adsabs/SciX_UAT_keywords huggingface dataset:
Modeling Magnetic Disk Wind State Transitions in Black Hole X-Ray Binaries

We analyze three prototypical black hole X-ray binaries, 4U 1630-472, GRO J1655-40, and H1743-322, in an effort to systematically understand the intrinsic state transition of the observed accretion disk winds between wind-on and wind-off states by utilizing state-of-the-art Chandra/HETGS archival data from multi-epoch observations. We apply our magnetically driven wind models in the context of magnetohydrodynamic (MHD) calculations to constrain (1) their global density slope (p), (2) their density (n17) at the foot point of the innermost launching radius, and (3) the abundances of heavier elements (AFe,S,Si). Incorporating the MHD winds into xstar photoionization calculations in a self-consistent manner, we create a library of synthetic absorption spectra given the observed X-ray continua. Our analysis clearly indicates a characteristic bimodal transition of multi-ion X-ray winds; i.e., the wind density gradient is found to steepen (from p ∼ 1.2-1.4 to ∼1.4-1.5) while its density normalization declines as the source transitions from the wind-on to the wind-off state. The model implies that the ionized wind remains physically present even in the wind-off state, despite its apparent absence in the observed spectra. Supersolar abundances for heavier elements are also favored. Our global multi-ion wind models, taking into account soft X-ray ions as well as Fe K absorbers, show that the internal wind condition plays an important role in wind transitions besides photoionization changes. Simulated XRISM/Resolve and Athena/X-IFU spectra are presented to demonstrate a high fidelity of the multi-ion wind model for a better understanding of these powerful ionized winds in the coming decades.

Keywords: accretion; black hole physics; low-mass x-ray binary stars; radiative magnetohydrodynamics; theoretical models; x-ray observatories; spectroscopy; compact binary stars
The Discovery of the Long-Period, Eccentric Planet Kepler-88 d and System Characterization with Radial Velocities and Photodynamical Analysis

We present the discovery of Kepler-88 d ( ${P}_{d}\,= $1403\pm 14\,\mathrm{days}, $M\sin {i}_{d}=965\pm 44\,{M}_{\oplus }=3.04\pm 0.13\,{M}_{{\rm{J}}}, ${e}_{d}=0.41\pm 0.03 ) based on six years of radial velocity (RV) follow-up from the W. M. Keck Observatory High Resolution Echelle Spectrometer spectrograph. Kepler-88 has two previously identified planets. Kepler-88 b (KOI-142.01) transits in the NASA Kepler photometry and has very large transit timing variations (TTVs). Nesvorný et al. performed a dynamical analysis of the TTVs to uniquely identify the orbital period and mass of the perturbing planet (Kepler-88 c), which was later was confirmed with RVs from the Observatoire de Haute-Provence (OHP). To fully explore the architecture of this system, we performed photodynamical modeling on the Kepler photometry combined with the RVs from Keck and OHP and stellar parameters from spectroscopy and Gaia. Planet d is not detectable in the photometry, and long-baseline RVs are needed to ascertain its presence. A photodynamical model simultaneously optimized to fit the RVs and Kepler photometry yields the most precise planet masses and orbital properties yet for b and c: ${P}_{b}=10.91647\pm 0.00014\,\mathrm{days}${M}_{b}=9.5\pm 1.2\,{M}_{\oplus }, ${P}_{c}=22.2649\pm 0.0007\,\mathrm{days}, and ${M}_{c}=214.0\pm 5.3\,{M}_{\oplus } . The photodynamical solution also finds that planets b and c have low eccentricites and low mutual inclination, are apsidally anti-aligned, and have conjunctions on the same hemisphere of the star. Continued RV follow-up of systems with small planets will improve our understanding of the link between inner planetary system architectures and giant planets.

Keywords: exoplanet astronomy; exoplanets; exoplanet systems; exoplanet detection methods
Analysis of High-precision TESS Photometry of the Black Hole X-Ray Binary Cygnus X-1: Evidence of Intrinsic Variability of the Luminous Blue Supergiant Component

We report on Transiting Exoplanet Survey Satellite (TESS) high-precision photometry of the iconic non-eclipsing 5.60 days (O9.7Iab+black hole) binary Cygnus X-1. Previous ground-based photometry reveals low-amplitude (~0.04 mag) ellipsoidal light-variations that arise from the tidal (and rotational) distortion of the O9.7Iab companion. Additional small light-variations have also been reported by many observers. Short-cadence TESS photometry was conducted over ~27 days during 2019 July-August. The photometry shows the expected ~5.60 days binary ellipsoidal variations, but in addition ~0.01-0.03 mag complex quasi-periodic brightness variations. The observations were analyzed to investigate the underlying extra-binary variability. We also determined a new time of minimum light and calculated an updated period and light elements. The quasi-periodic, (non-binary) light-variations likely arise from the complex pulsations of the blue supergiant.

Keywords: high mass x-ray binary stars; x-ray binary stars; o supergiant stars; stellar pulsations
Millimeter-wave Point Sources from the 2500 Square Degree SPT-SZ Survey: Catalog and Population Statistics

We present a catalog of emissive point sources detected in the SPT-SZ survey, a contiguous 2530 square degree area surveyed with the South Pole Telescope (SPT) from 2008-2011 in three bands centered at 95, 150, and 220 GHz. The catalog contains 4845 sources measured at a significance of 4.5σ or greater in at least one band, corresponding to detections above approximately 9.8, 5.8, and 20.4 mJy in 95, 150, and 220 GHz, respectively. The spectral behavior in the SPT bands is used for source classification into two populations based on the underlying physical mechanisms of compact, emissive sources that are bright at millimeter wavelengths: synchrotron radiation from active galactic nuclei and thermal emission from dust. The latter population includes a component of high-redshift sources often referred to as submillimeter galaxies (SMGs). In the relatively bright flux ranges probed by the survey, these sources are expected to be magnified by strong gravitational lensing. The survey also contains sources consistent with protoclusters, groups of dusty galaxies at high redshift undergoing collapse. We cross-match the SPT-SZ catalog with external catalogs at radio, infrared, and X-ray wavelengths and identify available redshift information. The catalog splits into 3980 synchrotron-dominated and 865 dust-dominated sources, and we determine a list of 506 SMGs. Ten sources in the catalog are identified as stars. We calculate number counts for the full catalog, and synchrotron and dusty components, using a bootstrap method and compare our measured counts with models. This paper represents the third and final catalog of point sources in the SPT-SZ survey.

Keywords: high-redshift galaxies; submillimeter astronomy; surveys
L 98-59: A Benchmark System of Small Planets for Future Atmospheric Characterization

The M3V dwarf star L 98-59 hosts three small (R < 1.6 R⊕) planets. The host star is bright (K = 7.1) and nearby (10.6 pc), making the system a prime target for follow-up characterization with the Hubble Space Telescope (HST) and the upcoming James Webb Space Telescope (JWST). Herein, we use simulated transmission spectroscopy to evaluate the detectability of spectral features with HST and JWST assuming diverse atmospheric scenarios (e.g., atmospheres dominated by H2, H2O, CO2, or O2). We find that H2O and CH4 present in a low mean molecular weight atmosphere could be detected with HST in one transit for the two outermost planets, while H2O in a clear steam atmosphere could be detected in six transits or fewer with HST for all three planets. We predict that observations using JWST/NIRISS would be capable of detecting a clear steam atmosphere in one transit for each planet and H2O absorption in a hazy steam atmosphere in two transits or less. In a clear, desiccated atmosphere, O2 absorption may be detectable for all three planets with NIRISS. If the L 98-59 planets possess a clear, Venus-like atmosphere, NIRSpec could detect CO2 within 26 transits for each planet, but the presence of H2SO4 clouds would significantly suppress CO2 absorption. The L 98-59 system is an excellent laboratory for comparative planetary studies of transiting multiplanet systems, and observations of the system via HST and JWST would present a unique opportunity to test the accuracy of the models presented in this study.

Keywords: exoplanet atmospheres; transmission spectroscopy; low mass stars; extrasolar rocky planets; exoplanets; near infrared astronomy; astronomy data modeling
Forecasts for Galaxy Formation and Dark Matter Constraints from Dwarf Galaxy Surveys

The abundance of faint dwarf galaxies is determined by the underlying population of low-mass dark matter (DM) halos and the efficiency of galaxy formation in these systems. Here, we quantify potential galaxy formation and DM constraints from future dwarf satellite galaxy surveys. We generate satellite populations using a suite of Milky Way (MW)–mass cosmological zoom-in simulations and an empirical galaxy–halo connection model, and assess sensitivity to galaxy formation and DM signals when marginalizing over galaxy–halo connection uncertainties. We find that a survey of all satellites around one MW-mass host can constrain a galaxy formation cutoff at peak virial masses of ${{ \mathcal M }}_{50}={10}^{8}\,{M}_{\odot }$ at the 1σ level; however, a tail toward low ${{ \mathcal M }}_{50}$ prevents a 2σ measurement. In this scenario, combining hosts with differing bright satellite abundances significantly reduces uncertainties on ${{ \mathcal M }}_{50}$ at the 1σ level, but the 2σ tail toward low ${{ \mathcal M }}_{50}$ persists. We project that observations of one (two) complete satellite populations can constrain warm DM models with m WDM ≈ 10 keV (20 keV). Subhalo mass function (SHMF) suppression can be constrained to ≈70%, 60%, and 50% that in cold dark matter (CDM) at peak virial masses of 108, 109, and 1010 M ⊙, respectively; SHMF enhancement constraints are weaker (≈20, 4, and 2 times that in CDM, respectively) due to galaxy–halo connection degeneracies. These results motivate searches for faint dwarf galaxies beyond the MW and indicate that ongoing missions like Euclid and upcoming facilities including the Vera C. Rubin Observatory and Nancy Grace Roman Space Telescope will probe new galaxy formation and DM physics.

Keywords: dark matter; dwarf galaxies; galaxy abundances; galaxy formation
Toward Precision Cosmology with Improved PNLF Distances Using VLT-MUSEI. Methodology and Tests

The [O III] λ5007 planetary nebula luminosity function (PNLF) is an established distance indicator that has been used for more than 30 yr to measure the distances of galaxies out to ~15 Mpc. With the advent of the Multi-Unit Spectroscopic Explorer on the Very Large Telescope (MUSE) as an efficient wide-field integral-field spectrograph, the PNLF method is due for a renaissance, as the spatial and spectral information contained in the instrument's data cubes provides many advantages over classical narrowband imaging. Here we use archival MUSE data to explore the potential of a novel differential emission-line filter (DELF) technique to produce spectrophotometry that is more accurate and more sensitive than other methods. We show that DELF analyses are superior to classical techniques in high surface brightness regions of galaxies, and we validate the method both through simulations and via the analysis of data from two early-type galaxies (NGC 1380 and NGC 474) and one late-type spiral (NGC 628). We demonstrate that with adaptive optics support or under excellent seeing conditions, the technique is capable of producing precision (≲0.05 mag) [O III] photometry out to distances of 40 Mpc while providing discrimination between planetary nebulae and other emission-line objects such as H II regions, supernova remnants, and background galaxies. These capabilities enable us to use MUSE to measure precise PNLF distances beyond the reach of Cepheids and the tip of the red giant branch method and become an additional tool for constraining the local value of the Hubble constant.

Keywords: hubble constant
Could Nearby Star-forming Galaxies Light Up the Pointlike Neutrino Sky?

Star-forming and starburst galaxies, which are well-known cosmic-ray reservoirs, are expected to emit gamma-rays and neutrinos predominantly via hadronic collisions. In this Letter, we analyze the 10 yr Fermi-LAT spectral energy distributions of 13 nearby galaxies by means of a physical model which accounts for high-energy proton transport in starburst nuclei and includes the contribution of primary and secondary electrons. In particular, we test the hypothesis that the observed gamma-ray fluxes are mostly due to star-forming activity, in agreement with the available star formation rates coming from IR and UV observations. Through this observation-based approach, we determine the most likely neutrino counterpart from star-forming and starburst galaxies and quantitatively assess the ability of current and upcoming neutrino telescopes to detect them as pointlike sources. Remarkably, we find that the cores of the Small Magellanic Cloud and the Circinus galaxy are potentially observable by KM3NeT/ARCA with 6 yr of observation. Moreover, most of the nearby galaxies are likely to be just a factor of a few below the KM3NeT and IceCube-Gen2 pointlike sensitivities. After investigating the prospects for detection of gamma-rays above TeV energies from these sources, we conclude that the joint observations of high-energy neutrinos and gamma-rays with upcoming telescopes will be an objective test for our emission model and may provide compelling evidence of star-forming activity as a tracer of neutrino production.

Keywords: starburst galaxies; star formation; gamma-rays; neutrino telescopes
Analysis of Polarimetry Data with Angular Uncertainties

For a track based polarimeter, such as the Imaging X-ray Polarimetry Explorer (IXPE), the sensitivity to polarization depends on the modulation factor, which is a strong function of energy. In previous work, a likelihood method was developed that would account for this variation in order to estimate the minimum detectable polarization (MDP). That method essentially required that the position angles of individual events should be known precisely. In a separate work, however, it was shown that using a machine-learning method for measuring event tracks can generate track angle uncertainties, which can be used in the analysis. Here, the maximum likelihood method is used as a basis for revising the estimate of the MDP in a general way that can include uncertainties in event track position angles. The resultant MDP depends solely upon the distribution of track angle uncertainties present in the input data. Due to the physics of the IXPE detectors, it is possible to derive a simple relationship between these angular uncertainties and the energy-dependent modulation function as a step in the process.

Keywords: polarimetry; astronomical techniques; x-ray astronomy
Constraints on the Size and Composition of the Ancient Martian Atmosphere from Coupled CO2-N2-Ar Isotopic Evolution Models

Present-day Mars is cold and dry, but mineralogical and morphological evidence shows that liquid water existed on the surface of ancient Mars. In order to explain this evidence and assess ancient Mars's habitability, one must understand the size and composition of the ancient atmosphere. Here we place constraints on the ancient Martian atmosphere by modeling the coupled, self-consistent evolution of atmospheric CO2, N2, and Ar on Mars from 3.8 billion years ago (Ga) to the present. Our model traces the evolution of these species' abundances and isotopic composition caused by atmospheric escape, volcanic outgassing, and crustal interaction. Using a Markov Chain Monte Carlo method to explore a plausible range of parameters, we find hundreds of thousands of model solutions that recreate the modern Martian atmosphere. These solutions indicate that Mars's atmosphere contained 0.3-1.5 bar CO2 and 0.1-0.5 bar N2 at 3.8 Ga. The global volume of deposited carbonates critically determines the ancient atmospheric composition. For example, a ~1 bar CO2 ancient atmosphere with 0.2-0.4 bar N2 requires ~0.9 bar CO2 deposited in carbonates primarily in open-water systems. With the joint analysis of C, N, and Ar isotopes, we refine the constraints on the relative strengths of outgassing and sputtering, leading to an indication of a reduced early mantle from which the outgassing is sourced. Our results indicate that a CO2-N2 atmosphere with a potential H2 component on ancient Mars is consistent with Mars's geochemical evolution and may explain the evidence for its past warm and wet climate.

Keywords: mars; astrobiology; atmospheric evolution; planetary science; planetary atmospheres
Searching for Extremely Blue UV Continuum Slopes at z = 7-11 in JWST/NIRCam Imaging: Implications for Stellar Metallicity and Ionizing Photon Escape in Early Galaxies

The ultraviolet (UV) continuum slope (β, where f λ ∝ λ β ) of galaxies is sensitive to a variety of properties, from the metallicity and age of the stellar population to dust attenuation throughout the galaxy. Considerable attention has focused on identifying reionization-era galaxies with very blue UV slopes (β < -3). Not only do such systems provide a signpost of low-metallicity stars, but they also identify galaxies likely to leak ionizing photons from their H II regions as such blue UV slopes require the reddening effect of nebular continuum to be diminished. In this paper we present a search for reionization-era galaxies with very blue UV colors in recent JWST/NIRCam imaging of the Extended Groth Strip field. We characterize UV slopes for a large sample of z ≃ 7-11 galaxies, finding a median of β = -2.0. Two lower luminosity (M UV ≃ -19.5) and lower stellar mass (6-10 × 107 M ⊙) systems exhibit extremely blue UV slopes (β = -2.9 to -3.1) and rest-optical photometry indicating weak nebular line emission. Each system is very compact (r e ≲ 260 pc) with very high star formation-rate surface densities. We model the spectral energy distributions (SEDs) with a suite of BEAGLE models with varying levels of ionizing photon escape. The SEDs cannot be reproduced with our fiducial (f esc,H II = 0) or alpha-enhanced (Z ⋆ < Z ISM) models. The combined blue UV slopes and weak nebular emission are best-fit by models with significant ionizing photon escape from H II regions (f esc,H II = 0.5-0.8) and extremely low-metallicity massive stars (Z ⋆ = 0.01-0.06 Z ⊙). The discovery of these galaxies highlights the potential for JWST to identify large numbers of candidate Lyman continuum leaking galaxies in the reionization era and suggests low-metallicity stellar populations may be common in dwarf galaxies at z > 7.

Keywords: high-redshift galaxies; galaxies; reionization; metallicity; chemical abundances
Is Thermohaline Mixing the Full Story? Evidence for Separate Mixing Events near the Red Giant Branch Bump

The abundances of mixing-sensitive elements including lithium, [C/N], and 12C/13C are known to change near the red giant branch bump. The explanation most often offered for these alterations is double diffusive thermohaline mixing in the stellar interior. In this analysis, we investigate the ability of thermohaline mixing to explain the observed timing of these chemical depletion events. Recent observational measurements of lithium and [C/N] show that the abundance of lithium decreases before the abundance of [C/N], whereas numerical simulations of the propagation of the thermohaline-mixing region computed with MESA show that the synthetic abundances drop simultaneously. We therefore conclude that thermohaline mixing alone cannot explain the distinct events of lithium depletion and [C/N] depletion, as the simultaneity predicted by simulations is not consistent with the observation of separate drops. We thus invite more sophisticated theoretical explanations for the observed temporal separation of these chemical depletion episodes as well as more extensive observational explorations across a range of masses and metallicities.

Keywords: stellar physics; stellar abundances; stellar evolution; stellar interiors
Search for an Isotropic Gravitational-wave Background with the Parkes Pulsar Timing Array

Pulsar timing arrays aim to detect nanohertz-frequency gravitational waves (GWs). A background of GWs modulates pulsar arrival times and manifests as a stochastic process, common to all pulsars, with a signature spatial correlation. Here we describe a search for an isotropic stochastic gravitational-wave background (GWB) using observations of 30 millisecond pulsars from the third data release of the Parkes Pulsar Timing Array (PPTA), which spans 18 yr. Using current Bayesian inference techniques we recover and characterize a common-spectrum noise process. Represented as a strain spectrum ${h}_{c}=A{(f/1{\mathrm{yr}}^{-1})}^{\alpha }$ , we measure $A={3.1}_{-0.9}^{+1.3}\times {10}^{-15}$ and α = -0.45 ± 0.20, respectively (median and 68% credible interval). For a spectral index of α = -2/3, corresponding to an isotropic background of GWs radiated by inspiraling supermassive black hole binaries, we recover an amplitude of $A={2.04}_{-0.22}^{+0.25}\times {10}^{-15}$ . However, we demonstrate that the apparent signal strength is time-dependent, as the first half of our data set can be used to place an upper limit on A that is in tension with the inferred common-spectrum amplitude using the complete data set. We search for spatial correlations in the observations by hierarchically analyzing individual pulsar pairs, which also allows for significance validation through randomizing pulsar positions on the sky. For a process with α = -2/3, we measure spatial correlations consistent with a GWB, with an estimated false-alarm probability of p ≲ 0.02 (approx. 2σ). The long timing baselines of the PPTA and the access to southern pulsars will continue to play an important role in the International Pulsar Timing Array.

Keywords: gravitational waves; gravitational wave astronomy; millisecond pulsars; pulsar timing method; bayesian statistics
Compact-object Mergers in the Galactic Center: Evolution in Triaxial Clusters

There is significant observational evidence that a large fraction of galactic centers, including those in the Milky Way and M31, host a supermassive black hole (SMBH) embedded in a triaxial nuclear star cluster. In this work, we study the secular orbital evolution of binaries in these environments and characterize the regions and morphological properties of nuclear star clusters that lead to gravitational wave mergers and/or tidal captures. We show that even a modest level of triaxiality in the density distribution of a cluster (an ellipsoid with axis ratios of 0.7 and 0.95) dramatically enhances the merger rates in the central parsecs of the Galaxy by a factor of up to ∼10-30 relative to a spherical density distribution. Moreover, we show that the merger fraction of binaries with semimajor axes in the range 10-100 au remains above 10% for the entire central parsec of the cluster, reaching values close to unity at a distance of ∼0.2-0.4 pc from the SMBH. We understand this large merger efficiency in terms of two distinct mechanisms: (I) eccentricity oscillations driven by the dominant axisymmetric part of the cluster potential that are enhanced by the slow modulation of a binary's angular momentum from the triaxial contribution, similar to the well-known octupole-level dynamics in three-body systems; and (II) chaotic diffusion of eccentricities arising when the nodal precession timescale of a binary's orbit about the SMBH becomes comparable to its characteristic secular timescale. Overall, our results indicate that galactic centers are significantly more collisional than previously thought, with mergers taking place up to the effective radii of their nuclear star clusters.

Keywords: galactic center; compact objects; gravitational wave sources; low-mass x-ray binary stars; star clusters; supermassive black holes; stellar dynamics