adsabs/SciX_UAT_keywords huggingface dataset:
Insight-HXMT Study of the Inner Accretion Disk in the Black Hole Candidate EXO 1846-031

We study the spectral evolution of the black hole candidate EXO 1846-031 during its 2019 outburst, in the 1-150 keV band, with the Hard X-ray Modulation Telescope. The continuum spectrum is well modeled with an absorbed disk-blackbody plus cutoff power law, in the hard, intermediate, and soft states. In addition, we detect an ≈6.6 keV Fe emission line in the hard intermediate state. Throughout the soft intermediate and soft states, the fitted inner disk radius remains almost constant; we suggest that it has settled at the innermost stable circular orbit (ISCO). However, in the hard and hard intermediate states, the apparent inner radius was unphysically small (smaller than the ISCO), even after accounting for the Compton scattering of some of the disk photons by the corona in the fit. We argue that this is the result of a high hardening factor, f col ≈ 2.0-2.7, in the early phases of the outburst evolution, well above the canonical value of 1.7 suitable for a steady disk. We suggest that the inner disk radius was already close to the ISCO in the low/hard state. Furthermore, we propose that this high value of the hardening factor in the relatively hard state was probably caused by the additional illuminating of the coronal irradiation onto the disk. Additionally, we estimate the spin parameter using the continuum-fitting method, over a range of plausible black hole masses and distances. We compare our results with the spin measured using the reflection-fitting method and find that the inconsistency of the two results is partly caused by different choices of f col.

Keywords: black hole physics; high energy astrophysics; accretion
Giant Outer Transiting Exoplanet Mass (GOT 'EM) Survey. III. Recovery and Confirmation of a Temperate, Mildly Eccentric, Single-transit Jupiter Orbiting TOI-2010

Large-scale exoplanet surveys like the Transiting Exoplanet Survey Satellite (TESS) mission are powerful tools for discovering large numbers of exoplanet candidates. Single-transit events are commonplace within the resulting candidate list due to the unavoidable limitation of the observing baseline. These single-transit planets often remain unverified due to their unknown orbital periods and consequent difficulty in scheduling follow-up observations. In some cases, radial velocity (RV) follow up can constrain the period enough to enable a future targeted transit detection. We present the confirmation of one such planet: TOI-2010 b. Nearly three years of RV coverage determined the period to a level where a broad window search could be undertaken with the Near-Earth Object Surveillance Satellite, detecting an additional transit. An additional detection in a much later TESS sector solidified our final parameter estimation. We find TOI-2010 b to be a Jovian planet (M P = 1.29 M Jup, R P = 1.05 R Jup) on a mildly eccentric orbit (e = 0.21) with a period of P = 141.83403 days. Assuming a simple model with no albedo and perfect heat redistribution, the equilibrium temperature ranges from about 360 to 450 K from apastron to periastron. Its wide orbit and bright host star (V = 9.85) make TOI-2010 b a valuable test bed for future low-insolation atmospheric analysis.

Keywords: exoplanet astronomy; exoplanet systems; exoplanet dynamics; exoplanet detection methods
The Green Bank North Celestial Cap Pulsar Survey. V. Pulsar Census and Survey Sensitivity

The Green Bank North Celestial Cap (GBNCC) pulsar survey will cover the entire northern sky (δ > -40°) at 350 MHz, and is one of the most uniform and sensitive all-sky pulsar surveys to date. We have created a pipeline to reanalyze GBNCC survey data to take a 350 MHz census of all pulsars detected by the survey, regardless of their discovery survey. Of the 1413 pulsars in the survey region, we were able to recover 670. For these we present measured signal-to-noise ratios (S/N), flux densities, pulse widths, profiles, and where appropriate, refined measurements of dispersion measures (DMs) (656 out of 670) and new or improved spectral indices (339 out of 670 total, 47 new, 292 improved). We also measure the period-pulse width relation at 350 MHz to scale as W∝ P-0.27. Detection scans for several hundred sources were reanalyzed in order to inspect pulsars' single pulse behavior and 223 were found to exhibit evidence of nulling. With a detailed analysis of measured and expected S/N values and the evolving radio frequency interference environment at 350 MHz, we assess the GBNCC survey's sensitivity as a function of spin period, DM, and sky position. We find the sky-averaged limiting flux density of the survey to be 0.74 mJy. Combining this analysis with PsrPopPy pulsar population simulations, we predict 60/5 nonrecycled/MSP discoveries in the survey's remaining 21,000 pointings, and we begin to place constraints on population model parameters.

Keywords: radio pulsars; radio astronomy; surveys
The Initial Mass Function Based on the Full-sky 20 pc Census of ∼3600 Stars and Brown Dwarfs

A complete accounting of nearby objects—from the highest-mass white dwarf progenitors down to low-mass brown dwarfs—is now possible, thanks to an almost complete set of trigonometric parallax determinations from Gaia, ground-based surveys, and Spitzer follow-up. We create a census of objects within a Sun-centered sphere of 20 pc radius and check published literature to decompose each binary or higher-order system into its separate components. The result is a volume-limited census of ∼3600 individual star formation products useful in measuring the initial mass function across the stellar (<8M ⊙) and substellar (≳5M Jup) regimes. Comparing our resulting initial mass function to previous measurements shows good agreement above 0.8M ⊙ and a divergence at lower masses. Our 20 pc space densities are best fit with a quadripartite power law, $\xi (M)={dN}/{dM}\propto {M}^{-\alpha }$ , with long-established values of α = 2.3 at high masses (0.55 < M < 8.00M ⊙), and α = 1.3 at intermediate masses (0.22 < M < 0.55M ⊙), but at lower masses, we find α = 0.25 for 0.05 < M < 0.22M ⊙, and α = 0.6 for 0.01 < M < 0.05M ⊙. This implies that the rate of production as a function of decreasing mass diminishes in the low-mass star/high-mass brown dwarf regime before increasing again in the low-mass brown dwarf regime. Correcting for completeness, we find a star to brown dwarf number ratio of, currently, 4:1, and an average mass per object of 0.41 M ⊙.

Keywords: initial mass function; stellar mass functions; brown dwarfs; trigonometric parallax; solar neighborhood; binary stars
The Origin of Exponential Star-forming Disks

The disk components of galaxies generally show an exponential profile extending over several scale lengths, both in mass and star formation rate, but the physical origin is not well understood. We explore a physical model in which the galactic gas disk is viewed as a "modified accretion disk" in which coplanar gas inflow, driven by viscous stresses in the disk, provides the fuel for star formation, which progressively removes gas as it flows inward. We show that magnetic stresses from magneto-rotational instability are the most plausible source of the required viscosity, and construct a simple physical model to explore this. A key feature is to link the magnetic field strength to the local star formation surface density, ${B}_{\mathrm{tot}}\propto {{\rm{\Sigma }}}_{\mathrm{SFR}}^{\alpha }$ . This provides a feedback loop between star formation and the flow of gas. We find that the model naturally produces stable steady-state exponential disks, as long as α ~ 0.15, the value indicated from spatially resolved observations of nearby galaxies. The disk scale length h R is set by the rate at which the disk is fed, by the normalization of the B tot-ΣSFR relation and by the circular velocity of the halo. The angular momentum distribution of the gas and stars within the disk is a consequence of the transfer of angular momentum that is inherent to the operation of an accretion disk, rather than the initial angular momentum of the inflowing material. We suggest that magnetic stresses likely play a major role in establishing the stable exponential form of galactic disks.

Keywords: galaxies; galaxy structure; galaxy formation; galaxy magnetic fields
First Wide Field-of-view X-Ray Observations by a Lobster-eye Focusing Telescope in Orbit

As a novel X-ray focusing technology, lobster-eye micropore optics (MPO) feature both a wide observing field of view and true imaging capability, promising sky monitoring with significantly improved sensitivity and spatial resolution in soft X-rays. Since first proposed by Angel, the optics have been extensively studied, developed and trialed over the past decades. In this Letter, we report on the first-light results from a flight experiment of the Lobster Eye Imager for Astronomy, a pathfinder of the wide-field X-ray telescope of the Einstein Probe mission. The piggyback imager, launched in 2022 July, has a mostly unvignetted field of view of 18.°6 × 18.°6. Its spatial resolution is in the range of 4'-7' in FWHM and the focal spot effective area is 2-3 cm2, both showing only mild fluctuations across the field of view. We present images of the Galactic center region, Sco X-1, and the diffuse Cygnus Loop nebular taken in snapshot observations over 0.5-4 keV. These are truly wide-field X-ray images of celestial bodies observed, for the first time, by a focusing imaging telescope. Initial analyses of the in-flight data show excellent agreement between the observed images and the on-ground calibration and simulations. The instrument and its characterization are briefly described, as well as the flight experiment. The results provide a solid basis for the development of the present and proposed wide-field X-ray missions using lobster-eye MPO.

Keywords: wide-field telescopes; x-ray astronomy; x-ray telescopes; time domain astronomy
Quasar Microlensing Variability Studies Favor Shallow Accretion Disk Temperature Profiles

We compare the microlensing-based continuum emission region size measurements in a sample of 15 gravitationally lensed quasars with estimates of luminosity-based thin disk sizes to constrain the temperature profile of the quasar continuum accretion region. If we adopt the standard thin disk model, we find a significant discrepancy between sizes estimated using the luminosity and those measured by microlensing of log(rL/rμ) = -0.57 ± 0.08 dex. If quasar continuum sources are simple, optically thick accretion disks with a generalized temperature profile $T(r)\propto {r}^{-\beta }$ , the discrepancy between the microlensing measurements and the luminosity-based size estimates can be resolved by a temperature profile slope 0.37 < β < 0.56 at 1σ confidence. This is shallower than the standard thin disk model (β = 0.75) at 3σ significance. We consider alternate accretion disk models that could produce such a temperature profile and reproduce the empirical continuum size scaling with black hole mass, including disk winds or disks with nonblackbody atmospheres.

Keywords: gravitational lensing; accretion; quasars
Machine-learning Cosmology from Void Properties

Cosmic voids are the largest and most underdense structures in the Universe. Their properties have been shown to encode precious information about the laws and constituents of the Universe. We show that machine-learning techniques can unlock the information in void features for cosmological parameter inference. We rely on thousands of void catalogs from the GIGANTES data set, where every catalog contains an average of 11,000 voids from a volume of $1\,{\left({h}^{-1}\,\mathrm{Gpc}\right)}^{3}$ . We focus on three properties of cosmic voids: ellipticity, density contrast, and radius. We train (1) fully connected neural networks on histograms from individual void properties and (2) deep sets from void catalogs to perform likelihood-free inference on the value of cosmological parameters. We find that our best models are able to constrain the value of Ω m , σ 8, and n s with mean relative errors of 10%, 4%, and 3%, respectively, without using any spatial information from the void catalogs. Our results provide an illustration for the use of machine learning to constrain cosmology with voids.

Keywords: cosmology; voids; large-scale structure of the universe
Spectroscopic Observations of High-speed Downflows in a C1.7 Solar Flare

In this paper, we analyze the high-resolution UV spectra for a C1.7 solar flare (SOL2017-09-09T06:51) observed by the Interface Region Imaging Spectrograph (IRIS). We focus on the spectroscopic observations at the locations where the cool lines of Si IV 1402.8 Å (∼104.8 K) and C II 1334.5/1335.7 Å (∼104.4 K) reveal significant redshifts with Doppler velocities up to ∼150 km s-1. These redshifts appear in the rise phase of the flare, then increase rapidly, reach the maximum in a few minutes, and proceed into the decay phase. Combining the images from IRIS and Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, we propose that the redshifts in the cool lines are caused by the downflows in the transition region and upper chromospheric layers, which likely result from a magnetic reconnection leading to the flare. In addition, the cool Si IV and C II lines show gentle redshifts (a few tens of km s-1) at some other locations, which manifest some distinct features from the above locations. This is supposed to originate from a different physical process.

Keywords: solar magnetic reconnection; active solar chromosphere; solar flares; ultraviolet astronomy
Dynamical Formation Scenarios for GW190521 and Prospects for Decihertz Gravitational-wave Astronomy with GW190521-like Binaries

The gravitational-wave (GW) detection of GW190521 has provided new insights on the mass distribution of black holes and new constraints for astrophysical formation channels. With independent claims of GW190521 having significant premerger eccentricity, we investigate what this implies for GW190521-like binaries that form dynamically. The Laser Interferometer Space Antenna (LISA) will also be sensitive to GW190521-like binaries if they are circular from an isolated formation channel. However, GW190521-like binaries that form dynamically may skip the LISA band entirely. To this end, we simulate GW190521 analogs that dynamically form via post-Newtonian binary-single scattering. From these scattering experiments, we find that GW190521-like binaries may enter the LIGO-Virgo band with significant eccentricity as suggested by recent studies, though well below an eccentricity of e10 Hz ≲ 0.7. Eccentric GW190521-like binaries further motivate the astrophysical science case for a decihertz GW observatory, such as the kilometer-scale version of the Midband Atomic Gravitational-wave Interferometric Sensor. We carry out a Fisher analysis to estimate how well the eccentricity of GW190521-like binaries can be constrained with such a decihertz detector. These eccentricity constraints would also provide additional insights into the possible environments that GW190521-like binaries form in.

Keywords: gravitational waves; gravitational wave astronomy; black holes
Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). XIII. Large-scale Feedback and Star Formation in a Low-luminosity Quasar at z = 7.07 on the Local Black Hole to Host Mass Relation

We present Atacama Large Millimeter/submillimeter Array [C II] 158 μm line and underlying far-infrared (FIR) continuum emission observations (0"70 × 0"56 resolution) toward HSC J124353.93+010038.5 (J1243+0100) at z = 7.07, the only low-luminosity (M1450 > -25 mag) quasar currently known at z > 7. The FIR continuum is bright (1.52 mJy) and resolved with a total luminosity of LFIR = 3.5 × 1012 L⊙. The spatially extended component is responsible for ~40% of the emission. The area-integrated [C II] spectrum shows a broad wing (FWHM = 997 km s-1, L[C II] = 1.2 × 109 L⊙), as well as a bright core (FWHM = 235 km s-1, L[C II] = 1.9 × 109 L⊙). This wing is the first detection of a galactic-scale quasar-driven outflow (atomic outflow rate >447 M⊙ yr-1) at z > 7. The estimated large mass-loading factor of the total outflow (e.g., ≳9 relative to the [C II]-based star formation rate) suggests that this outflow will soon quench the star formation of the host. The core gas dynamics are governed by rotation, with a rotation curve suggestive of a compact bulge (~3.3 × 1010 M⊙), although it is not yet spatially resolved. Finally, we found that J1243+0100 has a black hole mass-to-dynamical mass (and -to-bulge mass) ratio of ~0.4% (~1%), consistent with the local value within the uncertainties. Our results therefore suggest that the black hole-host coevolution relation is already in place at z ~ 7 for this object.

Keywords: quasars; agn host galaxies; active galaxies; interstellar medium; submillimeter astronomy; high-redshift galaxies; galaxy evolution
The Effect of Misalignment between the Rotation Axis and Magnetic Field on the Circumstellar Disk

The formation of circumstellar disks is investigated using three-dimensional resistive magnetohydrodynamic simulations in which the initial prestellar cloud has a misaligned rotation axis with respect to the magnetic field. We examine the effects of (i) the initial angle difference between the global magnetic field and the cloud rotation axis (θ0) and (ii) the ratio of the thermal to gravitational energy (α0). We study 16 models in total and calculate the cloud evolution until ∼5000 yr after protostar formation. Our simulation results indicate that an initial nonzero θ0 (>0) promotes disk formation but tends to suppress outflow driving for models that are moderately gravitationally unstable, α0 ≲ 1. In these models, a large-sized rotationally supported disk forms and a weak outflow appears, in contrast to a smaller disk and strong outflow in the aligned case (θ0 = 0). Furthermore, we find that when the initial cloud is highly unstable with small α0, the initial angle difference θ0 does not significantly affect the disk formation and outflow driving.

Keywords: magnetohydrodynamics; star formation; protostars; stellar jets; magnetic fields; protoplanetary disks
Discovery of a Proto–White Dwarf with a Massive Unseen Companion

We report the discovery of SDSS J022932.28+713002.7, a nascent extremely low-mass (ELM) white dwarf (WD) orbiting a massive (>1 M ⊙ at 2σ confidence) companion with a period of 36 hr. We use a combination of spectroscopy, including data from the ongoing fifth-generation Sloan Digital Sky Survey (SDSS-V), and photometry to measure the stellar parameters of the primary pre-ELM WD. The lightcurve of the primary WD exhibits ellipsoidal variation, which we combine with radial velocity data and PHOEBE binary simulations to estimate the mass of the invisible companion. We find that the primary WD has mass M 1 = M ⊙ and the unseen secondary has mass M 2 = M ⊙. The mass of the companion suggests that it is most likely a near-Chandrasekhar-mass WD or a neutron star. It is likely that the system recently went through a Roche lobe overflow from the visible primary onto the invisible secondary. The dynamical configuration of the binary is consistent with the theoretical evolutionary tracks for such objects, and the primary is currently in its contraction phase. The measured orbital period puts this system on a stable evolutionary path which, within a few gigayears, will lead to a contracted ELM WD orbiting a massive compact companion.

Keywords: binary stars; white dwarf stars; neutron stars; low mass stars
Analysis of XMM-Newton Observations of Supernova Remnant W49B and Clues to the Progenitor

W49B is a supernova remnant (SNR) discovered over 60 yr ago in early radio surveys. It has since been observed over the entire wavelength range, with the X-ray morphology resembling a centrally filled SNR. The nature of its progenitor star is still debated. Applying Smoothed Particle Inference techniques to analyze the X-Ray emission from W49B, we characterize the morphology and abundance distribution over the entire remnant. We also infer the density structure and derive the mass of individual elements present in the plasma. The morphology is consistent with an interaction between the remnant and a dense medium along the eastern edge, and some obstruction toward the west. We find a total mass of 130 $(\pm 16)$ M ${}_{\odot }$ and an estimated ejecta mass of 1.2 $(\pm 0.2)$ M ${}_{\odot }$ . Comparison of the inferred abundance values and individual element masses with a wide selection of SN models suggests that deflagration-to-detonation (DDT) Type Ia models are the most compatible, with Fe abundance being the major discriminating factor. The general agreement between our abundance measurements and those from previous studies suggests that disagreement between various authors is more likely due to the choice of models used for comparison, rather than the abundance values themselves. While our abundance results lean toward a Type Ia origin, ambiguities in the interpretation of various morphological and spectral characteristics of W49B do not allow us to provide a definitive classification.

Keywords: x-ray sources; supernovae; supernova remnants; nucleosynthesis; circumstellar matter; interstellar medium
Multi-Wavelength Study of 4C+28.07

4C+28.07 is a γ-ray flat-spectrum-radio-quasar-type source. It is often monitored at different frequencies, though long-term multi-wavelength data of this source have not been modeled in detail before. We have analyzed ~12 yr (2008 August-2020 May) of Fermi-LAT data with a binning of 10 day timescale and observed three distinctive flaring states. Each flaring state consists of different phases of activity, namely, pre-flare, flare, and post-flare regions. γ-ray spectral analysis of these different activity phases has been performed and the best-fit model for its spectra is found to be a log-parabola model. We have also studied the correlation of simultaneous γ-ray light curves with the optical & radio counterparts in these flaring states and report the DCF with 95&percnt; significance level. A large time delay is found between radio and gamma-ray data for two flares, indicating two zones of emission. We have fitted the multi-wavelength data with a two-zone leptonic model. In our two-zone leptonic model the maximum required power in the jet is 9.64 × 1046 erg s-1, which is lower than its Eddington luminosity 2.29 × 1047 erg s-1.

Keywords: active galaxies; gamma-rays