Sazuna/UAT_keywords huggingface dataset:
Asteroseismic Study of KUV03442+0719 with Parallax Constraints. Hydrogen atmosphere white dwarf KUV03442+0719 was first reported as a pulsator by Gianninas et al. in 2006. Follow-up campaigns by Su et al. revealed more periods. Some spectroscopic results suggest that KUV03442+0719 has a slightly below-average mass and an effective temperature of 11,000 K. However, Gaia data (parallax and magnitude) suggest that it may be a low-mass white dwarf. Such an object would have a helium core. We perform asteroseismic fitting of KUV03442+0719, modeling it both as a carbon/oxygen normal mass white dwarf, and a helium-core low-mass white dwarf. To perform the study, we perform a grid search with WDEC models, refined by simplex minimization of the best fits. Both analyses result in best-fit models that are comparable in terms of quality of fit. More pulsation data would be required to allow us to distinguish between the two scenarios. We present and contrast our results with expectations from stellar evolution. We also provide analytic formulae for a temperature-dependent mass-radius relationship for helium-core white dwarfs.

Keywords: Periodic variable stars, White dwarf stars, Stellar astronomy, DA stars, Compact objects, Stellar oscillations, Asteroseismology
Secondary Outflow Driven by the Protostar Ser-emb 15 in Serpens. We present the detection of a secondary outflow associated with a Class I source, Ser-emb 15, in the Serpens Molecular Cloud. We reveal two pairs of molecular outflows consisting of three lobes, that is, primary and secondary outflows, using Atacama Large Millimeter/submillimeter Array 12CO and SiO line observations at a resolution of ~318 au. The secondary outflow is elongated approximately perpendicular to the axis of the primary outflow in the plane of the sky. We also identify two compact structures, Sources A and B, within an extended structure associated with Ser-emb 15 in the 1.3 mm continuum emission at a resolution of ~40 au. The projected sizes of Sources A and B are 137 au and 60 au, respectively. Assuming a dust temperature of 20 K, we estimate the dust mass to be 2.4 × 10-3 M ⊙ for Source A and 3.3 × 10-4 M ⊙ for Source B. C18O line data imply rotational motion around the extended structure, but we cannot resolve rotational motion in Source A and/or B because the angular and frequency resolutions are insufficient. Therefore, we cannot conclude whether Ser-emb 15 is a single or binary system. Thus, either Source A or Source B could drive the secondary outflow. We discuss two scenarios that might explain the driving mechanism of the primary and secondary outflows: the Ser-emb 15 system is (1) a binary system composed of Sources A and B, or (2) a single-star system composed of Source A alone. In either case, the system could be a suitable target for investigating the disk and/or binary formation processes in complicated environments. Detecting these outflows should contribute to understanding complex star-forming environments, which may be common in the star formation processes.

Keywords: Circumstellar envelopes, Jets, Millimeter astronomy, Star forming regions, Star formation, Low mass stars, Protoplanetary disks, CO line emission, Radio continuum emission, Protostars, Radio astronomy, Common envelope binary stars
Rotation of a Stealth CME on 2012 October 5 Observed in the Inner Heliosphere. Coronal mass ejections (CMEs) are subject to changes in their direction of propagation, tilt, and other properties. This is because CMEs interact with the ambient solar wind and other large-scale magnetic field structures. In this work, we report on the observations of the 2012 October 5 stealth CME using coronagraphic and heliospheric images. We find clear evidence of a continuous rotation of the CME, i.e., an increase in the tilt angle, estimated using the graduated cylindrical shell (GCS) reconstruction at different heliocentric distances, up to 58 R ⊙. We find a further increase in the tilt at L1 estimated from the toroidal and cylindrical flux rope fitting on the in situ observations of interplanetary magnetic field (IMF) and solar wind parameters. This study highlights the importance of observations of Heliospheric Imager (HI), on board the Solar Terrestrial Relations Observatory. In particular, the GCS reconstruction of CMEs in the HI field of view promises to bridge the gap between the near-Sun and in situ observations at the L1. The changes in the CME tilt have significant implications for the space weather impact of stealth CMEs.

Keywords: Solar coronal mass ejections, Heliosphere
A Database of Magnetic and Thermodynamic Properties of Confined and Eruptive Solar Flares. Solar flares sometimes lead to coronal mass ejections that directly affect Earth's environment. However, a large fraction of flares, including on solar-type stars, are confined flares. What are the differences in physical properties between confined and eruptive flares? For the first time, we quantify the thermodynamic and magnetic properties of hundreds of confined and eruptive flares of GOES class C5.0 and above, 480 flares in total. We first analyze large flares of GOES class M1.0 and above observed by the Solar Dynamics Observatory, 216 flares in total, including 103 eruptive and 113 confined flares, from 2010 until 2016 April; we then look at the entire data set of 480 flares above class C5.0. We compare GOES X-ray thermodynamic flare properties, including peak temperature and emission measure, and active-region (AR) and flare-ribbon magnetic field properties, including reconnected magnetic flux and peak reconnection rate. We find that for fixed peak X-ray flux, confined and eruptive flares have similar reconnection fluxes; however, for fixed peak X-ray flux confined flares have on average larger peak magnetic reconnection rates, are more compact, and occur in larger ARs than eruptive flares. These findings suggest that confined flares are caused by reconnection between more compact, stronger, lower-lying magnetic fields in larger ARs that reorganizes a smaller fraction of these regions' fields. This reconnection proceeds at faster rates and ends earlier, potentially leading to more efficient flare particle acceleration in confined flares.

Keywords: Solar flares, Solar photosphere, The Sun, Solar surface, Solar physics, Eruptive phenomena, Solar magnetic fields, Stellar flares, Solar coronal mass ejections
High-soft to Low-hard State Transition in Black Hole X-Ray Binaries with GRMHD Simulations. To understand the decaying phase of outbursts in the black hole (BH) X-ray binaries (BH-XRBs), we performed very long general relativistic magnetohydrodynamic simulations of a geometrically thin accretion disk around a Kerr BH with slowly rotating matter injected from outside. We thoroughly studied the flow properties, dynamical behavior of the accretion rate, magnetic flux rate, and jet properties during the temporal evolution. Due to the interaction between the thin disk and injected matter, the accretion flow near the BH goes through different phases. The sequence of phases is: soft state → soft-intermediate state → hard-intermediate state → hard state → quiescent state. For the accretion rate (and hence the luminosity) to decrease (as observed) in our model, the mass injection should not decay slower than the angular momentum injection. We also observed quasiperiodic oscillations (QPOs) in the accretion flow. Throughout the evolution, we observed low-frequency QPOs (~10 Hz) and high-frequency QPOs (~200 Hz). Our simple unified accretion flow model for state transitions is able to describe outbursts in BH-XRBs.

Keywords: Accretion, Black hole physics, Magnetohydrodynamics, X-ray binary stars
Searching for Novel Chemistry in Exoplanetary Atmospheres Using Machine Learning for Anomaly Detection. The next generation of telescopes will yield a substantial increase in the availability of high-quality spectroscopic data for thousands of exoplanets. The sheer volume of data and number of planets to be analyzed greatly motivate the development of new, fast, and efficient methods for flagging interesting planets for reobservation and detailed analysis. We advocate the application of machine learning (ML) techniques for anomaly (novelty) detection to exoplanet transit spectra, with the goal of identifying planets with unusual chemical composition and even searching for unknown biosignatures. We successfully demonstrate the feasibility of two popular anomaly detection methods (local outlier factor and one-class support vector machine) on a large public database of synthetic spectra. We consider several test cases, each with different levels of instrumental noise. In each case, we use receiver operating characteristic curves to quantify and compare the performance of the two ML techniques.

Keywords: Exoplanet atmospheric composition , Transmission spectroscopy, Outlier detection, Clustering, Support vector machine, Exoplanet atmospheres
Khronometric Theories of Modified Newtonian Dynamics. In 2011 Blanchet and Marsat suggested a fully relativistic version of Milgrom's modified Newtonian dynamics in which the dynamical degrees of freedom consist of the spacetime metric and a foliation of spacetime, the khronon field. This theory is simpler than the alternative relativistic formulations. We show that the theory has a consistent nonrelativistic or slow-motion limit. Blanchet and Marsat showed that in the slow motion limit, the theory reproduces stationary solutions of modified Newtonian dynamics. We show that these solutions are stable to khronon perturbations in the low acceleration regime, for the cases of spherical, cylindrical, and planar symmetry. For nonstationary systems in the low acceleration regime, we show that the khronon field generally gives an order unity correction to the modified Newtonian dynamics. In particular, there will be an order unity correction to the MOND version of Kepler's third law, potentially relevant to ongoing efforts to test MOND using GAIA observations of wide binaries.

Keywords: Non-standard theories of gravity, Galaxy structure, Dark matter
Magellanic System Stars Identified in SMACS J0723.3-7327 James Webb Space Telescope Early Release Observations Images. We identify 71 distant stars in James Webb Space Telescope/NIRCam early release observations (ERO) images of the field of galaxy cluster SMACS J0723.3-7327 (SMACS 0723). Given the relatively small (~10°) angular separation between SMACS 0723 and the Large Magellanic Cloud (LMC), it is likely that these stars are associated with the LMC outskirts or the Leading Arm. This is further bolstered by a spectral energy distribution (SED) analysis, which suggests an excess of stars at a physical distance of 40-100 kpc, consistent with being associated with or located behind the Magellanic system. In particular, we find that the overall surface density of stars brighter than 27.0 mag in the field of SMACS 0723 is ~2.3 times that of stars in a blank field with similar Galactic latitude (the North Ecliptic Pole Time Domain Field), and that the density of stars in the SMACS 0723 field with SED-derived distances consistent with the Magellanic system is ~6.1 times larger than that of the blank field. The candidate stars at these distances are consistent with a stellar population at the same distance modulus with [Fe/H] = -1.0 and an age of ~5.0 Gyr. On the assumption that all of the 71 stars are associated with the LMC, then the stellar density of the LMC at the location of the SMACS 0723 field is ~740 stars kpc-3, which helps trace the density of stars in the LMC outskirts.

Keywords: Galactic archaeology, Stellar spectral types, James Webb Space Telescope
[C II] Spectral Mapping of the Galactic Wind and Starbursting Disk of M82 with SOFIA. M82 is an archetypal starburst galaxy in the local Universe. The central burst of star formation, thought to be triggered by M82's interaction with other members in the M81 group, is driving a multiphase galaxy-scale wind away from the plane of the disk that has been studied across the electromagnetic spectrum. Here, we present new velocity-resolved observations of the [C II] 158 μm line in the central disk and the southern outflow of M82 using the upGREAT instrument on board SOFIA. We also report the first detections of velocity-resolved (ΔV = 10 km s-1) [C II] emission in the outflow of M82 at projected distances of ≈1-2 kpc south of the galaxy center. We compare the [C II] line profiles to observations of CO and H I and find that likely the majority (&gt;55%) of the [C II] emission in the outflow is associated with the neutral atomic medium. We find that the fraction of [C II] actually outflowing from M82 is small compared to the bulk gas outside the midplane (which may be in a halo or tidal streamers), which has important implications for observations of [C II] outflows at higher redshift. Finally, by comparing the observed ratio of the [C II] and CO intensities to models of photodissociation regions, we estimate that the far-ultraviolet (FUV) radiation field in the disk is ~103.5 G 0, in agreement with previous estimates. In the outflow, however, the FUV radiation field is 2-3 orders of magnitudes lower, which may explain the high fraction of [C II] arising from the neutral medium in the wind.

Keywords: Starburst galaxies, Molecular gas, Interstellar atomic gas, Far infrared astronomy, Galaxy winds, Galaxy kinematics, Interstellar medium, Infrared galaxies
Modeling the Formation and Evolution of Solar Wind Microstreams: From Coronal Plumes to Propagating Alfvénic Velocity Spikes. We investigate the origin of mesoscale structures in the solar wind called microstreams, defined as enhancements in the solar wind speed and temperature that last several hours. They were first clearly detected in Helios and Ulysses solar wind data and are now omnipresent in the "young" solar wind measured by the Parker Solar Probe and Solar Orbiter. These recent data reveal that microstreams transport a profusion of Alfvénic perturbations in the form of velocity spikes and magnetic switchbacks. In this study, we use a very-high-resolution 2.5D MHD model of the corona and the solar wind to simulate the emergence of magnetic bipoles interacting with the preexisting ambient corona and the creation of jets that become microstreams propagating in the solar wind. Our high-resolution simulations reach sufficiently high Lundquist numbers that capture the tearing mode instability that develops in the reconnection region and produces plasmoids released with the jet into the solar wind. Our domain runs from the lower corona to 20 R ⊙, which allows us to track the formation process of plasmoids and their evolution into Alfvénic velocity spikes. We obtain perturbed solar wind flows lasting several hours with velocity spikes occurring at characteristic periodicities of about 19 minutes. We retrieve several properties of the microstreams measured in the pristine solar wind by the Parker Solar Probe, namely an increase in wind velocity of about 100 km s-1 during a stream's passage together with superposed velocity spikes of also about 100 km s-1 released into the solar wind.

Keywords: Solar wind, Magnetohydrodynamics, Solar coronal plumes, Solar magnetic reconnection
Chemical Evolution of Some Selected Complex Organic Molecules in Low-mass Star-forming Regions. The destiny of complex organic molecules (COMs) in star-forming regions is interlinked with various evolutionary phases. Therefore, identifying these species in diversified environments of identical star-forming regions would help to understand their physical and chemical heritage. We identified multiple COMs utilizing the Large Program Astrochemical Surveys At Institut de Radio Astronomie Millimétrique (IRAM) data, dedicated to chemical surveys in Sun-like star-forming regions with the IRAM 30 m telescope. It was an unbiased survey in the millimeter regime, covering the prestellar core, protostar, outflow region, and protoplanetary disk phase. Here, we report the transitions of seven COMs, namely, methanol (CH3OH), acetaldehyde (CH3CHO), methyl formate (CH3OCHO), ethanol (C2H5OH), propynal (HCCCHO), dimethyl ether (CH3OCH3), and methyl cyanide (CH3CN) in sources L1544, B1-b, IRAS4A, and SVS13A. We found a trend among these species from the derived abundances using the rotational diagram method and Monte Carlo Markov chain fitting. We have found that the abundances of all of the COMs, except for HCCCHO, increase from the L1544 (prestellar core) and peaks at IRAS16293-2422 (class 0 phase). It is noticed that the abundance of these molecules correlates with the luminosity of the sources. The obtained trend is also visible from the previous interferometric observations and considering the beam dilution effect.

Keywords: Interstellar molecules, Star forming regions, Interstellar abundances, Astrochemistry, Interstellar medium
The Hydrostatic Mass of A478: Discrepant Results from Chandra, NuSTAR, and XMM-Newton. Galaxy clusters are the most recently formed and most massive, gravitationally bound structures in the Universe. The number of galaxy clusters formed is highly dependent on cosmological parameters, such as the dark matter density, σ 8, and Ω m . The number density is a function of the cluster mass, which can be estimated from the density and temperature profiles of the intracluster medium under the assumption of hydrostatic equilibrium. The temperature of the plasma, hence its mass, is calculated from the X-ray spectra. However, effective-area calibration uncertainties in the soft band result in significantly different temperature measurements from various space-based X-ray telescopes. NuSTAR is potentially less susceptible to these issues than Chandra and XMM-Newton, having larger effective area, particularly at higher energies, enabling high-precision temperature measurements. In this work, we present analyses of Chandra, NuSTAR, and XMM-Newton data of A478 to investigate the nature of this calibration discrepancy. We find that NuSTAR temperatures are on average ~11% lower than those of Chandra, and XMM-Newton temperatures are on average ~5% lower than those of NuSTAR. This results in a NuSTAR mass at r 2500,Chandra of ${M}_{2500,\mathrm{NuSTAR}}\,=\,{3.39}_{-0.07}^{+0.07}\times {10}^{14}$ M ☉, which is ~10% lower than that of M 2500,Chandra and ~4% higher than M 2500,XMM-Newton.

Keywords: Galaxy clusters, X-ray astronomy
The Principal Component Analysis Filtering Method for an Unbiased Spectral Survey of Complex Organic Molecules. A variety of interstellar complex organic molecules (COMs) have been detected in various physical conditions. However, in the protostellar and protoplanetary environments, their complex kinematics make line profiles blend together and the line strength of weak lines weaker. In this paper, we utilize the principal component analysis technique to develop a filtering method that can extract COM spectra from the main kinematic component associated with COM emission and increase the signal-to-noise ratio (S/N) of spectra. This filtering method corrects non-Gaussian line profiles caused by the kinematics. For this development, we adopt the ALMA BAND 6 spectral survey data of V883 Ori, an eruptive young star with a Keplerian disk. A filter was, first, created using 34 strong and well-isolated COM lines and then applied to the entire spectral range of the data set. The first principal component (PC1) describes the most common emission structure of the selected lines, which is confined within the water sublimation radius (~0.″3) in the Keplerian disk of V883 Ori. Using this PC1 filter, we extracted high-S/N kinematics-corrected spectra of V883 Ori over the entire spectral coverage of ~50 GHz. The PC1-filtering method reduces the noise by a factor of ~2 compared to the average spectra over the COM emission region. One important advantage of this PC1-filtering method over the previously developed matched-filtering method is the ability to preserve the original integrated intensities of COM lines.

Keywords: Star formation, Astrochemistry
Shadow Implications: What Does Measuring the Photon Ring Imply for Gravity?. With the imaging and characterization of the horizon-scale images of M87* and Sgr A* by the Event Horizon Telescope (EHT), it has become possible to resolve the near-horizon region of astrophysical black holes. As a result, there has been considerable interest in the implications of the measurement of the shadow size, i.e., the asymptotic photon ring. We explore the general implications of such a measurement, identifying what is and, more importantly, is not constrained by such measurements, with applications to EHT and future instruments. We consider a general spherically symmetric metric, which effectively applies for a polar observer (appropriate for M87*) in the slow rotation limit. We propose a nonperturbative, nonparametric spacetime-domain characterization of shadow size and related measurements that makes explicit the nature and power (or lack thereof) of shadow-size-based constraints, and facilitates comparisons among observations and targets.

Keywords: Gravitation, Black hole physics, Very long baseline interferometry, Strong gravitational lensing
A Comparison between the Morphologies and Structures of Dwarf Galaxies with and without Active Massive Black Holes. We study the morphologies and structures of 57 dwarf galaxies that are representative of the general population of dwarf galaxies and compare their demographics to a sample of dwarf galaxies hosting optically selected active galactic nuclei (AGNs). The two samples span the same galaxy stellar mass (109 ≲ M ⋆/M ⊙ ≲ 109.5) and color range, and the observations are well-matched in physical resolution. The fractions of irregular galaxies (14%) and early types/ellipticals (~18%) are nearly identical among the two samples. However, among galaxies with disks (the majority of each sample), the AGN hosts almost always have a detectable (pseudo)bulge, while a large fraction of the non-AGN hosts are pure disk galaxies with no detectable (pseudo)bulge. Central point sources of light consistent with nuclear star clusters are detected in many of the non-AGN hosts. In contrast, central point sources detected in the AGN hosts are, on average, more than 2 orders of magnitude more luminous, suggesting the point sources in these objects are dominated by AGN light. The preference for (pseudo)bulges in dwarf AGN hosts may inform searches for massive black holes in dwarf galaxies and attempts to constrain the black hole occupation fraction, which, in turn, has implications for our understanding of black hole seeding mechanisms.

Keywords: AGN host galaxies, Intermediate-mass black holes, Dwarf galaxies, Active galactic nuclei
Internal Activities in a Solar Filament and Heating in Its Threads. Filaments are one of the most common features in the solar atmosphere and are of significance in solar, stellar, and laboratory plasma physics. Using data from the Chinese Hα Solar Explorer, the Solar Upper Transition Region Imager, and the Solar Dynamics Observatory, we report on multiwavelength imaging and spectral observations of the activation of a small filament. The filament activation produces several localized dynamic brightenings, which are probably produced by internal reconnections of the braided magnetic fields in the filament. The filament expands during the activation, and its threads reconnect with the ambient magnetic fields, which leads to the formation of hot arcades or loops overlying the filament. The thermal energy of each of these localized brightenings is estimated in the order of 1025-1027 erg, and the total energy is estimated to be ~1.77 × 1028 erg. Our observations demonstrate that the internal magnetic reconnections in the filament can lead to localized heating in the filament threads and prompt external reconnections with ambient corona structures and thus could contribute to the energy and mass transferring into the corona.

Keywords: Solar atmosphere, Solar magnetic reconnection, Astronomy data analysis, Solar physics, Solar filaments, Solar corona