Sazuna/UAT_keywords huggingface dataset:
A 34 yr Timing Solution of the Redback Millisecond Pulsar Terzan 5A. We present a 34 yr timing solution of the redback pulsar system Terzan 5A (Ter5A). Ter5A, also known as B1744‑24A or J1748‑2446A, has a 11.56 ms pulse period, a ~0.1 M⊙ dwarf companion star, and an orbital period of 1.82 hr. Ter5A displays highly variable eclipses and orbital perturbations. Using new timing techniques, we have determined a phase-connected timing solution for this system over 34 yr. This is the longest ever published for a redback pulsar. We find that the pulsar's spin variability is much larger than most globular cluster pulsars. In fact, of the nine redback pulsars with published or in-preparation long-term timing solutions, Ter5A is by far the noisiest. We see no evidence of strong correlations between orbital and spin variability of the pulsar. We also find that long-term astrometric timing measurements are likely too contaminated by this variability to be usable, and therefore they require careful short-term timing to determine reasonable positions. Finally, we measure an orbital period contraction of ‑2.5(3) × 10‑13, which is likely dominated by the general relativistic orbital decay of the system. The effects of the orbital variability due to the redback nature of the pulsar are not needed to explain the observed orbital period derivative, but they are constrained to less than ~30% of the observed value.

Keywords: Globular star clusters, Binary pulsars, Pulsar timing method, Millisecond pulsars
DIISC-VI (COS-DIISC): Ultraviolet Metal Absorption Relative to the H I Disk of Galaxies. As part of the Deciphering the Interplay between the Interstellar medium, Stars, and the Circumgalactic medium (DIISC) survey, we present the UV metal absorption features in the circumgalactic medium (CGM) near the H I gas disk (&lt;4.5RHI) of 31 nearby galaxies through quasar absorption-line spectroscopy. Of the ions under study, Si IIIλ1206 was most frequently detected (18 of 31 sight lines), while C IIλ1334 and Si IIλ1260 were detected in 17 and 15 of 31 sight lines, respectively. Many components were consistent with photoionization equilibrium models; most of the cold and cool gas phase clouds were found to have lengths smaller than 2 kpc. Sight lines with smaller impact parameters (ρ) normalized by the galaxy's virial radius (Rvir) and H I radius (RHI) tend to have more components and larger rest-frame equivalent widths (Wr) than those that probe the CGM at larger radii. In particular, we find that the location of metals are better traced by ρ/RHI rather than the traditional ρ/Rvir. Larger covering fractions are found closer to galaxies, with a radial decline that depends on the Wr limit used. Our results provide new insights into the spatial distribution of metals around the H I disks of low-redshift galaxies.

Keywords: Photoionization, Quasar absorption line spectroscopy, Quasar-galaxy pairs
Substellar Landmass Fraction and Atmospheric Circulation Regimes of Ultrashort-period Rocky Planets around White Dwarfs. White-dwarf (WD) systems are attractive candidates for planet detection and follow-up transmission spectroscopy campaigns. However, the climate and habitability of terrestrial planets around WDs still remain largely elusive, and a central question lies in the width and extent of their habitable zones (HZs) and how their climates may be shaped by their stellar environments. A recently published study, using a 3D general circulation model (GCM), found a novel atmospheric circulation pattern for ultrarapid rotators around WDs. This "bat-rotation" regime features mean equatorial subrotation and a displacement of the surface's hottest regions from the equator toward the midlatitudes. Here, we used a GCM of reduced complexity to simulate a large range of landmass fraction (LMF) assumptions on these planets and examine the regimes in which these planets would exhibit the new dynamical regime. We find that as the dayside LMF approaches 80%, the bat-rotator features begin to diminish and the circulation behavior becomes more akin to the thermally driven direction circulation patterns observed around slowly rotating planets. Our results suggest that the introduction of different surface characteristics would drastically modify previous predictions of the atmospheres of ultrashort-period planets in the HZ of WD stars.

Keywords: White dwarf stars, Astrobiology, Planetary atmospheres, Planetary climates
Elemental Abundances at Coronal Hole Boundaries as a Means to Investigate Interchange Reconnection and the Solar Wind. The origin of the slow solar wind is not well understood, unlike the fast solar wind that originates from coronal holes. In situ elemental abundances of the slow solar wind suggest that it originates from initially closed field lines that become open. Coronal hole boundary regions are a potential source of slow solar wind, as open field lines there interact with the closed loops through interchange reconnection. Our primary aim is to quantify the role of interchange reconnection at the boundaries of coronal holes. To this end, we have measured the relative abundances of different elements at these boundaries. Reconnection is expected to modulate the relative abundances through the first ionization potential (FIP) effect. For our analysis, we used spectroscopic data from the EUV imaging spectrometer on board Hinode. To account for the temperature structure of the observed region, we computed the differential emission measure (DEM). Using the DEM, we were able to infer the ratio between coronal and photospheric abundances, known as the FIP bias. By examining the variation of the FIP bias moving from the coronal hole to the quiet Sun, we have been able to constrain models of interchange reconnection. The FIP bias variation in the boundary region around the coronal hole has an approximate width of 30–60 Mm, comparable to the size of supergranules. This boundary region is also a source of open flux into interplanetary space. We find that there could be an additional ∼37-71% open flux that originates from this boundary region.

Keywords: Solar magnetic reconnection, Solar wind, Solar abundances, Solar physics, Solar magnetic fields, Solar coronal holes
The Core Mass Function across Galactic Environments. IV. The Galactic Center. The origin of the stellar initial mass function (IMF) and how it may vary with galactic environment is a matter of debate. Certain star formation theories involve a close connection between the IMF and the core mass function (CMF), so it is important to measure this CMF in a range of Milky Way locations. Here we study the CMF of three Galactic center clouds: G0.253+0.016 ("The Brick"), Sagittarius B2-Deep South field (Sgr B2-DS), and Sagittarius C (Sgr C). We use Atacama Large Millimeter/submillimeter Array 1 mm continuum images and identify cores as peaks in thermal dust emission via the dendrogram algorithm. We develop a completeness correction method via synthetic core insertion, utilizing a realistic mass-dependent size distribution. A power law   is fit to the CMFs &gt;2 M⊙. The Brick has a Salpeter-like index α = 1.28 ± 0.09, while the other regions have shallower indices: Sgr C has α = 0.99 ± 0.06, and Sgr B2-DS has α = 0.70 ± 0.03. When smoothed to a common resolution, the differences between the Brick and the others increase as we obtain α = 1.36 ± 0.12, α = 0.66 ± 0.06, and α = 0.62 ± 0.04, respectively, for masses ≳3 M⊙. Furthermore, we analyze the spatial distribution and mass segregation of cores: Sgr C and Sgr B2-DS show signs of mass segregation, but the Brick does not. We compare our results to several other CMFs from different Galactic regions derived with the same methods. Finally, we discuss how our results may help define an evolutionary sequence of star cluster formation and be used to test star formation theories.

Keywords: Galactic center, Star formation, Interstellar medium
Aggressively Dissipative Dark Dwarfs: The Effects of Atomic Dark Matter on the Inner Densities of Isolated Dwarf Galaxies. We present the first suite of cosmological hydrodynamical zoom-in simulations of isolated dwarf galaxies for a dark sector that consists of cold dark matter and a strongly dissipative subcomponent. The simulations are implemented in GIZMO and include standard baryons following the FIRE-2 galaxy formation physics model. The dissipative dark matter is modeled as atomic dark matter (aDM), which forms a dark hydrogen gas that cools in direct analogy to the Standard Model. Our suite includes seven different simulations of ∼1010 M⊙ systems that vary over the aDM microphysics and the dwarf's evolutionary history. We identify a region of aDM parameter space where the cooling rate is aggressive and the resulting halo density profile is universal. In this regime, the aDM gas cools rapidly at high redshifts, and only a small fraction survives in the form of a central dark gas disk; the majority collapses centrally into collisionless dark "clumps," which are clusters of subresolution dark compact objects. These dark clumps rapidly equilibrate in the inner galaxy, resulting in an approximately isothermal distribution that can be modeled with a simple fitting function. Even when only a small fraction (∼5%) of the total dark matter is strongly dissipative, the central densities of classical dwarf galaxies can be enhanced by over an order of magnitude, providing a sharp prediction for observations.

Keywords: Hydrodynamical simulations, Cold dark matter, Dwarf galaxies, N-body simulations, Dark matter, Particle astrophysics
Submillimeter Variability in the Envelope and Warped Protostellar Disk of the Class 0 Protostar HOPS 358. The James Clerk Maxwell Telescope (JCMT) Transient Survey recently discovered that the Class 0 protostar HOPS 358 decreased in 350 GHz continuum brightness by ∼25% over the course of 4 yr before brightening again for the next 4. The JCMT light curve can be fit by a long-timescale dip lasting roughly 8 yr. A shorter-timescale periodicity is also apparent with a period of 1.75 yr and a small 3% amplitude. NEOWISE monitoring reveals that the mid-infrared wavelength brightness of HOPS 358 follows a similar long-term pattern in time. Here, we present a study of nine epochs of Atacama Large Millimeter/submillimeter Array (ALMA) observations of HOPS 358 taken over the course of the decline and subsequent rise in brightness seen with the JCMT to test whether the variation seen on ∼15″ scales, covering both disk and envelope, is also observed on smaller, &lt;1″ scales that primarily probe HOPS 358's protostellar disk. We detect both HOPS 358 and its southern companion, HOPS 358B, in our ALMA observations and find that at least one of the two is varying. Assuming that HOPS 358 is the variable, the light curve has the same shape as that found by the JCMT. Additionally, our high-resolution ALMA imaging of HOPS 358 reveals that the disk is warped, with a 16° warp at a disk radius of 35 au, about halfway through the extent of the disk. The physical origin of the warp and how it relates to the variability seen toward HOPS 358, however, remain unclear.

Keywords: Protostars, Pre-main sequence stars, Star formation, Protoplanetary disks
Redshift Drift Effect through the Observation of the H I 21 cm Signal with SKA. This study presents the findings of using the Square Kilometre Array (SKA) telescope to measure redshift drift via the H I 21 cm signal, employing semiannual observational intervals within a redshift of around z ∼ 1 with a main goal of directly gauging the Universe's expansion acceleration rate with mm s‑1 precision. The SKA can detect over 1 billion H I 21 cm emissions from individual galaxies to redshift z ∼ 2 and thousands of absorption lines from damped Lyα systems against bright quasars to redshift z ∼ 13 with a sensitivity limit of 100 mJy. By utilizing SKA's high spectral resolution settings (0.001, 0.002, 0.005, 0.01 Hz) to detect redshift drift, particularly focusing on the 0.001 and 0.002 Hz configuration, one aims to achieve the necessary mm s‑1 in precision measurement by the 0.5 yr observation period. The velocity drift rate, crucially determined by the two operational regimes within 0.01–0.21 mm s‑1 and 0.031–0.17 mm s‑1, exceeds the theoretical accuracy limit of 1.28 mm s‑1. The analysis thoroughly restricts cosmological parameters related to dark energy using the Sandage–Loeb (SL) signal from the H I 21 cm emission and absorption lines. It estimates a H0 of about 70 km s‑1 Mpc‑1, Ωm near 0.3, and w close to ‑1, w0 around ‑1, and wa approaching ‑0.1. These results strongly endorse the SL effect as an effective method for confirming cosmic acceleration and exploring the dark sector in real-time cosmology with the SKA.

Keywords: Cosmology, Cosmological models, Extragalactic radio sources, Damped Lyman-alpha systems, Accelerating universe, Dark energy
The Average Stellar Population Age and Metallicity of Intermediate-redshift Quiescent Galaxies. The HectoMAP spectroscopic survey provides a unique mass-limited sample of more than 35,000 quiescent galaxies (Dn4000 &gt; 1.5) covering the redshift range 0.2 &lt; z &lt; 0.6. We segregate galaxies in bins of properties based on stellar mass, Dn4000, and redshift to construct a set of high signal-to-noise spectra representing a massive (M* &gt; 1010 M⊙) quiescent population at intermediate redshift. These high-quality summed spectra enable full spectrum fitting and the related extraction of the average stellar population age and metallicity. The average galaxy age increases with the central Dn4000 as expected. The correlation is essentially invariant with stellar mass; thus, Dn4000 is a robust proxy for quiescent galaxy stellar population age. HectoMAP provides the first quiescent sample at intermediate redshift comparable with z ∼ 0 mass-complete data sets. Scaling relations derived from the HectoMAP summed spectra connect stellar age and metallicity with quiescent galaxy stellar mass up to z ∼ 0.5. Anticorrelation between the equivalent width (EW) of the [O II] emission line and stellar age, together with the mild increase in stellar age with stellar mass, supports a broad range of timescales for the mass assembly of intermediate-redshift quiescent systems. On average, the most massive galaxies (M* &gt; 1011 M⊙) assemble the bulk of their stars at earlier epochs. A strong increase in the average stellar metallicity with stellar mass, along with the correlation between the [O II] EW and metallicity at 0.2 &lt; z &lt; 0.4, suggests that lower mass galaxies are more likely to have experienced recent star formation episodes; related feedback from massive stars affects the chemical enrichment of these galaxies.

Keywords: Quenched galaxies, Galaxy ages, Galaxy evolution, Galaxy spectroscopy, Metallicity
The Neutron Star Merger Delay-time Distribution, R-process "Knees," and the Metal Budget of the Galaxy. For a sample of 18 currently known recycled millisecond pulsars (rMSPs) that are in double neutron star (DNS) systems, and 42 rMSPs with similar properties that are not in DNS pairs, we analyze the distributions of the characteristic age, τc, and the time-until-merger of the double systems, τgw. Based on the τc distribution of non-DNS rMSPs, we argue that τc is a reasonable estimator of true pulsar age and that rMSPs are active as pulsars for a long (≳Hubble) time. Among the DNSs there is an excess of young systems (small τc) with short life expectancy (small τgw) compared to model expectations for the distributions of τc and τgw if, at birth, DNSs have a delay-time distribution (DTD) of the form   (expected generically for close binaries), or for that matter, from expectations from any single power-law DTD. A two-population DNS model solves the problem: the data are best fit by the combination of a "fast" population with DTD going as  , and a "slow" population of DNSs, with DTD proportional to  . The fast population can be equivalently represented by a shallow power-law DTD with an exponential cutoff beyond τgw ∼ 300 Myr. The fast population completely dominates, by a factor A ≈ 10–100, the numbers of DNSs that merge within a Hubble time, and that presumably lead to short gamma-ray bursts and kilonova explosions. Using a simple, empirically based, chemical-evolution calculation, we show that the fast/steep kilonova DTD, convolved with the measured star formation history of the Milky Way's thick-disk population, naturally reproduces the "knee" structure seen in abundance-ratio diagrams of thick-disk stars, for europium and for two other r-process elements. As a corollary, we show, based again solely on empirical input concerning iron production by supernovae, that the Milky Way is nearly a "closed box" that has retained at least ∼70%–90% of the metals produced over the Galaxy's lifetime.

Keywords: Neutron stars, Galaxy chemical evolution, Millisecond pulsars, R-process, Gamma-ray bursters, Binary pulsars
A Systematic Study of Millihertz Quasiperiodic Oscillations in GS 1826‑238. We performed a systematic investigation of millihertz quasiperiodic oscillations (mHz QPOs) in the low-mass X-ray binary GS 1826‑238 observed with NICER and Insight-HXMT. We discovered 37 time intervals exhibiting mHz QPOs out of 106 Good Time Interval (GTI) samples in the frequency range of 3–17 mHz at a significance level of &gt;99.99%. The source remains in a soft state in our study. No significant differences are found between the samples with and without mHz QPOs according to positions in the color–color and hardness–intensity diagrams. These QPOs were discovered at an accretion rate of  , similar to other sources. The broadband spectrum of GS 1826–238 can be modeled as a combination of a multicolor blackbody from the accretion disk and a Comptonization with seed photons emitted from the neutron star (NS) surface. The flux modulations of mHz QPOs are related to variations of the temperature of Comptonization seed photons, consistent with the marginally stable burning theory.

Keywords: Low-mass x-ray binary stars, Neutron stars, Accretion
The Persistent Shift in Spin-down Rate Following the Largest Crab Pulsar Glitch Rules Out External Torque Variations due to Starquakes. It was previously believed that the long-term persistent increase in the spin-down rate of the Crab pulsar following a glitch is direct evidence of a starquake-induced glitch or at least related to a starquake. Using radio data covering 1710 days following the 2017 glitch, we obtain an extreme persistent increase of the spin-down rate, which allows us to test the two prevailing models related to a starquake through an interrelation analysis between the glitch size (the amplitude of the frequency step at a glitch) and the persistent increase in the spin-down rate of the star. Our results do not support the hypothesis that glitches induce the external torque variation of the Crab pulsar, which may indicate no occurrence of a starquake during the Crab pulsar glitch. This can explain why no changes in the radio and X-ray flux, pulse profile, and spectrum of the Crab pulsar have been observed. We also suggest an internal mechanism due to superfluidity as an explanation for the long-term persistent shift in the spin-down rate of the Crab pulsar following the relatively large glitches.

Keywords: Neutron stars, Pulsars
Barium Abundances of Common Stars in the Gaia-ESO Survey and the LAMOST Medium-resolution Survey. Barium (Ba) abundance has been used as a crucial tracer of both slow and rapid neutron-capture processes to constrain the evolutionary models of the Galaxy. In this study, we aim to establish a reference sample with high-resolution spectra and high-quality stellar parameters from the Gaia-ESO Survey (GES). This sample explores the non─local thermodynamic equilibrium (NLTE) effects on the Ba abundances and will support future measurements of Ba abundances for the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) medium-resolution survey (MRS). The sample is composed of 85 common stars of LAMOST MRS DR9 and GES DR5.1, complemented by four metal-poor ([Fe/H] &lt; −1 dex) stars from AMBRE-UVES. The stars cover the ranges of stellar parameters as 4152 K ≤ Teff ≤ 6866 K, 1.37 4.57, and −2.40 dex ≤ [Fe/H] ≤ +0.25 dex. We derive the Ba abundances from three Ba II absorption lines at λλ5853, 6141, and 6496 Å of R = 47,000 UVES spectra through the spectral synthesis method using the local thermodynamic equilibrium (LTE) and NLTE assumptions. Compared to the GES catalog, the LTE Ba abundances obtained by us from the Ba II λ5853 line are the closest to the GES LTE results. The NLTE hypothesis is found to show various impacts on the three lines. The maximum differences from LTE abundances are 0.2, 0.5, and 0.6 dex for the Ba II lines at λλ5853, 6141, and 6496 Å, respectively. The NLTE corrections present opposite signs around [Fe/H] = −2.0 dex for the Ba II line at λ5853. Stars with higher temperatures or higher Ba abundances suffer larger NLTE effects. A more consistent result of the three lines confirms the necessity of taking NLTE effects into account when determining the Ba abundances.

Keywords: Stellar abundances
Disparities in Magnetic Cloud Observations between Two Spacecraft Having Small Radial and Angular Separations near 1 au. Studies for inferring the global characteristics of coronal mass ejections (CMEs) from multipoint local in situ observations have been undertaken previously, but limited studies have utilized measurements from multiple spacecraft with sufficiently small radial and angular separations. In the present study, we investigate a magnetic cloud (MC) region of a CME observed in situ during 2023 September 24–26 by the STEREO-A and Wind spacecraft near 1 au, which had radial and angular separations of 0.03 au and 3 4, respectively. We examine the disparities in the estimates of the arrival times of CME substructures, the MC axis, and its orientation between the two spacecraft. We also propose an approach for identifying the MC axis's arrival and have compared it with the arrival of the size center and time center to understand the nonisotropic compression of the MC along its angular extent. Using minimum variance analysis, we note that the orientation of the MC is slightly out of the ecliptic at Wind but not at STEREO-A. We also compare the magnetic field parameters from the start to the end of the MC at both spacecraft and note a significant noncoherency in the MC toward its trailing portion. Our analysis confirms that the MC has a stronger compression at the rear portion at STEREO-A than at Wind, with its trailing edge arriving later at Wind. Our study highlights substantial differences in CME characteristics even at mesoscales across the angular extent, and therefore one needs to analyze several such cases to better understand the flux rope structure.

Keywords: Solar coronal mass ejections