Sazuna/UAT_keywords huggingface dataset:
ALMA Observations of Massive Clouds in the Central Molecular Zone: External-pressure-confined Dense Cores and Salpeter-like Core Mass Functions. We present Atacama Large Millimeter/submillimeter Array Band 6 (1.3 mm) observations of dense cores in three massive molecular clouds within the central molecular zone (CMZ) of the Milky Way, including the Dust Ridge cloud e, Sgr C, and the 20 km s−1 cloud, at a spatial resolution of 2000 au. Among the 834 cores identified from the 1.3 mm continuum, we constrain temperatures and linewidths of 253 cores using local thermodynamic equilibrium methods to fit the H2CO and/or CH3CN spectra. We determine their masses using the 1.3 mm dust continuum and derived temperatures, and then evaluate their virial parameters using the H2CO and/or CH3CN linewidths and construct the core mass functions (CMFs). We find that the contribution of external pressure is crucial for the virial equilibrium of the dense cores in the three clouds, which contrasts with the environment in the Galactic disk where dense cores are already bound, even without the contribution of external pressure. With our new temperature estimates we also find that the CMFs show a Salpeter-like slope in the high-mass (≳3─6 M⊙) end, a change from previous works. Combined with the possible top-heavy initial mass functions (IMFs) in the CMZ, our result suggests that gas accretion and further fragmentation may play important roles in transforming the CMF to the IMF.

Keywords: Galactic center, Star formation, Molecular clouds
Analysis of the Internal Radial Gradient of Chemical Abundances in Spiral Galaxies from CALIFA. The study of chemical evolution is of paramount importance for understanding the evolution of galaxies. Models and observations propose an inside-out mechanism in the formation of spiral galaxy disks, implying a negative radial gradient of elemental abundances when represented on a logarithmic scale. However, in some instances, the observed chemical abundance gradients deviate from a single negative straight line, revealing inner drops or outer flattenings, particularly in more massive galaxies. This study analyzes oxygen abundance gradients in spiral galaxies based on observations from the Calar Alto Legacy Integral Field Area survey. Our focus is specifically on examining oxygen abundance gradient profiles, as obtained with data from H II regions, with a special emphasis on the inner radial gradient. We employ an automated fitting procedure to establish correlations between the physical properties of galaxies and bulges and the presence of these inner drops, seeking potential explanations for these variations in gradient. We find that the different criteria used in the literature to distinguish H II regions from other ionization sources in the galaxies, such as active galactic nuclei, significantly impact the results, potentially altering abundance gradient profiles and uncovering galaxies with distinct inner drops. Additionally, we analyze the abundance radial gradients to investigate the impact of diffuse ionized gas (DIG) decontamination on oxygen abundances over these inner drops. We observe that DIG, concentrated mainly in the central regions of galaxies, can modify oxygen abundance gradient profiles if left unaddressed.

Keywords: Galaxy chemical evolution, Galaxy bulges, Chemical abundances, Galaxy disks, Galaxy abundances, H II regions
A Search for Radio Millisecond Pulsar Companions around Extremely Low-mass White Dwarfs with Ellipsoidal Variability. Extremely low-mass (ELM) white dwarfs (WDs) are helium-core WDs with masses less than 0.3 M⊙. Short-period ELM WD binaries that exhibit ellipsoidal variations may harbor heavier companions, either massive WDs or millisecond pulsars (MSPs). In this study, we selected ∼12,000 ELM WDs or their candidates, and searched for ellipsoidal-like lightcurves with orbital periods shorter than 1 day, by using the public data from Zwicky Transient Facility. Finally, 23 such systems were found, with 17 being newly discovered. We selected nine high-priority targets likely to evolve from the Roche lobe overflow channel and estimated their companion masses from the extracted ellipsoidal variation amplitude. Among them, four targets have companion masses exceeding 1 M⊙. We performed a search for radio pulsations from six of these targets by using Five-hundred-meter Aperture Spherical radio Telescope. However, no convincing radio pulse signals were found, resulting in upper limits for the radio flux at around 8 μJy. Given the nondetection of radio pulsations from a total of 11 similar systems, the fraction of ellipsoidal ELM WDs around MSPs is estimated to be below 15 %. We anticipate that multiwavelength studies of more ellipsoidal-like ELM WDs will further constrain the fraction.

Keywords: Close binary stars, Ellipsoidal variable stars, White dwarf stars, Millisecond pulsars
Observations of Microlensed Images with Dual-field Interferometry: On-sky Demonstration and Prospects. Interferometric observations of gravitational microlensing events offer an opportunity for precise, efficient, and direct mass and distance measurements of lensing objects, especially those of isolated neutron stars and black holes. However, such observations have previously been possible for only a handful of extremely bright events. The recent development of a dual-field interferometer, GRAVITY Wide, has made it possible to reach out to significantly fainter objects and increase the pool of microlensing events amenable to interferometric observations by 2 orders of magnitude. Here, we present the first successful observation of a microlensing event with GRAVITY Wide and the resolution of microlensed images in the event OGLE-2023-BLG-0061/KMT-2023-BLG-0496. We measure the angular Einstein radius of the lens with subpercent precision, θE = 1.280 ± 0.009 mas. Combined with the microlensing parallax detected from the event light curve, the mass and distance to the lens are found to be 0.472 ± 0.012 M⊙ and 1.81 ± 0.05 kpc, respectively. We present the procedure for the selection of targets for interferometric observations and discuss possible systematic effects affecting GRAVITY Wide data. This detection demonstrates the capabilities of the new instrument, and it opens up completely new possibilities for the follow-up of microlensing events and future routine discoveries of isolated neutron stars and black holes.

Keywords: Gravitational microlensing, Optical interferometry
Strong-lensing Analysis of SPT-CL J2325−4111 and SPT-CL J0049−2440, Two Powerful Cosmic Telescopes (R<SUB>E</SUB> &gt; 40″) from the SPT Clusters Sample. We report the results from a study of two massive (M500c &gt; 6.0 × 1014 M⊙) strong-lensing clusters selected from the South Pole Telescope cluster survey for their large Einstein radius (RE &gt; 40″), SPT-CL J2325−4111 and SPT-CL J0049−2440. Ground-based and shallow Hubble Space Telescope (HST) imaging indicated extensive strong-lensing evidence in these fields, with giant arcs spanning 18″ and 31″, respectively, motivating further space-based imaging follow-up. Here, we present multiband HST imaging and ground-based Magellan spectroscopy of the fields, from which we compile detailed strong-lensing models. The lens models of SPT-CL J2325−4111 and SPT-CL J0049−2440 were optimized using nine and eight secure multiply imaged systems with a final image-plane rms of 0 63 and 0 73, respectively. From the lensing analysis, we measure a projected mass density within 500 kpc of M(&lt;500 kpc) = (7.30 ± 0.07) × 1014 M⊙ and  M⊙ for these two clusters, and subhalo mass ratios of 0.12 ± 0.01 and  , respectively. Both clusters produce a large area with high magnification (μ ≥ 3) for a source at z = 9,  arcmin2 and  arcmin2, respectively, placing them in the top tier of strong-lensing clusters. We conclude that these clusters are spectacular sightlines for further observations that will reduce the systematic uncertainties due to cosmic variance. This paper provides the community with two additional well-calibrated cosmic telescopes, as strong as the Frontier Fields and suitable for studies of the highly magnified background Universe.

Keywords: Galaxy clusters, Strong gravitational lensing, Galactic and extragalactic astronomy, High-redshift galaxies, Dark matter
JWST Imaging of Edge-on Protoplanetary Disks. IV. Mid-infrared Dust Scattering in the HH 30 Disk. We present near- and mid-infrared (IR) broadband imaging observations of the edge-on protoplanetary disk around HH 30 with the James Webb Space Telescope/Near Infrared Camera and the Mid-Infrared Instrument (MIRI). We combine these observations with archival optical/near-IR scattered light images obtained with the Hubble Space Telescope and a millimeter-wavelength dust continuum image obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) with the highest spatial resolution ever obtained for this target. Our multiwavelength images clearly reveal the vertical and radial segregation of micron-sized and submillimeter-sized grains in the disk. In the near- and mid-IR, the images capture not only bireflection nebulae separated by a dark lane but also diverse dynamical processes occurring in the HH 30 disk, such as spiral- and tail-like structures, a conical outflow, and a collimated jet. In contrast, the ALMA image reveals a flat dust disk in the disk midplane. By performing radiative transfer simulations, we show that grains of about 3 μm in radius or larger are fully vertically mixed to explain the observed mid-IR scattered light flux and its morphology, whereas millimeter-sized grains are settled into a layer with a scale height of ≳1 au at 100 au from the central star. We also find a tension in the disk inclination angle inferred from optical/near-IR and millimeter observations, with the latter being closer to exactly edge-on. Finally, we report the first detection of the proper motion of an emission knot associated with the mid-IR collimated jet detected by combining two epochs of our MIRI 12.8 μm observations.

Keywords: Planet formation, Dust continuum emission, Protoplanetary disks, Radiative transfer
Dust Scattering Albedo at Millimeter Wavelengths in the TW Hya Disk. Planetary bodies are formed by coagulation of solid dust grains in protoplanetary disks. Therefore, it is crucial to constrain the physical and chemical properties of the dust grains. In this study, we measure the dust albedo at millimeter wavelength, which depends on dust properties at the disk midplane. Since the albedo and dust temperature are generally degenerate in observed thermal dust emission, it is challenging to determine them simultaneously. We propose to break this degeneracy by using multiple optically thin molecular lines as a dust─albedo-independent thermometer. In practice, we employ pressure-broadened CO line wings that provide an exceptionally high signal-to-noise ratio as an optically thin line. We model the CO J = 2─1 and 3─2 spectra observed by the Atacama Large Millimeter/submillimeter Array at the inner region (r &lt; 6 au) of the TW Hya disk and successfully derive the midplane temperature. Combining multiband continuum observations, we constrain the albedo spectrum at 0.9─3 mm for the first time without assuming a dust opacity model. The albedo at these wavelengths is high, ~0.5─0.8, and broadly consistent with the L. Ricci et al., DIANA, and DSHARP dust models. Even without assuming dust composition, we estimate the maximum grain size to be ~340 μm, the power-law index of the grain size distribution to be &gt;−4.1, and the porosity to be &lt;0.96. The derived dust size may suggest efficient fragmentation with a threshold velocity of ~0.08 m s−1. We also note that the absolute flux uncertainty of ~10% (1σ) is measured and used in the analysis, which is approximately twice the usually assumed value.

Keywords: Dust composition, Protoplanetary disks, Planet formation
Long-term Evolution of Sco X-1: Implications for the Current Spin Frequency and Ellipticity of the Neutron Star. Sco X-1 is the brightest observed extrasolar X-ray source, which is a neutron star (NS) low-mass X-ray binary (LMXB) and is thought to have a strong potential for continuous gravitational waves (CW) detection due to its high accretion rate and relative proximity. Here, we compute the long-term evolution of its parameters, particularly the NS spin frequency (ν) and the surface magnetic field (B), to probe its nature and its potential for CW detection. We find that Sco X-1 is an unusually young (∼7 × 106 yr) LMXB and constrain the current NS mass to ∼1.4–1.6 M⊙. Our computations reveal a rapid B decay, with the maximum current value of ∼1.8 × 108 G, which can be useful to constrain the decay models. Note that the maximum current ν value is ∼550 Hz, implying that, unlike what is generally believed, a CW emission is not required to explain the current source properties. However, ν will exceed an observed cutoff frequency of ∼730 Hz, and perhaps even the NS breakup frequency, in the future without a CW emission. The minimum NS mass quadrupole moment (Q) to avoid this is ∼(2–3) × 1037 g cm2, corresponding to a CW strain of ∼10‑26. Our estimation of current ν values can improve the CW search sensitivity.

Keywords: Neutron stars, Accretion, X-ray binary stars, Gravitational waves, Low-mass x-ray binary stars
Exploring Magnetic Fields in Molecular Clouds through Denoising Diffusion Probabilistic Models. Accurately measuring magnetic field strength in the interstellar medium, including giant molecular clouds, remains a significant challenge. We present a machine learning approach using denoising diffusion probabilistic models (DDPMs) to estimate magnetic field strength from synthetic observables such as column density, orientation angles of the dust continuum polarization vector, and line-of-sight (LOS) nonthermal velocity dispersion. We trained three versions of the DDPM model: the 1-channel DDPM (using only column density), the 2-channel DDPM (incorporating both column density and polarization angles), and the 3-channel DDPM (which combines column density, polarization angles, and LOS nonthermal velocity dispersion). The code and trained model are available on GitHub at https://github.com/xuduo117/DDPM_Bmag. We assessed the models on both synthetic test samples and new simulation data that were outside the training set's distribution. The 3-channel DDPM consistently outperformed both the other DDPM variants and the power-law fitting approach based on column density alone, demonstrating its robustness in handling previously unseen data. Additionally, we compared the performance of the Davis–Chandrasekhar–Fermi (DCF) methods, both classical and modified, to the DDPM predictions. The classical DCF method overestimated the magnetic field strength by approximately an order of magnitude. Although the modified DCF method showed improvement over the classical version, it still fell short of the precision achieved by the 3-channel DDPM.

Keywords: Magnetohydrodynamics, Astrostatistics techniques, Convolutional neural networks, Molecular clouds, Astrostatistics, Interstellar magnetic fields, Interstellar medium
Black Hole Supernovae, Their Equation of State Dependence, and Ejecta Composition. Recent literature on core-collapse supernovae suggests that a black hole (BH) can form within ∼1 s of shock revival, while still culminating in a successful supernova. We refer to these as BH supernovae, as they are distinct from other BH formation channels in both timescale and impact on the explosion. We simulate these events self-consistently from core collapse until 20–50 days after collapse using three axisymmetric models of a 60 M⊙ zero-age main-sequence progenitor star and investigate how the composition of the ejecta is impacted by the BH formation. We employ Skyrme-type equations of state (EOSs) and vary the uncertain nucleonic effective mass, which affects the pressure inside the proto–neutron star through the thermal part of the EOS. This results in different BH formation times and explosion energies at BH formation, yielding final explosion energies between 0.06 and 0.72 × 1051 erg with 21.8–23.3 M⊙ of ejecta, of which 0–0.018 M⊙ is 56Ni. Compared to expectations from 1D simulations, we find more nuanced EOS dependences of the explosion dynamics, the mass of the BH remnant, and the elemental composition of the ejecta. We investigate why the explosions survive despite the massive overburden and link the shape of the diagnostic energy curve and character of the ejecta evolution to the progenitor structure.

Keywords: Neutron stars, Hydrodynamical simulations, Supernova neutrinos, Gravitational instability, Explosive nucleosynthesis, Black holes, Core-collapse supernovae, Supernova dynamics, Shocks, General relativity, Radiative transfer simulations, Supernovae
Influence of Effective Nucleon Mass on Equation of State for Supernova Simulations and Neutron Stars. We investigate the influence of the effective nucleon mass on the equation of state (EOS), which is constructed for simulations of core-collapse supernovae and binary neutron star mergers, within the relativistic mean-field (RMF) framework. The study introduces a new RMF parameter set, TM1m, which is a modification of the TM1e model with an adjusted effective mass, maintaining the saturation properties of nuclear matter. The TM1m model, with a larger effective mass ratio (M*/M ~ 0.8) compared to the TM1e model (M*/M ~ 0.63), is employed to construct a new EOS table, EOS5. This EOS table is designed to offer insights into the influence of the effective nucleon mass on the EOS within a relativistic framework, particularly above the saturation density. The results of EOS5 are compared with those obtained from other models, including both relativistic and nonrelativistic approaches. The properties of cold neutron stars, calculated using the TM1m model, are compatible with the existence of a 2 M⊙ pulsar and the latest constraints on the tidal deformability and radii of a canonical 1.4 M⊙ neutron star, derived from astrophysical observations.

Keywords: Neutron stars, Core-collapse supernovae
Relativistic Binary Precession: Impact on Eccentric Massive Binary Black Hole Accretion and Hydrodynamics. Recent hydrodynamical simulations have shown that circumbinary gas disks drive the orbits of massive binary black holes (BHs) to become eccentric, even when general relativistic (GR) corrections to the orbit are significant. Here, we study the GR apsidal precession of eccentric equal-mass massive binary BHs in circumbinary disks via two-dimensional hydrodynamical simulations. We perform a suite of simulations comparing precessing and nonprecessing binaries across a range of eccentricities, semimajor axes, and precession rates. We find that the GR precession of the binary's semimajor axis can introduce a dominant modulation in the binary's accretion rate and the corresponding high-energy electromagnetic light curves. We discuss the conditions under which this occurs and its detailed characteristics and mechanism. Finally, we discuss the potential to observe these precession signatures in electromagnetic- and gravitational-wave observations, as well as the precession signal's unique importance as a potential tool to constrain the mass, eccentricity, and semimajor axis of binary merger events.

Keywords: Accretion, Black holes, Gravitational wave sources, Gravitational wave astronomy, General relativity
Sporadic Dips from Extended Debris Transiting the Metal-rich White Dwarf SBSS 1232+563. We present the discovery of deep but sporadic transits in the flux of SBSS 1232+563, a metal-rich white dwarf polluted by disrupted exoplanetary debris. Nearly 25 yr of photometry from multiple sky surveys reveal evidence of occasional dimming of the white dwarf, most notably evident in an 8 month long event in 2023 that caused a &gt;40% drop in flux from the star. In-transit follow-up shows additional short-timescale (minutes- to hours-long) dimming events. Transiting Exoplanet Survey Satellite photometry suggests a coherent 14.842 hr signal that could represent the dominant orbital period of debris. Six low-resolution spectra collected at various transit depths over two decades show no evidence of significant changes in the observed elemental abundances. SBSS 1232+563 demonstrates that debris transits around white dwarfs can be sporadic, with many years of inactivity before large-amplitude dimming events.

Keywords: White dwarf stars, Debris disks, Transits, Variable stars
Multi-observatory Study of Young Stellar Energetic Flares (MORYSEF): No Evidence for Abnormally Strong Stellar Magnetic Fields after Powerful X-Ray Flares. We explore the empirical power-law relationship between X-ray luminosity (LX) and total surface magnetic flux (Φ), established across solar magnetic elements, time- and disk-averaged emission from the Sun, older active stars, and pre-main-sequence (PMS) stars. Previous models of large PMS X-ray flares, lacking direct magnetic field measurements, showed discrepancies from this baseline law, which MHD simulations attribute to unusually strong magnetic fields during flares. To test this, we used nearly simultaneous Chandra X-ray and HET-HPF near-infrared observations of four young Orion stars, measuring surface magnetic fields during or just after powerful PMS X-ray flares. We also modeled these PMS X-ray flares, incorporating their measured magnetic field strengths. Our findings reveal magnetic field strengths at the stellar surface typical of nonflaring PMS stars, ruling out the need for abnormally strong fields during flares. Both PMS and solar flares deviate from the LX–Φ law, with PMS flares exhibiting a more pronounced deviation, primarily due to their much larger active regions on the surface and larger flaring loop volumes above the surface compared to their solar counterparts. These deviations likely stem from the fact that powerful flares are driven by magnetic reconnection, while baseline X-ray emission may involve less efficient mechanisms like Alfvén wave heating. Our results also indicate a preference for dipolar magnetic loops in PMS flares, consistent with Zeeman–Doppler imaging of fully convective stars. This requirement for giant dipolar loops aligns with MHD predictions of strong dipoles supported by polar magnetic surface active regions in fast-rotating, fully convective stars.

Keywords: Solar flares, Stellar x-ray flares, The Sun, Stellar magnetic fields, Pre-main sequence stars, Stellar flares, Solar magnetic fields, X-ray stars