Sazuna/UAT_keywords huggingface dataset:
Constraining the Cosmic Merger History of Intermediate-mass Black Holes with Gravitational Wave Detectors. Intermediate-mass black holes (IMBHs) have not been detected beyond any reasonable doubt through either dynamical or accretion signatures. Gravitational waves (GWs) represent an unparalleled opportunity to survey the sky and detect mergers of IMBHs, making it possible for the first time to constrain their formation, growth, and merger history across cosmic time. While the current network LIGO-Virgo-KAGRA is significantly limited in detecting mergers of IMBH binaries, the next generation of ground-based observatories and space-based missions promise to shed light on the IMBH population through the detection of several events per year. Here, we assess this possibility by determining the optimal network of the next generation of GW observatories to reconstruct the IMBH merger history across cosmic time. We show that Voyager, the Einstein Telescope, and Cosmic Explorer will be able to constrain the distribution of the primary masses of merging IMBHs up to ~103 M ⊙ and with mass ratio ≳0.1, while LISA will complementary do so at higher mass and smaller mass ratios. Therefore, a network of next-generation ground-based and space-based observatories will potentially reconstruct the merger history of IMBHs. Moreover, IMBHs with masses ≲5 × 103 M ⊙ could be observed in multiband up to a redshift of z ≈ 4, ushering in a new era of GW astronomy.

Keywords: Black hole physics, Intermediate-mass black holes, Gravitational wave detectors, Black holes, Gravitational wave sources, Gravitational wave astronomy, Gravitational waves, Astrophysical black holes
Proton and Electron Temperatures in the Solar Wind and Their Correlations with the Solar Wind Speed. The heating and acceleration of the solar wind remains one of the unsolved fundamental problems in heliophysics. It is usually observed that the proton temperature T  i  is highly correlated with the solar wind speed V SW, while the electron temperature T  e  shows anticorrelation or no clear correlation with the solar wind speed. Here, we inspect both Parker Solar Probe (PSP) and WIND data, and compare the observations with simulation results. PSP observations below 30 solar radii clearly show a positive correlation between the proton temperature and the wind speed and a negative correlation between the electron temperature and the wind speed. One year (2019) of WIND data confirm that the proton temperature is positively correlated with the solar wind speed, but the electron temperature increases with the solar wind speed for slow wind, while it decreases with the solar wind speed for fast wind. Using a 1D Alfvén-wave-driven solar wind model with different proton and electron temperatures, we find, for the first time, that if most of the dissipated Alfvén wave energy heats the ions instead of the electrons, a positive T  i -V SW correlation and a negative T  e -V SW correlation arise naturally. If the electrons gain a small but finite portion of the dissipated wave energy, the T  e -V SW correlation evolves with the radial distance to the Sun, such that the negative correlation gradually turns positive. The model results show that Alfvén waves are one of the possible explanations for the observed evolution of the proton and electron temperatures in the solar wind.

Keywords: Solar coronal heating, Solar wind, Alfven waves
Black Hole Ultracompact X-Ray Binaries: Galactic Low-frequency Gravitational Wave Sources. In the Galaxy, close binaries with compact objects are important low-frequency gravitational wave (GW) sources. As potential low-frequency GW sources, neutron star/white dwarf (WD) ultracompact X-ray binaries (UCXBs) have been investigated extensively. Using the Modules for Experiments in Stellar Astrophysics code, we systematically explored the evolution of black hole (BH)-main-sequence star (MS) binaries to determine whether their descendants can be detected by space-borne GW detectors. Our simulations showed that BH-MS binaries with an initial orbital period less than the bifurcation period can evolve into BH UCXBs that can be detected by LISA. Such an evolutionary channel would form compact mass-transferring BH-WD systems rather than detached BH-WD systems. The calculated X-ray luminosities of BH UCXBs that can be detected by LISA at a distance d = 1 kpc are ~1033-1035 erg s-1 (~1034-1035 erg s-1 for d = 10 kpc); hence, it is possible to detect their electromagnetic counterparts. It is worth emphasizing that only some BH-MS systems with an initial orbital period very close to the bifurcation period can evolve toward low-frequency GW sources whose chirp masses can be measured. The maximum GW frequency of BH UCXBs forming via the BH-MS pathway is about 3 mHz, which is smaller than the minimum GW frequency (6.4 mHz) of mass-transferring BH-WDs originating from a dynamic process. Furthermore, we obtain an initial parameter space (donor-star masses and orbital periods) of progenitors of BH UCXB-GW sources, which can be applied to future population synthesis simulations. By a rough estimation, we predict that LISA would only be able to detect a few BH UCXB-GW sources formed by the BH-MS channel.

Keywords: X-ray binary stars, Black holes, White dwarf stars, Gravitational wave sources, Stellar evolution
Turbulence Driving by Interstellar Pickup Ions in the Outer Solar Wind. We revisit the question of how the unstable scattering of interstellar pickup ions (PUIs) may drive turbulence in the outer solar wind and why the energy released into fluctuations by this scattering appears to be significantly less than the standard bispherical prediction. We suggest that energization of the newly picked-up ions by the ambient turbulence during the scattering process can result in a more spherical distribution of PUIs and reduce the generated fluctuation energy to a level consistent with the observations of turbulent intensities and core solar wind heating. This scenario implies the operation of a self-regulation mechanism that maintains the observed conditions of turbulence and heating in the PUI-dominated solar wind.

Keywords: Interplanetary turbulence, Pickup ions, Solar wind
In Situ Observations of Whistler-mode Waves in Magnetic Reconnection at Mars. Whistler-mode waves are one of the most important plasma waves potentially affecting the triggering and development processes of magnetic reconnection. They are widely present in the Earth's reconnection ion diffusion region but have not yet been reported in Mars'. Based on in situ measurements from MAVEN, the Mars Atmosphere and Volatile Evolution mission, we report for the first time whistler-mode waves in the ion diffusion region at the center of the current sheet in the Martian magnetotail. Simultaneously, pancake electron distributions with high temperature anisotropy are observed. Linear instability analyses imply that these unstable electrons can trigger the observed whistler-mode waves. Such findings not only fill the gap in observations of whistler-mode waves in the magnetic reconnection at Mars but also enrich our understanding of their generation mechanism in the reconnection region at unmagnetized planets.

Keywords: Space plasmas, Solar magnetic reconnection
Magnetic Fields, Star Formation Rates, and Gas Densities at Sub-kiloparsec Scales in a Pilot Sample of Nearby Galaxies. We have estimated the magnetic field strengths of a sample of seven galaxies using their nonthermal synchrotron radio emission at meter wavelengths, and assuming energy equipartition between magnetic fields and cosmic-ray particles. We tested for deviation of magnetic fields from energy equipartition with cosmic-ray particles, and found that deviations of ~25% are typical for the sample galaxies. Spatially resolved star formation rates (SFRs) were estimated for the seven galaxies along with five galaxies studied previously. For the combined sample of 12 galaxies, the equipartition magnetic fields (B eq) are correlated with the SFR surface densities (ΣSFR) at sub-kiloparsec scales with B eq ∝ ${{\rm{\Sigma }}}_{\mathrm{SFR}}^{0.31\pm 0.06}$ , consistent with model predictions. We estimated gas densities (ρ gas) for a subsample of seven galaxies using archival observations of the CO rotational transitions and the atomic hydrogen (H I) 21 cm line and studied the spatially resolved correlation between the magnetic fields and ρ gas. Magnetic fields and gas densities are found to be correlated at sub-kiloparsec scale as B eq ∝ ${\rho }_{\mathrm{gas}}^{0.40\pm 0.09}$ . This is broadly consistent with models, which typically predict B ∝ ${\rho }_{\mathrm{gas}}^{0.5}$ .

Keywords: Star formation, Magnetic fields, Interstellar medium, Radio continuum emission
SCATTER: A New Common Envelope Formalism. One of the most mysterious astrophysical states is the common envelope (CE) phase of binary evolution, in which two stars are enshrouded by the envelope shed by one of them. Interactions between the stars and the envelope shrinks the orbit. The CE can lead to mergers or to a subsequent phase of interactions. Mergers may involve any combination of two compact objects and/or stars. Some involving white dwarfs may produce Type Ia supernovae, while merging neutron stars may yield gamma-ray bursts, and merging compact objects of all kinds produce gravitational radiation. Since CEs can arise from a variety of different initial conditions, and due to the complexity of the processes involved, it is difficult to predict their end states. When many systems are being considered, as in population synthesis calculations, conservation principles are generally employed. Here we use angular momentum in a new way to derive a simple expression for the final orbital separation. This method provides advantages for the study of binaries and is particularly well suited to higher-order multiples, now considered to be important in the genesis of potential mergers. Here we focus on CEs in binaries, and the follow-up paper extends our formalism to multiple-star systems within which a CE occurs.

Keywords: Binary stars, White dwarf stars, Gravitational wave astronomy, Type Ia supernovae, Common envelope evolution, Common envelope binary stars
Photometric Metallicity and Distance Estimates for 136,000 RR Lyrae Stars from Gaia Data Release 3. We present a sample of 135,873 RR Lyrae stars (RRLs) with precise photometric metallicity and distance estimates from our newly calibrated P-ϕ 31-R 21-[Fe/H]/P-R 21-[Fe/H] and G-band absolute magnitude-metallicity relations. The P-ϕ 31-R 21-[Fe/H] and P-R 21-[Fe/H] relations for type RRab and type RRc stars are obtained from nearly 2700 Gaia-identified RRLs, with precise ϕ 31 and R 21 measurements from light curves and metallicity estimates from spectroscopy. Using a few hundreds of nearby RRLs, with accurate distances estimated from the parallax measurements in Gaia Early Data Release 3, new G-band absolute magnitude-metallicity relations and near-IR period-absolute magnitude-metallicity relations are constructed. External checks, using other high-resolution spectroscopic samples of field RRLs and RRL members of globular clusters, show that the typical uncertainties in our photometric metallicity estimates are about 0.24 and 0.16 dex for type RRab and type RRc stars, respectively, without significant systematic bias with respect to the high-resolution spectroscopic metallicity measurements. The accuracies of these metallicity estimates are much improved, especially for type RRab stars, when compared to those provided by Gaia Data Release 3. Validations of our distance estimates, again using members of globular clusters, show that the typical distance errors are only 3%-4%. The distance moduli μ 0 = 18.503 ± 0.001 (stat) ± 0.040 (syst) mag for the Large Magellanic Cloud (LMC) and μ 0 = 19.030 ± 0.003 (stat) ± 0.043 (syst) mag for the Small Magellanic Cloud (SMC) are estimated from our type RRab star sample and are in excellent agreement with previous measurements. The mean metallicities of the LMC and SMC derived in this work are also consistent with previous determinations. Using our sample, a steep metallicity gradient of -0.024 ± 0.001 dex kpc-1 is found for the LMC, while a negligible metallicity gradient is obtained for the SMC.

Keywords: Magellanic Clouds, RR Lyrae variable stars, Metallicity, Distance indicators
WOCS 4540: Detailed Analysis of a very Long Orbital Period Blue Straggler. WOCS 4540 is the longest orbital period (P orb = 3030 days) blue straggler star (BSS)-white dwarf (WD) pair in the old open cluster NGC 188. It also contains one of the most luminous BSS in the cluster. Prior Hubble Space Telescope Cosmic Origins Spectrograph spectroscopy measured a WD mass of 0.53 M ⊙, indicative of a carbon-oxygen WD and suggesting previous mass transfer from an asymptotic giant branch (AGB) star. Detailed modeling of the system evolution, including red giant branch phase wind mass transfer, AGB wind Roche-lobe overflow, and regular Roche-lobe overflow, is done with Modules for Experiments in Stellar Astrophysics. The best-fit model produces excellent agreement with a wide array of observational constraints on the BSS, the WD, and the binary system. To produce the observed luminosity and effective temperature of the BSS, all three donor mass-transfer mechanisms contribute similarly to build a 1.5 M ⊙ BSS. The overall mass-transfer efficiency is 55%. Regular Roche-lobe overflow occurs only during the largest AGB thermal pulse, but yields a very high accretion rate at 75% efficiency and briefly (less than 1 Myr) a very high luminosity boost from the accretor.

Keywords: Binary stars, Close binary stars, White dwarf stars, Open star clusters, Blue straggler stars, Stellar evolution
A Census of the Low Accretors. II. Accretion Properties. Much is known about the processes driving accretion from protoplanetary disks onto low-mass pre-main-sequence stars (T Tauri stars). Nevertheless, it is unclear how accretion stops. To determine the accretion properties and their relation to stellar properties and gain insight into the last stages of accretion, we present a detailed analysis of 24 low and possible accretors, previously identified using the He I λ10830 line. We model moderate-resolution Hα profiles of these stars using magnetospheric accretion flow models that account for the chromospheric contribution at the line center. Based on parameters derived from the fits of 20 stars that can be reproduced with the models, we find a power-law relation between the disk truncation radius and the mass accretion rate consistent with predictions from theory and simulations. Comparing the corotation and truncation radii, we find that most of our targets are accreting in the unstable regime and rule out the propeller as the main process stopping accretion. For the truncation radius to be the same as the magnetic radius, the dipole magnetic field and/or the efficiency parameter ξ need to be smaller than previously determined, suggesting that higher-order fields dominate in low accretion rates. Lastly, we determine that the lowest accretion rates that can be detected by Hα line modeling are (1-3) × 10-11 M ☉ yr-1 for M3 stars and (3-5) × 10-11 M ☉ yr-1 for K5 stars. These limits are lower than the observed accretion rates in our sample, suggesting that we have reached a physical lower limit. This limit, $\dot{M}\sim {10}^{-10}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ , is consistent with EUV-dominated photoevaporation.

Keywords: T Tauri stars, Protoplanetary disks, Stellar accretion, H I line emission
On the Spatial Distribution of <SUP>13</SUP>CO Structures within <SUP>12</SUP>CO Molecular Clouds. We look into the 2851 12CO molecular clouds harboring 13CO structures to reveal the distribution of the projected angular separations and radial velocity separations between their internal 13CO structures. The projected angular separations are determined using the minimal spanning tree algorithm. We find that ~50% of the angular separations fall in a narrow range of ~3'-7' with a median of ~5', and the corresponding radial velocity separations mainly range from ~0.3 to 2.5 km s-1. The mean and standard deviation of the angular separations of the internal 13CO structures within 12CO clouds appear to be universal, independent of the 12CO cloud angular areas and the counts of their internal 13CO structures. We also reveal a scaling relation between the 12CO cloud angular area and its harbored 13CO structure count. These results suggest there is a preferred angular separation between 13CO structures in these 12CO clouds, considering the distance effects. According to that, we propose an alternative picture for the assembly and destruction of molecular clouds: there is a fundamental separation for the internal structures of molecular clouds, the build-up and destruction of molecular clouds proceeds under this fundamental unit.

Keywords: Interstellar molecules, Molecular clouds, Interstellar medium
ALMA Fragmented Source Catalog in Orion (FraSCO). I. Outflow Interaction within an Embedded Cluster in OMC-2/FIR 3, FIR 4, and FIR 5. We present a high-angular resolution (~1″) and wide-field ( $2\buildrel{\,\prime}\over{.} 9\times 1\buildrel{\,\prime}\over{.} 9$ ) image of the 1.3 mm continuum, CO(J = 2-1) and SiO(J = 5-4) line emissions toward an embedded protocluster, FIR 3, FIR 4, and FIR 5, in the Orion Molecular Cloud 2 obtained from the Atacama Large Millimeter/submillimeter Array. We identify 51 continuum sources, 36 of which are newly identified in this study. Their dust masses, projected sizes, and H2 gas number densities are estimated to be 3.8 × 10-5-1.1 × 10-2 M ⊙, 290-2000 au, and 6.4 × 106-3.3 × 108 cm-3, respectively. The results of a Jeans analysis show that ~80% of the protostellar sources and ~15% of the prestellar sources are gravitationally bound. We identify 12 molecular outflows traced in the CO(J = 2-1) emission, six of which are newly detected. We spatially resolve shocked gas structures traced by the SiO(J = 5-4) emission in this region for the first time. We identify shocked gas originating from outflows and other shocked regions. These results provide direct evidence of an interaction between dust condensation, FIR 4, and an energetic outflow driven by HOPS-370 located within FIR 3. A comparison of the outflow dynamical timescales, fragmentation timescales, and protostellar ages shows that the previously proposed triggered star formation scenario in FIR 4 is not strongly supported. We also discuss the spatial distribution of filaments identified in our continuum image by comparing it with a previously identified hub-fiber system in the N2H+ line.

Keywords: Millimeter astronomy, Protostars, Protoclusters, Giant molecular clouds
Discovery of Hydrogen Radio Recombination Lines at z = 0.89 toward PKS 1830-211. We report the detection of stimulated hydrogen radio recombination line (RRL) emission from ionized gas in a z = 0.89 galaxy using 580-1670 MHz observations from the MeerKAT Absorption Line Survey. The RRL emission originates in a galaxy that intercepts and strongly lenses the radio blazar PKS 1830-211 (z = 2.5). This is the second detection of RRLs outside of the local Universe and the first clearly associated with hydrogen. We detect effective H144α (and H163α) transitions at observed frequencies of 1156 (798) MHz by stacking 17 (27) RRLs with 21σ (14σ) significance. The RRL emission contains two main velocity components and is coincident in velocity with H I 21 cm and OH 18 cm absorption. We use the RRL spectral line energy distribution and a Bayesian analysis to constrain the density (n  e ) and the volume-averaged path length (ℓ) of the ionized gas. We determine $\mathrm{log}({n}_{e})={2.0}_{-0.7}^{+1.0}$ cm-3 and $\mathrm{log}({\ell })=-{0.7}_{-1.1}^{+1.1}$ pc toward the northeast (NE) lensed image, likely tracing the diffuse thermal phase of the ionized ISM in a thin disk. Toward the southwest (SW) lensed image, we determine $\mathrm{log}({n}_{e})={3.2}_{-1.0}^{+0.4}$ cm-3 and $\mathrm{log}({\ell })=-{2.7}_{-0.2}^{+1.8}$ pc, tracing gas that is more reminiscent of H scii regions. We estimate a star formation (surface density) rate of ΣSFR ~ 0.6 M ⊙ yr-1 kpc-2 or SFR ~ 50 M ⊙ yr-1, consistent with a star-forming main-sequence galaxy of M ⋆ ~ 1011 M ⊙. The discovery presented here opens up the possibility of studying ionized gas at high redshifts using RRL observations from current and future (e.g., SKA and ngVLA) radio facilities.

Keywords: Radio spectroscopy, Quasar absorption line spectroscopy, Radio galaxies, Interstellar medium, Galaxies
Cosmicflows-4. With Cosmicflows-4, distances are compiled for 55,877 galaxies gathered into 38,065 groups. Eight methodologies are employed, with the largest numbers coming from the correlations between the photometric and kinematic properties of spiral galaxies (TF) and elliptical galaxies (FP). Supernovae that arise from degenerate progenitors (type Ia SNe) are an important overlapping component. Smaller contributions come from distance estimates from the surface brightness fluctuations of elliptical galaxies and the luminosities and expansion rates of core-collapse supernovae (SNe II). Cepheid period-luminosity relation and tip of the red giant branch observations founded on local stellar parallax measurements along with the geometric maser distance to NGC 4258 provide the absolute scaling of distances. The assembly of galaxies into groups is an important feature of the study in facilitating overlaps between methodologies. Merging between multiple contributions within a methodology and between methodologies is carried out with Bayesian Markov chain Monte Carlo procedures. The final assembly of distances is compatible with a value of the Hubble constant of H 0 = 74.6 km s-1 Mpc-1 with the small statistical error of ±0.8 km s-1 Mpc-1 but a large potential systematic error of ~3 km s-1 Mpc-1. Peculiar velocities can be inferred from the measured distances. The interpretation of the field of peculiar velocities is complex because of large errors on individual components and invites analyses beyond the scope of this study.

Keywords: Galaxy distances, Large-scale structure of the universe, Observational cosmology, Distance indicators, Hubble constant
Solar-cycle and Latitude Variations in the Internetwork Magnetism. The importance of the quiet-Sun magnetism is that it is always there to a greater or lesser extent, being a constant provider of energy, independently of the solar cycle phase. The open questions about the quiet-Sun magnetism include those related to its origin. Most people claim that the local dynamo action is the mechanism that causes it. This fact would imply that the quiet-Sun magnetism is nearly the same at any location over the solar surface and at any time. Many works claim that the quiet Sun does not have any variation at all, although a few of them raise doubt on this claim and find mild evidence of a cyclic variation in the the quiet-Sun magnetism. In this work, we detect clear variations in the internetwork magnetism both with latitude and solar cycle. In terms of latitude, we find an increase in the averaged magnetic fields toward the solar poles. We also find long-term variations in the averaged magnetic field at the disk center and solar poles, and both variations are almost anticorrelated. These findings do not support the idea that the local dynamo action is the unique factory of the quiet-Sun magnetism.

Keywords: Solar cycle, Quiet sun, Solar dynamo, Solar physics, Solar magnetic fields