Swift J0243.6+6124 during the 2017-2018 Outburst Observed by the MAXI GSC. This paper reports on the X-ray emission evolution of the ultraluminous Galactic X-ray pulsar Swift J0243.6+6124 during the giant outburst from 2017 October to 2018 January as observed by the MAXI GSC all-sky survey. The 2-30 keV light curve and the energy spectra confirm the source luminosity LX assuming an isotropic emission reached 2.5 × 1039 erg s-1, 10 times higher than the Eddington limit for a 1.4 M⊙ neutron star. When the source was luminous with LX ≳ 0. 9 × 1038 erg s-1, it generally exhibited a negative correlation on a hardness-intensity diagram. However, two hardness ratios, a soft color (=4-10 keV/2-4 keV) and a hard color (=10-20 keV/4-10 keV), showed somewhat different behavior across a characteristic luminosity of Lc ≃ 5 × 1038 erg s-1. The soft color changed more than the hard color when LX &lt; Lc, whereas the opposite was observed above Lc. The spectral change above Lc was represented by a broad enhanced feature at ∼6 keV on top of the canonical cutoff power-law continuum. The pulse profiles, derived daily, made the transition from a single-peak to a double-peak as the source brightened across Lc. These spectral and pulse-shape properties can be interpreted by a scenario in which the accretion columns on the neutron-star surface, producing the Comptonized X-ray emission, gradually became taller as LX increases. The broad 6 keV enhancement could be a result of cyclotron-resonance absorption at ∼10 keV, corresponding to a surface magnetic field Bs ≃ 1.1 × 1012 G. The spin-frequency derivatives calculated with the Fermi GBM data showed a smooth positive correlation with LX up to the outburst peak, and its linear coefficient is comparable to those of typical Be binary pulsars whose Bs are (1-8) × 1012 G. These results suggest that the Bs of Swift J0243.6+6124 is a few times 1012 G.

Keywords: Neutron stars, High mass x-ray binary stars, Accretion, Binary pulsars
Figuring Out Gas &amp; Galaxies in Enzo (FOGGIE). II. Emission from the z = 3 Circumgalactic Medium. Observing the circumgalactic medium (CGM) in emission provides 3D maps of the spatial and kinematic extent of the gas that fuels galaxies and receives their feedback. We present mock emission-line maps of highly resolved CGM gas from the Figuring Out Gas &amp; Galaxies in Enzo (FOGGIE) project and link these maps back to physical and spatial properties of the gas. In particular, we examine the ionization source leading to most O VI emission and how resolution affects the physical properties of the gas generating the emission. Finally, when increasing the spatial resolution alone, the total luminosity of the line emission increases by an order of magnitude for some lines considered. Current integral field unit instruments like Keck Cosmic Web Imager and Multi Unit Spectroscopic Explorer should be able to detect the brightest knots and filaments of such emission, and use this to infer the bulk kinematics of the CGM gas with respect to the galaxy. We conclude that the spatial resolution of simulated CGM gas can significantly influence the distribution of gas temperatures, densities, and metallicities that contribute to a given observable region. Greater spatial resolution than has been typically included in cosmological simulations to date is needed to properly interpret observations in terms of the underlying gas structure driving emission.

Keywords: Extragalactic astronomy, Hydrodynamical simulations, Circumgalactic medium
Global Hydromagnetic Simulations of Protoplanetary Disks with Stellar Irradiation and Simplified Thermochemistry. Outflows driven by large-scale magnetic fields likely play an important role in the evolution and dispersal of protoplanetary disks and in setting the conditions for planet formation. We extend our 2D-axisymmetric nonideal MHD model of these outflows by incorporating radiative transfer and simplified thermochemistry, with the dual aims of exploring how heating influences wind launching and illustrating how such models can be tested through observations of diagnostic spectral lines. Our model disks launch magnetocentrifugal outflows primarily through magnetic tension forces, so the mass-loss rate increases only moderately when thermochemical effects are switched on. For typical field strengths, thermochemical and irradiation heating are more important than magnetic dissipation. We furthermore find that the entrained vertical magnetic flux diffuses out of the disk on secular timescales as a result of nonideal MHD. Through postprocessing line radiative transfer, we demonstrate that spectral line intensities and moment-1 maps of atomic oxygen, the HCN molecule, and other species show potentially observable differences between a model with a magnetically driven outflow and one with a weaker, photoevaporative outflow. In particular, the line shapes and velocity asymmetries in the moment-1 maps could enable the identification of outflows emanating from the disk surface.

Keywords: Magnetohydrodynamics, Astrochemistry, Protoplanetary disks, Stellar accretion disks, Radiative transfer simulations
Multiple Outflows in the High-mass Cluster-forming Region G25.82-0.17. We present results of continuum and spectral line observations with Atacama Large Millimeter/submillimeter Array (ALMA) and 22 GHz water (H2O) maser observations using the KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry) array (KaVA) toward a high-mass star-forming region, G25.82-0.17. Multiple 1.3 mm continuum sources are revealed, indicating the presence of young stellar objects (YSOs) at different evolutionary stages, namely an ultracompact H II region, G25.82-E, a high-mass young stellar object (HM-YSO), G25.82-W1, and starless cores, G25.82-W2 and G25.82-W3. Two SiO outflows, at N-S and SE-NW orientations, are identified. The CH3OH 8-1-70 E line, known to be a Class I CH3OH maser at 229 GHz, is also detected, showing a mixture of thermal and maser emission. Moreover, the H2O masers are distributed in a region ∼0"25 shifted from G25.82-W1. The CH3OH 224-215 E line shows a compact ringlike structure at the position of G25.82-W1 with a velocity gradient, indicating a rotating disk or envelope. Assuming Keplerian rotation, the dynamical mass of G25.82-W1 is estimated to be &gt;25 M⊙ and the total mass of 20-84 M⊙ is derived from the 1.3 mm continuum emission. The driving source of the N-S SiO outflow is G25.82-W1 while that of the SE-NW SiO outflow is uncertain. Detection of multiple high-mass starless/protostellar cores and candidates without low-mass cores implies that HM-YSOs could form in individual high-mass cores as predicted by the turbulent core accretion model. If this is the case, the high-mass star formation process in G25.82 would be consistent with a scaled-up version of low-mass star formation.

Keywords: Star forming regions, Stellar jets, Young massive clusters, Very long baseline interferometry, Young stellar objects, Star formation, Astrophysical masers, Circumstellar disks, Protostars, Radio interferometry
Rotation, Convective Core Overshooting, and Period Changes in Classical Cepheid Stellar Evolution Models. Classical Cepheids are powerful probes of both stellar evolution and near-field cosmology thanks to their great luminosities, pulsations, and their adherence to the Leavitt (period-luminosity) Law. However, there still exist a number of questions regarding their evolution, such as the roles of rotation, convective core overshooting, and winds. ln particular, how do these processes impact Cepheid evolution and the predicted fundamental properties such as stellar mass? In this work, we compare a sample of Cepheids with measured rates of period change with new evolution models to test the impact of these first two processes. In our previous study we found that enhanced mass loss is crucial for describing the sample, and here we continue that analysis but for rotational mixing and core overshooting. We show that while rotation is important for stellar evolution studies, rotation itself is insufficient to model the distribution of period change rates from the observed sample. On the other hand, convective core overshooting is needed to explain the magnitude of the rates of period change, but does not explain the number of stars with positive and negative period change rates. In conclusion, we determine that convective core overshooting and stellar rotation alone are not enough to account for the observed distribution of Cepheid rates of period change and another mechanism, such as pulsation-driven mass loss, may be required.

Keywords: Fundamental parameters of stars, Stellar mass loss, Delta Cepheid variable stars, Stellar evolution
Compact Intermediate-mass Black Hole X-Ray Binaries: Potential LISA Sources?. The scientific aim of the space gravitational-wave (GW) detector Laser Interferometer Space Antenna (LISA) that was scheduled to launch in the early 2030s is to detect the low-frequency GW signals in the Galaxy. Its main candidate GW sources are compact binaries of white dwarfs and neutron stars. In this work, we examine whether compact intermediate-mass black hole (IMBH) X-ray binaries could be potential LISA sources. Our simulations indicate that an IMBH binary with a 1000 M⊙ IMBH and a 3 M⊙ donor star in an initial orbital period near the so-called bifurcation period of 0.77 day could evolve into an ultra-compact X-ray binary, which will emit GW signals with a maximum frequency of 2.5 mHz. According to the evolutionary tracks of characteristic strain, IMBH X-ray binaries with the initial donor-star masses of 1-3 M⊙ and the initial orbital periods slightly less than the bifurcation periods will be detectable by the LISA in a distance of 15 kpc. Assuming each of 60 Galactic globular clusters hosts a 1000 M⊙ IMBH, the maximum number of compact IMBH X-ray binaries that LISA will detect in the Galaxy should be less than ten. Therefore, the detectability of compact IMBH X-ray binaries by the LISA is not optimistic.

Keywords: Galaxy clusters, X-ray binary stars, Black holes, Gravitational waves, Stellar evolution
Polycyclic Aromatic Hydrocarbons as a Source for {\mathrm{CH}}_{N}(+) (N = 4-6) and C<SUB>3</SUB>H<SUB>2</SUB> in the Interstellar Medium. Photoionization and dissociation of anthracene, phenanthrene, and pentacene in the multiphoton regime at 266 nm wavelength were performed. ${\mathrm{CH}}_{n}^{+}$ (n = 4-6) ions were observed as fragments, and their yields as a function of laser intensity were studied. H-migration and "roaming" mechanisms leading to the formation of these fluxional ions from polycyclic aromatic hydrocarbons (PAHs) are proposed. The present results show higher photostability of PAHs with bent structure and suggest PAHs in the UV regions of interstellar medium as a prominent source for ${\mathrm{CH}}_{n}^{+}$ (n = 4-6).

Keywords: Photoionization, Polycyclic aromatic hydrocarbons, Photodissociation regions, Dense interstellar clouds, Interstellar clouds