Sazuna/UAT_keywords huggingface dataset:
Intriguing Revelations from Lithium, Beryllium, and Boron. This is a report on some highlights of research on the rare light elements, lithium (Li), beryllium (Be), and boron (B), that were presented at my Henry Norris Russell Lecture in 2020 January. It is not a comprehensive review of work on these light elements, but contains sections on Big Bang nucleosynthesis of Li and the rarity of these light elements. It includes information on how they are observed, both historically and currently, and the difficulties entailed in determining their abundances. The production of Li, Be, and B is ongoing, so the youngest stars contain the most Li in their atmospheres and they have had less time to destroy it. All three elements are readily destroyed in stellar interiors, but have differing degrees of susceptibility to the particular nuclear fusion reactions which deplete their surface content. This feature makes them remarkably good probes into the otherwise unobservable interiors of stars and provides insights into internal-mixing processes. It also enhances the use of two or more of the three in sorting out the various processes at work in the insides of stars.

Keywords: Stellar abundances, Stellar atmospheres, Stellar evolution
The Hydrogen-poor Superluminous Supernovae from the Zwicky Transient Facility Phase I Survey. I. Light Curves and Measurements. During the Zwicky Transient Facility (ZTF) Phase I operations, 78 hydrogen-poor superluminous supernovae (SLSNe-I) were discovered in less than 3 yr, constituting the largest sample from a single survey. This paper (Paper I) presents the data, including the optical/UV light curves and classification spectra, while Paper II in this series will focus on the detailed analysis of the light curves and modeling. Our photometry is primarily taken by ZTF in the g, r, and i bands, and with additional data from other ground-based facilities and Swift. The events of our sample cover a redshift range of z = 0.06 - 0.67, with a median and 1σ error (16% and 84% percentiles) of ${z}_{\mathrm{med}}={0.265}_{-0.135}^{+0.143}$ . The peak luminosity covers -22.8 mag ≤ M  g,peak ≤ -19.8 mag, with a median value of $-{21.48}_{-0.61}^{+1.13}$ mag. The light curves evolve slowly with a mean rest-frame rise time of t rise = 41.9 ± 17.8 days. The luminosity and timescale distributions suggest that low-luminosity SLSNe-I with a peak luminosity ~-20 mag or extremely fast-rising events (&lt;10 days) exist, but are rare. We confirm previous findings that slowly rising SLSNe-I also tend to fade slowly. The rest-frame color and temperature evolution show large scatters, suggesting that the SLSN-I population may have diverse spectral energy distributions. The peak rest-frame color shows a moderate correlation with the peak absolute magnitude, i.e., brighter SLSNe-I tend to have bluer colors. With optical and UV photometry, we construct the bolometric luminosity and derive a bolometric correction relation that is generally applicable for converting g, r-band photometry to the bolometric luminosity for SLSNe-I.

Keywords: Supernovae
The Hydrogen-poor Superluminous Supernovae from the Zwicky Transient Facility Phase I Survey. II. Light-curve Modeling and Characterization of Undulations. We present analysis of the light curves (LCs) of 77 hydrogen-poor superluminous supernovae (SLSNe I) discovered during the Zwicky Transient Facility Phase I operation. We find that the majority (67%) of the sample can be fit equally well by both magnetar and ejecta-circumstellar medium (CSM) interaction plus 56Ni decay models. This implies that LCs alone cannot unambiguously constrain the physical power sources for an SLSN I. However, 23% of the sample show inverted V-shape, steep-declining LCs or features of long rise and fast post-peak decay, which are better described by the CSM+Ni model. The remaining 10% of the sample favors the magnetar model. Moreover, our analysis shows that the LC undulations are quite common, with a fraction of 18%-44% in our gold sample. Among those strongly undulating events, about 62% of them are found to be CSM-favored, implying that the undulations tend to occur in the CSM-favored events. Undulations show a wide range in energy and duration, with median values (and 1σ errors) being as $1.7{ \% }_{-0.7 \% }^{+1.5 \% }\,{E}_{\mathrm{rad},\mathrm{total}}$ and ${28.8}_{-9.1}^{+14.4}$ days, respectively. Our analysis of the undulation timescales suggests that intrinsic temporal variations of the central engine can explain half of the undulating events, while CSM interaction (CSI) can account for the majority of the sample. Finally, all of the well-observed He-rich SLSNe Ib either have strongly undulating LCs or the LCs are much better fit by the CSM+Ni model. These observations imply that their progenitor stars have not had enough time to lose all of the He-envelopes before supernova explosions, and H-poor CSM are likely to present in these events.

Keywords: Supernovae
Solar Coronal Density Turbulence and Magnetic Field Strength at the Source Regions of Two Successive Metric Type II Radio Bursts. We report spectral and polarimeter observations of two weak, low-frequency (≈85-60 MHz) solar coronal type II radio bursts that occurred on 2020 May 29 within a time interval ≈2 minutes. The bursts had fine structures, and were due to harmonic plasma emission. Our analysis indicates that the magnetohydrodynamic shocks responsible for the first and second type II bursts were generated by the leading edge (LE) of an extreme-ultraviolet flux rope/coronal mass ejection (CME) and interaction of its flank with a neighboring coronal structure, respectively. The CME deflected from the radial direction by ≈25° during propagation in the near-Sun corona. The estimated power spectral density and magnetic field strength (B) near the location of the first burst at heliocentric distance r ≈ 1.35 R ☉ are ≈2 × 10-3 W2m and ≈1.8 G, respectively. The corresponding values for the second burst at the same r are ≈10-3 W2m and ≈0.9 G. The significant spatial scales of the coronal turbulence at the location of the two type II bursts are ≈62-1 Mm. Our conclusions from the present work are that the turbulence and magnetic field strength in the coronal region near the CME LE are higher compared to the corresponding values close to its flank. The derived estimates of the two parameters correspond to the same r for both the CME LE and its flank, with a delay of ≈2 minutes for the latter.

Keywords: The Sun, Radio bursts, Solar radio emission, Solar magnetic fields, Solar corona, Solar coronal mass ejections
Radio and γ-ray Evidence for the Supernova Origin of High-velocity Cloud Complex M. Using λ21 cm galactic neutral hydrogen data from the HI4PI survey and 0.75-30 MeV γ-ray emission from the Imaging Compton Telescope, we have searched for the origin event that accelerated high-velocity cloud Complex M. Radio plots of l - b, l - v, and b - v show a cavity centered at (l, b) ~ (150°, 50.°) and extending about ±33°. The best view of the cavity is at a velocity of -25 km s-1, which shows a circular cross section on the back (receding) face. Complex M, at -85 km s-1, is on the front (approaching) face. The γ-ray emission reveals several minima, the largest centered at (l, b) ~(150°, 50.°) and coincident with the position and extent of the cavity seen in the radio data. Using the known distance to Complex M and assuming that the cavity is spherical, we can bootstrap the distance to the original, explosive source of the cavity D = 307 pc, calculate the radius of the cavity R = 166 pc, and approximate the expansion velocity V  E  ≈ 40 km s-1 of the cavity. The total energy of the expanding cavity is 3.0 ± 1.0 × 1050 erg, well within the range of a single supernova. These results indicate that this explosion took place about four million years ago. As the blast wave from this supernova propagated outwards, it began to sweep up interstellar gas and carved out the Local Chimney, a low-density extension of the Local Bubble that reaches into the galactic halo.

Keywords: Gamma-ray astronomy, Radio astronomy
A Red Giants' Toy Story. II. Understanding the Red-giant Branch Bump. The Red-Giant Branch Bump (RGBB) is one of the most noteworthy features in the red-giant luminosity function of stellar clusters. It is caused by the passage of the hydrogen-burning shell through the composition discontinuity left at the point of the deepest penetration by the convective envelope. When crossing the discontinuity the usual trend in increasing luminosity reverses for a short time before it increases again, causing a zig-zag in the evolutionary track. In spite of its apparent simplicity the actual physical reason behind the decrease in luminosity is not well understood and several different explanations have been offered. Here we use a recently proposed simple toy model for the structure of low-mass RGs, together with previous results, to show beyond reasonable doubt that the change in luminosity at the RGBB can be traced to the change in the mean molecular weight of the layers on top of the burning shell. And that these changes happen on a nuclear timescale. The change in the effective mean molecular weight, as the burning shell approaches the discontinuity, causes a drop in the temperature of the burning shell which is attenuated by the consequent feedback contraction of the layers immediately below the burning shell. Our work shows that, when applied correctly, including the feedback on the structure of the core together with the increase in the mass of the core, shell-source homology relations do a great quantitative job in explaining the properties of full evolutionary models at the RGBB.

Keywords: Stellar interiors, Stellar structures, Red giant branch, Red giant stars, Red giant bump
Revision of the γ-Ray Emission from SNR CTB 109 with the Fermi Large Area Telescope. CTB 109 is a middle-aged shell-type supernova remnant (SNR) with bright thermal X-ray emission. We reanalyze the GeV γ-ray emission from CTB 109 using 13 yr of Pass 8 data recorded by the Fermi Large Area Telescope. The γ-ray emission of CTB 109 shows a center bright morphology, which is well consistent with its thermal X-ray emission rather than the shell-type structure in the radio band. The spectral analysis shows an evident spectral curvature at ~several GeV for the GeV γ-ray spectrum, which can naturally explain the lack of TeV γ-ray emission from CTB 109. Although either a leptonic or a hadronic model could fit the multiwavelength observations of CTB 109, the hadronic model is favored considering its γ-ray morphology and the spectral curvature of the GeV spectrum. The unusual γ-ray spectrum of CTB 109 with other SNRs and the luminosity-diameter squared relation make CTB 109 distinguished both from the young-aged SNRs with hard GeV γ-ray spectra and several old-aged SNRs interacting with molecular clouds.

Keywords: Supernova remnants, Gamma-ray astronomy, Gamma-ray sources
The Statistical Polarization Properties of Coherent Curvature Radiation by Bunches: Application to Fast Radio Burst Repeaters. Fast radio bursts (FRBs) are extragalactic radio transients with a millisecond duration and an extremely high brightness temperature. Very recently, some highly circularly polarized bursts were found in a repeater, FRB 20201124A. The significant circular polarization might be produced by coherent curvature radiation by bunches with the line of sight (LOS) deviating from the bunch central trajectories. In this work, we carry out simulations to study the statistical properties of burst polarization within the framework of coherent curvature radiation by charged bunches in the neutron star magnetosphere for repeating FRBs. The flux is almost constant within the opening angle of the bunch. However, when the LOS derives from the bunch opening angle, the larger the derivation, the larger the circular polarization but the lower the flux. We investigate the statistical distribution of circular polarization and flux of radio bursts from an FRB repeater, and find that most of the bursts with high circular polarization have a relatively low flux. Besides, we find that most of the depolarization degrees of bursts have a small variation in a wide frequency band. Furthermore, we simulate the polarization angle (PA) evolution and find that most bursts show a flat PA evolution within the burst phases, and some bursts present a swing of the PA.

Keywords: Magnetars, Radio bursts, Radiative processes, Radio transient sources
MeV Gamma-Ray Source Contribution to the Inner Galactic Diffuse Emission. The origin of the inner Galactic emission, measured by COMPTEL with a flux of ~10-2 MeV cm-2 s-1 sr-1 in the 1-30 MeV energy range from the inner Galactic region, has remained unsettled since its discovery. In this paper, we elaborate on a model of individual MeV gamma-ray sources unresolved by COMPTEL. This is conducted for sources crossmatched between the Swift-BAT and Fermi-LAT catalogs by interpolating the energy spectra in the hard X-ray and GeV gamma-ray ranges, as well as unmatched sources between the two catalogs. We find that the source contribution to the COMPTEL emission would be at least ~20%. Combined with the Galactic diffuse emission, which is not well constrained, the COMPTEL emission can be roughly reproduced in some cases.

Keywords: Diffuse radiation, Gamma-ray sources, Galactic cosmic rays, Gamma-rays, Cosmic rays
The IGRINS YSO Survey. III. Stellar Parameters of Pre-main-sequence Stars in Ophiuchus and Upper Scorpius. We used the Immersion GRating Infrared Spectrometer (IGRINS) to determine fundamental parameters for 61 K- and M-type young stellar objects (YSOs) located in the Ophiuchus and Upper Scorpius star-forming regions. We employed synthetic spectra and a Markov chain Monte Carlo approach to fit specific K-band spectral regions and determine the photospheric temperature (T), surface gravity ( $\mathrm{log}g$ ), magnetic field strength (B), projected rotational velocity ( $v\sin i$ ), and K-band veiling (r  K ). We determined B for ~46% of our sample. Stellar parameters were compared to the results from Taurus-Auriga and the TW Hydrae association presented in Paper I of this series. We classified all the YSOs in the IGRINS survey with infrared spectral indices from Two Micron All Sky Survey and Wide-field Infrared Survey Explorer photometry between 2 and 24 μm. We found that Class II YSOs typically have lower $\mathrm{log}g$ and $v\sin i$ , similar B, and higher K-band veiling than their Class III counterparts. Additionally, we determined the stellar parameters for a sample of K and M field stars also observed with IGRINS. We have identified intrinsic similarities and differences at different evolutionary stages with our homogeneous determination of stellar parameters in the IGRINS YSO survey. Considering $\mathrm{log}g$ as a proxy for age, we found that the Ophiuchus and Taurus samples have a similar age. We also find that Upper Scorpius and TWA YSOs have similar ages, and are more evolved than Ophiuchus/Taurus YSOs.

Keywords: Fundamental parameters of stars, High resolution spectroscopy, Pre-main sequence stars, Infrared sources
NOEMA Detection of Circumnuclear Molecular Gas in X-Ray Weak Dual Active Galactic Nuclei: No Evidence for Heavy Obscuration. Dual active galactic nuclei (AGNs), which are the manifestation of two actively accreting supermassive black holes (SMBHs) hosted by a pair of merging galaxies, are a unique laboratory for studying the physics of SMBH feeding and feedback during an indispensable stage of galaxy evolution. In this work, we present NOEMA CO(2-1) observations of seven kiloparsec-scale dual-AGN candidates drawn from a recent Chandra survey of low redshift, optically classified AGN pairs. These systems are selected because they show unexpectedly low 2-10 keV X-ray luminosities for their small physical separations signifying an intermediate-to-late stage of merger. Circumnuclear molecular gas traced by the CO(2-1) emission is significantly detected in six of the seven pairs and 10 of the 14 nuclei, with an estimated mass ranging between (0.2-21) × 109 M ⊙. The primary nuclei, i.e., the ones with the higher stellar velocity dispersion, tend to have a higher molecular gas mass than the secondary. Most CO-detected nuclei show a compact morphology, with a velocity field consistent with a kiloparsec-scale rotating structure. The inferred hydrogen column densities range between 5 × 1021-2 × 1023 cm-2, but mostly at a few times 1022 cm-2, in broad agreement with those derived from X-ray spectral analysis. Together with the relatively weak mid-infrared emission, the moderate column density argues against the prevalence of heavily obscured, intrinsically luminous AGNs in these seven systems, but favors a feedback scenario in which AGN activity triggered by a recent pericentric passage of the galaxy pair can expel circumnuclear gas and suppress further SMBH accretion.

Keywords: Active galaxies, Active galactic nuclei, Galaxy mergers, CO line emission, Submillimeter astronomy, Interacting galaxies, Interferometry
A Combined Radio Multi-Survey Catalog of Fermi Unassociated Sources. Approximately one-third of existing γ-ray sources identified by the Fermi Gamma-Ray Space Telescope are considered to be unassociated, with no known counterpart at other frequencies/wavelengths. These sources have been the subject of intense scrutiny and observational effort during the observatory's mission lifetime, and here we present a method of leveraging existing radio catalogs to examine these sources without the need for specific dedicated observations, which can be costly and complex. Via the inclusion of many sensitive low-frequency catalogs we specifically target steep-spectrum sources such as pulsars. This work has found steep-spectrum radio sources contained inside 591 Fermi unassociated fields, with at least 21 of them being notable for having pulsar-like γ-ray properties as well. We also identify a number of other fields of interest based on various radio and γ-ray selections.

Keywords: Radio source catalogs, High energy astrophysics, Surveys, Active galaxies, Pulsars, Radio continuum emission, Gamma-ray astronomy, Spectral index, Radio astronomy
Magnetic-field Induced Deformation in Hybrid Stars. The effects of strong magnetic fields on the deconfinement phase transition expected to take place in the interior of massive neutron stars are studied in detail for the first time. For hadronic matter, the very general density-dependent relativistic mean field model is employed, while the simple, but effective vector-enhanced bag model is used to study quark matter. Magnetic-field effects are incorporated into the matter equation of state and in the general-relativity solutions, which also satisfy Maxwell's equations. We find that for large values of magnetic dipole moment, the maximum mass, canonical mass radius, and dimensionless tidal deformability obtained for stars using spherically symmetric Tolman-Oppenheimer-Volkoff (TOV) equations and axisymmetric solutions attained through the LORENE library differ considerably. The deviations depend on the stiffness of the equation of state and on the star mass being analyzed. This points to the fact that, unlike what was assumed previously in the literature, magnetic field thresholds for the approximation of isotropic stars and the acceptable use of TOV equations depend on the matter composition and interactions.

Keywords: Neutron stars, Nuclear astrophysics, Compact objects, Magnetars, Magnetic fields
Detection of Quasiperiodic Oscillations in the Blazar S4 0954+658 with TESS. We report the detection of several quasiperiodicities around 0.6-2.5 days in the optical emission of the blazar S4 0954+658. The source was observed by the Transiting Exoplanet Survey Satellite in six sectors and it showed these features in all but one of them, with a quasiperiodic oscillation of 1.52 days apparently present in portions of four of them. We used the generalized Lomb-Scargle periodogram method to search for significant signals and we confirmed them using a weighted wavelet transform for time-frequency domain analyses. We discuss several possible explanations for these rapid quasiperiodic variations and suggest that an origin in the innermost part of the accretion disk is most likely. Within this framework, we provide estimates for the mass of the black hole at the core of this blazar.

Keywords: Optical astronomy, Blazars, Black hole physics, Active galactic nuclei
Reconstructing the Assembly of Massive Galaxies. II. Galaxies Develop Massive and Dense Stellar Cores as They Evolve and Head toward Quiescence at Cosmic Noon. We use the spectral energy distribution fitting code PROSPECTOR to reconstruct the nonparametric star formation history (SFH) of massive ( $\mathrm{log}{M}_{* }\gt 10.3$ ) star-forming galaxies (SFGs) and quiescent galaxies (QGs) at redshift z obs ~ 2 to investigate the joint evolution of star formation activity and structural properties. Compared to extended SFGs, compact SFGs are more likely to have experienced multiple star formation episodes, with the fractional mass formed during the older (≥1 Gyr) episode being larger, suggesting that high-redshift SFGs assembled their central regions earlier and then kept growing in central mass as they become more compact. The SFH of compact QGs does not significantly differ from the average for this category, and shows an early burst followed by a gradual decline of the star formation rate. The SFH of extended QGs, however, is similar to that of post-starburst galaxies, and their morphology is also frequently disturbed. Knowledge of the SFH also enables us to empirically reconstruct the structural evolution of individual galaxies. While the progenitor effect is clearly observed and accounted for in our analysis, it alone is insufficient to explain the observed structural evolution. We show that, as they evolve from star-forming phase to quiescence, galaxies grow massive dense stellar cores. Quenching begins at the center and then propagates outward to the rest of the structure. We discuss possible physical scenarios for the observed evolution and find that our empirical constraints are in good quantitative agreement with the model predictions from dissipative accretion of gas to the center followed by massive starbursts before final quiescence (wet compaction).

Keywords: Galaxy formation, Galaxy structure, Galaxy evolution, Galaxy quenching, High-redshift galaxies
A Component of the Smith High-velocity Cloud Now Crossing the Galactic Plane. We have identified a new structure in the Milky Way: a leading component of the Smith high-velocity cloud that is now crossing the Galactic plane near longitude 25°. Using new 21 cm H I data from the Green Bank Telescope (GBT), we measured the properties of several dozen clouds that are part of this structure. Their kinematics is consistent with that of the Smith Cloud with a V LSR exceeding that permitted by circular rotation in their direction. Most of the clouds in the leading component show evidence that they are interacting with disk gas allowing the location of the interaction to be estimated. The leading component crosses the Galactic plane at a distance from the Sun of 9.5 kpc, about 4.5 kpc from the Galactic Center. Its H I mass may be as high as 106 M ⊙, comparable to the mass of the neutral component of the Smith Cloud, but only a fraction of this is contained in clouds that are resolved in the GBT data. Like the Smith Cloud, the leading component appears to be adding mass and angular momentum to the interstellar medium in the inner Galaxy. We suggest that the Smith Cloud is not an isolated object, but rather part of a structure that stretches more than 40° (~7 kpc) across the sky, in two pieces separated by a gap of ~1 kpc.

Keywords: High-velocity clouds, Neutral hydrogen clouds, Circumgalactic medium, Milky Way evolution, Milky Way Galaxy