Sazuna/UAT_keywords huggingface dataset:
The Mg-K Anticorrelation in ω Centauri. We present [K/Fe] abundance ratios for a sample of 450 stars in ω Centauri, using high-resolution spectra acquired with the multiobject spectrograph FLAMES@VLT. Abundances for Fe, Na, and Mg were also derived. We detected intrinsic K variations in the analyzed stars. Moreover, [K/Fe] shows a significant correlation with [Na/Fe] and an anticorrelation with [Mg/Fe]. The presence of a clear-cut Mg-K anticorrelation makes ω Centauri the third stellar system, after NGC 2419 and NGC 2808, hosting a subpopulation of stars with [Mg/Fe] &lt; 0.0 dex, K-enriched in the case of ω Centauri by ~0.3 dex with respect to Mg-rich stars ([Mg/Fe] &gt; 0.0 dex). The correlation/anticorrelation between K and other light elements involved in chemical anomalies supports the idea that the spread in [K/Fe] can be associated with the same self-enrichment process typical of globular clusters. We suggest that significant variations in K abundances perhaps can be found in the most massive and/or metal-poor globular clusters as a manifestation of an extreme self-enrichment process. Theoretical models face problems explaining K production in globular clusters. Indeed, models where asymptotic giant branch stars are responsible for the Mg-K anticorrelation only qualitatively agree with the observations. Finally, we discovered a peculiar star with an extraordinary K overabundance ([K/Fe] = +1.60 dex) with respect to the other stars with similar [Mg/Fe]. We suggest that this K-rich star could be formed from the pure ejecta of AGB stars before dilution with pristine material.

Keywords: Chemical abundances
Gravitational-wave Emission from a Primordial Black Hole Inspiraling inside a Compact Star: A Novel Probe for Dense Matter Equation of State. Primordial black holes of planetary masses captured by compact stars are widely studied to constrain their composition fraction of dark matter. Such a capture may lead to an inspiral process and be detected through gravitational-wave signals. In this Letter, we study the postcapture inspiral process by considering two different kinds of compact stars, i.e., strange stars and neutron stars. The dynamical equations are numerically solved, and the gravitational-wave emission is calculated. It is found that the Advanced LIGO can detect the inspiraling of a 10-5 M ⊙ primordial black hole at a distance of 10 kpc, while a Jovian-mass case can even be detected at megaparsecs. Promisingly, the next generation of gravitational-wave detectors can detect cases of 10-5 M ⊙ primordial black holes up to ~1Mpc and Jovian-mass cases at several hundred megaparsecs. Moreover, the kilohertz gravitational-wave signal shows significant differences for strange stars and neutron stars, potentially making it a novel probe to the dense matter equation of state.

Keywords: Neutron stars, Nuclear astrophysics, Gravitational waves, Primordial black holes
Tidally Tilted Pulsations in HD 265435, a Subdwarf B Star with a Close White Dwarf Companion. Tidally tilted pulsators (TTPs) are an intriguing new class of oscillating stars in binary systems; in such stars, the pulsation axis coincides with the line of apsides, or tidal axis, of the binary. All three TTPs discovered so far have been δ Scuti stars. In this Letter, we report the first conclusive discovery of tidally tilted pulsations in a subdwarf B (sdB) star. HD 265435 is an sdB-white dwarf binary with a 1.65 hr period that has been identified and characterized as the nearest potential Type Ia supernova progenitor. Using TESS 20 s cadence data from Sectors 44 and 45, we show that the pulsation axis of the sdB star has been tidally tilted into the orbital plane and aligned with the tidal axis of the binary. We identify 31 independent pulsation frequencies, 27 of which have between 1 and 7 sidebands separated by the orbital frequency (ν orb) or multiples thereof. Using the observed amplitude and phase variability due to tidal tilting, we assign ℓ and m values to most of the observed oscillation modes and use these mode identifications to generate preliminary asteroseismic constraints. Our work significantly expands our understanding of TTPs, as we now know that (i) they can be found in stars other than δ Scuti pulsators, especially highly evolved stars that have lost their H-rich envelopes, and (ii) tidally tilted pulsations can be used to probe the interiors of stars in very tight binaries.

Keywords: Asteroseismology, Tidal distortion, B subdwarf stars, Pulsation modes
The Turbulent Properties of the Sub-Alfvénic Solar Wind Measured by the Parker Solar Probe. For the first time, Parker Solar Probe (PSP) observed the sub-Alfvénic solar wind where the solar wind bulk speed drops below the local Alfvén speed for an extended period of time. Here, we report on the turbulent properties of the sub-Alfvénic region. We analyze the turbulence correlation length and the energy transfer and compare the results with nearby super-Alfvénic regions. As the Alfvén speed is larger or comparable to the solar wind speed in the intervals studied, we use a modified Taylor's hypothesis to account for wave propagation. We find that the wave propagation speed affects the analysis of the correlation lengths of the forward and backward propagating z ± modes. In the sub-Alfvénic region, the correlation length of the z - mode is shorter than that of the outward propagating z + mode, although the correlation time of the z - mode is about 10 times larger than that of the z + mode. For the energy transfer, we use both incompressible and compressible formulations to calculate the energy flux based on third-order structure functions. The incompressible energy cascade rates for the forward and backward propagating modes are computed separately using the modified Taylor's hypothesis. The averaged compressible cascade rate is higher in the sub-Alfvénic interval than the nearby downstream super-Alfvénic region, which may be due to the lower fluctuation amplitude in the latter super-Alfvénic interval. Longer incursions of the PSP in the sub-Alfvénic winds in the future will give us better statistics.

Keywords: Interplanetary turbulence, Solar wind
Temporal Scattering, Depolarization, and Persistent Radio Emission from Magnetized Inhomogeneous Environments near Repeating Fast Radio Burst Sources. Some repeating fast radio burst (FRB) sources exhibit complex polarization behaviors, including frequency-dependent depolarization, variation of rotation measure (RM), and oscillating spectral structures of polarized components. Very recently, Feng et al. reported that active repeaters exhibit conspicuous frequency-dependent depolarization and a strong correlation between RM scatter (σ RM) and the temporal scattering time (τ s), ${\sigma }_{\mathrm{RM}}\propto {\tau }_{{\rm{s}}}^{1.0\pm 0.2}$ , both of which can be well described by multipath propagation through a magnetized inhomogeneous plasma screen. This observation strongly suggests that the temporal scattering and RM scatter originate from the same region. Besides, a particular finding of note in Feng et al. is that the FRBs with compact persistent radio sources (PRSs) tend to have extreme σ RM. In this work, we focus on some theoretical predictions of the relations among temporal scattering, depolarization by RM scatter, and PRSs contributed by the magnetized plasma environment close to a repeating FRB source. The behaviors of the RM scatter imply that the magnetized plasma environment is consistent with a supernova remnant or pulsar wind nebula, and the predicted σ RM-τ s relation is ${\sigma }_{\mathrm{RM}}\propto {\tau }_{{\rm{s}}}^{(0.54-0.83)}$ for different astrophysical scenarios. We further make a general discussion of PRSs that does not depend on specific astrophysical scenarios. We show that the specific luminosity of a PRS should have a positive correlation with the RM contributed by the plasma screen. This is consistent with the observations of FRB 121102 and FRB 190520B.

Keywords: Radio bursts, Gravitational waves, Interstellar medium, Radio continuum emission, Radio transient sources
Eclipse Timing the Milky Way's Gravitational Potential. We show that a small but measurable shift in the eclipse midpoint time of eclipsing binary (EBs) stars of ~0.1 s over a decade baseline can be used to directly measure the Galactic acceleration of stars in the Milky Way at ~kiloparsec distances from the Sun. We consider contributions to the period drift rate from dynamical mechanisms other than the Galaxy's gravitational field and show that the Galactic acceleration can be reliably measured using a sample of Kepler EBs with orbital and stellar parameters from the literature. The contribution from tidal decay we estimate here is an upper limit assuming the stars are not tidally synchronized. We find there are about 200 detached EBs that have estimated timing precision better than 0.5 s, and for which other dynamical effects are subdominant to the Galactic signal. We illustrate the method with a prototypical, precisely timed EB using an archival Kepler light curve and a modern synthetic HST light curve (which provides a decade baseline). This novel method establishes a realistic possibility to constrain dark matter substructure and the Galactic potential using eclipse timing to measure Galactic accelerations, along with other emerging new methods, including pulsar timing and extreme-precision radial velocity observations. This acceleration signal grows quadratically with time. Therefore, given baselines established in the near future for distant EBs, we can expect to measure the period drift in the future with space missions like JWST and the Roman Space Telescope.

Keywords: Transits, Milky Way dynamics, Planetary dynamics, Eclipsing binary stars, Dark matter
A Disk Instability Model for the Quasi-periodic Eruptions of GSN 069. GSN 069 is a recently discovered quasi-periodic eruption (QPE) source recurring about every 9 hr. The mechanism for the QPEs of GSN 069 is still unclear. In this work, a disk instability model is constructed to explain GSN 069 based on Pan et al. (PLC21), where the authors proposed a toy model for the repeating changing-look active galactic nuclei. We improve the work of PLC21 by including a nonzero viscous torque condition on the inner boundary of the disk and adopting a general form for the viscous stress torque in the Kerr metric. It is found that the 0.4-2 keV light curves, the light curves at different energy bands, and the phase-resolved X-ray spectrum of GSN 069 can all be qualitatively reproduced by our model. Furthermore, the profiles of light curves in QPEs can be significantly changed by the parameter μ in the viscous torque equation, which implies that our model may also be applied to other QPEs.

Keywords: Active galactic nuclei, Galaxy accretion disks, Magnetic fields
Hot Circumsingle Disks Drive Binary Black Hole Mergers in Active Galactic Nucleus Disks. Binary black hole (BBH) mergers, particularly those with component masses in the pair-instability gap, may be produced by hierarchical mergers in the disks surrounding Active Galactic Nuclei (AGNs). While the interaction of an embedded BBH with an AGN disk is typically assumed to facilitate a merger, recent high-resolution hydrodynamical simulations challenge this assumption. However, these simulations often have simplified treatments for gas thermodynamics. In this work, we model the possible consequence of various feedback from an embedded BBH with a simple model that maintains an enhanced temperature profile around each binary component. We show that when the minidisks around each BH become hotter than the background by a factor of three, the BBH orbital evolution switches from expansion to contraction. By analyzing the gravitational torque profile, we find that this change in direction is driven by a weakening of the minidisk spirals and their positive torque on the binary. Our results highlight the important role of thermodynamics around BBHs and its effect on their orbital evolution, suggesting that AGN disks could be efficient factories for BBH mergers.

Keywords: Black hole physics, Hydrodynamical simulations, Black holes, Gravitational wave sources, Orbital evolution, Active galactic nuclei
Markovian Features of the Solar Wind at Subproton Scales. The interplanetary magnetic field carried out from the Sun by the solar wind displays fluctuations over a wide range of scales. While at large scales, say at frequencies lower than 0.1-1 Hz, fluctuations display the universal character of fully developed turbulence with a well-defined Kolmogorov-like inertial range, the physical and dynamical properties of the small-scale regime as well as their connection with the large-scale ones are still a debated topic. In this work we investigate the near-Sun magnetic field fluctuations at subproton scales by analyzing the Markov property of fluctuations and recovering basic information about the nature of the energy transfer across different scales. By evaluating the Kramers-Moyal coefficients we find that fluctuations in the subproton range are well described as a Markovian process with Probability Density Functions (PDFs) modeled via a Fokker-Planck (FP) equation. Furthermore, we show that the shape of the PDFs is globally scale-invariant and similar to the one recovered for the stationary solution of the FP equation at different scales. The relevance of our results on the Markovian character of subproton scale fluctuations is also discussed in connection with the occurrence of turbulence in this domain.

Keywords: Space plasmas, Magnetohydrodynamics, Heliosphere, Interplanetary turbulence, Solar wind, Interplanetary physics
A Search for H-Dropout Lyman Break Galaxies at z 12-16. We present two bright galaxy candidates at z ~ 12-13 identified in our H-dropout Lyman break selection with 2.3 deg2 near-infrared deep imaging data. These galaxy candidates, selected after careful screening of foreground interlopers, have spectral energy distributions showing a sharp discontinuity around 1.7 μm, a flat continuum at 2-5 μm, and nondetections at &lt;1.2 μm in the available photometric data sets, all of which are consistent with a z &gt; 12 galaxy. An ALMA program targeting one of the candidates shows a tentative 4σ [O III] 88 μm line at z = 13.27, in agreement with its photometric redshift estimate. The number density of the z ~ 12-13 candidates is comparable to that of bright z ~ 10 galaxies and is consistent with a recently proposed double-power-law luminosity function rather than the Schechter function, indicating little evolution in the abundance of bright galaxies from z ~ 4 to 13. Comparisons with theoretical models show that the models cannot reproduce the bright end of rest-frame ultraviolet luminosity functions at z ~ 10-13. Combined with recent studies reporting similarly bright galaxies at z ~ 9-11 and mature stellar populations at z ~ 6-9, our results indicate the existence of a number of star-forming galaxies at z &gt; 10, which will be detected with upcoming space missions such as the James Webb Space Telescope, Nancy Grace Roman Space Telescope, and GREX-PLUS.

Keywords: Galaxy formation, High-redshift galaxies, Galaxy evolution
Where and How Does a Decay-index Profile Become Saddle-like?. The decay index of solar magnetic fields is known as an important parameter in regulating solar eruptions from the standpoint of the torus instability. In particular, a saddle-like profile of decay index, which hosts a local torus-stable regime at higher altitudes than where the decay index first exceeds the instability threshold, is found to be associated with some confined or two-step eruptions. To understand the occurrence of such a profile, we employed dipoles to emulate different kinds of photospheric flux distributions. Corroborated by observations of representative active regions, our major results are as follows: (1) in bipolar configurations the critical height increases away from the AR center along the polarity inversion line (PIL) and its average is roughly half of the centroid distance between opposite polarities; (2) in quadrupolar configurations saddle-like profiles appear above the PIL when the two dipoles oriented in the same direction are significantly more separated in this direction than in the perpendicular direction, and when the two dipoles are oriented differently or have unequal fluxes; and (3) saddle-like profiles in quadrupolar configurations are associated with magnetic skeletons such as a null point or a hyperbolic flux tube, and the role of such profiles in eruptions is anticipated to be double-edged if magnetic reconnection is involved.

Keywords: Solar magnetic fields, Solar flares, Solar coronal mass ejections
CLEAR: Paschen-β Star Formation Rates and Dust Attenuation of Low-redshift Galaxies. We use Paschen-β (Paβ; 1282 nm) observations from the Hubble Space Telescope G141 grism to study the star formation and dust-attenuation properties of a sample of 29 low-redshift (z &lt; 0.287) galaxies in the CANDELS Lyα Emission at Reionization survey. We first compare the nebular attenuation from Paβ/Hα with the stellar attenuation inferred from the spectral energy distribution, finding that the galaxies in our sample are consistent with an average ratio of the continuum attenuation to the nebular gas of 0.44, but with a large amount of excess scatter beyond the observational uncertainties. Much of this scatter is linked to a large variation between the nebular dust attenuation as measured by (space-based) Paβ to (ground-based) Hα to that from (ground-based) Hα/Hβ. This implies there are important differences between attenuation measured from grism-based/wide-aperture Paβ fluxes and the ground-based/slit-measured Balmer decrement. We next compare star formation rates (SFRs) from Paβ to those from dust-corrected UV. We perform a survival analysis to infer a census of Paβ emission implied by both detections and nondetections. We find evidence that galaxies with lower stellar mass have more scatter in their ratio of Paβ to attenuation-corrected UV SFRs. When considering our Paβ detection limits, this observation supports the idea that lower-mass galaxies experience "burstier" star formation histories. Together, these results show that Paβ is a valuable tracer of a galaxy's SFR, probing different timescales of star formation and potentially revealing star formation that is otherwise missed by UV and optical tracers.

Keywords: Starburst galaxies, Star formation, Interstellar dust extinction
Test Particle Energization of Heavy Ions in Magnetohydrodynamic Turbulence. In the present work, we study the energization and displacement of heavy ions through the use of test particles interacting with the electromagnetic fields of magnetohydrodynamic (MHD) turbulence. These fields are obtained from pseudospectral direct numerical solutions of the compressible three-dimensional MHD equations with a strong background magnetic field. We find particle energization to be predominantly perpendicular as the ions become heavier (lower charge-to-mass ratio) and that high displacement is detrimental for perpendicular energization. On the other hand, perpendicular displacement is unaffected by the charge-to-mass ratio, which we explain with a simple guide center model. Using Voronoi tessellation along with this model, we analyze preferential concentration and find that particles behave as tracers in the perpendicular plane, clustering in regions with ∇⊥ · u ⊥ &lt; 0. These regions also have (∇ × E ) z  &lt; 0, which is optimal for perpendicular energization, thus providing a mechanism to understand precedent results.

Keywords: Interplanetary turbulence, Pickup ions, Magnetohydrodynamics
Cosmic Tidal Reconstruction with Halo Fields. The gravitational coupling between large-scale perturbations and small-scale perturbations leads to anisotropic distortions of the small-scale matter distribution. The measured local small-scale power spectrum can thus be used to infer the large-scale matter distribution. In this paper, we present a new tidal reconstruction algorithm for reconstructing large-scale modes using the full three-dimensional tidal shear information. We apply it to simulated dark matter halo fields and find the reconstructed large-scale density field correlates well with the original matter density field on large scales, improving upon the previous tidal reconstruction method, which only uses two transverse shear fields. This has profound implications for recovering lost 21 cm radial modes due to foreground subtraction and constraining primordial non-Gaussianity using the multitracer method with future cosmological surveys.

Keywords: Cosmology, Dark matter distribution, Large-scale structure of the universe, Gravitational interaction, Non-Gaussianity, Astronomical methods, N-body simulations
A New Method for the Reconstruction of Strongly Lensed Galaxies with Resolved Kinematics. Integral field spectroscopy of high-redshift galaxies has become a powerful tool for understanding their dynamics and evolutionary states. However, in the case of gravitationally lensed systems, it has proved difficult to model both lensing and intrinsic kinematics in a way that takes full advantage of the information available in the spectral domain. In this paper, we introduce a new method for pixel-based source reconstruction that alters standard regularization schemes for two-dimensional (2D) data in a way that leverages kinematic information in a physically motivated but flexible fashion, and that is better suited to the three-dimensional (3D) nature of integral field data. To evaluate the performance of this method, we compare its results to those of a more traditional 2D nonparametric approach using mock Atacama Large Millimeter/submillimeter Array (ALMA) observations of a typical high-redshift dusty star-forming galaxy. We find that 3D regularization applied to an entire data cube reconstructs a source's intensity and velocity structure more accurately than 2D regularization applied to separate velocity channels. Cubes reconstructed with 3D regularization also have more uniform noise and resolution properties and are less sensitive to the signal-to-noise ratio of individual velocity channels than the results of 2D regularization. Our new approach to modeling integral field observations of lensed systems can be implemented without making restrictive a priori assumptions about intrinsic kinematics, and opens the door to new observing strategies that prioritize spectral resolution over spatial resolution (e.g., for multiconfiguration arrays like ALMA).

Keywords: Galaxy dynamics, Gravitational lensing, Galaxy evolution, Galaxy kinematics, High-redshift galaxies, Galaxies
Diffusive Shock Acceleration at Oblique High Mach Number Shocks. The current paradigm of cosmic-ray (CR) origin states that the greater part of galactic CRs is produced by supernova remnants. The interaction of supernova ejecta with the interstellar medium after a supernova's explosions results in shocks responsible for CR acceleration via diffusive shock acceleration (DSA). We use particle-in-cell (PIC) simulations and a combined PIC-magnetohydrodynamic (PIC-MHD) technique to investigate whether DSA can occur in oblique high Mach number shocks. Using the PIC method, we follow the formation of the shock and determine the fraction of the particles that gets involved in DSA. With this result, we use PIC-MHD simulations to model the large-scale structure of the plasma and the magnetic field surrounding the shock and find out whether or not the reflected particles can generate upstream turbulence and trigger DSA. We find that the feasibility of this process in oblique shocks depends strongly on the Alfvénic Mach number, and the DSA process is more likely to be triggered at high Mach number shocks.

Keywords: Supernova remnants, Shocks, Plasma astrophysics, Interstellar medium