Sazuna/UAT_keywords huggingface dataset:
A Tidal Disruption Event Candidate Discovered in the Active Galactic Nucleus SDSS J022700.77-042020.6. We report the discovery of a tidal disruption event (TDE) candidate occurring in the active galactic nucleus (AGN) SDSS J022700.77-042020.6. A sudden increase in flux from J0227-0420 during the second half of 2009 appears in the long-term optical, UV, and near-IR (NIR) light curves. A plateau phase, following an initial decline, is seen in the near-UV (NUV) and optical light curves. We find possible evidence that the plateau in the NUV band may lag behind the optical ones by ∼70-80 days with also a much shorter duration, that is, ∼7-15 days against ∼40-50 days. The long-term NUV/optical (after the plateau phase), NIR, and mid-infrared (MIR) light curves can be well characterized with a form of L(t) ∝ t-β, consistent with the expectation of a TDE. The plateaus can be explained if stellar streams collide with the preexisting disk at different radii. Though the overall fallback rate decreases, the material in the outer disk drifts inward and increases the local accretion rate in the inner region, producing the NUV/optical plateaus. The possible lag is then attributed to viscosity delay. The index β of the NIR J, H, and Ks bands (∼1.4-3.3) is steeper than that of the UV/optical (∼0.7-1.3) and MIR bands (∼0.9-1.8), which may suggest that a certain fraction of the dust in the inner region of the torus may be sublimated during the TDE phase. Our results indicate that, due to collisions between stellar debris and the preexisting disk, the light curves of TDEs occurring in AGNs may show distinctive features, which may shed new light on the accretion process.

Keywords: Tidal disruption, Active galactic nuclei
Detecting Pair-instability Supernovae at z ≲ 5 with the James Webb Space Telescope. Pair-instability supernovae (PISNe) are the ultimate cosmic lighthouses, capable of being observed at z ≳ 25 and revealing the properties of primordial stars at cosmic dawn. But it is now understood that the spectra and light curves of these events evolved with redshift as the universe became polluted with heavy elements because chemically enriched stars in this mass range typically lose most of their hydrogen envelopes and explode as bare helium cores. The light curves of such transients can be considerably dimmer in the near-infrared today than those of primordial PISNe of equal energy and progenitor mass. Here, we calculate detection rates for PISNe whose progenitors lost their outer layers to either line-driven winds or rotation at z ≲ 10, their detection limit in redshift for the James Webb Space Telescope (JWST). We find that JWST may be able to detect only Population II (metal-poor) PISNe over the redshift range of z ≲ 4, but not their Population III (metal-free) counterparts.

Keywords: Early universe, Supernovae
Cosmic-Ray Acceleration in Radio-jet Shear Flows: Scattering Inside and Outside the Jet. A steady-state, analytical model of energetic particle acceleration in radio-jet shear flows due to cosmic-ray viscosity is explored, including particle scattering both into and out of the shear flow acceleration region. This involves solving a mixed Dirichlet-Von Neumann boundary value problem at the edge of the jet. The spectrum of the accelerated particles is harder than the free-escape case from the edge of the jet. The flow velocity u = u(r) ez is along the axis of jet (the z-axis). u is independent of distance z along the jet axis, and u(r) is a monotonically decreasing function of cylindrical radius r from the jet axis. The scattering time $\tau {(r,p)={\tau }_{0}(p/{p}_{0})}^{\alpha }$ where p is the particle momentum in the fluid frame in the shear flow region 0 &lt; r &lt; r2, and $\tau {(r,p)={\tau }_{0}(p/{p}_{0})}^{\alpha }{(r/{r}_{2})}^{s}$ outside the jet (r &gt; r2). Green's functions are obtained for monoenergetic injection of particles with momentum p = p0 at radius r = r1 (0 &lt; r1 &lt; r2). The Green's function and Green's formula are used to determine solutions for a general spectrum of particles at $r=\infty $ . Solutions are obtained corresponding to a monoenergetic spectrum at infinity. We discuss the implications of these results for the acceleration of ultra-high-energy cosmic-rays in active galactic nucleus jet sources. Leaky box models of particle acceleration in shear flows, including synchrotron losses and particle escape, are used to describe the momentum spectrum of accelerated particles. The use of the relativistic telegrapher transport equation model is discussed.

Keywords: Relativistic jets, Radio jets, Ultra-high-energy cosmic radiation, Cosmic rays
Absolute Dimensions of the Unevolved F-type Eclipsing Binary BT Vulpeculae. We report extensive differential V-band photometry and high-resolution spectroscopy for the 1.14 day, detached, double-lined eclipsing binary BT Vul (F0+F7). Our radial-velocity monitoring and light-curve analysis lead to absolute masses and radii of ${M}_{1}=1.5439\pm 0.0098\,{{ \mathcal M }}_{\odot }^{{\rm{N}}}$ and ${R}_{1}=1.536\pm 0.018\,{{ \mathcal R }}_{\odot }^{{\rm{N}}}$ for the primary, and ${M}_{2}=1.2196\pm 0.0080\,{{ \mathcal M }}_{\odot }^{{\rm{N}}}$ and ${R}_{2}=1.151\pm 0.029\,{{ \mathcal R }}_{\odot }^{{\rm{N}}}$ for the secondary. The effective temperatures are 7270 ± 150 K and 6260 ± 180 K, respectively. Both stars are rapid rotators, and the orbit is circular. A comparison with stellar evolution models from the MESA Isochrones and Stellar Tracks series shows excellent agreement with these determinations, for a composition of $[\mathrm{Fe}/{\rm{H}}]=+0.08$ and an age of 350 Myr. The two components of BT Vul are very near the zero-age main sequence.

Keywords: CCD photometry, Fundamental parameters of stars, Spectroscopy, Eclipsing binary stars, Radial velocity, Stellar evolution
Evidence for He I 10830 Å Absorption during the Transit of a Warm Neptune around the M-dwarf GJ 3470 with the Habitable-zone Planet Finder. Understanding the dynamics and kinematics of outflowing atmospheres of hot and warm exoplanets is crucial to understanding the origins and evolutionary history of the exoplanets near the evaporation desert. Recently, ground-based measurements of the meta-stable helium atom's resonant absorption at 10830 Å has become a powerful probe of the base environment which is driving the outflow of exoplanet atmospheres. We report evidence for the He I 10830 Å in absorption (equivalent width ∼0.012 ± 0.002 Å) in the exosphere of a warm Neptune orbiting the M-dwarf GJ 3470, during three transits using the Habitable Zone Planet Finder near-infrared spectrograph. This marks the first reported evidence for He I 10830 Å atmospheric absorption for a planet orbiting an M-dwarf. Our detected absorption is broad and its blueshifted wing extends to -36 km s-1, the largest reported in the literature to date. We modeled the state of helium atoms in the exosphere of GJ3470b based on assumptions on the UV and X-ray flux of GJ 3470, and found our measurement of flux-weighted column density of meta-stable state helium $({N}_{\mathrm{He}{}_{3}^{2}{\rm{S}}}=2.4\times {10}^{10}\,{\mathrm{cm}}^{-2})$ , derived from our transit observations, to be consistent with the model, within its uncertainties. The methodology developed here will be useful to study and constrain the atmospheric outflow models of other exoplanets like GJ 3470b, which are near the edge of the evaporation desert.

Keywords: High resolution spectroscopy, Exoplanet atmospheric composition , Exosphere, Exoplanet astronomy, Exoplanet atmospheres, Near infrared astronomy
Formation of NH<SUB>2</SUB>CHO and CH<SUB>3</SUB>CHO upon UV Photoprocessing of Interstellar Ice Analogs. Complex organic molecules (COMs) can be produced by energetic processing of interstellar ice mantles accreted on top of dust grains. Two COMs with proposed energetic ice formation pathways are formamide and acetaldehyde. Both have been detected in solar system comets and in different circumstellar and interstellar environments. In this work, we study the NH2CHO and CH3CHO formation upon UV photoprocessing of CO:NH3 and CO:CH4 ice samples. The conversion from ${\mathrm{NH}}_{\dot{2}}$ radicals to NH2CHO is 2-16 times higher than the conversion from ${\mathrm{CH}}_{\dot{3}}$ radicals to CH3CHO under the explored experimental conditions, likely because the formation of the latter competes with the formation of larger hydrocarbons. In addition, the conversion of ${\mathrm{NH}}_{\dot{2}}$ into NH2CHO at 10 K increases with the NH3 abundance in the ice, and also with the temperature in CO-dominated CO:NH3 ices. This is consistent with the presence of a small ${\mathrm{NH}}_{\dot{2}}$ and HCO. reorientation barrier for the formation of NH2CHO, which is overcome with an increase in the ice temperature. The measured NH2CHO and CH3CHO formation efficiencies and rates are similar to those found during electron irradiation of the same ice samples under comparable conditions, suggesting that both UV photons and cosmic rays would have similar contributions to the solid-state formation of these species in space. Finally, the measured conversion yields (up to one order of magnitude higher for NH2CHO) suggest that in circumstellar environments, where the observed NH2CHO/CH3CHO abundance ratio is ∼0.1, there are likely additional ice and/or gas-phase formation pathways for CH3CHO.

Keywords: Interstellar molecules, Laboratory astrophysics, Ice formation
The Viability of the 3 + 1 Neutrino Model in the Supernova Neutrino Process. Adopting the 3 + 1 neutrino mixing parameters by the IceCube and short baseline experiments, we investigate the sterile-active neutrino oscillation effects on the supernova neutrino process. For the sterile neutrino (νs), we study two different luminosity models. First, we presume that the νs does not interact with other particles through the standard interactions apart from the oscillation with the active neutrinos. Second, we consider the νs directly produced by νe scattering with the matter. In both cases, we find that the pattern of neutrino oscillations drastically impacts on the νs in supernova environments. In particular multiple resonances occur, and consequently affect thermal neutrino-induced reaction rates. As a result, 7Li, 7Be, 11B, 11C, 92Nb, 98Tc, and 138La yields in the ν-process change. Among those nuclei, we constrain the 7Li and 11B yields using the analysis of observed SiC X grains. Based on the meteoritic data, we conclude that the second model can be allowed, while the first model is excluded. The viability of the second model depends on the sterile neutrino temperature and the neutrino mass hierarchy.

Keywords: Neutrino oscillations, Supernova neutrinos, Nuclear astrophysics, Nucleosynthesis
Thermal Components in Gamma-Ray Bursts. II. Constraining the Hybrid Jet Model. In explaining the physical origin of the jet composition of gamma-ray bursts (GRBs), a more general picture, I.e., the hybrid jet model (which introduced another magnetization parameter σ0 on the basis of the traditional fireball model), has been well studied in Gao &amp; Zhang. However, it still has not yet been applied to a large GRB sample. Here, we first employ the "top-down" approach of Gao &amp; Zhang to diagnose the photosphere properties at the central engine to see how the hybrid model can account for the observed data as well, through applying a Fermi GRB sample (eight bursts) with the detected photosphere component, as presented in Li (our Paper I). We infer all physical parameters of a hybrid problem with three typical values of the radius of the jet base (r0 = 107, 108, and 109 cm). We find that the dimensionless entropy for all the bursts shows η ≫ 1 while the derived (1+σ0) for five bursts (GRB 081224, GRB 110721A, GRB 090719, GRB 100707, and GRB 100724) is larger than unity, indicating that in addition to a hot fireball component, another cold Poynting-flux component may also play an important role. Our analysis also shows that in a few time bins for all r0 in GRB 081224 and GRB 110721A, the magnetization parameter at ∼1015 cm (1+σr15) is greater than unity, which implies that internal-collision-induced magnetic reconnection and turbulence may be the mechanism to power the nonthermal emission, rather than internal shocks. We conclude that the majority of bursts (probably all) can be well explained by the hybrid jet problem.

Keywords: Gamma-ray bursts, Relativistic jets, Astronomy data analysis
Observational Evidence for the Origin of High-energy Neutrinos in Parsec-scale Nuclei of Radio-bright Active Galaxies. Observational information on high-energy astrophysical neutrinos is being continuously collected by the IceCube observatory. However, the sources of the neutrinos are still unknown. In this study, we use radio very long baseline interferometry (VLBI) data for a complete VLBI flux density-limited sample of active galactic nuclei (AGNs). We address the problem of the origin of astrophysical neutrinos with energies above 200 TeV in a statistical manner. It is found that AGNs positionally associated with IceCube events have typically stronger parsec-scale cores than the rest of the sample. The posttrial probability of a chance coincidence is 0.2%. We select the four strongest AGNs as highly probable associations: 3C 279, NRAO 530, PKS 1741-038, and OR 103. Moreover, we find an increase of radio emission at frequencies above 10 GHz around neutrino arrival times for several other VLBI-selected AGNs on the basis of RATAN-600 monitoring. The most pronounced example of such behavior is PKS 1502+106. We conclude that AGNs with bright Doppler-boosted jets constitute an important population of neutrino sources. High-energy neutrinos are produced in their central parsec-scale regions, probably in proton-photon interactions at or around the accretion disk. Radio-bright AGNs that are likely associated with neutrinos have very diverse γ-ray properties, suggesting that γ-rays and neutrinos may be produced in different regions of AGNs and not directly related. A small viewing angle of the jet-disk axis is, however, required to detect either of them.

Keywords: Quasars, Neutrino astronomy, Active galaxies, Galaxy jets, Radio continuum emission
Energetic Neutral Atom Flux from the Inner Heliosheath and Its Connection to Termination Shock Properties. We present statistical comparisons between energetic neutral atom (ENA) fluxes obtained using a global simulation of the heliosphere and data collected by the Interstellar Boundary Explorer (IBEX) spacecraft. The simulation of the inner heliosheath (IHS) ENA flux is based on a 3D steady-state heliosphere, while the data are from the IBEX-Hi instrument over the time period 2009-2015. The statistical comparison is performed by calculating the chi-square value between the simulated ENA fluxes and the data for each line of sight in the sky. A comparison with exposure-averaged data for solar minimum and solar maximum conditions is also performed to see the effect of solar wind (SW) properties on the IHS ENA fluxes. The model matches well with the data in the flanks and parts of the nose of the heliosphere, whereas the match is poor in the downwind tail, ribbon, and polar regions. We interpret these results to mean that (I) heliosheath plasma in the polar region consists of advected fast (or slow) SW during the solar minimum (or maximum) condition, and (II) heliospheric termination shock parameters are likely different over the poles. A poor match at around 30° north and south of the downwind direction is likely due to the existence of a mixture of plasma that comes from fast and slow SW. While our results are consistent with a single heliotail, the shape of the heliosphere continues to be an area of active research, and more data and further modeling are needed to determine its true structure.

Keywords: Termination shock, Heliosheath, Heliosphere, Pickup ions
Star Formation Occurs in Dense Gas, but What Does "Dense" Mean?. We report results of a project to map HCN and ${\mathrm{HCO}}^{+}$ $J=1\to 0$ emission toward a sample of molecular clouds in the inner Galaxy, all containing dense clumps that are actively engaged in star formation. We compare these two molecular line tracers with millimeter continuum emission and extinction, as inferred from 13CO, as tracers of dense gas in molecular clouds. The fraction of the line luminosity from each tracer that comes from the dense gas, as measured by ${A}_{{\rm{V}}}\gt 8$ mag, varies substantially from cloud to cloud. In all cases, a substantial fraction (in most cases, the majority) of the total luminosity arises in gas below the ${A}_{{\rm{V}}}\gt 8$ mag threshold and outside the region of strong millimeter continuum emission. Measurements of $L(\mathrm{HCN})$ toward other galaxies will likely be dominated by such gas at lower surface densities. Substantial, even dominant, contributions to the total line luminosity can arise in gas with densities typical of the cloud as a whole (n ∼ 100 cm-3). Defining the dense clump from the HCN or ${\mathrm{HCO}}^{+}$ emission itself, similarly to previous studies, leads to a wide range of clump properties, with some being considerably larger and less dense than in previous studies. HCN and ${\mathrm{HCO}}^{+}$ have a similar ability to trace dense gas for the clouds in this sample. For the two clouds with low virial parameters, 13CO is definitely a worse tracer of the dense gas, but for the other four, it is equally good (or bad) at tracing dense gas.

Keywords: Star formation, Molecular clouds, Interstellar medium
Onset of Magnetic Explosion in Solar Coronal Jets in Quiet Regions on the Central Disk. We examine the initiation of 10 coronal jet eruptions in quiet regions on the central disk, thereby avoiding near-limb spicule-forest obscuration of the slow-rise onset of the minifilament eruption. From the Solar Dynamics Observatory/Atmospheric Imaging Assembly 171 Å 12 s cadence movie of each eruption, we (1) find and compare the start times of the minifilament's slow rise, the jet-base bright point, the jet-base-interior brightening, and the jet spire, and (2) measure the minifilament's speed at the start and end of its slow rise. From (a) these data, (b) prior observations showing that each eruption was triggered by magnetic flux cancelation under the minifilament, and (c) the breakout-reconnection current sheet observed in one eruption, we confirm that quiet-region jet-making minifilament eruptions are miniature versions of CME-making filament eruptions, and surmise that in most quiet-region jets: (1) the eruption starts before runaway reconnection starts, (2) runaway reconnection does not start until the slow-rise speed is at least ∼1 km s-1, and (3) at and before eruption onset, there is no current sheet of appreciable extent. We therefore expect that (I) many CME-making filament eruptions are triggered by flux cancelation under the filament, (II) emerging bipoles seldom, if ever, directly drive jet production because the emergence is seldom, if ever, fast enough, and (III) at a separatrix or quasi-separatrix in any astrophysical setting of a magnetic field in low-beta plasma, a current sheet of appreciable extent can be built only dynamically by a magnetohydrodynamic convulsion of the field, not by quasi-static gradual converging of the field.

Keywords: Solar activity, Solar flares, Solar magnetic reconnection, Solar fibrils
Emission Signatures from Subparsec Binary Supermassive Black Holes. III. Comparison of Models with Observations. We present a method for comparing the Hβ emission-line profiles of observed supermassive black hole (SBHB) candidates and models of subparsec SBHBs in circumbinary disks. Using the approach based on principal component analysis, we infer the values of the binary parameters for the spectroscopic SBHB candidates and evaluate the parameter degeneracies, representative of the uncertainties intrinsic to such measurements. We find that as a population, the SBHB candidates favor the average value of the semimajor axis corresponding to log(a/M) ≈ 4.20 ± 0.42 and comparable mass ratios, q &gt; 0.5. If the SBHB candidates considered are true binaries, this result would suggest that there is a physical process that allows initially unequal-mass systems to evolve toward comparable mass ratios (e.g., accretion that occurs preferentially onto the smaller of the black holes) or point to some, yet unspecified, selection bias. Our method also indicates that the SBHB candidates equally favor configurations in which the mini-disks are coplanar or misaligned with the binary orbital plane. If confirmed for true SBHBs, this finding would indicate the presence of a physical mechanism that maintains misalignment of the mini-disks down to subparsec binary separations (e.g., precession driven by gravitational torques). The probability distributions of the SBHB parameters inferred for the observed SBHB candidates and our control group of AGNs are statistically indistinguishable, implying that this method can in principle be used to interpret the observed emission-line profiles once a sample of confirmed SBHBs is available but cannot be used as a conclusive test of binarity.

Keywords: Supermassive black holes, Astronomy data modeling, Active galaxies, Galaxy nuclei, Galaxy mergers
Star-Gas Misalignment in Galaxies. I. The Properties of Galaxies from the Horizon-AGN Simulation and Comparisons to SAMI. Recent integral field spectroscopy observations have found that about 11% of galaxies show star-gas misalignment. The misalignment possibly results from external effects such as gas accretion, interaction with other objects, and other environmental effects, hence providing clues to these effects. We explore the properties of misaligned galaxies using Horizon-AGN, a large-volume cosmological simulation, and compare the results with those of the Sydney-AAO Multi-object integral field spectrograph (SAMI) Galaxy Survey. Horizon-AGN can match the overall misalignment fraction and reproduces the distribution of misalignment angles found by observations surprisingly closely. The misalignment fraction is found to be highly correlated with galaxy morphology both in observations and in the simulation: early-type galaxies are substantially more frequently misaligned than late-type galaxies. The gas fraction is another important factor associated with misalignment in the sense that misalignment increases with decreasing gas fraction. However, there is a significant discrepancy between the SAMI and Horizon-AGN data in the misalignment fraction for the galaxies in dense (cluster) environments. We discuss possible origins of misalignment and disagreement.

Keywords: Galaxy kinematics, Galaxy evolution, Galaxies