Sazuna/UAT_keywords huggingface dataset:
Upper Limits on the Radio Pulses from Magnetars and a Central Compact Object with FAST. Magnetars and central compact objects (CCOs) are subgroups of neutron stars that show a number of properties distinguished from canonical radio pulsars. We performed radio observations of three magnetars, SGR 0418+5729, 1E 2259+586, and 4U 0142+61, and a CCO, PSR J1852+0040, with the Five-hundred-meter Aperture Spherical radio Telescope at 1.25 GHz, aiming to search for radio pulsations in their quiescent states. During two observation epochs, no radio pulses have been detected toward any target above a significance of signal-to-noise ratio = 7 from either the direct folding or blind search. We provided the most stringent upper limit of radio flux (≲2–4 μJy) for the magnetars and the CCO. For the magnetars with long periods, the real upper limits are likely 1 order of magnitude larger due to the red noise. The deep radio observations suggest that these magnetars and the CCO are indeed radio-quiet sources or unfavorably beamed.

Keywords: Neutron stars, Magnetars, Pulsars
The Reliability of Accretion Disk Inclination Derived from X-Ray Spectroscopy of Active Galaxies. The inclination angle of substructures in active galaxies gives insights into physical components from scales of the vicinity of the central black hole to the entire host galaxy. We use the self-consistent reflection spectral model RELXILL to measure the inclination of the inner region of accretion disks with broadband (0.3─78 keV) X-ray observations, systematically studying the reliability of this methodology. To test the capability of the model to return statistically consistent results, we analyze multiepoch joint XMM-Newton and NuSTAR data of the narrow-line Seyfert 1 galaxy I Zwicky 1 and the broad-line radio galaxy 3C 382, which exhibit different degrees of spectral complexity and reflection features. As expected, we find that adding more data for analysis narrows the confidence interval and that multiepoch joint observations return optimal measurements; however, even single-epoch data can be well fitted if the reflection component is sufficiently dominant. Mock spectra are used to test the capability of RELXILL to recover input parameters from typical single-epoch joint observations. We find that inclination is well recovered at 90% confidence, with improved constraints at higher reflection fraction and higher inclination. Higher iron abundance and corona temperature tighten the constraints as well, but the effect is not as significant as a higher reflection fraction. The spin, however, has little effect in reflection-based inclination measurements. We conclude that broadband reflection spectroscopy can reliably measure inner accretion disk inclination.

Keywords: Accretion, Supermassive black holes, Active galaxies, X-ray active galactic nuclei
Probing the Nature of Rotation in the Pleiades, Alpha Persei, and Hyades Clusters. Unraveling the internal kinematics of open clusters is crucial for understanding their formation and evolution. However, there is a dearth of research on this topic, primarily due to the lack of high-quality kinematic data. Using the exquisite-precision astrometric parameters and radial velocities provided by Gaia data release 3, we investigate the internal rotation in three of the most nearby and best-studied open clusters, namely the Pleiades, Alpha Persei, and Hyades clusters. Statistical analyses of the residual motions of the member stars clearly indicate the presence of three-dimensional rotation in the three clusters. The mean rotation velocities of the Pleiades, Alpha Persei, and Hyades clusters within their tidal radii are estimated to be 0.24 ± 0.04, 0.43 ± 0.08, and 0.09 ± 0.03 km s‑1, respectively. Similar to the Praesepe cluster that we have studied before, the rotation of the member stars within the tidal radii of these three open clusters can be well interpreted by Newton's theorem. No expansion or contraction is detected in the three clusters either. Furthermore, we find that the mean rotation velocity of open clusters may be positively correlated with the cluster mass, and the rotation is likely to diminish as open clusters age.

Keywords: Stellar kinematics, Open star clusters
Solar Wind Density and Core Temperature Derived from the PSP Quasi-thermal Noise Measurements. Quasi-thermal noise (QTN) spectroscopy is a valuable method to deduce important parameters in space plasma, such as plasma density and temperature, especially when direct particle measurements are not available. The present study develops a new fitting method to fit the QTN spectra observed by the Parker Solar Probe (PSP) with a comprehensive theoretical QTN spectral model. By combining the steepest descent and Levenberg–Marquardt algorithms, the new method is more flexible with initial guess values but still yields reliable solar wind electron density and temperature values. The new method is applied to derive the solar wind density and core temperature from the QTN measurements during 10 encounters of PSP. The electron density and temperature values obtained vary with the radial distance from the Sun as n  e  ∝ r ‑2.12 and T  e  ∝ r ‑0.71, both of which are consistent with existing models and previous results.

Keywords: Space probes, Solar wind, Space plasmas, Plasma physics
Two High-amplitude δ Scuti–γ Doradus Hybrids Constrained by the Radial Fundamental p and Equally Spaced g Modes. Based on 2 minutes cadence TESS data, we investigate pulsations of TIC 65138566 and TIC 139729335 and discover them to be two new high-amplitude δ Scuti stars with equally spaced g modes. We recognize the radial fundamental mode f 1 = 18.3334 c d‑1 and the first overtone f 3 = 23.6429 c d‑1 for TIC 65138566, and identify the highest peak f 1 = 19.0955 c d‑1 as the radial fundamental mode for TIC 139729335. For g modes, both stars display a regular period spacing of 2413 s. Through detailed seismological analysis, we deduce that these period-spacing patterns correspond to modes with ℓ = 1. Moreover, our analysis reveals that with increases in masses and metallicities, the star should display a higher degree of evolution to match a specific period spacing Π0. Conversely, the star should have a lower extent of evolution to match the radial fundamental mode. These two contradictory behaviors allow us to precisely obtain stellar physical parameters. TIC 65138566 and TIC 139729335 are determined to be two main-sequence stars that have almost the same range of masses and metallicities, with M = 1.36 ± 0.06 M ⊙ and Z = 0.005 ± 0.002. The hydrogen abundance in the core of TIC 65138566 is estimated to be about 0.28, while TIC 139729335 has a slightly higher value of around 0.31. Finally, we suggest that the high-amplitude δ Scuti–γ Doradus star TIC 308396022 is a main-sequence star with M = 1.54 ± 0.08 M ⊙, Z = 0.007 ± 0.001, and X c = 0.18 ± 0.02.

Keywords: Gamma Doradus variable stars, Asteroseismology, Delta Scuti variable stars
Ejecta─Circumstellar Medium Interaction in High-density Environment Contribution to Kilonova Emission: Application to GRB 191019A. The nearby long-duration GRB 191019A recently detected by Swift lacks an associated supernova and belongs to a host galaxy with little star formation activity, suggesting that the origin of this burst is the result of a merger of two compact objects with dynamical interactions in a high-density medium of an active galactic nucleus. Given the potential motivation of this event, and given that it occurs in such a high-density environment, the ejecta─circumstellar medium (CSM) interaction cannot be ignored as possibly contributing to the kilonova emission. Here, we theoretically calculate the kilonova emission by considering the contribution of the ejecta─CSM interaction in a high-density environment. We find that the contribution to the kilonova emission from the ejecta─CSM interaction will dominate at a later time, and a smaller ejecta mass will have a stronger kilonova emission from the ejecta─CSM interaction. Moreover, we try to apply it to GRB 191019A, but we find that it is difficult to identify the possible kilonova emission from the observations, due to the contribution of the bright host galaxy. On the other hand, less injected mass (less than M ej = 2 × 10−5 M ☉) will be required if one can detect the kilonova emission associated with a GRB 191019A─like event in the future. The r-process-powered and spin energy contributions from the magnetar are also discussed.

Keywords: Gamma-ray bursts
Atmospheric Chemistry of Secondary and Hybrid Atmospheres of Super Earths and Sub-Neptunes. The atmospheres of small exoplanets likely derive from a combination of geochemical outgassing and primordial gases left over from formation. Secondary atmospheres, such as those of Earth, Mars, and Venus, are sourced by outgassing. Persistent outgassing into long-lived, primordial, hydrogen–helium envelopes produces hybrid atmospheres of which there are no examples in the solar system. We construct a unified theoretical framework for calculating the outgassing chemistry of both secondary and hybrid atmospheres, where the input parameters are the surface pressure, oxidation, and sulfidation states of the mantle, as well as the primordial atmospheric hydrogen, helium, and nitrogen content. Nonideal gases (quantified by the fugacity coefficient) and nonideal mixing of gaseous components (quantified by the activity coefficient) are considered. Both secondary and hybrid atmospheres exhibit a rich diversity of chemistries, including hydrogen-dominated atmospheres. The abundance ratio of carbon dioxide to carbon monoxide serves as a powerful diagnostic for the oxygen fugacity of the mantle, which may conceivably be constrained by James Webb Space Telescope spectra in the near future. Methane-dominated atmospheres are difficult to produce and require specific conditions: atmospheric surface pressures exceeding ∼10 bar, a reduced (poorly oxidized) mantle, and diminished magma temperatures (compared to modern Earth). Future work should include photochemistry in these calculations and clarify the general role of atmospheric escape. Exoplanet science should quantify the relationship between the mass and oxygen fugacity for a sample of super Earths and sub-Neptunes; such an empirical relationship already exists for solar system bodies.

Keywords: Exoplanet atmospheric composition , Exoplanet atmospheres, Exoplanets
High-contrast JWST-MIRI Spectroscopy of Planet-forming Disks for the JDISC Survey. The JWST Disk Infrared Spectral Chemistry Survey (JDISCS) aims to understand the evolution of the chemistry of inner protoplanetary disks using the Mid-InfraRed Instrument (MIRI) on the James Webb Space Telescope (JWST). With a growing sample of &gt;30 disks, the survey implements a custom method to calibrate the MIRI Medium Resolution Spectrometer (MRS) to contrasts of better than 1:300 across its 4.9–28 μm spectral range. This is achieved using observations of Themis family asteroids as precise empirical reference sources. The high spectral contrast enables precise retrievals of physical parameters, searches for rare molecular species and isotopologues, and constraints on the inventories of carbon- and nitrogen-bearing species. JDISCS also offers significant improvements to the MRS wavelength and resolving power calibration. We describe the JDISCS calibrated data and demonstrate their quality using observations of the disk around the solar-mass young star FZ Tau. The FZ Tau MIRI spectrum is dominated by strong emission from warm water vapor. We show that the water and CO line emission originates from the disk surface and traces a range of gas temperatures of ∼500–1500 K. We retrieve parameters for the observed CO and H2O lines and show that they are consistent with a radial distribution represented by two temperature components. A high water abundance of n(H2O) ∼ 10‑4 fills the disk surface at least out to the 350 K isotherm at 1.5 au. We search the FZ Tau environs for extended emission, detecting a large (radius of ∼300 au) ring of emission from H2 gas surrounding FZ Tau, and discuss its origin.

Keywords: Water vapor, Infrared spectroscopy, Astrochemistry, James Webb Space Telescope, Protoplanetary disks, Astronomy data reduction
Ejection Patterns in the DG Tau Jet over the Last 40 yr: Insights into Mass Accretion Variability. We aim to clarify the link between mass accretion and ejection by analyzing DG Tau's jet observations from optical and near-infrared data spanning 1984─2019, alongside photometric variations between 1983 and 2015. We classified 12 moving knot groups among 17 total knot groups based on their constant proper motions and comparable radial velocities. A strong correlation emerges between the deprojected flow velocities of the knots and the photometric magnitudes of DG Tau. From 1983 to 1995, as the deprojected ejection velocities surged from ∼273 ± 15 to ∼427 ± 16 km s−1, the photometric magnitudes (V) concurrently brightened from 12.3 to 11.4. Notably, when DG Tau became brighter than 12.2 in the V band, its (B − V) color shifted bluer than its intrinsic color range of K5─M0. During this period, the launching point of the jet in the protoplanetary disk moved closer to 0.06 au from the star in 1995. Following a V magnitude drop from 11.7 to 13.4 in 1998, the star may have experienced significant extinction due to a dust wall created by the disk wind during the ejection of the high-velocity knot in 1999. Since then, the magnitude became fainter than 12.2, the (B − V) and (V − R) colors became redder, and the deprojected velocities consistently remained below 200 km s−1. The launching point of the jet then moved away to ∼0.45 au by 2008. The prevailing factor influencing photometric magnitude appears to be the active mass accretion causing the variable mass ejection velocities. * Based on observations obtained at the international Gemini Observatory, a program of NSF's NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership.

Keywords: Young stellar objects, Herbig-Haro objects, Star forming regions, Star formation
Stellar Cycle and Evolution of Polar Spots in an M+WD Binary. Stellar activity cycles reveal continuous relaxation and induction of magnetic fields. The activity cycle is typically traced through the observation of cyclic variations in total brightness or Ca H&amp;K emission flux of stars, as well as cyclic variations in the orbital periods of binary systems. In this work, we report the identification of a semidetached binary system (TIC 16320250) consisting of a white dwarf (0.67 M ⊙) and an active M dwarf (0.56 M ⊙). The long-term multiband optical light curves spanning twenty years revealed three repeated patterns, suggestive of a possible activity cycle of about 10 years of the M dwarf. Light-curve fitting indicates the repeated variation is caused by the evolution, particularly the motion, of polar spots. The significant Ca H&amp;K, Hα, ultra-violet, and X-ray emissions imply that the M dwarf is one of the most magnetically active stars. We propose that in the era of large time-domain photometric sky surveys (e.g., ASAS-SN, Zwicky Transient Facility, LSST, Sitian), long-term light-curve modeling can be a valuable tool for tracing and revealing stellar activity cycle, especially for stars in binary systems.

Keywords: Neutron stars, White dwarf stars, Binary stars, Stellar activity
Turbulent Heating of Solar Wind Plasma Downstream of Magnetohydrodynamic Shocks. Interplanetary (IP) shocks are believed to play a significant role in both amplifying the background level of turbulent fluctuations and in heating the bulk solar wind (SW). This study investigates the thermodynamic properties downstream of IP shocks. We examine the temperature, density, and specific entropy changes in the shocked plasma, taking into consideration the geometric aspects of IP shock propagation within the expanding SW. Specifically, in our analysis, we account for the fact that any particular temporal range of one-point measurement may correspond to vastly different physically relevant temporal and/or spatial dimensions, such as the age of the shocked plasma and/or radial distance to the place where the plasma encountered the shock. Thus, our approach resolves the contradictions in previously reported temperature and specific entropy profiles in downstream regions and suggests that downstream regions exhibit greater turbulent heating compared to the pristine SW. This may contribute to the overall heating of the SW plasma. The paper presents a phenomenological parameter to predict specific entropy profiles and demonstrates the consistency of the proposed model with observations. We discuss the implications of these results for the thermodynamics of the SW beyond 1 au.

Keywords: Interplanetary turbulence, Solar wind, Interplanetary shocks
What Is Missing from the Local Stellar Halo?. The Milky Way's stellar halo, which extends to &gt;100 kpc, encodes the evolutionary history of our Galaxy. However, most studies of the halo to date have been limited to within a few kiloparsecs of the Sun. Here, we characterize differences between this local halo and the stellar halo in its entirety. We construct a composite stellar halo model by combining observationally motivated N-body simulations of the Milky Way's nine most massive disrupted dwarf galaxies that account for almost all of the mass in the halo. We find that (i) the representation by mass of different dwarf galaxies in the local halo compared to the whole halo can be significantly overestimated (e.g., the Helmi streams) or underestimated (e.g., Cetus) and (ii) properties of the overall halo (e.g., net rotation) inferred via orbit integration of local halo stars are significantly biased because, for example, highly retrograde debris from Gaia-Sausage-Enceladus is missing from the local halo. Therefore, extrapolations from the local to the global halo should be treated with caution. From analysis of a sample of 11 Milky Way–like simulated halos, we contextualize these results and identify a population of recently accreted (≲5 Gyrs) and disrupted galaxies on high-angular-momenta orbits that are entirely missing from local samples and likely awaiting discovery in the outer halo. Our results motivate the need for surveys of halo stars extending out to the Galaxy's virial radius.

Keywords: Galaxy formation, Milky Way formation, Galaxy stellar halos, Milky Way Galaxy physics, Milky Way stellar halo, Galaxy evolution, Milky Way evolution, Milky Way Galaxy
The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). X. Hot Gas Reveals Deeply Embedded Star Formation. Massive infrared dark clouds (IRDCs) are considered to host the earliest stages of high-mass star formation. In particular, 70 μm dark IRDCs are the colder and more quiescent clouds. At a scale of about 5000 au using formaldehyde (H2CO) emission, we investigate the kinetic temperature of dense cores in 12 IRDCs obtained from the pilot Atacama Large Millimeter/submillimeter Array Survey of 70 μm dark High-mass clumps in Early Stages (ASHES). Compared to the 1.3 mm dust continuum and other molecular lines, such as C18O and deuterated species, we find that H2CO is mainly sensitive to low-velocity outflow components rather than to quiescent gas expected in the early phases of star formation. The kinetic temperatures of these components range from 26 to 300 K. The Mach number reaches about 15 with an average value of about 4, suggesting that the velocity distribution of gas traced by H2CO is significantly influenced by a supersonic nonthermal component. In addition, we detect warm line emission from HC3N and OCS in 14 protostellar cores, which requires high excitation temperatures (E  u /k ∼ 100 K). These results show that some of the embedded cores in the ASHES fields are in an advanced evolutionary stage, previously unexpected for 70 μm dark IRDCs.

Keywords: Infrared dark clouds, Massive stars, Star forming regions, Protoclusters, Star formation, Interstellar medium, Protostars
The Disk Orientations of Perseus Protostellar Multiples at ∼8 au Resolution. We present a statistical characterization of circumstellar disk orientations toward 12 protostellar multiple systems in the Perseus molecular cloud using the Atacama Large Millimeter/submillimeter Array at Band 6 (1.3 mm) with a resolution of ∼25 mas (∼8 au). This exquisite resolution enabled us to resolve the compact inner-disk structures surrounding the components of each multiple system and to determine the projected 3D orientation of the disks (position angle and inclination) to high precision. We performed a statistical analysis on the relative alignment of disk pairs to determine whether the disks are preferentially aligned or randomly distributed. We considered three subsamples of the observations selected by the companion separations a &lt; 100 au, a &gt; 500 au, and a &lt; 10,000 au. We found for the compact (&lt;100 au) subsample, the distribution of orientation angles is best described by an underlying distribution of preferentially aligned sources (within 30°) but does not rule out distributions with 40% misaligned sources. The wide companion (&gt;500 au) subsample appears to be consistent with a distribution of 40%─80% preferentially aligned sources. Similarly, the full sample of systems with companions (a &lt; 10,000 au) is most consistent with a fractional ratio of at most 80% preferentially aligned sources and rules out purely randomly aligned distributions. Thus, our results imply the compact sources (&lt;100 au) and the wide companions (&gt;500 au) are statistically different.

Keywords: Protostars, Young stellar objects, Radio interferometry
Ultraviolet Quasiperiodic Eruptions from Star–Disk Collisions in Galactic Nuclei. "Quasiperiodic eruptions" (QPE) are recurrent nuclear transients with periods of several hours to almost a day, which thus far have been detected exclusively in the X-ray band. We have shown that many of the key properties of QPE flares (period, luminosity, duration, emission temperature, alternating long-short recurrence time behavior, and source rates) are naturally reproduced by a scenario involving twice-per-orbit collisions between a solar-type star on a mildly eccentric orbit, likely brought into the nucleus as an extreme mass-ratio inspiral (EMRI), and the gaseous accretion disk of a supermassive black hole (SMBH). The flare is generated by the hot shocked debris expanding outwards from either side of the disk midplane, akin to dual miniature supernovae. Here, we consider the conditions necessary for disk–star collisions to generate lower-temperature flares that peak in the ultraviolet (UV) instead of the X-ray band. We identify a region of parameter space at low SMBH mass M • ∼ 105.5 M ⊙ and QPE periods P ≳ 10 hr for which the predicted flares are sufficiently luminous L UV ∼ 1041 erg s‑1 to outshine the quiescent disk emission at these wavelengths. The prospects to discover such "UV QPEs" with future satellite missions such as ULTRASAT and Ultraviolet Explorer depend on the prevalence of very low-mass SMBHs and the occurrence rate of stellar EMRIs onto them. For gaseous disks produced by the tidal disruption of stars, we predict that X-ray QPEs will eventually shut off, only to later reappear as UV QPEs as the accretion rate continues to drop.

Keywords: X-ray transient sources, Supermassive black holes, Tidal disruption, Ultraviolet transient sources