Sazuna/UAT_keywords huggingface dataset:
Photochemical Runaway in Exoplanet Atmospheres: Implications for Biosignatures. About 2.5 billion years ago, microbes learned to harness plentiful solar energy to reduce CO2 with H2O, extracting energy and producing O2 as waste. O2 production from this metabolic process was so vigorous that it saturated its photochemical sinks, permitting it to reach "runaway" conditions and rapidly accumulate in the atmosphere despite its reactivity. Here we argue that O2 may not be unique: diverse gases produced by life may experience a "runaway" effect similar to O2. This runaway occurs because the ability of an atmosphere to photochemically cleanse itself of trace gases is generally finite. If produced at rates exceeding this finite limit, even reactive gases can rapidly accumulate to high concentrations and become potentially detectable. Planets orbiting smaller, cooler stars, such as the M dwarfs that are the prime targets for the James Webb Space Telescope (JWST), are especially favorable for runaway, due to their lower UV emission compared to higher-mass stars. As an illustrative case study, we show that on a habitable exoplanet with an H2-N2 atmosphere and net surface production of NH3 orbiting an M dwarf (the "Cold Haber World" scenario), the reactive biogenic gas NH3 can enter runaway, whereupon an increase in the surface production flux of one order of magnitude can increase NH3 concentrations by three orders of magnitude and render it detectable by JWST in just two transits. Our work on this and other gases suggests that diverse signs of life on exoplanets may be readily detectable at biochemically plausible production rates.

Keywords: Extrasolar rocky planets, Exoplanet atmospheric composition , Planetary atmospheres, Transmission spectroscopy, Biosignatures, Habitable planets
A Model-based Technique for Ad Hoc Correction of Instrumental Polarization in Solar Spectropolarimetry. We present a new approach for correcting instrumental polarization by modeling the nondepolarizing effects of a complex series of optical elements to determine physically realizable Mueller matrices. Provided that the Mueller matrix of the optical system can be decomposed into a general elliptical diattenuator and general elliptical retarder, it is possible to model the crosstalk between both the polarized and unpolarized states of the Stokes vector and then use the acquired science observations to determine the best-fit free parameters. Here we implement a minimization for solar spectropolarimetric measurements containing photospheric spectral lines sensitive to the Zeeman effect using physical constraints provided by polarized line and continuum formation. This model-based approach is able to provide an accurate correction even in the presence of large amounts of polarization crosstalk and conserves the physically meaningful magnitude of the Stokes vector, a significant improvement over previous ad hoc techniques.

Keywords: Calibration, Solar physics, Spectropolarimetry, Solar magnetic fields
Organic Carbonyls Are Poor Biosignature Gases in Exoplanet Atmospheres but May Generate Significant CO. The search for signs of life beyond Earth is a crucial driving motivation of exoplanet science, fueling new work on biosignature gases in habitable exoplanet atmospheres. We study carbonyls, a category of molecules containing the C=O double bond, following our proposal to systematically identify plausible biosignature gas candidates from a list of all small volatile molecules. We rule out carbonyls as biosignature gases due to both their high water solubility and their high photolysis rate, despite their ubiquitous production by life on Earth, their critical importance in Earth's life biochemistry, and their uniquely identifiable molecular spectral features in mid- to low-resolution spectroscopy. Even in scenarios where life is a large net source of carbonyls, we demonstrate that detection of carbonyls is not possible on even the most ideal habitable exoplanet, because only 10 ppb of carbonyls can accumulate under our most optimistic assumptions. Moreover, high biological fluxes of organic carbon gases, while mathematically possible, are likely biologically unattainable due to the resulting huge waste of carbon-a main building block for life. Our simulations show that photochemical processing of carbonyls leads to generation of CO in quantities that can reengineer the atmosphere, affirming the ambiguity of CO as an antibiosignature. Overall, we find that the expression of a carbonyl-producing biosphere by CO, though potentially detectable by the James Webb Space Telescope, is unable to be uniquely traced back to carbonyls. While carbonyls fail as a bioindicator, by investigating them we have made a significant step toward systematically assessing the biosignature gas potential of all small volatile molecules.

Keywords: Markov chain Monte Carlo, Exoplanet atmospheric composition , Biosignatures, Habitable planets
Investigating the Stability of Mass Transfer in Neutron Star-helium White Dwarf Binaries. Neutron star-helium white dwarf (NS+He WD) binaries are important evolutionary products of close-orbit binary star systems. They are often observed as millisecond pulsars and may continue evolving into ultracompact X-ray binaries (UCXBs) and continuous gravitational wave (GW) sources that will be detected by space-borne GW observatories, such as LISA, TianQin, and Taiji. Nevertheless, the stability of NS+He WD binaries undergoing mass transfer has not been well studied and is still under debate. In this paper, we model the evolution of NS+He WD binaries with WD masses ranging from 0.17-0.45 M ⊙, applying the detailed stellar evolution code MESA. Contrary to previous studies based on hydrodynamics, we find that apparently all NS+He WD binaries undergo stable mass transfer. We find for such UCXBs that the larger the WD mass, the larger the maximum mass-transfer rate and the smaller the minimum orbital period during their evolution. Finally, we demonstrate numerically and analytically that there is a tight correlation between WD mass and GW frequency for UCXBs, independent of NS mass.

Keywords: Neutron stars, X-ray binary stars, White dwarf stars, Compact binary stars, Gravitational wave sources
Retrieval Study of Brown Dwarfs across the L-T Sequence. A large suite of 228 atmospheric retrievals is performed on a curated sample of 19 brown dwarfs spanning the L0-T8 spectral types using the open-source Helios-r2 retrieval code, which implements the method of short characteristics for radiative transfer and a finite-element description of the temperature-pressure profile. Surprisingly, we find that cloud-free and cloudy (both gray and nongray) models are equally consistent with the archival SpeX data from the perspective of Bayesian model comparison. Only upper limits for cloud properties are inferred if log-uniform priors are assumed, but the cloud optical depth becomes constrained if a uniform prior is used. Water is detected in all 19 objects, and methane is detected in all of the T dwarfs, but no obvious trend exists across effective temperature. As carbon monoxide is only detected in a handful of objects, the inferred carbon-to-oxygen ratios are unreliable. The retrieved radius generally decreases with effective temperature, but the values inferred for some T dwarfs are implausibly low and may indicate missing physics or chemistry in the models. For the early L dwarfs, the retrieved surface gravity depends on whether the gray-cloud or non-gray-cloud model is preferred. Future data are necessary for constraining cloud properties and the vertical variation of chemical abundances, the latter of which is needed for distinguishing between the chemical instability and traditional cloud interpretation of the L-T transition.

Keywords: Atmospheric composition, Brown dwarfs, Atmospheric clouds
Nuclear Matter and Neutron Stars from Relativistic Brueckner-Hartree-Fock Theory. The momentum and isospin dependence of the single-particle potential for the in-medium nucleon are the key quantities in the Relativistic Brueckner-Hartree-Fock (RBHF) theory. It depends on how to extract the scalar and the vector components of the single-particle potential inside nuclear matter. In contrast to the RBHF calculations in the Dirac space with the positive-energy states (PESs) only, the single-particle potential can be determined in a unique way by the RBHF theory together with the negative-energy states, i.e., the RBHF theory in the full Dirac space. The saturation properties of symmetric and asymmetric nuclear matter in the full Dirac space are systematically investigated based on the realistic Bonn nucleon-nucleon potentials. In order to further specify the importance of the calculations in the full Dirac space, the neutron star properties are investigated. The direct URCA process in neutron star cooling will happen at density ρ DURCA = 0.43, 0.48, 0.52 fm-3 with proton fractions of Y  p,DURCA = 0.13. The radii of a 1.4M ⊙ neutron star are predicated as ${R}_{1.4{M}_{\odot }}=11.97,12.13,12.27$ km, and their tidal deformabilities are ${{\rm{\Lambda }}}_{1.4{M}_{\odot }}=376,405,433$ for potential Bonn A, B, C. Compared with the results obtained in the Dirac space with PESs only, the full-Dirac-space RBHF calculation predicts the softest symmetry energy, which would be more favored by the gravitational wave detection of GW170817. Furthermore, the results from the full-Dirac-space RBHF theory are consistent with the recent astronomical observations of massive neutron stars and simultaneous mass-radius measurement.

Keywords: Nuclear physics
Detection of a Superluminous Spiral Galaxy in the Heart of a Massive Galaxy Cluster. It is well established that brightest cluster galaxies (BCGs), residing in the centers of galaxy clusters, are typically massive and quenched galaxies with cD or elliptical morphology. An optical survey suggested that an exotic galaxy population, superluminous spiral and lenticular galaxies, could be the BCGs of some galaxy clusters. Because the cluster membership and the centroid of a cluster cannot be accurately determined based solely on optical data, we followed up a sample of superluminous disk galaxies and their environments using XMM-Newton X-ray observations. Specifically, we explored seven superluminous spiral and lenticular galaxies that are candidate BCGs. We detected massive galaxy clusters around five superluminous disk galaxies and established that one superluminous spiral, 2MASX J16273931+3002239, is the central BCG of a galaxy cluster. The temperature and total mass of the cluster are ${{kT}}_{500}={3.55}_{-0.20}^{+0.18}$ keV and M 500 = (2.39 ± 0.19) × 1014 M ☉. We identified the central galaxies of the four clusters that do not host superluminous disk galaxies at their cores, and established that the centrals are massive elliptical galaxies. However, for two of the clusters, the offset superluminous spirals are brighter than the central galaxies, implying that the superluminous disk galaxies are the brightest cluster galaxies. Our results demonstrate that superluminous disk galaxies are rarely the central systems of galaxy clusters. This is likely because galactic disks are destroyed by major mergers, which are more frequent in high-density environments. We speculate that the disks of superluminous disk galaxies in cluster cores may have been reformed due to mergers with gas-rich satellites.

Keywords: X-ray astronomy, Galaxy clusters, High energy astrophysics, Spiral galaxies, Giant galaxies, Galactic and extragalactic astronomy, Extragalactic astronomy, Brightest cluster galaxies, Intracluster medium
Search for the Birefringence of Gravitational Waves with the Third Observing Run of Advanced LIGO-Virgo. Gravitational waves would attain birefringence during their propagation from distant sources to the Earth, when the charge, parity, and time reversal (CPT) symmetry is broken. If it was sizeable enough, such birefringence could be measured by the Advanced LIGO, Virgo, and KAGRA detector network. In this work, we place constraints on the birefringence of gravitational waves with the third observing run of this network, i.e., two catalogs GWTC-2 and GWTC-3. For the dispersion relation ω 2 = k 2 ± 2ζ k 3, our analysis shows the up-to-date strictest limit on the CPT-violating parameter, i.e., $\zeta ={4.07}_{-5.79}^{+5.91}\times {10}^{-17}{\rm{m}}$ , at 68% confidence level. This limit is stricter by ~5 times when compared to the existing one (~2× 10-16 m) and stands for the first ~10 GeV-scale test of the CPT symmetry in gravitational waves. The results of the Bayes factor strongly disfavor the birefringence scenario of gravitational waves.

Keywords: Gravitational wave astronomy, General relativity, Gravitational waves
Probing the Early History of Cosmic Reionization by Future Cosmic Microwave Background Experiments. Cosmic reionization imprints its signature on the temperature and polarization anisotropies of the cosmic microwave background (CMB). Advances in CMB telescopes have already placed a significant constraint on the history of reionization. As near-future CMB telescopes target the maximum sensitivity, or observations limited only by the cosmic variance (CV), we hereby forecast the potential of future CMB observations in constraining the history of reionization. In this study, we perform Markov Chain Monte Carlo analysis for CV-limited E-mode polarization observations such as the Lite (Light) satellite for the studies of B-mode polarization and Inflation from cosmic background Radiation Detection (LiteBIRD), based on a few different methods that vary in the way of sampling reionization histories. We focus especially on estimating the very early history of reionization that occurs at redshifts z &gt; 15, which is quantified by the partial CMB optical depth due to free electrons at z &gt; 15, τ  z&gt;15. We find that reionization with τ  z&gt;15 ~ 0.008, which is well below the current upper limit τ  z&gt;15 ~ 0.02, is achievable by reionization models with minihalo domination in the early phase and can be distinguished from those with τ  z&gt;15 ≲ 5 × 10-4 through CV-limited CMB polarization observations. An accurate estimation of τ  z&gt;15, however, remains somewhat elusive. We investigate whether resampling the E-mode polarization data with limited spherical-harmonic modes may resolve this shortcoming.

Keywords: Reionization, Cosmic microwave background radiation, Population III stars
HyGAL: Characterizing the Galactic Interstellar Medium with Observations of Hydrides and Other Small Molecules. I. Survey Description and a First Look Toward W3(OH), W3 IRS5, and NGC 7538 IRS1. The HyGAL Stratospheric Observatory for Infrared Astronomy legacy program surveys six hydride molecules-ArH+, OH+, H2O+, SH, OH, and CH-and two atomic constituents-C+ and O-within the diffuse interstellar medium (ISM) by means of absorption-line spectroscopy toward 25 bright Galactic background continuum sources. This detailed spectroscopic study is designed to exploit the unique value of specific hydrides as tracers and probes of different phases of the ISM, as demonstrated by recent studies with the Herschel Space Observatory. The observations performed under the HyGAL program will allow us to address several questions related to the life cycle of molecular material in the ISM and the physical processes that impact the phase transition from atomic to molecular gas, such as: (1) What is the distribution function of the H2 fraction in the ISM? (2) How does the ionization rate due to low-energy cosmic rays vary within the Galaxy? (3) What is the nature of interstellar turbulence (e.g., typical shear or shock velocities), and what mechanisms lead to its dissipation? In this overview, we discuss the observing strategy, the synergies with ancillary and archival observations of other small molecules, and the data reduction and analysis schemes we adopted; and we present the first results obtained toward three of the survey targets, W3(OH), W3 IRS5, and NGC 7538 IRS1. Robust measurements of the column densities of these hydrides-obtained through widespread observations of absorption lines-help address the questions raised, and there is a very timely synergy between these observations and the development of theoretical models, particularly pertaining to the formation of H2 within the turbulent ISM. The provision of enhanced HyGAL data products will therefore serve as a legacy for future ISM studies.

Keywords: Diffuse interstellar bands, Interstellar abundances, Molecular spectroscopy, Astrochemistry, Interstellar medium
No Redshift Evolution of Galaxies' Dust Temperatures Seen from 0 &lt; z &lt; 2. Some recent literature has claimed there to be an evolution in galaxies' dust temperatures toward warmer (or colder) spectral energy distributions (SEDs) between low and high redshift. These conclusions are driven by both theoretical models and empirical measurement. Such claims sometimes contradict one another and are prone to biases in samples or SED fitting techniques. What has made direct comparisons difficult is that there is no uniform approach to fitting galaxies' infrared/millimeter SEDs. Here we aim to standardize the measurement of galaxies' dust temperatures with a python-based SED fitting procedure, MCIRSED. 1 1 Publicly available at github.com/pdrew32/mcirsed. We draw on reference data sets observed by Infrared Astronomical Satellite, Herschel, and SCUBA-2 to test for redshift evolution out to z ~ 2. We anchor our work to the L IR-λ peak plane, where there is an empirically observed anticorrelation between IR luminosity and rest-frame peak wavelength (an observational proxy for luminosity-weighted dust temperature) such that $\left\langle {\lambda }_{\mathrm{peak}}\right\rangle ={\lambda }_{{\rm{t}}}{({L}_{\mathrm{IR}}/{L}_{{\rm{t}}})}^{\eta }$ where η = -0.09 ± 0.01, Lt = 1012 L ⊙, and λ t = 92 ± 2 μm. We find no evidence for redshift evolution of galaxies' temperatures, or λ peak, at fixed L IR from 0 &lt; z &lt; 2 with &gt;99.99% confidence. Our finding does not preclude evolution in dust temperatures at fixed stellar mass, which is expected from a nonevolving L IR-λ peak relation and a strongly evolving SFR-M⋆ relation. The breadth of dust temperatures ( ${\sigma }_{\mathrm{log}{\lambda }_{\mathrm{peak}}}$ ) at a given L IR is likely driven by variation in galaxies' dust geometries and sizes, and it does not evolve. Testing for L IR-λ peak evolution toward higher redshift (z ~ 5-6) requires better sampling of galaxies' dust SEDs near their peaks (observed ~200-600 μm) with ≲1 mJy sensitivity. This poses a significant challenge to current instrumentation.

Keywords: Dust continuum emission, Spectral energy distribution, Galaxy evolution
Long-term Evolution of a Supernova Remnant Hosting a Double Neutron Star Binary. An ultra-stripped supernova (USSN) is a type of core-collapse supernova explosion proposed to be a candidate formation site of a double neutron star (DNS) binary. We investigate the dynamical evolution of an ultra-stripped supernova remnant (USSNR), which should host a DNS at its center. By accounting for the mass-loss history of the progenitor binary using a model developed by a previous study, we construct the large-scale structure of the circumstellar medium (CSM) up to a radius ~100 pc, and simulate the explosion and subsequent evolution of a USSN surrounded by such a CSM environment. We find that the CSM encompasses an extended region characterized by a hot plasma with a temperature ~108 K located around the termination shock of the wind from the progenitor binary (~10 pc), and the USSNR blast wave is drastically weakened while penetrating through this hot plasma. Radio continuum emission from a young USSNR is sufficiently bright to be detectable if it inhabits our galaxy but faint compared to the observed Galactic supernova remnants (SNRs), and thereafter declines in luminosity through adiabatic cooling. Within our parameter space, USSNRs typically exhibit a low radio luminosity and surface brightness compared to the known Galactic SNRs. Due to the small event rate of USSNe and their relatively short observable life span, we calculate that USSNRs account for only ~0.1%-1% of the total SNR population. This is consistent with the fact that no SNR hosting a DNS binary has been discovered in the Milky Way so far.

Keywords: Supernova remnants
Gas and Dust Shadows in the TW Hydrae Disk. We present new observations of CO J = 2 - 1 emission from the protoplanetary disk around TW Hya. Emission is detected out to 240 au (4″) and found to exhibit azimuthal variations up to 20% beyond 180 au (3″), with the west side of the disk brighter than the east. This asymmetry is interpreted as tracing the shadow previously seen in scattered light. A re-analysis of the multi-epoch observations of the dust shadow in scattered light from Debes et al. suggests that an oscillatory motion would provide a better model of the temporal evolution of the dust shadow rather than orbital motion. Both models predict an angular offset between the dust shadow and the gas shadow of up to ~100°. We attribute this offset to the finite rate at which dust grains and gas molecules can exchange heat, dominated by the collisional rate between gas molecules and dust grains, t coll. The angular offsets derived are equivalent to collisional timescales that range from the near-instantaneous up to t coll ~ 10 yr, depending on whether a straight or curved dust shadow, as suggested by Hubble Space Telescope observations reported by Debes et al., is adopted. The inferred range of t coll are consistent with those predictions based on representative gas densities, temperatures, gas-to-dust ratios and grain sizes. These results represent the first time empirical constraints can be placed on t coll.

Keywords: Protoplanetary disks, Planet formation, Interferometry
Yellow Post-asymptotic-giant-branch Stars as Standard Candles. I. Calibration of the Luminosity Function in Galactic Globular Clusters. We use the results of a survey for low-surface-gravity stars in Galactic (and LMC) globular clusters to show that "yellow" post-asymptotic-branch (yPAGB) stars are likely to be excellent extragalactic standard candles, capable of producing distances to early-type galaxies that are accurate to a couple of percent. We show that the mean bolometric magnitude of the 10 yPAGB stars in globular clusters is &lt;M bol&gt; = -3.38 ± 0.03, a value that is ~0.2 mag brighter than that predicted from the latest post-horizontal-branch evolutionary tracks. More importantly, we show that the observed dispersion in the distribution is only 0.10 mag, i.e., better than the scatter for individual Cepheids. We describe the physics that can produce such a small dispersion and show that, if one restricts surveys to the color range 0.0 ≲ (B - V)0 ≲ 0.5, then samples of nonvariable yPAGB stars can be identified quite easily with a minimum of contamination. The extremely bright absolute V magnitudes of these stars (&lt;M  V &gt; = -3.37) make them, by far, the visually brightest objects in old stellar populations and ideal Population II standard candles for measurements out to ~10 Mpc with current instrumentation. A Hubble Space Telescope survey in the halos of galaxies in the M81 and Sculptor groups could therefore serve as an effective cross-check on both the Cepheid and tip-of-the-red-giant-branch distance scales.

Keywords: Globular star clusters, Galaxy distances, Post-asymptotic giant branch, Asymptotic giant branch