Sazuna/UAT_keywords huggingface dataset:
AstroSat UVIT Observations of Her X-1. An observation of the X-ray binary system Her X-1/HZ Her by the AstroSat UltraViolet Imaging Telescope (UVIT) was carried out in 2018. The observation was taken with the far ultra-violet (FUV) camera of UVIT with the CaF2 filter (125-175 nm band) and lasted ≃0.6 of one binary orbit. Her X-1 was in the late main high state at 35 day phase ≃0.20. Clear orbital modulation of the UVIT light curve is seen, showing egress from eclipse of the neutron star and double-peak shape half an orbital period later. The FUV emission from Her X-1 is shown to arise partly from the accretion disk and partly from the X-ray heated face of Hz Her. We carry out modeling of the system using the Shape code and fit the FUV light curve. New constraints are obtained for the geometric parameters of the tilted and twisted accretion disk around the neutron star, and improvements to the basic disk model are suggested.

Keywords: Neutron stars, X-ray binary stars
The Physical Properties of S0 Galaxy PGC 26218: The Origin of Starburst and Star Formation. We present 2D-spectroscopic observations from the Centro Astronómico Hispano Alemán 3.5 m telescope and millimeter observations from the NOrthern Extended Millimeter Array of the nearby S0 galaxy PGC 26218, which shows central star formation activity and post-starburst features in the disk. We estimate the star formation rate (SFR = 0.28 ± 0.01 M⊙ yr-1) and molecular gas mass ( $\mathrm{log}{M}_{{{\rm{H}}}_{2}}=7.60\pm 0.15\ {M}_{\odot }$ ) of PGC 26218 based on the extinction-corrected Hα emission line and the CO-H2 conversion factor (αCO) of the Milky Way, respectively. We find that PGC 26218 follows the star-forming main sequence (SFMS) and the Kennicutt-Schmidt law. Comparing the kinematics of CO(J = 1-0), stars, and Hα, we find that the rotational axis of CO(J = 1-0) is 45° different from that of Hα. In addition, the profile of the CO(J = 1-0) emission line shows asymmetry and has an inflow component of ∼46 km s-1. With the decomposition of the optical image, we confirm that PGC 26218 shows multiple nuclear structures. The projected offset between the most luminous optical center and the center of CO(J = 1-0) is 5"2 (∼0.6 kpc) and the latter overlaps with one of the optical cores. These results indicate that PGC 26218 may have experienced a gas-rich minor merger, extending its star formation and locating it in the SFMS.

Keywords: Lenticular galaxies, Starburst galaxies, Star formation
Periodic Modulation: Newly Emergent Emission Behavior in Pulsars. Periodic modulations are seen in normal pulsars (P &gt; 0.1 s) over timescales ranging from a few seconds to several minutes. Such modulations have usually been associated with the phenomenon of subpulse drifting. A number of recent studies have shown subpulse drifting to exhibit very specific physical characteristics: (I) drifting is seen only in conal components of the pulse profile and is absent in central core emission; (II) drifting pulsars are distributed over a narrow range of spin-down energy loss ( $\dot{E}$ ), where pulsars with $\dot{E}\,\lt $ 2 × 1032 erg s-1 show this behavior; and (III) drifting periodicity (P3) is anti-correlated with $\dot{E}$ , such that pulsars with lower values of $\dot{E}$ tend to have longer P3. These detailed characterizations of drifting behavior, on the other hand, also revealed the presence of other distinct periodic modulations, which can be broadly categorized into two types, periodic nulling, and periodic amplitude modulation. In contrast to drifting, these periodic phenomena are seen across the entire profile in both the core and conal components simultaneously and are not restricted to any specific $\dot{E}$ range. In this work we have assembled an exhaustive list of around 70 pulsars that show such periodic modulations, 22 of which were newly detected using observations from the Giant Meterwave Radio Telescope and the remaining compiled from past publications. The presence of such a significant group in the pulsar population suggests periodic modulations to be newly emergent phenomena in pulsars, with a physical origin that is distinct from that of subpulse drifting.

Keywords: Pulsars, Radio pulsars
On the Production of Polyols and Hydroxycarboxylic Acids in Interstellar Analogous Ices of Methanol. This laboratory work studied the production of complex organic molecules in pure methanol (CH3OH) ices exposed to ionizing radiation in the form of energetic electrons. The chemical evolution of the ices during the electron irradiation at 10 K and subsequent warm-up phase to 300 K was monitored online and in situ via Fourier Transform Infrared spectrometry. Polyols and hydroxycarboxylic acids related absorptions were observed in the infrared spectra of the irradiated ices and residues at room temperature. The residues were analyzed via two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC × GC-TOFMS). Four polyols and five hydroxycarboxylic acids were detected. All of these compounds, except 1, 3-propanediol and 1, 3-butanediol, have been identified in the Murchison and Bell meteorites. The most abundant species, ethylene glycol, has also been found in the interstellar medium (ISM). Our findings suggest that other polyols and acids may also be present in methanol-rich star-forming regions. The non-detection of higher order sugars, such as those found in the ultraviolet photon-processed, 13C-methanol (13CH3OH):water (H2O):ammonia (NH3), and 13CH3OH: H2O ice mixtures, indicates that the type of radiation source or more likely the prevalent NH3 and/or H2O molecules in the ISM are critical to the abiotic formation of the bio-essential sugars. Experiments are currently being designed to elucidate the roles of each component.

Keywords: Meteorite composition, Laboratory astrophysics, Astrochemistry, Interstellar medium, Pre-biotic astrochemistry
Radius-to-frequency Mapping and FRB Frequency Drifts. We build a model of radius-to-frequency mapping in magnetospheres of neutron stars and apply it to frequency drifts observed in fast radio bursts (FRBs). We assume that an emission patch propagates along the dipolar magnetic field lines, producing coherent emission with frequency, direction, and polarization defined by the local magnetic field. The observed temporal evolution of the frequency depends on the relativistic effects of time contraction and the curvature of the magnetic field lines. The model generically produces linear scaling of the drift rate, $\dot{\omega }\propto -\omega $ , matching both numerically and parametrically the rates observed in FBRs; a more complicated behavior of $\dot{\omega }$ is also possible. Fast rotating magnetospheres produce higher drifts rates for similar viewing parameters than the slowly rotating ones. In the case of repeaters, the same source may show variable drift patterns depending on the observing phase. We expect rotational of polarization position angle through a burst, though by smaller amount than in radio pulsars. All of these findings compare favorably with properties of FBRs, strengthening their possible loci in the magnetospheres of neutron stars.

Keywords: Neutron stars, Magnetars, Pulsars, Radio transient sources
Modeling the Upper kHz QPOs of 4U 1728-34 with X-Ray Reverberation. While kilohertz quasi-periodic oscillations (kHz QPOs) have been well studied for decades since their initial discovery, the cause of these signals remains unknown, as no model has been able to accurately predict all of their spectral and timing properties. Separately, X-ray reverberation lags have been detected in active galactic nuclei and stellar-mass black hole binaries, and reverberation may be expected to occur in neutron star systems as well, producing lags of the same amplitude as the lags measured of the kHz QPOs. Furthermore, the detection of a relativistically reflected Fe K line in the time-averaged spectra of many neutron star systems provides an additional motivation for testing reverberation. While it has been shown that the lag-energy properties of the lower kHz QPOs are unlikely to be produced by X-ray reverberation, the upper kHz QPOs have not yet been explored. We therefore model the upper kHz QPO lag-energy spectra using relativistic ray-tracing functions and apply them to archival Rossi X-Ray Timing Explorer data on 4U 1728-34 where upper kHz QPOs have been detected. By modeling the time-averaged spectra in which upper kHz QPOs had been significantly detected, we determine the reflected flux fraction across all energies and produce a model for the lag-energy spectra from X-ray reverberation. We explore the dependence of the modeled lag properties on several different types of reflection models but are unable to successfully reproduce the measured lags of 4U 1728-34. We conclude that reverberation alone does not explain the measured time lags detected in upper kHz QPOs.

Keywords: Accretion, Neutron stars, Low-mass x-ray binary stars
Balmer Break Galaxy Candidates at z ∼ 6: A Potential View on the Star Formation Activity at z ≳ 14. We search for galaxies with a strong Balmer break (Balmer break galaxies; BBGs) at z ∼ 6 over a 0.41 deg2 effective area in the COSMOS field. Based on rich imaging data, including data obtained with the Atacama Large Millimeter/submillimeter Array (ALMA), three candidates are identified by their extremely red K-[3.6] colors, as well as by nondetection in the X-ray, optical, far-infrared, and radio bands. The nondetection in the deep ALMA observations suggests that they are not dusty galaxies but BBGs at z ∼ 6, although contamination from active galactic nuclei at z ∼ 0 cannot be completely ruled out for the moment. Our spectral energy distribution analyses reveal that the BBG candidates at z ∼ 6 have stellar masses of ≈5 × 1010 M☉ dominated by old stellar populations with ages of ≳ 700 Myr. Assuming that all three candidates are real BBGs at z ∼ 6, we estimate the stellar mass density to be ${2.4}_{-1.3}^{+2.3}\times {10}^{4}\,{M}_{\odot }$ Mpc-3. This is consistent with an extrapolation from the lower-redshift measurements. The onset of star formation in the three BBG candidates is expected to be several hundred million yr before the observed epoch of z ∼ 6. We estimate the star formation rate density (SFRD) contributed by progenitors of the BBGs to be 2.4-12 × 10-5 M☉ yr-1 Mpc-3 at z &gt; 14 (99.7% confidence range). Our result suggests a smooth evolution of the SFRD beyond z = 8.

Keywords: Early universe, Galaxy formation, Star formation, High-redshift galaxies
The Molecular Outflow from R Mon. We have mapped the young Herbig Be star R Mon in CO(3-2) and 13CO(3-2) with Atacama Pathfinder EXperiment in Chile and analyzed unpublished Herschel images. We find that R Mon is embedded in a small cloud with a gas temperature of ∼20 K and a total mass of ∼70 ${M}_{\odot }$ . We confirm that R Mon drives a bipolar molecular outflow, which is blueshifted north of R Mon. The blueshifted outflow has excavated the molecular cloud north of R Mon, creating the reflection nebula NGC 2261 and filling it with high-velocity gas. At "high" velocities the orientation of the outflow is approximately n-s, which agrees with the optical jet, suggesting that the accretion disk is e-w. The outflow velocities are modest, ±9 km s-1. The outflow is rather massive, ∼0.56 ${M}_{\odot }$ in the blueshifted outflow lobe. The outflow is completely optically thick in CO(3-2) toward R Mon, indicating that its envelope is ≲2000 au. The mass of the accretion disk and surrounding envelope determined from an isothermal graybody fit is ∼0.34 ${M}_{\odot }$ . We estimate a mass-loss rate of ∼(1-3) × 10-5 ${M}_{\odot }$ yr-1, corresponding to an accretion rate of (1-9) × 10-6 ${M}_{\odot }$ yr-1. We find that R Mon has bolometric luminosity of &lt;1000 ${L}_{\odot }$ . R Mon is still in an active accretion phase, contributing to the observed luminosity. Hence, R Mon cannot be a B0 star; it must be a late B star or even an early A star.

Keywords: Accretion, Herbig Ae/Be stars, Interstellar molecules, Jets, Pre-main sequence stars, Dark interstellar clouds, Reflection nebulae
Two Quasi-periodic Fast-propagating Magnetosonic Wave Events Observed in Active Region NOAA 11167. We report a detailed observational study of two quasi-periodic fast-propagating (QFP) magnetosonic wave events that occurred on 2011 March 9 and 10, respectively. Interestingly, both the events have two wave trains (WTs): a strong main one (WT-1) and a small and weak secondary one (WT-2). Peculiar and common characteristics of the two events are observed, namely, (1) the two QFP waves are accompanied with brightenings during the whole stage of the eruptions; (2) both the two main WTs are nearly propagating along the same direction; (3) extreme-ultraviolet (EUV) waves are found to be associated with the two events. Investigating various aspects of the target events, we argue that (1) the second event is accompanied with a flux rope eruption during the whole stage; (2) the second event eruption produces a new filament-like dark feature; (3) the ripples of the two WT-2 QFP waves seem to result from different triggering mechanisms. Based on the obtained observational results, we propose that the funnel-like coronal loop system is indeed playing an important role in the two WT-1 QFP waves. The development of the second WT-2 QFP wave can be explained as due to the dispersion of the main EUV front. The coexistence of the two events offers thereby a significant opportunity to reveal what driving mechanisms and structures are tightly related to the waves.

Keywords: Space plasmas, Magnetohydrodynamics, Solar flares, Solar extreme ultraviolet emission, Solar active regions, Solar coronal waves, Solar corona
A Timing Study of MAXI J1820+070 Based on Swift/XRT and NICER Monitoring in 2018/19. We present a detailed timing analysis of the bright black hole X-ray binary MAXI J1820+070 (ASASSN-18ey), during its first detected outburst lasting from 2018 March until 2019 October based on Swift/XRT window timing mode observations, corresponding UVOT data and NICER observations. The light curves clearly show four outbursts, with the source remaining in the hard state during its first outburst, while the rise of the second outburst corresponds with the transition to the soft state. A similar double outburst of GX339-4 has been observed in 2004. Here it is followed by two hard-state only outbursts. In many observations the power density spectra showed type-C quasi-periodic oscillations (QPOs) with characteristic frequencies below 1 Hz, which suggests that the source stayed in a state of low effective accretion for large parts of its outburst. The absence of other types of QPOs hinders a precise determination of the state transitions, but from combining NICER and Swift/XRT data, we find that MAXI J1820+070 went from the hard-intermediate to the soft state in less than one day. The covariance ratios derived from NICER data show an increase toward lower energies, which indicate that the source should make a transition to the soft state. This transition finally took place, after MAXI J1820+070 stayed in the hard state at rather constant luminosity for about 116 days. The steepness of the increase of the covariance ratios is not correlated with the amount of rms variability and it does not show a monotonic evolution along the outburst.

Keywords: Low-mass x-ray binary stars, Transient sources, Stellar mass black holes, Close binary stars
Statistical Results for Solar Energetic Electron Spectra Observed over 12 yr with STEREO/SEPT. This work presents a statistical analysis of near-relativistic solar energetic electron event spectra near 1 au. We use measurements of the Solar Electron and Proton Telescope (SEPT) on board STEREO in the energy range of 45-425 keV and utilize the SEPT electron event list containing all electron events observed by STEREO A and STEREO B from 2007 through 2018. We select 781 events with significant signal-to-noise ratios for our analysis and fit the spectra with single or broken-power-law functions of energy. We find 437 events showing broken power laws and 344 events only showing a single power law in the energy range of SEPT. For those events with broken power laws, we find a mean break energy of about 120 keV. We analyze the dependence of the spectral index on the rise times and peak intensities of the events as well as on the presence of relativistic electrons. The results show a relation between the power law spectral index and the rise times of the events with softer spectra belonging to rather impulsive events. Long rise-time events are associated with hard spectra as well as with the presence of higher-energy (&gt;0.7 MeV) electrons. This group of events cannot be explained by a pure flare scenario but suggests an additional acceleration mechanism, involving a prolonged acceleration and/or injection of the particles. A dependence of the spectral index on the longitudinal separation from the parent solar source region was not found. A statistical analysis of the spectral indices during impulsively rising events where the rise times are below 20 minutes is also shown.

Keywords: Solar flares, Heliosphere, Solar energetic particles, Solar coronal mass ejection shocks, Interplanetary particle acceleration, Radio bursts, Spectral index
Asymmetries of Heavy Elements in the Young Supernova Remnant Cassiopeia A. Supernova remnants (SNRs) offer the means to study supernovae (SNe) long after the original explosion and can provide a unique insight into the mechanism that governs these energetic events. In this work, we examine the morphologies of X-ray emission from different elements found in the youngest known core-collapse SNR in the Milky Way, Cassiopeia A. The heaviest elements exhibit the highest levels of asymmetry, which we relate to the burning process that created the elements and their proximity to the center of explosion. Our findings support recent model predictions that the material closest to the source of explosion will reflect the asymmetries inherent to the SN mechanism. Additionally, we find that the heaviest elements are moving more directly opposed to the neutron star (NS) than the lighter elements. This result is consistent with NS kicks arising from ejecta asymmetries.

Keywords: Neutron stars, Astronomy data modeling, Core-collapse supernovae, X-ray telescopes, Supernova remnants, X-ray observatories, Spectroscopy
Detecting Gravitational Scattering of Interstellar Objects Using Pulsar Timing. Gravitational scattering events, in which the path of an interstellar object is deflected by a pulsar or the solar system, give rise to reflex motion that can potentially be detected using pulsar timing. We determine the form of the timing signal expected from a gravitational scattering event, which is ramp-like and resembles the signal produced by a glitch or a gravitational wave burst with memory (BWM), and investigate the prospects for detecting such a signal using a pulsar timing array. The level of timing precision currently achieved for some millisecond pulsars makes it possible to detect objects as small as 10-10 M⊙, less than the mass of the dwarf planet Ceres, at impact parameters as large as $1\,\mathrm{au}$ . The signals produced by gravitational scattering could provide independent constraints on models of dark matter involving asteroid-mass objects or subhalos, and should be considered as potential false positives in searches for BWMs.

Keywords: Pulsar timing method, Millisecond pulsars, Pulsars, Free floating planets, Hyperbolic orbit, Dark matter
Multiwavelength Emission from Galactic Jets: The Case of the Microquasar SS433. SS433 is a Galactic microquasar with powerful jets, where very-high-energy particles are produced. We study particle acceleration in the jets of SS433 through the use of recent multiwavelength data from radio to TeV gamma-ray. We first present a general framework for the particle acceleration, cooling, and transport in relativistic jets. We then apply this to two X-ray knots in the jets of SS433, focusing on leptonic emission. Our detailed treatment of particle transport and evolution produces substantially different predictions from previous papers. For both regions, our model can account for the multiwavelength data except for the GeV data. This suggests that GeV emission is mostly from different regions and/or mechanisms. We find that the acceleration process should be efficient, which could be realized by diffusive shock acceleration close to the Bohm limit. Provided that protons are accelerated at the same efficiency as electrons, our results imply that SS433 is a PeVatron, I.e., can accelerate protons beyond a PeV. Future hard X-ray and MeV gamma-ray observations can critically test our models by detecting the spectral turnover or cutoff.

Keywords: X-ray astronomy, Binary stars, Relativistic jets, Non-thermal radiation sources, Cosmic ray sources, Gamma-ray astronomy, Astrophysical black holes
The Stark Effect, Zeeman Effect, and Transition Dipole Moments for the B<SUP>2</SUP>Σ<SUP>+</SUP>-X<SUP>2</SUP>Σ<SUP>+</SUP> Band of Aluminum Monoxide, AlO. The experimentally measured radiative lifetimes and branching ratios were combined to determine the transition dipole moments for the B2Σ+(V = 0-3) → X2Σ+(V = 0-6) bands of aluminum monoxide, AlO, and compared with theoretical predictions. The B2Σ+-X2Σ+ (0, 1) band of a molecular beam sample of AlO was recorded at high spectral resolution both field-free and in the presence of static electric and magnetic fields. The 27Al(I = 5/2) hyperfine interaction in the B2Σ+(V = 0) state was analyzed. The observed Stark shifts were analyzed to produce permanent electric dipole moments of 1.94(8) D and 4.45(3) D for the B2Σ+(V = 0) and X2Σ+(V = 1) states, respectively. It is demonstrated that the observed Zeeman spectra can be simulated using an effective Hamiltonian with the associated expected g-factors for both the X2Σ+(V = 1) and B2Σ+(V = 0) states.

Keywords: Radio astronomy, Molecular spectroscopy, Circumstellar clouds, Circumstellar dust, Transition probabilities, Magnetic fields, Line intensities, Circumstellar gas
V346 Nor: The Post-outburst Life of a Peculiar Young Eruptive Star. FU Orionis-type objects (FUors) are young low-mass stars undergoing powerful accretion outbursts. The increased accretion is often accompanied by collimated jets and energetic, large-scale molecular outflows. The extra heating during the outburst may also induce detectable geometrical, chemical, and mineralogical changes in the circumstellar material, affecting possible planet formation around these objects. V346 Nor is a southern FUor with peculiar spectral characteristics. Decades after the beginning of its outburst, it unexpectedly underwent a fading event around 2010 due to a decrease in the mass accretion rate onto the star by at least two orders of magnitude. Here we present optical and near-infrared photometry and spectroscopy obtained after the minimum. Our light curves show a gradual re-brightening of V346 Nor, with its Ks-band brightness only 1.5 mag below the outburst brightness level. Our Very Large Telescope (VLT)/XSHOOTER spectroscopic observations display several strong forbidden emission lines toward the source from various metals and molecular hydrogen, suggesting the launch of a new jet. Our N-band spectrum obtained with VLT/VISIR outlines a deeper silicate absorption feature than before, indicating that the geometry of the circumstellar medium has changed in the post-outburst period compared to peak brightness.

Keywords: Infrared astronomy, Circumstellar matter, Star formation