Sazuna/UAT_keywords huggingface dataset:
Globular Clusters in NGC 4839 Falling into Coma: Evidence for the Second Infall?. NGC 4839 is the brightest galaxy (cD) of the NGC 4839 group at R ≈ 1 Mpc in the southwest of the Coma cluster, which is known to be falling into Coma. However, it has been controversial whether it is in the first phase of infall or in the second phase of infall after passing the Coma center. We present a wide field study of globular clusters (GCs) in NGC 4839 and its environment based on Hyper Suprime-Cam gr images in the Subaru archive. We compare the GC system of NGC 4839 with that of NGC 4816, which is the brightest member (S0) of the nearby group and lies at a similar distance in the west from the Coma center. Interestingly the spatial distribution of the GCs in NGC 4839 is significantly more compact than that of the GCs in NGC 4816. In addition, the radial number density profile of the GCs in NGC 4839 shows an abrupt drop at R N4839 ≈ 80 kpc, while that of the GCs in NGC 4816 shows a continuous slow decline even in the outer region at 80 &lt; R N4816 &lt; 500 kpc. The effective radius of the NGC 4839 GC system is about 3 times smaller than that of the NGC 4816 GC system. This striking difference can be explained if NGC 4839 lost a significant fraction of the GCs in its outskirt when it passed through Coma. This supports strongly the second-infall scenario where the NGC 4839 passed the Coma center about 1.6 Gyr ago, and began the second infall after reaching the apocenter in the southwest recently.

Keywords: Globular star clusters, Coma Cluster, Rich galaxy clusters, Giant elliptical galaxies, Galaxy groups, Intracluster medium, Early-type galaxies
Probing the Stellar Wind of the Wolf-Rayet Star in IC 10 X-1. IC 10 X-1 is an eclipsing high-mass X-ray binary containing a stellar-mass black hole (BH) and a Wolf-Rayet (WR) donor star with an orbital period of P = 34.9 hr. This binary belongs to a group of systems that can be the progenitors of gravitational-wave sources; hence understanding the dynamics of systems such as IC 10 X-1 is of paramount importance. The prominent He II 4686 emission line (previously used in mass estimates of the BH) is out of phase with the X-ray eclipse, suggesting that this line originates somewhere in the ionized wind of the WR star or in the accretion disk. We obtained 52 spectra from the GEMINI/GMOS archive, observed between 2001 and 2019. We analyzed the spectra both individually, and after binning them by orbital phase to improve the signal-to-noise ratio. The radial-velocity curve from the stacked data is similar to historical results, indicating the overall parameters of the binary have remained constant. However, the He II line profile shows a correlation with the X-ray hardness-ratio values; also, we report a pronounced skewness of the line profile, and the skewness varies with orbital phase. These results support a paradigm wherein the He II line tracks structures in the stellar wind that are produced by interactions with the BH's ionizing radiation and the accretion flow. We compare the observable signatures of two alternative hypotheses proposed in the literature: wind irradiation plus shadowing, and accretion disk hotspot; and we explore how the line-profile variations fit into each of these models.

Keywords: Black hole physics, Spectroscopic binary stars, Wolf-Rayet stars, Stellar winds, Eclipsing binary stars, Stellar spectral lines
Relativistic Correction to the r-mode Frequency in Light of Multimessenger Constraints. The r-mode oscillations of rotating neutron stars are promising candidates for continuous gravitational-wave (GW) observations. The r-mode frequencies for slowly rotating Newtonian stars are well known and independent of the equation of state (EOS), but for neutron stars several mechanisms can alter the r-mode frequency for which the relativistic correction is dominant and relevant for most of the neutron stars. The most sensitive searches for continuous GWs are those for known pulsars for which GW frequencies are in targeted narrow frequency bands of a few hertz. In this study, we investigate the effect of several state-of-the-art multimessenger constraints on the r-mode frequency for relativistic, slowly rotating, barotropic stars. Imposing these recent constraints on the EOS, we find that the r-mode frequency range is slightly higher than that from the previous study and the narrowband frequency range can increase by up to 25% for the most promising candidate PSR J0537-6910 depending on the range of compactness. We also derive universal relations between r-mode frequency and dimensionless tidal deformability that can be used to estimate the dynamical tide of the r-mode resonant excitation during the inspiral signal. These results can be used to construct the parameter space for r-mode searches in GW data and also constrain the nuclear EOS following a successful r-mode detection.

Keywords: Neutron stars, Gravitational wave sources, Pulsars
The GMRT High Resolution Southern Sky Survey for Pulsars and Transients. IV. Discovery of Four New Pulsars with an FFA Search. The fast Fourier transform (FFT) based periodicity search methods provide an efficient way to search for millisecond and binary pulsars but encounter significant sensitivity degradation while searching for long period and short duty cycle pulsars. An alternative to FFT-based search methods called the fast folding algorithm (FFA) search provides superior sensitivity to search for signals with long periods and short duty cycles. In the GMRT High Resolution Southern Sky (GHRSS) survey, we are using an FFA-based pipeline to search for isolated pulsars in a period range of 100 ms to 100 s. We have processed 2800 degree2 of the sky coverage away from the Galactic plane and discovered six new pulsars. Here, we report the discovery of four of these pulsars with the FFA search pipeline. This includes a narrow duty cycle pulsar, J1936-30, which shows nulling behavior with an extreme nulling fraction of ~90%. Two of the GHRSS discoveries from the FFA search lie in narrow duty cycle ranges beyond the limit of the existing population. The implementation of FFA search in the GHRSS survey and other pulsar surveys is expected to recover the missing population of long period and short duty cycle pulsars.

Keywords: Neutron stars, Observational astronomy, Radio pulsars
Jets and Rings in Images of Spinning Black Holes. We develop a "dual-cone" model for millimeter wavelength emission near a spinning black hole. The model consists of optically thin, luminous cones of emission, centered on the spin axis, which are meant to represent jet walls. The resulting image is dominated by a thin ring. We first consider the effect of the black hole's spin on the image and show that the dominant effect is to displace the ring perpendicular to the projection of the spin axis on the sky by $2{a}_{* }\sin i+{ \mathcal O }({a}_{* }^{3})$ . This effect is lower order in a * than changes in the shape and size of the photon ring itself but is undetectable without a positional reference. We then show that the centerline of the jet can provide a suitable reference: its location is exactly independent of spin if the observer is outside the cone and nearly independent of spin if the observer is inside the cone. If astrophysical uncertainties can be controlled, then spin displacement is large enough to be detectable by future space very long baseline interferometry missions. Finally, we consider ring substructure in the dual-cone model and show that features in total intensity are not universal and depend on the cone-opening angle.

Keywords: Black holes, Kerr black holes, Relativistic jets, General relativity, Radiative transfer, Astrophysical black holes
Catalog of Magnetic White Dwarfs with Hydrogen Dominated Atmospheres. White dwarfs are excellent research laboratories as they reach temperatures, pressures, and magnetic fields that are unattainable on Earth. To better understand how these three physical parameters interact with each other and with other stellar features, we determined the magnetic field strength for a total of 804 hydrogen-rich white dwarfs (WDs) of which 287 are not in the literature. We fitted the spectra observed with the Sloan Digital Sky Survey using atmospheric models that consider the Zeeman effect due to the magnetic field at each point in the stellar disk. Comparing magnetic and nonmagnetic WDs, the literature already shows that the magnetic ones have on average higher mass than the nonmagnetic. In addition to that, magnetic fields are more common in cooler WDs than in hotter WDs. In consonance, we found that those with higher magnetic field strengths tend to have higher masses, and lower temperatures, for which models indicate the crystallization process has already started. This reinforces the hypothesis that the field is being generated and/or amplified in the cooling process of the white dwarf. Our sample constitutes the largest number of white dwarfs with determined magnetic fields to date.

Keywords: White dwarf stars, DA stars
Deep Search for Gamma-Ray Emission from the Accreting X-Ray Pulsar 1A 0535+262. Binary systems are a well-established subclass of gamma-ray sources. The high mass X-ray binary pulsar 1A 0535+262 has been considered to be a possible gamma-ray emitter for a long time, although former gamma-ray searches using the Fermi Large Area Telescope (LAT) and VERITAS data resulted in upper limits only. We aim at a deep search for gamma-ray emission and pulsations from 1A 0535+262 using more than 13 yr of Fermi-LAT data. The analysis was performed for both the whole Fermi-LAT data set, as well as for the X-ray outbursts that 1A 0535+262 has experienced since the launch of Fermi. Various X‑ray observations have been used to generate the ephemeris for the pulsation search. We also investigate the long-term gamma-ray flux variability and perform orbital phase-resolved analysis for the outbursts. We did not detect any steady or pulsed gamma-ray emission from 1A 0535+262 during the whole Fermi-LAT mission span or its X-ray outbursts. We thus derived the deepest gamma-ray luminosity upper limits to date at the 95% confidence level to be around (2.3-4.7) × 1032 erg s-1 depending on different spectral indices assumed, which results in a ratio of L  γ  to L X (2-150 keV) being (1.9-3.9) × 10-6.

Keywords: Gamma-ray sources, X-ray binary stars, Binary pulsars
The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XXIV. Differences in Internal Kinematics of Multiple Stellar Populations. Our understanding of the kinematic properties of multiple stellar populations (mPOPs) in Galactic globular clusters (GCs) is still limited compared to what we know about their chemical and photometric characteristics. Such limitation arises from the lack of a comprehensive observational investigation of this topic. Here we present the first homogeneous kinematic analysis of mPOPs in 56 GCs based on high-precision proper motions computed with Hubble Space Telescope data. We focused on red-giant-branch stars, for which the mPOP tagging is clearer, and measured the velocity dispersion of stars belonging to first (1G) and second generations (2G). We find that 1G stars are generally kinematically isotropic even at the half-light radius, whereas 2G stars are isotropic at the center and become radially anisotropic before the half-light radius. The radial anisotropy is induced by a lower tangential velocity dispersion of 2G stars with respect to the 1G population, while the radial component of the motion is comparable. We also show possible evidence that the kinematic properties of mPOPs are affected by the Galactic tidal field, corroborating previous observational and theoretical results suggesting a relation between the strength of the external tidal field and some properties of mPOPs. Although limited to the GCs' central regions, our analysis leads to new insights into the mPOP phenomenon, and provides the motivation for future observational studies of the internal kinematics of mPOPs.

Keywords: Globular star clusters, Proper motions, Stellar kinematics
Prospects for 21 cm Galaxy Cross-correlations with HERA and the Roman High-latitude Survey. The cross-correlation between the 21 cm field and the galaxy distribution is a potential probe of the Epoch of Reionization (EoR). The 21 cm signal traces neutral gas in the intergalactic medium and, on large spatial scales, this should be anticorrelated with the high-redshift galaxy distribution, which partly sources and tracks the ionized gas. In the near future, interferometers such as the Hydrogen Epoch of Reionization Array (HERA) are projected to provide extremely sensitive measurements of the 21 cm power spectrum. At the same time, the Nancy Grace Roman Space Telescope (Roman) will produce the most extensive catalog to date of bright galaxies from the EoR. Using seminumeric simulations of reionization, we explore the prospects for measuring the cross-power spectrum between the 21 cm and galaxy fields during the EoR. We forecast a 12σ detection between HERA and Roman, assuming an overlapping survey area of 500 deg2, redshift uncertainties of σ  z  = 0.01 (as expected for the high-latitude spectroscopic survey of Lyα-emitting galaxies), and an effective Lyα emitter duty cycle of f LAE = 0.1. Thus the HERA-Roman cross-power spectrum may be used to help verify 21 cm detections from HERA. We find that the shot-noise in the galaxy distribution is a limiting factor for detection, and so supplemental observations using Roman should prioritize deeper observations, rather than covering a wider field of view. We have made a public GitHub repository containing key parts of the calculation, which accompanies this paper: https://github.com/plaplant/21cm_gal_cross_correlation.

Keywords: Cosmology, Reionization, Large-scale structure of the universe
Protoneutron Star Convection Simulated with a New General Relativistic Boltzmann Neutrino Radiation Hydrodynamics Code. We investigate protoneutron star (PNS) convection using our newly developed general relativistic Boltzmann neutrino radiation hydrodynamics code. This is a pilot study for more comprehensive investigations later. As such, we take a snapshot of a PNS at 2.3 s after bounce from a 1D PNS cooling calculation and run our simulation for ~160 ms in 2D under axisymmetry. The original PNS cooling calculation neglected convection entirely and the initial conditions were linearly unstable to convection. We find in our 2D simulation that convection is instigated there indeed and expands inward after being full-fledged. The convection then settled to a quasi-steady state after ~100 ms, being sustained by the negative Y  e  gradient, which is in turn maintained by neutrino emissions. It enhances the luminosities and mean energies of all species of neutrinos compared to 1D. Taking advantage of the Boltzmann solver, we analyse the possible occurrence of neutrino fast flavor conversion (FFC). We found that FFC is likely to occur in regions where Y  e  is lower, and that the growth rate can be as high as ~10-1 cm-1.

Keywords: Neutron stars, Supernova neutrinos, Core-collapse supernovae, Neutrino oscillations, Radiative transfer simulations
Evidence for a Low Lyman Continuum Escape Fraction in Three Massive, Ultraviolet-bright Galaxies at z &gt; 7. Although low-mass star-forming galaxies are the leading candidates of the reionization process, we cannot conclusively rule out high-mass star-forming galaxies as candidates. While most simulations indicate the former is the best candidate, some models suggest that at z ≥ 6 massive, UV-bright galaxies - "oligarchs" - account for at least 80% of the ionizing budget. To test this hypothesis, we target massive ( ${\mathrm{log}}_{10}({\text{}}{M}_{\star }[{\text{}}{M}_{\odot }])\gt 10$ ), UV-bright (M UV ~ -22) Lyα emitters at z &gt; 7 in archival data, observed with similar resolution spectrographs (Very Large Telescope/X-shooter and Keck/MOSFIRE). To increase the reliability of our conclusions, we stack all spectra and obtain a deep-stacked spectrum of 24.75 hr. The stacked Lyα profile displays a clear asymmetric red peak and an absence of a blue peak. We additionally estimate the intrinsic stacked Lyα profile of our targets by correcting for intergalactic medium (IGM) transmission using a range of neutral hydrogen fractions, finding no significant change in the profile. We measure a velocity offset V red &gt; 300 km s-1 and an asymmetry in our red peak A ~ 3. Using various models and estimators, such as the peak separation, the asymmetry of the red peak, the ratio between Lyα and Hβ, and the β slope, we conclude that the escape fraction in these three UV-bright, massive (~1010 M ☉), z ≥ 7 galaxies is f esc(LyC) ≤ 10%.

Keywords: Lyman-alpha galaxies, Reionization, High-redshift galaxies
Nonthermal X-Rays from Pulsation-driven Shocks in Cepheids. Rapid X-ray phase-dependent flux enhancement in the archetype classical Cepheid star δ Cep was observed by XMM-Newton and Chandra. We jointly analyze thermal and nonthermal components of the time-resolved X-ray spectra prior to, during, and after the enhancement. A comparison of the timescales of shock particle acceleration and energy losses is consistent with the scenario of a pulsation-driven shock wave traveling into the stellar corona and accelerating electrons to ~GeV energies, and with Inverse Compton (IC) emission from the UV stellar background leading to the observed X-ray enhancement. The index of the nonthermal IC photon spectrum, assumed to be a simple power law in the [1-8] keV energy range, radially integrated within the shell [3-10] stellar radii, is consistent with an enhanced X-ray spectrum powered by shock-accelerated electrons. An unlikely ~100-fold amplification via turbulent dynamo of the magnetic field at the shock propagating through density inhomogeneities in the stellar corona is required for the synchrotron emission to dominate over the IC; the lack of time correlation between radio synchrotron and stellar pulsation contributes to make synchrotron as an unlikely emission mechanism for the flux enhancement. Although current observations cannot rule out a high-flux two-temperature thermal spectrum with a negligible nonthermal component, this event might confirm for the first time the association of Cepheids pulsation with shock-accelerated GeV electrons.

Keywords: X-ray transient sources, Shocks, Cepheid variable stars
A Disk Wind Driving the Rotating Molecular Outflow in CB 26. We present the 12CO (J = 2-1) sensitive molecular line and 1.3 mm continuum observations from the Submillimeter Array (SMA) of the bipolar outflow associated with the young star located in the Bok globule known as CB 26. The SMA observations were carried out in its extended configuration allowing us to study the kinematics and structure of the outflow with about 1″ or 140 au resolution. We find that the dusty and edge-on circumstellar disk related to the outflow has a projected spatial (deconvolved) size of 196 ± 31 × 42 ± 29 au with a total (gas+dust) mass of 0.031 ± 0.015 M ⊙. We estimated a dynamical mass for the central object of 0.66 ± 0.03 M ⊙, and the mass of the molecular outflow of 5 ± 1.5 × 10-5 M ⊙. All these values are consistent with recent estimations. The observations confirm that the outflow rotation has a similar orientation to that of the edge-on disk. For the outflow, we find that the following quantities: the rotation velocity (~1-3 km s-1), specific angular momentum (~200-700 au km s-1), and launching radius (~15-35 au) decrease with the height above the midplane, as observed in other molecular rotating outflows. The radius (~180-280 au) and expansion velocity (~2-4 km s-1) also increase with the height above the disk midplane for z &lt; 0 au; however, for z &gt; 0 au these quantities do not exhibit this behavior. Estimations of the outflow linear momentum rate, outflow angular momentum rate, and accretion luminosity seem to be well explained by the presence of a disk wind in CB 26.

Keywords: Stellar winds, Star formation
Tracking Hidden Magnetospheric Fluctuations in Accretion-powered Pulsars With a Kalman Filter. X-ray flux and pulse period fluctuations in an accretion-powered pulsar convey important information about the disk-magnetosphere interaction. It is shown that simultaneous flux and period measurements can be analysed with a Kalman filter based on the standard magnetocentrifugal accretion torque to generate accurate time-dependent estimates of three hidden state variables, which fluctuate stochastically and cannot be measured directly: the mass accretion rate, the Maxwell stress at the disk-magnetosphere boundary, and the radiative efficiency of accretion onto the stellar surface. The inferred fluctuation statistics carry implications for the physics of hydromagnetic instabilities at the disk-magnetosphere boundary and searches for continuous gravitational radiation from low-mass X-ray binaries.

Keywords: Neutron stars, Accretion, Gravitational waves, Pulsars
Caught in the Act: A Metal-rich High-velocity Cloud in the Inner Galaxy. We characterize the chemical and physical conditions in an outflowing high-velocity cloud (HVC) in the inner Galaxy. We report a supersolar metallicity of [O/H] = +0.36 ± 0.12 for the HVC at v LSR = 125.6 km s-1 toward the star HD 156359 (l = 328.°7, b = -14.°5, d = 9 kpc, z = -2.3 kpc). Using archival observations from the Far-Ultraviolet Spectroscopic Explorer (FUSE), the Hubble Space Telescope Imaging Spectrograph, and the European Southern Observatory Fiber-fed Extended Range Optical Spectrograph we measure high-velocity absorption in H I, O I, C II, N II, Si II, Ca II, Si III, Fe III, C IV, Si IV, N V, and O VI. We measure a low H I column density of log N(H I) = 15.54 ± 0.05 in the HVC from multiple unsaturated H I Lyman series lines in the FUSE data. We determine a low dust depletion level in the HVC from the relative strength of silicon, iron, and calcium absorption relative to oxygen, with [Si/O] = -0.33 ± 0.14, [Fe/O] = -0.30 ± 0.20, and [Ca/O] = -0.56 ± 0.16. Analysis of the high-ion absorption using collisional ionization models indicates that the hot plasma is multiphase, with the C IV and Si IV tracing 104.9 K gas and N V and O VI tracing 105.4 K gas. The cloud's metallicity, dust content, kinematics, and close proximity to the disk are all consistent with a Galactic wind origin. As the HD 156359 line of sight probes the inner Galaxy, the HVC appears to be a young cloud caught in the act of being entrained in a multiphase Galactic outflow and driven out into the halo.

Keywords: Galactic winds, Galactic center, High-velocity clouds, Chemical abundances, Ultraviolet astronomy