Sazuna/UAT_keywords huggingface dataset:
Different Degrees of Nitrogen and Carbon Depletion in the Warm Molecular Layers of Protoplanetary Disks. Observations have revealed that the elemental abundances of carbon and oxygen in the warm molecular layers of some protoplanetary disks are depleted compared to those in the interstellar medium by a factor of ~10-100. Meanwhile, little is known about nitrogen. To investigate the time evolution of nitrogen, carbon, and oxygen elemental abundances in disks, we develop a one-dimensional plane-parallel model that incorporates dust settling, turbulent diffusion of dust and ices, as well as gas-ice chemistry including the chemistry driven by stellar UV/X-rays and galactic cosmic rays. We find that gaseous CO in the warm molecular layer is converted to CO2 ice and locked up near the midplane via the combination of turbulent mixing (i.e., the vertical cold finger effect) and ice chemistry driven by stellar UV photons. On the other hand, gaseous N2, the main nitrogen reservoir in the warm molecular layer, is less processed by ice chemistry and exists as it is. Then, nitrogen depletion occurs solely through the vertical cold finger effect of N2. As the binding energy of N2 is lower than that of CO and CO2, the degree of nitrogen depletion is smaller than that of carbon and oxygen depletion, leading to higher elemental abundance of nitrogen than that of carbon and oxygen. This evolution occurs within 1 Myr and proceeds further, when the α parameter for the diffusion coefficient is ≳10-3. Consequently, the N2H+/CO column density ratio increases with time. How the vertical transport affects the midplane ice composition is briefly discussed.

Keywords: Interstellar molecules, Protoplanetary disks, Astrochemistry
Large-amplitude Bidirectional Anisotropy of Cosmic-Ray Intensity Observed with Worldwide Networks of Ground-based Neutron Monitors and Muon Detectors in 2021 November. We analyze the cosmic-ray variations during a significant Forbush decrease observed with worldwide networks of ground-based neutron monitors and muon detectors during 2021 November 3-5. Utilizing the difference between primary cosmic-ray rigidities monitored by neutron monitors and muon detectors, we deduce the rigidity spectra of the cosmic-ray density (or omnidirectional intensity) and the first- and second-order anisotropies separately for each hour of data. A clear two-step decrease is seen in the cosmic-ray density with the first ~2% decrease after the interplanetary shock arrival followed by the second ~5% decrease inside the magnetic flux rope (MFR) at 15 GV. Most strikingly, a large bidirectional streaming along the magnetic field is observed in the MFR with a peak amplitude of ~5% at 15 GV, which is comparable to the total density decrease inside the MFR. The bidirectional streaming could be explained by adiabatic deceleration and/or focusing in the expanding MFR, which have stronger effects for pitch angles near 90°, or by selective entry of GCRs along a leg of the MFR. The peak anisotropy and density depression in the flux rope both decrease with increasing rigidity. The spectra vary dynamically, indicating that the temporal variations of density and anisotropy appear different in neutron monitor and muon detector data.

Keywords: Galactic cosmic rays
Binary Interaction Dominates Mass Ejection in Classical Novae. Recent observations suggest our understanding of mass loss in classical novae is incomplete, motivating a new theoretical examination of the physical processes responsible for nova mass ejection. In this paper, we perform hydrodynamical simulations of classical nova outflows using the stellar evolution code MESA. We find that, when the binary companion is neglected, white dwarfs with masses ≳0.8 M ☉ successfully launch radiation-pressure-driven optically thick winds that carry away most of the envelope. However, for most of the mass-loss phase, these winds are accelerated at radii beyond the white dwarf's Roche radius assuming a typical cataclysmic variable donor. This means that, before a standard optically thick wind can be formed, mass loss will instead be initiated and shaped by binary interaction. An isotropic, optically thick wind is only successfully launched when the acceleration region recedes within the white dwarf's Roche radius, which occurs after most of the envelope has already been ejected. The interaction between these two modes of outflow-a first phase of slow, binary-driven, equatorially focused mass loss encompassing most of the mass ejection and a second phase consisting of a fast, isotropic, optically thick wind-is consistent with observations of aspherical ejecta and signatures of multiple outflow components. We also find that isolated lower-mass white dwarfs ≲0.8 M ☉ do not develop unbound optically thick winds at any stage, making it even more crucial to consider the effects of the binary companion on the resulting outburst.

Keywords: White dwarf stars, Cataclysmic variable stars, Classical novae
Comparison of Exact and Approximate MHD Slow Body Mode Solutions in Photospheric Waveguides. In this study, we explore the possibility of simplifying the modeling of magnetohydrodynamic slow body modes observed in photospheric magnetic structures such as the umbrae of sunspots and pores. The simplifying approach assumes that the variation of the eigenvalues of slow body waves can be derived by imposing that the longitudinal component of velocity with respect to the tube axis is zero at the boundary of the magnetic flux tube, which is in good agreement with observations. To justify our approach, we compare the results of our simplified model for slow body modes in cylindrical flux tubes with the model prediction obtained by imposing the continuity of the radial component of the velocity and total pressure at the boundary of the flux tube. Our results show that, to a high accuracy (less than 1% for the considered model), the conditions of continuity of the component of transversal velocity and pressure at the boundary can be neglected when modeling slow body modes under photospheric conditions.

Keywords: Magnetohydrodynamics, Sunspots, Solar photosphere
Calibrating the Cepheid Period-Wesenheit Relation in the Gaia Bands Using Galactic Open-cluster Cepheids. Establishing the period-Wesenheit relation requires independent and accurate distance measurements of classical Cepheids (DCEPs). The precise distances provided by associated open clusters independently calibrate the period-Wesenheit relations of DCEPs. 51 DCEPs associated with open clusters are compiled using the constraints of five-dimensional astrometric information. By directly using Gaia data release 3 parallaxes, the period-Wesenheit relation in the Gaia G band is calibrated as ${W}_{G}=(-3.06\pm 0.11)\mathrm{log}P+(-2.96\pm 0.10)$ . Compared with the results derived from directly adopting the DCEP parallaxes or from using distance moduli, the Wesenheit magnitudes based on the cluster-averaged parallaxes exhibit a tighter relation with the period. Besides, there is a systematic offset between the observed Wesenheit absolute magnitudes of distant open-cluster DCEPs and their fitted magnitudes. After considering a parallax zeropoint correction, the systematic offset can be reduced, yielding a probably better period-Wesenheit relation of ${W}_{G}=(-2.94\pm 0.12)\mathrm{log}P+(-2.93\pm 0.11)$ .

Keywords: Open star clusters, Cepheid variable stars, Cepheid distance
Shocks in the Outflow of the RS Oph 2021 Eruption Observed with X-Ray Gratings. The 2021 outburst of the symbiotic recurrent nova RS Oph was observed with the Chandra High Energy Transmission Gratings (HETG) on day 18 after optical maximum and with XMM-Newton and its Reflection Grating Spectrographs (RGS) on day 21, before the supersoft X-ray source emerged and when the emission was due to shocked ejecta. The absorbed flux in the HETG 1.3-31 Å range was 2.6 × 10-10 erg cm-2 s-1, three orders of magnitude lower than the γ-ray flux measured on the same date. The spectra are well fitted with two components of thermal plasma in collisional ionization equilibrium, one at a temperature ≃ 0.75 keV and the other at a temperature in the 2.5-3.4 keV range. With the RGS we measured an average flux of 1.53 × 10-10 erg cm-2 s-1 in the 5-35 Å range, but the flux in the continuum and especially in the lines in the 23-35 Å range decreased during the 50 ks RGS exposure by almost 10%, indicating short-term variability on a timescale of hours. The RGS spectrum can be fitted with three thermal components, respectively at plasma temperatures between 70 and 150 eV, 0.64 keV, and 2.4 keV. The post-maximum epochs of the exposures fall between those of two grating spectra observed in the 2006 eruption on days 14 and 26: they are consistent with a similar spectral evolution, but in 2021 cooling seems to have been more rapid. Iron is depleted in the ejecta with respect to solar values, while nitrogen is enhanced.

Keywords: Classical novae
Searching for Supernova Bursts in Super-Kamiokande IV. Super-Kamiokande has been searching for neutrino bursts characteristic of core-collapse supernovae continuously, in real time, since the start of operations in 1996. The present work focuses on detecting more distant supernovae whose event rate may be too small to trigger in real time, but may be identified using an offline approach. The analysis of data collected from 2008 to 2018 found no evidence of distant supernovae bursts. This establishes an upper limit of 0.29 yr-1 on the rate of core-collapse supernovae out to 100 kpc at 90% C.L. For supernovae that fail to explode and collapse directly to black holes the limit reaches to 300 kpc.

Keywords: Particle astrophysics, Supernova neutrinos, Core-collapse supernovae
Cluster Cepheids with High Precision Gaia Parallaxes, Low Zero-point Uncertainties, and Hubble Space Telescope Photometry. We present Hubble Space Telescope (HST) photometry of 17 Cepheids in open clusters and their cluster mean parallaxes from Gaia EDR3. These parallaxes are more precise than those from individual Cepheids (G &lt; 8 mag) previously used to measure the Hubble constant because they are derived from an average of &gt;300 stars per cluster. Cluster parallaxes also have smaller systematic uncertainty because their stars lie in the range (G &gt; 13 mag) where the Gaia parallax calibration is the most comprehensive. Cepheid photometry employed in the period-luminosity relation was measured using the same HST instrument (WFC3) and filters (F555W, F814W, F160W) as extragalactic Cepheids in Type Ia supernova hosts. We find no evidence of residual parallax offset in this magnitude range, zp = -3 ± 4 μas, consistent with the results from Lindegren et al. and most studies. The Cepheid luminosity (at P = 10 d and solar metallicity) in the HST near-infrared, Wesenheit magnitude system derived from the cluster sample is ${M}_{H,1}^{W}=-5.902\pm 0.025$ mag and -5.890 ± 0.018 mag with or without simultaneous determination of a parallax offset, respectively. These results are similar to measurements from field Cepheids, confirming the accuracy of the Gaia parallaxes over a broad range of magnitudes. The SH0ES distance ladder calibrated only from this sample gives H 0 = 72.9 ± 1.3 and H 0 = 73.3 ± 1.1 km s-1 Mpc-1 with or without offset marginalization; combined with all other anchors we find H 0 = 73.01 ± 0.99 and 73.15 ± 0.97 km s-1 Mpc-1, respectively, a 5% or 7% reduction in the uncertainty in H 0 and a ~5.3σ Hubble tension relative to Planck+ΛCDM. It appears increasingly difficult to reconcile two of the best-measured cosmic scales, parallaxes from Gaia and the angular size of the acoustic scale of the cosmic microwave background, using the simplest form of ΛCDM to connect the two.

Keywords: Hubble constant, Cepheid distance
Variable Star Classification with a Multiple-input Neural Network. In this experiment, we created a Multiple-Input Neural Network, consisting of convolutional and multilayer neural networks. With this setup the selected highest-performing neural network was able to distinguish variable stars based on the visual characteristics of their light curves, while taking also into account additional numerical information (e.g., period, reddening-free brightness) to differentiate visually similar light curves. The network was trained and tested on Optical Gravitational Lensing Experiment-III (OGLE-III) data using all OGLE-III observation fields, phase-folded light curves, and period data. The neural network yielded accuracies of 89%-99% for most of the main classes (Cepheids, δ Scutis, eclipsing binaries, RR Lyrae stars, Type-II Cepheids), only the first-overtone anomalous Cepheids had an accuracy of 45%. To counteract the large confusion between the first-overtone anomalous Cepheids and the RRab stars we added the reddening-free brightness as a new input and only stars from the LMC field were retained to have a fixed distance. With this change we improved the neural network's result for the first-overtone anomalous Cepheids to almost 80%. Overall, the Multiple-input Neural Network method developed by our team is a promising alternative to existing classification methods.

Keywords: Delta Scuti variable stars, Classification, Neural networks, Astronomy data analysis, RR Lyrae variable stars, Cepheid variable stars, Eclipsing binary stars
Comparing the Performance of a Solar Wind Model from the Sun to 1 au Using Real and Synthetic Magnetograms. The input of the solar wind models plays a significant role in accurate solar wind predictions at 1 au. This work introduces a synthetic magnetogram produced from a dynamo model as an input for magnetohydrodynamics simulations. We perform a quantitative study that compares the space weather modeling framework (SWMF) results for the observed and synthetic solar magnetogram input. For each case, we compare the results for extreme ultraviolet images and extract the simulation data along the Earth trajectory to compare with in situ observations. We initialize the SWMF using the real and synthetic magnetograms for a set of Carrington rotations within solar cycles 23 and 24. Our results help quantify the ability of dynamo models to be used as input to solar wind models and thus provide predictions for the solar wind at 1 au.

Keywords: Solar cycle, Solar wind, Solar physics, Solar magnetic fields, Magnetohydrodynamical simulations
X-Ray Polarization Detection of Cassiopeia A with IXPE. We report on a ~5σ detection of polarized 3-6 keV X-ray emission from the supernova remnant Cassiopeia A (Cas A) with the Imaging X-ray Polarimetry Explorer (IXPE). The overall polarization degree of 1.8% ± 0.3% is detected by summing over a large region, assuming circular symmetry for the polarization vectors. The measurements imply an average polarization degree for the synchrotron component of ~2.5%, and close to 5% for the X-ray synchrotron-dominated forward shock region. These numbers are based on an assessment of the thermal and nonthermal radiation contributions, for which we used a detailed spatial-spectral model based on Chandra X-ray data. A pixel-by-pixel search for polarization provides a few tentative detections from discrete regions at the ~ 3σ confidence level. Given the number of pixels, the significance is insufficient to claim a detection for individual pixels, but implies considerable turbulence on scales smaller than the angular resolution. Cas A's X-ray continuum emission is dominated by synchrotron radiation from regions within ≲1017 cm of the forward and reverse shocks. We find that (i) the measured polarization angle corresponds to a radially oriented magnetic field, similar to what has been inferred from radio observations; (ii) the X-ray polarization degree is lower than in the radio band (~5%). Since shock compression should impose a tangential magnetic-field structure, the IXPE results imply that magnetic fields are reoriented within ~1017 cm of the shock. If the magnetic-field alignment is due to locally enhanced acceleration near quasi-parallel shocks, the preferred X-ray polarization angle suggests a size of 3 × 1016 cm for cells with radial magnetic fields.

Keywords: Supernova remnants, Shocks, Polarimetry, X-ray astronomy
The Quest for New Correlations in the Realm of the Gamma-Ray Burst-Supernova Connection. Gamma-ray bursts (GRBs) are very energetic cosmological transients. Long GRBs are usually associated with Type Ib/c supernovae (SNe), and we refer to them as GRB-SNe. Since the associated SN for a given GRB is observed only at low redshift, a possible selection effect exists when we consider intrinsically faint sources that cannot be observed at high redshift. Thus, it is important to explore the possible relationships between GRB and SN parameters after these have been corrected for astrophysical biases due to the instrumental selection effects and redshift evolution of the variables involved. So far, only GRB prompt emission properties have been checked against the SN Ib/c properties without considering the afterglow (AG). This work investigates the existence of relationships among GRBs' prompt and AG and associated SN properties. We investigate 91 bidimensional correlations among the SN and GRB observables before and after their correction for selection biases and evolutionary effects. As a result of this investigation, we find hints of a new correlation with a Pearson correlation coefficient &gt;0.50 and a probability of being drawn by chance &lt;0.05. This correlation is between the luminosity at the end of the GRB optical plateau emission and the rest-frame peak time of the SN. According to this relation, the brightest optical plateaus are accompanied by the largest peak times. This correlation is corrected for selection biases and redshift evolution and may provide new constraints for the astrophysical models associated with the GRB-SN connection.

Keywords: Gamma-ray bursts, Core-collapse supernovae
The Role of Binarity and Stellar Rotation in the Split Main Sequence of NGC 2422. In addition to the extended main-sequence turnoffs widely found in young and intermediate-age (~600 Myr to 2 Gyr old) star clusters, some younger clusters even exhibit split main sequences (MSs). Different stellar rotation rates are proposed to account for the bifurcated MS pattern, with red and blue MSs (rMS and bMS) populated by fast and slowly rotating stars, respectively. Using photometry from Gaia Early Data Release 3, we report a Galactic open cluster with a bifurcated MS, NGC 2422 (~90 Myr). We exclude the possibilities that the bifurcated MS pattern is caused by photometric noise or differential reddening. We aim to examine if stellar rotation can account for the split MS. We use spectra observed with the Canada-France-Hawaii Telescope and the Southern African Large Telescope and directly measured $v\sin i$ , the projected rotational velocities, for stars populating the bMS and rMS. We find that their $v\sin i$ values are weakly correlated with their loci in the color-magnitude diagram because of contamination caused by a large fraction of rMS stars with low projected rotational velocities. Based on the spectral energy distribution fitting method, we suggest that these slowly rotating stars at the rMS may hide a binary companion, which breaks the expected $v\sin i$ -color correlation. Future time-domain studies focusing on whether these slowly rotating stars are radial velocity variables are crucial to test the roles of stellar rotation and binarity in generating the split MSs.

Keywords: Open star clusters, Stellar rotation, Star clusters
Transient Radio Emission from Low-redshift Galaxies at z &lt; 0.3 Revealed by the VLASS and FIRST Surveys. We present the discovery of a sample of 18 low-redshift (z &lt; 0.3) galaxies with transient nuclear radio emission. These galaxies are not detected or are weakly detected in the Faint Images of the Radio Sky at Twenty cm survey, performed from 1993-2009, but have brightened significantly in radio flux (by a factor of ≳5) in the epoch I (2017-2019) observations of the Very Large Array Sky Survey (VLASS). All 18 galaxies have been detected in VLASS epoch II observations, from 2020-2021, from which the radio flux has been found to evolve slowly (with variability amplitudes of ≳40%) over a period of about 3 yr. 15 galaxies have been observed in the Rapid ASKAP Continuum Survey, and a flat or inverted spectral slope between 888 MHz and 3 GHz is found. Based on the Sloan Digital Sky Survey spectra taken before the radio brightening, 14 of the 18 galaxies can be classified as LINERs or normal galaxies with weak or no nuclear activity. Most galaxies are red and massive, with more than half having central black hole masses above 108M⊙. We find that only one galaxy in our sample displays an optical flare lasting for at least two months, with a long decay in the infrared light curve that can be explained as the dust-heated echo emission of a central optical flare, such as a stellar tidal disruption event. We discuss several possibilities for the transient radio emission and conclude that it is likely associated with a newborn radio jet triggered by short sporadic fueling of a supermassive black hole. Such a scenario can be tested with further multifrequency radio observations of these sources, via measuring their radio flux variability and spectral evolution.

Keywords: Surveys, Radio jets, Radio transient sources
CO(J = 1 - 0) Observations toward the Filamentary Cloud in the Galactic Region of 153.°60 ≤ l ≤ 156.°50 and 1.°85 ≤ b ≤ 3.°50. We present observations of the J = 1 - 0 transition lines of 12CO, 13CO, and C18O toward the Galactic region of 153.°60 ≤ l ≤ 156.°50 and 1.°85 ≤ b ≤ 3.°50, using the Purple Mountain Observatory 13.7 m millimeter telescope. Based on the 13CO data, one main filament and five subfilaments are found together as a network structure in the velocity interval of [-42.5, -30.0] km s-1. The kinematic distance of this molecular cloud is estimated to be ~4.5 kpc. The median length, width, excitation temperature, and line mass of these filaments are ~49 pc, ~2.9 pc, ~8.9 K, and ~39 M ⊙ pc-1, respectively. The velocity structures along these filaments exhibit oscillatory patterns, which are likely caused by the fragmentation or accretion process along these filaments. The maximum accretion rate is estimated to be ~700 M ⊙ pc-1. A total of ~162 13CO clumps and ~103 young stellar objects are identified in this region. Most of the clumps are in gravitationally bound states. Three H II regions (G154.359+2.606, SH2-211, and SH2-212) are found to be located in the apexes of the filaments. Intense star-forming activity is found along the entire filamentary cloud. The observed results may help us to better understand the link between filaments and massive star formation.

Keywords: Interstellar filaments, Young stellar objects, Molecular clouds, Star forming regions