Sazuna/UAT_keywords huggingface dataset:
Eclipsing Binaries in the Open Cluster Ruprecht 147. III. The Triple System EPIC 219552514 at the Main-sequence Turnoff. Spectroscopic observations are reported for the 2.75 day, double-lined, detached eclipsing binary EPIC 219552514 located at the turnoff of the old nearby open cluster Ruprecht 147. A joint analysis of our radial-velocity measurements and the K2 light curve leads to masses of ${M}_{1}={1.509}_{-0.056}^{+0.063}\,{M}_{\odot }$ and ${M}_{2}={0.649}_{-0.014}^{+0.015}\,{M}_{\odot }$ for the primary and secondary, along with radii of ${R}_{1}={2.505}_{-0.031}^{+0.026}\,{R}_{\odot }$ and ${R}_{2}={0.652}_{-0.012}^{+0.013}\,{R}_{\odot }$ , respectively. The effective temperatures are 6180 ± 100 K for the F7 primary and 4010 ± 170 K for the late K secondary. The orbit is circular, and the stars' rotation appears to be synchronized with the orbital motion. This is the third eclipsing system analyzed in the same cluster, following our earlier studies of EPIC 219394517 and EPIC 219568666. By comparison with stellar evolution models from the PARSEC series, we infer an age of ${2.67}_{-0.55}^{+0.39}$ Gyr that is consistent with the estimates for the other two systems. EPIC 219552514 is a hierarchical triple system, with the period of the slightly eccentric outer orbit being 463 days. The unseen tertiary is either a low-mass M dwarf or a white dwarf.

Keywords: Stellar ages, Fundamental parameters of stars, Eclipsing binary stars, Open star clusters, Stellar evolution
Magnetic Field Structure in Spheroidal Star-forming Clouds. II. Estimating Field Structure from Observed Maps. This paper presents models to estimate the structure of density and magnetic field strength in spheroidal condensations from maps of their column density and their polarization of magnetically aligned dust grains. The density model is obtained by fitting a column density map with an embedded p = 2 Plummer spheroid of any aspect ratio and inclination. The magnetic properties are based on the density model, the Davis-Chandrasekhar-Fermi (DCF) model of Alfvénic fluctuations, and the spheroid flux freezing (SFF) model of mass and flux conservation in Paper I. The field strength model has the resolution of the column density map, which is finer than the resolution of the DCF estimate of field strength. The models are applied to ALMA observations of the envelope of the protostar BHR 71 IRS1. Column density fits give the density model from (2.0 ± 0.4) × 105 to (7 ± 1) × 107 cm-3. The density model predicts the field directions map, which fits the polarization map best within 1100 au, with standard deviation of angle differences of 17°. In this region, the DCF mean field strength is 0.7 ± 0.2 mG, and the envelope mass is supercritical, with a ratio of mass to magnetic critical mass of 1.5 ± 0.4. The SFF field strength profile scales with the DCF field strength from 60 ± 10 μG to 3 ± 1 mG. The spatial resolution of the SFF field strength estimate is finer than the DCF resolution by a factor of ∼7, and the peak SFF field strength exceeds the DCF field strength by a factor of ∼4.

Keywords: Interstellar magnetic fields, Star formation
A Comparison of Rotating and Binary Stellar Evolution Models: Effects on Massive Star Populations. Both rotation and interactions with binary companions can significantly affect massive star evolution, altering interior and surface abundances, mass loss rates and mechanisms, observed temperatures and luminosities, and their ultimate core-collapse fates. The Geneva and the Binary Population and Spectral Synthesis (BPASS) stellar evolution codes include detailed treatments of the effects of rotation and binary evolution, respectively, and can illustrate the impact of these phenomena on massive stars and stellar populations. However, a direct comparison of these two widely used codes is vital if we hope to use their predictions for interpreting observations. In particular, rotating and binary models will predict different young stellar populations, impacting the outputs of stellar population synthesis (SPS) and the resulting interpretation of large samples of massive stars based on commonly used tools such as star count ratios. Here we compare the Geneva and BPASS evolutionary models, using an interpolated SPS scheme introduced in our previous work and a novel Bayesian framework to present the first in-depth direct comparison of massive stellar populations produced from single, rotating, and binary nonrotating evolution models. We calculate both models' predicted values of star count ratios and compare the results to observations of massive stars in Westerlund 1, h + χ Persei, and both Magellanic Clouds. We also consider the limitations of both the observations and the models, and how to quantitatively include observational completeness limits in SPS models. We demonstrate that the methods presented here, when combined with robust stellar evolutionary models, offer a potential means of estimating the physical properties of massive stars in large stellar populations.

Keywords: Local Group, Binary stars, Stellar populations, Massive stars, Galaxy stellar content, Stellar types, Stellar rotation, Star counts
Ca hnk: The Calcium-rich Transient Supernova 2016hnk from a Helium Shell Detonation of a Sub-Chandrasekhar White Dwarf. We present observations and modeling of SN 2016hnk, a Ca-rich supernova (SN) that is consistent with being the result of a He-shell double-detonation explosion of a C/O white dwarf. We find that SN 2016hnk is intrinsically red relative to typical thermonuclear SNe and has a relatively low peak luminosity ( MB = -15.4 mag), setting it apart from low-luminosity SNe Ia. SN 2016hnk has a fast-rising light curve that is consistent with other Ca-rich transients (tr = 15 days). We determine that SN 2016hnk produced 0.03 ± 0.01 M⊙ of 56Ni and 0.9 ± 0.3 M⊙ of ejecta. The photospheric spectra show strong, high-velocity Ca II absorption and significant line blanketing at λ &lt; 5000 Å, making it distinct from typical (SN 2005E-like) Ca-rich SNe. SN 2016hnk is remarkably similar to SN 2018byg, which was modeled as a He-shell double-detonation explosion. We demonstrate that the spectra and light curves of SN 2016hnk are well modeled by the detonation of a 0.02 ${M}_{\odot }$ helium shell on the surface of a 0.85 ${M}_{\odot }$ C/O white dwarf. This analysis highlights the second observed case of a He-shell double-detonation and suggests a specific thermonuclear explosion that is physically distinct from SNe that are defined simply by their low luminosities and strong [Ca II] emission.

Keywords: Observational astronomy, White dwarf stars, Type Ia supernovae, Supernovae
Gamma-Ray Burst Afterglows in the Multimessenger Era: Numerical Models and Closure Relations. Gamma-ray bursts (GRBs) associated with gravitational wave events are, and will likely continue to be, viewed at a larger inclination than GRBs without gravitational wave detections. As demonstrated by the afterglow of GW 170817A, this requires an extension of the common GRB afterglow models, which typically assume emission from an on-axis top-hat jet. We present a characterization of the afterglows arising from structured jets, providing a framework covering both successful and choked jets. We compute new closure relations for decelerating structured jets and compare them with the established relations for energy injection and refreshed shock models. The temporal slope before the jet break is found to be a simple function of the ratio between the viewing angle and effective opening angle of the jet. A numerical model to calculate synthetic light curves and spectra is publicly available as the open-source Python package afterglowpy.

Keywords: Publicly available software, Open source software, Gamma-ray bursts, Theoretical models, Computational astronomy, High energy astrophysics, Astronomy software, Relativistic jets, Transient sources, Computational methods, Shocks, Astrophysical fluid dynamics
Laboratory Study of Bilateral Supernova Remnants and Continuous MHD Shocks. Many supernova remnants (SNRs), such as G296.5+10.0, exhibit an axisymmetric or barrel shape. Such morphologies have previously been linked to the direction of the Galactic magnetic field, although this remains uncertain. These SNRs generate magnetohydrodynamic shocks in the interstellar medium, modifying its physical and chemical properties. The ability to study these shocks through observations is difficult due to the small spatial scales involved. In order to answer these questions, we perform a scaled laboratory experiment in which a laser-generated blast wave expands under the influence of a uniform magnetic field. The blast wave exhibits a spheroidal shape, whose major axis is aligned with the magnetic field, in addition to a more continuous shock front. The implications of our results are discussed in the context of astrophysical systems.

Keywords: Galaxy magnetic fields, Magnetohydrodynamics, Astrophysical magnetism, Supernova remnants, Interstellar magnetic fields, Shocks, Magnetic fields
Single-pulse Modeling and the Bi-drifting Subpulses of Radio Pulsar B1839-04. We study the bi-drifting pulsar B1839-04, where the observed subpulse drift direction in the two leading pulse components is opposite from that in the two trailing components. Such diametrically opposed apparent motions challenge our understanding of an underlying structure. We find that for the geometry spanned by the observer and the pulsar magnetic and rotation axes, the observed bi-drifting in B1839-04 can be reproduced assuming a nondipolar configuration of the surface magnetic field. Acceptable solutions are found to either have relatively weak (∼1012 G) or strong (∼1014 G) surface magnetic fields. Our single-pulse modeling shows that a global electric potential variation at the polar cap that leads to a solid-body-like rotation of spark forming regions is favorable in reproducing the observed drift characteristics. This variation of the potential additionally ensures that the variability is identical in all pulse components resulting in the observed phase locking of subpulses. Thorough and more general studies of pulsar geometry show that a low ratio of impact factor to opening angle (β/ρ) increases the likelihood of bi-drifting to be observed. We thus conclude that bi-drifting is visible when our line of sight crosses close to the magnetic pole.

Keywords: Pulsars
Variability of the Great Disk Shadow in Serpens. We present dual-epoch Hubble Space Telescope imaging of the great disk shadow in the Serpens star-forming region. The near-infrared images show strong variability of the disk shadow, revealing dynamics of the inner disk on timescales of months. The Great Shadow is projected onto the Serpens reflection nebula by an unresolved protoplanetary disk surrounding the young intermediate-mass star SVS2/CK3/EC82. Since the shadow extends out to a distance of at least 17,000 au, corresponding to a light-travel time of 0.24 yr, the images may reveal detailed changes in the disk scale height and position angle on timescales as short as a day, corresponding to the angular resolution of the images, and up to the 1.11 yr span between two observing epochs. We present a basic retrieval of temporal changes in the disk density structure, based on the images. We find that the inner disk changes position angle on timescales of months, and that the change is not axisymmetric, suggesting the presence of a non-axisymmetric dynamical forcing on ∼1 au size scales. We consider two different scenarios, one in which a quadrupolar disk warp orbits the central star, and one in which an unequal-mass binary orbiting out of the disk plane displaces the photocenter relative to the shadowing disk. Continued space-based monitoring of the great disk shadow is required to distinguish between these scenarios, and could provide unique and detailed insight into the dynamics of inner protoplanetary disks not available through other means.

Keywords: Reverberation mapping, Protoplanetary disks, Exoplanet formation
The Semiforbidden C III] λ1909 Emission in the Rest-ultraviolet Spectra of Green Pea Galaxies. We used the Space Telescope Imaging Spectrograph on the Hubble Space Telescope (HST) to observe the semiforbidden C III] λλ1907, 1909 doublet emission in green pea galaxies at 0.13 ≤ z ≤ 0.3. We detect C III] emission in 7/10 galaxies with C III] equivalent widths (EWs) that range from 2 to 10 Å, confirming that C III] emission is almost ubiquitous in low-mass, low-metallicity (12+log(O/H) &lt; 8.4) galaxies that are characterized by strong optical [O III] λ5007 emission. The composite UV spectrum shows evidence for the He II λ1640 emission line and interstellar absorption features (e.g., C IV λλ1548, 1550, Al III λλ1854, 1862). We do not detect the O III] λλ1661, 1666 emission with &gt;3σ significance. The observed C III] emission line strengths are consistent with the predictions from photoionization models that incorporate the effects of binary stellar evolution with young stellar ages ≤3-5 Myr and high ionization parameters (log U &gt; -2). The hard ionizing radiation from young massive stars and high nebular temperatures at low metallicities can account for the observed high EWs of C III] λ1909 and [O III] λ5007 emission lines. Some of the star-forming galaxies at high redshift and local blue compact dwarf galaxies show offsets from the EW(C III]) versus EW([O III]) model grids, indicating an additional contribution to the continuum emission from composite stellar populations or different C/O abundances, nebular temperatures, and electron densities than assumed in the photoionization models. The green pea galaxies do not show a significant correlation between the Lyα and C III] EWs, and the observed scatter is likely due to the variations in the optical depth of Lyα to the neutral gas. Green pea galaxies are likely to be density-bounded, and we examined the dependence of C III] emission on the Lyman continuum optical depth. The potential LyC leaker galaxies in our sample have high C III] EWs that can only be reproduced by starburst ages as young as &lt;3 Myr and harder ionizing spectra than the nonleakers. Among the galaxies with similar metallicities and ionization parameters, the C III] EW appears to be stronger for those with higher optical depth to LyC, as expected from the photoionization models. There are various factors that affect the C III] emission line strengths, and further investigation of a larger sample of C III] emitters is necessary to calibrate the dependence of C III] emission on the escape of LyC radiation and enable application of the C III] diagnostics to galaxies in the reionization epoch.

Keywords: Starburst galaxies, Emission line galaxies, H II regions, Spectroscopy, High-redshift galaxies
Fake Massive Black Holes in the Milli-Hertz Gravitational-wave Band. In gravitational-wave (GW) astronomy accurate measurement of the source parameters, such as mass, relies on accurate waveform templates. Currently, templates are developed assuming that a source, such as a stellar-mass binary black hole (BBH), is residing in a vacuum. However, astrophysical models predict that BBHs could form in gaseous environments, such as common envelopes, stellar cores, and accretion disks of active galactic nuclei. Here we revisit the impact of gas on the GW waveforms of BBHs with a focus on the early inspiral phase when the GW frequency is around milli-Hertz. We show that for these BBHs, gas friction could dominate the dynamical evolution and hence duplicate chirp signals. The relevant hydrodynamical timescale, τgas, could be much shorter than the GW radiation timescale, τgw, in the above astrophysical scenarios. As a result, the observed chirp mass is higher than the real one by a factor of ${(1+{\tau }_{\mathrm{gw}}/{\tau }_{\mathrm{gas}})}^{3/5}$ if the gas effect is ignored in the data analysis. This kind of error also results in an overestimation of the source distance by a factor of $(1+{\tau }_{\mathrm{gw}}/{\tau }_{\mathrm{gas}})$ . By performing matched-filtering analysis in the milli-Hertz band, we prove that the gas-dominated signals are practically indistinguishable from the chirp signals of those more massive BBHs residing in a vacuum environment. Such fake massive objects in the milli-Hertz band, if not appropriately accounted for in the future, may alter our understanding of the formation, evolution, and detection of BBHs.

Keywords: Accretion, Hydrodynamics, Active galactic nuclei, Gravitational wave sources
Cosmological Evolution of Flat-spectrum Radio Quasars Based on the Swift/BAT 105 Month Catalog and Their Contribution to the Cosmic MeV Gamma-Ray Background Radiation. We present a new X-ray luminosity function of flat-spectrum radio quasars (FSRQs) utilizing the latest Swift/BAT 105 month X-ray source catalog. Contrary to previous studies of FSRQs in the X-ray band, using the luminosity-dependent density evolution model we find that FSRQs show evolutionary peaks at z ∼ 1-2 depending on luminosities. Our result is rather consistent with the evolution of FSRQs seen in the radio and GeV bands, although the number density is a factor of 5-10 smaller. We further explore the contribution of FSRQs to the cosmic MeV gamma-ray background radiation. We find that FSRQs can explain only ∼3% of the observed MeV gamma-ray background fluxes around 1 MeV, indicating other populations are required. Future MeV gamma-ray observations will be keys for understanding the origin of the MeV gamma-ray background radiation.

Keywords: Relativistic jets, Galaxy jets
2MASS J04435686+3723033 B: A Young Companion at the Substellar Boundary with Potential Membership in the β Pictoris Moving Group. We present a detailed characterization of 2MASS J04435750+3723031, a low-mass companion orbiting the young M2 star 2MASS J04435686+3723033 at 7"6 (550 au) with potential membership in the 23 Myr β Pictoris moving group (βPMG). Using near-infrared (NIR) spectroscopy of the companion from IRTF/SpeX, we have found a spectral type of M6 ± 1 and indications of youth through age-sensitive absorption lines and a low surface gravity index (VL-G). A young age is supported by Hα emission and lithium absorption in the host. We reevaluate the membership of this system and find that it is a marginally consistent kinematic match to the βPMG using Gaia parallaxes and new radial velocities for the host and companion. If this system does belong to the βPMG, it would be a kinematic outlier and the companion would be overluminous compared to other similar ultracool objects like PZ Tel B; this would suggest that 2M0443+3723 B could be a close binary (≈52+52 MJup if equal-flux, compared with 99 ± 5 MJup if single), and would make it the sixth substellar companion in this group. To test this hypothesis, we acquired NIR adaptive optics images with Keck II/NIRC2, but they do not resolve the companion to be a binary down to the diffraction limit of ∼3 au. If 2M0443+3723 AB does not belong to any moving group, then its age is more uncertain. In this case it is still young (≲30 Myr), and the implied mass of the companion would be between ∼30 and 110 MJup.

Keywords: Close binary stars, Brown dwarfs, Direct imaging, Low mass stars
3D Numerical Simulations of Solar Quiet Chromosphere Wave Heating. Despite numerous observational and theoretical attempts, the heating problem of the solar chromosphere still remains unsolved. We develop a novel 3D two-fluid model that accounts for dynamics of charged species and neutrals, and use it to perform the numerical simulations of granulation driven jets and associated waves in a quiet region of the solar chromosphere. The energy carried by the waves is dissipated through ion-neutral collisions, which are sufficient to balance radiative energy losses and to sustain the quasi-stationary atmosphere whose ion and neutral number densities, ionization fraction, and temperature profiles are relatively close to the observationally based semi-empirical model. Additional verification of our results is provided by a good fit of the numerically predicted waveperiod variations with height to the recent observational data. These observational validations of the numerical results demonstrate that the wave heating problem of a quiet region of the chromosphere may be solved.

Keywords: Quiet sun
Zwicky Transient Facility Constraints on the Optical Emission from the Nearby Repeating FRB 180916.J0158+65. The discovery rate of fast radio bursts (FRBs) is increasing dramatically thanks to new radio facilities. Meanwhile, wide-field instruments such as the 47 deg2 Zwicky Transient Facility (ZTF) survey the optical sky to study transient and variable sources. We present serendipitous ZTF observations of the Canadian Hydrogen Intensity Mapping Experiment (CHIME) repeating source FRB 180916.J0158+65 that was localized to a spiral galaxy 149 Mpc away and is the first FRB suggesting periodic modulation in its activity. While 147 ZTF exposures corresponded to expected high-activity periods of this FRB, no single ZTF exposure was at the same time as a CHIME detection. No &gt;3σ optical source was found at the FRB location in 683 ZTF exposures, totaling 5.69 hr of integration time. We combined ZTF upper limits and expected repetitions from FRB 180916.J0158+65 in a statistical framework using a Weibull distribution, agnostic of periodic modulation priors. The analysis yielded a constraint on the ratio between the optical and radio fluences of η ≲ 200, corresponding to an optical energy Eopt ≲ 3 × 1046 erg for a fiducial 10 Jy ms FRB (90% confidence). A deeper (but less statistically robust) constraint of η ≲ 3 can be placed assuming a rate of $r(\gt 5\,\mathrm{Jy}\,\mathrm{ms})=1\,{\mathrm{hr}}^{-1}$ and 1.2 ± 1.1 FRB occurring during exposures taken in high-activity windows. The constraint can be improved with shorter per-image exposures and longer integration time, or observing FRBs at higher Galactic latitudes. This work demonstrated how current surveys can statistically constrain multiwavelength counterparts to FRBs even without deliberately scheduled simultaneous radio observation.

Keywords: Neutron stars, Optical bursts, Transient sources, Radio bursts, Compact objects
Hot Corinos Chemical Diversity: Myth or Reality?. After almost 20 years of hunting, only about a dozen hot corinos, hot regions enriched in interstellar complex organic molecules (iCOMs), are known. Of them, many are binary systems with the two components showing drastically different molecular spectra. Two obvious questions arise. Why are hot corinos so difficult to find and why do their binary components seem chemically different? The answer to both questions could be a high dust opacity that would hide the molecular lines. To test this hypothesis, we observed methanol lines at centimeter wavelengths, where dust opacity is negligible, using the Very Large Array interferometer. We targeted the NGC 1333 IRAS 4A binary system, for which one of the two components, 4A1, has a spectrum deprived of iCOMs lines when observed at millimeter wavelengths, while the other component, 4A2, is very rich in iCOMs. We found that centimeter methanol lines are similarly bright toward 4A1 and 4A2. Their non-LTE analysis indicates gas density and temperature ( $\geqslant 2\times {10}^{6}$ cm-3 and 100-190 K), methanol column density (∼1019 cm-2), and extent (∼35 au in radius) similar in 4A1 and 4A2, proving that both are hot corinos. Furthermore, the comparison with previous methanol line millimeter observations allows us to estimate the optical depth of the dust in front of 4A1 and 4A2, respectively. The obtained values explain the absence of iCOMs line emission toward 4A1 at millimeter wavelengths and indicate that the abundances toward 4A2 are underestimated by ∼30%. Therefore, centimeter observations are crucial for the correct study of hot corinos, their census, and their molecular abundances.

Keywords: Chemical abundances, Astrochemistry, Star formation, Interstellar medium, Protostars