Sazuna/UAT_keywords huggingface dataset:
The Cosmic Merger Rate Density Evolution of Compact Binaries Formed in Young Star Clusters and in Isolated Binaries. Next generation ground-based gravitational-wave detectors will observe binary black hole (BBH) mergers up to redshift $z\gtrsim 10$ , probing the evolution of compact binary (CB) mergers across cosmic time. Here, we present a new data-driven model to estimate the cosmic merger rate density (MRD) evolution of CBs, by coupling catalogs of CB mergers with observational constraints on the cosmic star formation rate (SFR) density and on the metallicity evolution of the universe. We adopt catalogs of CB mergers derived from recent N-body and population-synthesis simulations, to describe the MRD of CBs formed in young star clusters (hereafter, dynamical CBs) and in the field (hereafter, isolated CBs). The local MRD of dynamical BBHs is ${{ \mathcal R }}_{\mathrm{BBH}}={64}_{-20}^{+34}$ Gpc-3 yr-1, consistent with the 90% credible interval from the first and second observing runs (O1 and O2) of the LIGO-Virgo collaboration, and with the local MRD of isolated BBHs ( ${{ \mathcal R }}_{\mathrm{BBH}}={50}_{-37}^{+71}$ Gpc-3 yr-1). The local MRD of dynamical and isolated black hole-neutron star binaries is ${{ \mathcal R }}_{\mathrm{BHNS}}={41}_{-23}^{+33}$ and ${49}_{-34}^{+48}$ Gpc-3 yr-1, respectively. Both values are consistent with the upper limit inferred from O1 and O2. Finally, the local MRD of dynamical binary neutron stars (BNSs, ${{ \mathcal R }}_{\mathrm{BNS}}={151}_{-38}^{+59}$ Gpc-3 yr-1) is a factor of two lower than the local MRD of isolated BNSs ( ${{ \mathcal R }}_{\mathrm{BNS}}={283}_{-75}^{+97}$ Gpc-3 yr-1). The MRD for all CB classes grows with redshift, reaching its maximum at $z\in [1.5,2.5]$ , and then decreases. This trend springs from the interplay between cosmic SFR, metallicity evolution, and delay time of binary compact objects.

Keywords: Neutron stars, Binary stars, Star formation, Gravitational waves, Astrophysical black holes
Particle Acceleration in Strong Turbulence in the Earth's Magnetotail. In many space, astrophysical, and laboratory plasmas the energy contained in the magnetic field or plasma flow exceeds the thermal energy. Magnetic field ( ${\boldsymbol{B}}$ ) annihilation, often enabled by magnetic reconnection, transfers magnetic energy to particles. Shocks transfer bulk flow energy to particles. If there is a sufficiently large energy transfer, strong turbulence (∣ $\delta {\boldsymbol{B}}$ ∣/∣ B∣ ∼ 1) develops, which, in turn, can result in nonthermal acceleration. In this article, we investigate acceleration in a finite-sized region of strong turbulence driven by magnetic reconnection with analytical modeling and test-particle simulations. This research is based on detailed observations in the Earth's magnetotail. We find that the primary transfer of magnetic energy to particle energy is advanced by large-amplitude electric field structures ( ${\boldsymbol{E}}$ ) generated by the strong turbulence. To no surprise, ion energization is dominated by intense DC ${\boldsymbol{E}}$ , ${\boldsymbol{E}}$ near the ion cyclotron frequency (fci), and/or ${\boldsymbol{E}}$ variations at scales near the ion gyroradius. Electron energization comes from higher-frequency ${\boldsymbol{E}}$ . The turbulent cascade continuously regenerates ${\boldsymbol{E}}$ near fci and higher frequencies. Importantly, the turbulence also creates magnetic depletions that can trap particles and considerably increase their dwell time in regions of strong energization, which substantially enhances nonthermal acceleration. Moreover, energization is primarily perpendicular to ${\boldsymbol{B}}$ , so particles have difficulty escaping regions of depleted ${\boldsymbol{B}}$ , which can lead to near runaway acceleration. We discuss how this process may be active in large-scale settings such as supernova shells and may contribute, at least in in part, to the development of the cosmic ray spectrum.

Keywords: Space plasmas
Observations of Particle Acceleration in Magnetic Reconnection-driven Turbulence. The Magnetospheric Multiscale Mission observes, in detail, charged particle heating and substantial nonthermal acceleration in a region of strong turbulence ( $| \delta {\boldsymbol{B}}| /| {\boldsymbol{B}}| \sim 1$ , where ${\boldsymbol{B}}$ is the magnetic field) that surrounds a magnetic reconnection X-line. Magnetic reconnection enables magnetic field annihilation in a volume that far exceeds that of the diffusion region. The formidable magnetic field annihilation breaks into strong, intermittent turbulence with magnetic field energy as the driver. The strong, intermittent turbulence appears to generate the necessary conditions for nonthermal acceleration. It creates intense, localized currents ( ${\boldsymbol{J}}$ ) and unusually large-amplitude electric fields ( ${\boldsymbol{E}}$ ). The combination of turbulence-generated ${\boldsymbol{E}}$ and ${\boldsymbol{J}}$ results in a significant net positive mean of ${\boldsymbol{J}}\cdot {\boldsymbol{E}}$ , which signifies particle energization. Ion and electron heating rates are such that they experience a fourfold increase from their initial temperature. Importantly, the strong turbulence also generates magnetic holes or depletions in $| {\boldsymbol{B}}| $ that can trap particles. Trapping considerably increases the dwell time of a subset of particles in the turbulent region, which results in significant nonthermal particle acceleration. The direct observation of strong turbulence that is enabled by magnetic reconnection with nonthermal particle acceleration has far-reaching implications, since turbulence in plasmas is pervasive and may occupy significant volumes of the interstellar medium and intergalactic space. For example, strong turbulence from magnetic field annihilation in the supernova nebulae may dominate large volumes. As such, this observed energization process could plausibly contribute to the supply and development of the cosmic-ray spectrum.

Keywords: Space plasmas, Plasma astrophysics, Plasma physics
TauREx3 PhaseCurve: A 1.5D Model for Phase-curve Description. In recent years, retrieval analysis of exoplanet atmospheres have been very successful, providing deep insights on the composition and the temperature structure of these worlds via transit and eclipse methods. Analysis of spectral phase-curve observations, which in theory provide even more information, are still limited to a few planets. In the next decade, new facilities such as NASA-James Webb Space Telescope and ESA-Ariel will revolutionize the field of exoplanet atmospheres and we expect that a significant time will be spent on spectral phase-curve observations. Most current models are still limited in their analysis of phase-curve data as they do not consider the planet atmosphere as a whole or they require large computational resources. In this paper we present a semi-analytical model that will allow computing exoplanet emission spectra at different phase angles. Our model provides a way to simulate a large number of observations while being only about four times slower than the traditional forward model for plane-parallel primary eclipse. This model, which is based on the newly developed TauREx 3 framework, will be further developed to allow for phase-curve atmospheric retrievals.

Keywords: Atmospheric composition, Exoplanet atmospheres, Spectroscopy
Small Sensitivity of the Simulated Climate of Tidally Locked Aquaplanets to Model Resolution. Tidally locked terrestrial planets around low-mass stars are the prime targets of finding potentially habitable exoplanets. Several atmospheric general circulation models have been employed to simulate their possible climates; however, model intercomparisons showed that there are large differences in the results of the models even when they are forced with the same boundary conditions. In this paper, we examine whether model resolution contributes to the differences. Using the atmospheric general circulation model ExoCAM coupled to a 50 m slab ocean, we examine three different horizontal resolutions (440 km × 550 km, 210 km × 280 km, and 50 km × 70 km in latitude and longitude) and three different vertical resolutions (26, 51, and 74 levels) under the same dynamical core and the same schemes of radiation, convection, and clouds. Among the experiments, the differences are within 5 K in global-mean surface temperature and within 0.007 in planetary albedo. These differences are from cloud feedback, water vapor feedback, and the decreasing trend of relative humidity with increasing resolution. Relatively small-scale downdrafts between upwelling columns over the substellar region are better resolved and the mixing between dry and wet air parcels and between anvil clouds and their environment are enhanced as the resolution is increased. These reduce atmospheric relative humidity and high-level cloud fraction, causing a lower clear-sky greenhouse effect, a weaker cloud longwave radiation effect, and subsequently a cooler climate with increasing model resolution. Overall, the sensitivity of the simulated climate of tidally locked aquaplanets to model resolution is small.

Keywords: Astrobiology, Habitable planets, Exoplanet atmospheres, Exoplanet surfaces
New Ammonia Masers in the High-mass Star-forming Region Sgr B2(N). We report a systemic search for nonmetastable NH3 masers toward a high-mass star-forming region Sgr B2(N) using the Shanghai 65 m Tianma radio telescope with its Ku-band (12-18 GHz) and K-band (18-26.5 GHz) receivers. A total of 18 maser emission transitions were detected, and eight of these are newly identified NH3 maser transitions in interstellar space. Most (five) of the new maser transitions were found from the Ku-band observations which were absent from previous searches. Rotation diagram analysis for the 18 quasi-thermal transitions derived a high gas kinematic temperature (∼400 K) and an extremely high H2 column density (∼5 × 1025 cm-2). Such conditions suggest that the NH3 masers are likely pumped by vibrational excitation. Compared with quiet maser activity observed more than 20 yr ago, NH3 masers may be bursting in our observation time when the gas kinematic temperature might increase from ∼150 to ∼400 K. As extreme conditions (either high gas kinematic temperature and/or high gas column density) are required to excite nonmetastable NH3 masers, it can be argued that the detected NH3 maser outburst may be linked to a more intensive accretion-burst event from an high-mass young stellar object in the Sgr B2(N) region.

Keywords: Molecular gas, Interstellar line emission, Galactic center, Molecular spectroscopy, Molecular clouds, Star formation, Interstellar masers
Radio Emission from Ultra-stripped Supernovae as Diagnostics for Properties of the Remnant Double Neutron Star Binaries. An ultra-stripped supernova (SN) is an explosion of a helium or C+O star whose outer envelope has been stripped away by a companion neutron star. A double neutron star (DNS) binary is believed to be left after the explosion, which will emit the gravitational wave later at the coalescence. Recent detections of a few candidates for the ultra-stripped SN have constrained the properties of the explosion and the progenitor, but little information is given as to whether the remnant DNS binary will merge within the cosmic age. A large fraction of the material stripped away from the helium star through the binary interaction is expected to escape from the system and form circumstellar material (CSM). The CSM should be traced by radio emission induced by the collision with the SN ejecta. Based on the stellar evolution models previously developed, we calculate the expected radio luminosities from ultra-stripped SNe. We find that high radio luminosity at its maximum can be an indicator of small separation of a DNS binary leading to its merger within the cosmic age. Our results can be used to optimize the strategy for the radio follow-up observations such as observational epochs and frequencies.

Keywords: Supernovae, Gravitational wave sources
Low-albedo Surfaces of Lava Worlds. Hot super-Earths are exoplanets with short orbital periods (&lt;10 days), heated by their host stars to temperatures high enough for their rocky surfaces to become molten. A few hot super-Earths exhibit high geometric albedos (&gt;0.4) in the Kepler band (420-900 nm). We are motivated to determine whether reflection from molten lava and quenched glasses (a product of rapidly cooled lava) on the surfaces of hot super-Earths contribute to the observationally inferred high geometric albedos. We experimentally measure reflection from rough- and smooth-textured quenched glasses of both basalt and feldspar melts. For lava reflectance values, we use specular reflectance values of molten silicates from non-crystalline solids literature. Integrating the empirical glass reflectance function and non-crystalline solids reflectance values over the dayside surface of the exoplanet at secondary eclipse yields an upper limit for the albedo of a lava-quenched glass planet surface of ∼0.1. We conclude that lava planets with solid (quenched glass) or liquid (lava) surfaces have low albedos. The high albedos of some hot super-Earths are most likely explained by atmospheres with reflective clouds (or, for a narrow range of parameter space, possibly Ca/Al oxide melt surfaces). Lava planet candidates in TESS data can be identified for follow-up observations and future characterization.

Keywords: Super Earths, Experimental techniques, Exoplanet surface composition, Exoplanet surface characteristics, Interdisciplinary astronomy, Exoplanet atmospheres
The Rise and Fall of ASASSN-18pg: Following a TDE from Early to Late Times. We present nearly 500 days of observations of the tidal disruption event (TDE) ASASSN-18pg, spanning from 54 days before peak light to 441 days after peak light. Our data set includes X-ray, UV, and optical photometry, optical spectroscopy, radio observations, and the first published spectropolarimetric observations of a TDE. ASASSN-18pg was discovered on 2018 July 11 by the All-Sky Automated Survey for Supernovae (ASAS-SN) at a distance of d = 78.6 Mpc; with a peak UV magnitude of m ≃ 14, it is both one of the nearest and brightest TDEs discovered to-date. The photometric data allow us to track both the rise to peak and the long-term evolution of the TDE. ASASSN-18pg peaked at a luminosity of L ≃ 2.4 × 1044 erg s-1, and its late-time evolution is shallower than a flux ∝t-5/3 power-law model, similar to what has been seen in other TDEs. ASASSN-18pg exhibited Balmer lines and spectroscopic features consistent with Bowen fluorescence prior to peak, which remained detectable for roughly 225 days after peak. Analysis of the two-component Hα profile indicates that, if they are the result of reprocessing of emission from the accretion disk, the different spectroscopic lines may be coming from regions between ∼10 and ∼60 lt-days from the black hole. No X-ray emission is detected from the TDE, and there is no evidence of a jet or strong outflow detected in the radio. Our spectropolarimetric observations indicate that the projected emission region is likely not significantly aspherical, with the projected emission region having an axis ratio of ≳0.65.

Keywords: Accretion, Black hole physics, Supermassive black holes, Black holes, Tidal disruption, Galaxy accretion disks
A Dynamical Survey of Stellar-mass Black Holes in 50 Milky Way Globular Clusters. Recent numerical simulations of globular clusters (GCs) have shown that stellar-mass black holes (BHs) play a fundamental role in driving cluster evolution and shaping their present-day structure. Rapidly mass-segregating to the center of GCs, BHs act as a dynamical energy source via repeated superelastic scattering, delaying the onset of core collapse and limiting mass segregation for visible stars. While recent discoveries of BH candidates in Galactic and extragalactic GCs have further piqued interest in BH-mediated cluster dynamics, numerical models show that even if significant BH populations remain in today's GCs, they are not typically in directly detectable configurations. We demonstrated in Weatherford et al. that an anticorrelation between a suitable measure of mass segregation (Δ) in observable stellar populations and the number of retained BHs in GC models can be applied to indirectly probe BH populations in real GCs. Here we estimate the number and total mass of BHs in 50 Milky Way GCs from the Advanced Camera for Surveys GC Survey. For each GC, Δ is measured between observed main-sequence populations and fed into correlations between Δ and BH retention found in our CMC Cluster Catalog's models. We demonstrate that the range in measured Δ from our models matches that for observed GCs to a remarkable degree. Our results constitute the largest sample of GCs for which BH populations have been predicted to date using a self-consistent and robust statistical approach. We identify NGC 2808, 5927, 5986, 6101, and 6205 to retain especially large BH populations, each with a total BH mass exceeding 103 ${M}_{\odot }$ .

Keywords: Globular star clusters, Stellar kinematics, Stellar mass black holes, Astrostatistics, Computational methods, N-body simulations
Nuclear Reaction Screening, Weak Interactions, and r-process Nucleosynthesis in High Magnetic Fields. Coulomb screening and weak interactions in a hot, magnetized plasma are investigated. Coulomb screening is evaluated in a relativistic thermal plasma in which electrons and positrons are in equilibrium. In addition to temperature effects, effects on weak screening from a strong external magnetic field are evaluated. In high fields, the electron transverse momentum components are quantized into Landau levels. The characteristic plasma screening length at high temperatures and at high magnetic fields is explored. In addition to changes to the screening length, changes in weak interaction rates are estimated. It is found that high fields can result in increased β-decay rates as the electron and positron spectra are dominated by Landau levels. Finally, the effects studied here are evaluated in a simple r-process model. It is found that relativistic Coulomb screening has a small effect on the final abundance distribution. While changes in weak interaction rates in strong magnetic fields can have an effect on the r-process evolution and abundance distribution, the field strength required to have a significant effect may be larger than what is currently thought to be typical of the r-process environment in collapsar jets or neutron star mergers. If r-process sites exist in fields $\gtrsim {10}^{14}$ G, effects from fields on weak decays could be significant.

Keywords: Magnetic stars, Nucleosynthesis, R-process, Magnetars, Magnetic fields
Ultradiffuse Galaxies in the Coma Cluster: Probing Their Origin and AGN Occupation Fraction. Ultradiffuse galaxies (UDGs) exhibit low surface brightness, but their optical extent is comparable to that of Milky Way-type galaxies. In this work, we utilize Chandra X-ray observations of 404 UDGs in the Coma cluster and address two crucial goals. First, we constrain the formation scenario of UDGs by probing the X-ray emission originating from diffuse gas and from the population of unresolved low-mass X-ray binaries (LMXBs) residing in globular clusters (GCs). It is expected that both the luminosity of the hot gas and the number of GCs, and hence the luminosity from GC-LMXBs, are proportional to the total mass of the dark matter halo. We do not detect statistically significant emission from the hot gas or from GC-LMXBs. The upper limits on the X-ray luminosities suggest that the bulk of the UDGs reside in low-mass dark matter halos, implying that they are genuine dwarf galaxies. This conclusion agrees with our previous results obtained for isolated UDGs, arguing that UDGs are a homogeneous population of galaxies. Second, we constrain the AGN occupation fraction of UDGs, i.e., the fraction of UDGs that are occupied by an active galactic nucleus, for the first time. To this end, we cross-correlate the position of detected X-ray sources in the Coma cluster with the position of UDGs. We identify two UDGs that have a luminous X-ray source at 3"0 and 3"2 from their center, which could be off-center AGNs. However, Monte Carlo simulations suggest that one of these sources could be the result of spatial coincidence with a background AGN. Therefore, we place an upper limit of ≲0.5% on the AGN occupation fraction of UDGs.

Keywords: X-ray photometry, Dwarf galaxies, Coma Cluster, Galaxy evolution, Low surface brightness galaxies
Brackett-γ as a Gold-standard Test of Star Formation Rates Derived from SED Fitting. Using a local reference sample of 21 galaxies, we compare observations of the 2.16 μm Brackett-γ (Brγ) hydrogen recombination line with predictions from the Prospector Bayesian inference framework, which was used to fit the broadband photometry of these systems. This is a clean test of the spectral-energy-distribution-derived star formation rates (SFRs), as dust is expected to be optically thin at this wavelength in nearly all galaxies; thus, the internal conversion of SFR to predicted line luminosity does not depend strongly on the adopted dust model and posterior dust parameters, as is the case for shorter-wavelength lines such as Hα. We find that Prospector predicts Brγ luminosities and equivalent widths with small offsets (∼0.05 dex) and scatter (∼0.2 dex), consistent with measurement uncertainties, though we caution that the derived offset is dependent on the choice of stellar isochrones. We demonstrate that even when the Prospector-derived dust attenuation does not well describe, e.g., Hα line properties or observed reddening between Hα and Brγ, the underlying SFRs are accurate, as verified by the dust-free Brγ comparison. Finally, we discuss in what ways Brγ might be able to help constrain model parameters when treated as an input to the model, and we comment on its potential as an accurate monochromatic SFR indicator in the era of JWST multiobject near-IR spectroscopy.

Keywords: Star formation, Galaxy evolution, Galaxy processes
SN 2019ehk: A Double-peaked Ca-rich Transient with Luminous X-Ray Emission and Shock-ionized Spectral Features. We present panchromatic observations and modeling of the Calcium-rich supernova (SN) 2019ehk in the star-forming galaxy M100 (d ≍ 16.2 Mpc) starting 10 hr after explosion and continuing for ∼300 days. SN 2019ehk shows a double-peaked optical light curve peaking at t = 3 and 15 days. The first peak is coincident with luminous, rapidly decaying Swift-XRT-discovered X-ray emission ( ${L}_{{\rm{x}}}\approx {10}^{41}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ at 3 days; Lx ∝ t-3), and a Shane/Kast spectral detection of narrow Hα and He II emission lines (v ≍ 500 $\mathrm{km}\,{{\rm{s}}}^{-1}$ ) originating from pre-existent circumstellar material (CSM). We attribute this phenomenology to radiation from shock interaction with extended, dense material surrounding the progenitor star at r &lt; 1015 cm and the resulting cooling emission. We calculate a total CSM mass of ∼7 × 10-3 ${M}_{\odot }$ (MHe/MH ≍6) with particle density n ≍ 109 cm-3. Radio observations indicate a significantly lower density n &lt; 104 cm-3 at larger radii r &gt; (0.1-1) × 1017 cm. The photometric and spectroscopic properties during the second light-curve peak are consistent with those of Ca-rich transients (rise-time of tr = 13.4 ± 0.210 days and a peak B-band magnitude of MB = -15.1 ± 0.200 mag). We find that SN 2019ehk synthesized (3.1 ± 0.11) × 10-2 ${M}_{\odot }$ of ${}^{56}\mathrm{Ni}$ and ejected Mej = (0.72 ± 0.040) ${M}_{\odot }$ total with a kinetic energy Ek = (1.8 ± 0.10) × 1050 erg. Finally, deep HST pre-explosion imaging at the SN site constrains the parameter space of viable stellar progenitors to massive stars in the lowest mass bin (∼10 ${M}_{\odot }$ ) in binaries that lost most of their He envelope or white dwarfs (WDs). The explosion and environment properties of SN 2019ehk further restrict the potential WD progenitor systems to low-mass hybrid HeCO WD+CO WD binaries.

Keywords: Core-collapse supernovae, Stellar phenomena, White dwarf stars, Transient sources, Stellar mass loss, X-ray telescopes, Supernovae