adsabs/SciX_UAT_keywords huggingface dataset:
The Disk Reverberation Mapping of X-Ray Weak Quasars: A Case Study of SDSS J153913.47+395423.4

The widely adopted "lamppost" thermal reprocessing model, in which the variable UV/optical emission is a result of the accretion-disk reprocessing of the highly fluctuating X-ray emission, can be tested by measuring interband time lags in quasars spanning a range of X-ray power. This work reports the interband time lag in an apparent X-ray-weak quasar, SDSS J153913.47+395423.4. A significant cross correlation with a time delay of ~33 days (observed frame) is detected in the Zwicky Transient Facility g and r light curves of SDSS J153913.47+395423.4. The observed X-ray power seems to be too weak to account for the observed interband cross correlation with time delay. Hence the X-ray-weak quasar SDSS J153913.47+395423.4 is either intrinsically X-ray normal (but observationally X-ray weak), or the X-ray emission is not the only mechanism to drive UV/optical variability. In the former case, the required X-ray power is at least 19 times stronger than observed, which requires either an exceptionally anisotropic corona or Compton-thick obscuration. Alternatively, the corona-heated accretion-disk reprocessing or the EUV torus models may account for the observed time lags.

Keywords: supermassive black holes; quasars; accretion; active galactic nuclei
A Near-infrared-faint, Far-infrared-luminous Dusty Galaxy at z ∼ 5 in COSMOS-Web

A growing number of far-infrared (FIR) bright sources completely invisible in deep extragalactic optical surveys hint at an elusive population of z > 4 dusty, star-forming galaxies. Cycle 1 JWST surveys are now detecting their rest-frame optical light, which provides key insight into their stellar properties and statistical constraints on the population as a whole. This work presents the JWST Near Infrared Camera (NIRCam) counterpart from the COSMOS-Web survey to an FIR SCUBA-2 and Atacama Large Millimeter/submillimeter Array (ALMA) source, AzTECC71, which was previously undetected at wavelengths shorter than 850 μm. AzTECC71, among the reddest galaxies in COSMOS-Web with F277W - F444W ~ 0.9, is undetected in NIRCam/F150W and F115W and fainter in F444W than other submillimeter galaxies identified in COSMOS-Web by 2-4 magnitudes. This is consistent with the system having both a lower stellar mass and higher redshift than the median dusty, star-forming galaxy. With deep ground- and space-based upper limits combined with detections in F277W, F444W, and the FIR including ALMA Band 6, we find a high probability (99%) that AzTECC71 is at z > 4 with ${z}_{\mathrm{phot}}={5.7}_{-0.7}^{+0.8}$ . This galaxy is massive ( $\mathrm{log}\,{M}_{* }/{M}_{\odot }\sim 10.7$ ) and infrared-luminous ( $\mathrm{log}\,{L}_{\mathrm{IR}}/{L}_{\odot }\sim 12.7$ ), comparable to other optically undetected but FIR-bright dusty, star-forming galaxies at z > 4. This population of luminous, infrared galaxies at z > 4 is largely unconstrained but comprises an important bridge between the most extreme dust-obscured galaxies and more typical high-redshift star-forming galaxies. If further FIR-selected galaxies that drop out of the F150W filter in COSMOS-Web have redshifts z > 4 like AzTECC71, then the volume density of such sources may be ~3-10 × greater than previously estimated.

Keywords: far infrared astronomy; high-redshift galaxies; ultraluminous infrared galaxies; galaxy evolution
Extended X-Ray Emission in Compton Thick AGN with Deep Chandra Observations

We present the spatial analysis of five Compton thick (CT) active galactic nuclei (AGNs), including MKN 573, NGC 1386, NGC 3393, NGC 5643, and NGC 7212, for which high-resolution Chandra observations are available. For each source, we find hard X-ray emission (>3 keV) extending to ∼kiloparsec scales along the ionization cone, and for some sources, in the cross-cone region. This collection represents the first, high-signal sample of CT AGN with extended hard X-ray emission for which we can begin to build a more complete picture of this new population of AGN. We investigate the energy dependence of the extended X-ray emission, including possible dependencies on host galaxy and AGN properties, and find a correlation between the excess emission and obscuration, suggesting a connection between the nuclear obscuring material and the galactic molecular clouds. Furthermore, we find that the soft X-ray emission extends farther than the hard X-rays along the ionization cone, which may be explained by a galactocentric radial dependence on the density of molecular clouds due to the orientation of the ionization cone with respect to the galactic disk. These results are consistent with other CT AGN with observed extended hard X-ray emission (e.g., ESO 428-G014 and the Ma et al. CT AGN sample), further demonstrating the ubiquity of extended hard X-ray emission in CT AGN.

Keywords: x-ray active galactic nuclei; active galaxies; agn host galaxies
Spectroscopic Orbits of 11 Nearby, Mid-to-late M-dwarf Binaries

We present the spectroscopic orbits of 11 nearby, mid-to-late M dwarf binary systems in a variety of configurations: 2 single-lined binaries (SB1s), 7 double-lined binaries (SB2s), 1 double-lined triple (ST2), and 1 triple-lined triple (ST3). Eight of these orbits are the first published for these systems, while five are newly identified multiples. We obtained multi-epoch, high-resolution spectra with the TRES instrument on the 1.5 m Tillinghast Reflector at the Fred Lawrence Whipple Observatory located on Mt. Hopkins in AZ. Using the TiO molecular bands at 7065-7165 Å, we calculated radial velocities for these systems, from which we derived their orbits. We find LHS 1817 to have in a 7 hr period a companion that is likely a white dwarf, due to the ellipsoidal modulation we see in our MEarth-North light-curve data. We find G 123-45 and LTT 11586 to host companions with minimum masses of 41 MJup and 44 MJup with orbital periods of 35 and 15 days, respectively. We find 2MA 0930+0227 to have a rapidly rotating stellar companion in a 917 day orbital period. GJ 268, GJ 1029, LP 734-34, GJ 1182, G 258-17, and LTT 7077are SB2s with stellar companions with orbital periods of 10, 96, 34, 154, 5, and 84 days; LP 655-43 is an ST3 with one companion in an 18 day orbital period and an outer component in a longer undetermined period. In addition, we present radial velocities for both components of L 870-44AB and for the outer components of LTT 11586 and LP 655-43.

Keywords: spectroscopic binary stars; solar neighborhood; m dwarf stars; white dwarf stars; orbital elements; substellar companion stars
Confinement of the Solar Tachocline by Dynamo Action in the Radiative Interior

A major outstanding problem in solar physics is the confinement of the solar tachocline, the thin shear layer that separates nearly solid-body rotation in the radiative interior from strong differential rotation in the convection zone. Here, we present the first 3D, global solar simulation that displays a magnetically confined tachocline. The nonaxisymmetric magnetism is initially built in the convection zone and then diffusively imprints downward, similar to the proposed fast magnetic confinement scenario by the Sun's cyclic dynamo field. Additionally, the field is locally amplified throughout the radiative interior by vigorous horizontal motions that seem to arise from a combination of equatorial Rossby waves and shear, magnetic, and buoyancy instabilities. Our work thus supports prior studies proposing dynamo action in the radiative interior, and suggests that horizontal motions could play a key role in driving this deep dynamo.

Keywords: solar differential rotation; solar interior; solar convective zone; solar radiative zone; solar dynamo; internal waves; astrophysical fluid dynamics; magnetohydrodynamics; magnetohydrodynamical simulations
Open Star Clusters and Their Asymmetrical Tidal Tails

Stars that evaporate from their star cluster by the energy equipartition process end up in either a leading or a trailing tidal tail. In Newtonian gravitation and for open star clusters in the solar vicinity, the tidal threshold, or práh, for escape is symmetrical, such that the leading and trailing tails are equally populated. The data from six independent teams that applied the convergent point method to map out the tidal tails of four open clusters (the Hyades, Praesepe, Coma Berenices, and COIN-Gaia 13) using Gaia DR2 and DR3 are here applied to test for the expected symmetry. All tidal tails contain more stars in the leading tail. The combined confidence amounts to an 8σ falsification of the práh symmetry. The same test using Milgromian dynamics leads to consistency with the data. More effort needs to be exerted on this matter, but the data indicate with high confidence that the tidal práh of an open star cluster is asymmetrical, with the corresponding confidence that Newtonian gravitation is falsified. Open star clusters depopulate more rapidly in Milgromian than in Newtonian dynamics, and the COIN-Gaia 13 cluster is here found to be nearly completely dissolved. In view of these results, the wide-binary star test and the finding of a Keplerian Galactic rotation curve are briefly discussed.

Keywords: open star clusters; star clusters; tidal tails; gravitation; newtonian gravitation; modified newtonian dynamics
A Warm Jupiter Transiting an M Dwarf: A TESS Single-transit Event Confirmed with the Habitable-zone Planet Finder

We confirm the planetary nature of a warm Jupiter transiting the early M dwarf TOI-1899 using a combination of available TESS photometry; high-precision, near-infrared spectroscopy with the Habitable-zone Planet Finder; and speckle and adaptive optics imaging. The data reveal a transiting companion on an ∼29 day orbit with a mass and radius of $0.66\pm 0.07\ {M}_{{\rm{J}}}$ and ${1.15}_{-0.05}^{+0.04}\ {R}_{{\rm{J}}}$ , respectively. The star, TOI-1899, is the lowest-mass star known to host a transiting warm Jupiter, and we discuss the follow-up opportunities afforded by a warm ( ${T}_{\mathrm{eq}}\sim 362$ K) gas giant orbiting an M0 star. Our observations reveal that TOI-1899.01 is a puffy warm Jupiter, and we suggest additional transit observations to both refine the orbit and constrain the true dilution observed in TESS.

Keywords: exoplanets
A2626 and Friends: Large- and Small-scale Structure

New MMT/Hectospec spectroscopy centered on the galaxy cluster A2626 and covering a ~1.8 deg2 area out to z ~ 0.46 more than doubles the number of galaxy redshifts in this region. The spectra confirm four clusters previously identified photometrically. A2625, which was previously thought to be a close neighbor of A2626, is in fact much more distant. The new data show six substructures associated with A2626 and five more associated with A2637. There is also a highly collimated collection of galaxies and galaxy groups between A2626 and A2637 having at least three and probably four substructures. At larger scales, the A2626-A2637 complex is not connected to the Pegasus-Perseus filament.

Keywords: galaxy clusters; galaxy spectroscopy; abell clusters; redshift surveys
The Diagnostic Potential of JWST in Characterizing Elusive AGNs

It is now clear that a significant population of accreting black holes are undetected by commonly employed optical, mid-infrared color, X-ray, and radio selection methods as a result of obscuration or contamination of the emission from the nuclear region caused by star formation in the host galaxy. These elusive active galactic nuclei (AGNs) are an important component of the AGN population. They are often found in mergers, where significant black hole growth likely takes place, and in the lowest-mass galaxies or galaxies that lack classical bulges, a demographic that places important constraints on models of supermassive black hole seed formation and merger-free models of AGN fueling. In this work, we demonstrate the power of the James Webb Space Telescope (JWST) in uncovering and characterizing these elusive AGNs. We present an integrated modeling approach in which both the line and emergent continuum are predicted from gas exposed to the ionizing radiation from a young starburst and an AGN, focusing specifically on the spectral diagnostics available through JWST, and provide predictions on the detectability of key diagnostic lines by the near- and mid-infrared spectrometers, assuming typical conditions for the gas. We demonstrate the crucial need for JWST in uncovering low-level accretion activity even in nearby galaxies and out to redshifts of ≈1-3, depending on the ionization parameter, and gas phase metallicity. We present a redshift-dependent selection strategy that can be used to identify promising elusive AGN candidates for future follow-up study. The full suite of simulations is available online, where users can select specific parameters and retrieve the predicted continuum and infrared line luminosities from our models.

Keywords: active galactic nuclei; low-luminosity active galactic nuclei; agn host galaxies; interstellar medium; photoionization; infrared astronomy; galaxy mergers; astrophysical black holes; intermediate-mass black holes
Convective Penetration in Early-type Stars

Observations indicate that the convective cores of stars must ingest a substantial amount of material from the overlying radiative zone, but the extent of this mixing and the mechanism that causes it remain uncertain. Recently, Anders et al. developed a theory of convective penetration and calibrated it with 3D numerical hydrodynamics simulations. Here we employ that theory to predict the extent of convective boundary mixing (CBM) in early-type main-sequence stars. We find that convective penetration produces enough mixing to explain core masses inferred from asteroseismology and eclipsing binary studies, and matches observed trends in mass and age. While there are remaining uncertainties in the theory, this agreement suggests that most CBM in early-type main-sequence stars arises from convective penetration. Finally, we provide a fitting formula for the extent of core convective penetration for main-sequence stars in the mass range from 1.1-60 M ⊙.

Keywords: stellar physics; stellar evolutionary models; stellar convective zones
Where Did the Outskirts Go? Outer Stellar Halos as a Sensitive Probe of Supernova Feedback

A recent comparison by Merritt of simulated and observed Milky Way-mass galaxies has identified a significant tension between the outskirts (r > 20 kpc) of the stellar halos in simulated and observed galaxies. Using observations from the Dragonfly telescope and simulated galaxies from the Illustris-TNG100 project, Merritt found that the outskirts of stellar halos in simulated galaxies have surface densities 1-2 dex higher than those of observed galaxies. In this paper, we compare two suites of 15 simulated Milky Way-like galaxies, each drawn from the same initial conditions, simulated with the same hydrodynamical code, but with two different models for feedback from supernovae. We find that the McMaster Unbiased Galaxy Simulations (MUGS), which use an older "delayed-cooling" model for feedback, also produce too much stellar mass in the outskirts of the halo, with median surface densities well above observational constraints. The MUGS2 simulations, which instead use a new, physically motivated "superbubble" model for stellar feedback, have 1-2 dex lower outer stellar halo masses and surface densities. The MUGS2 simulations generally match both the median surface density profile as well as the scatter in stellar halo surface density profiles seen in observed stellar halos. We conclude that there is no "missing outskirts" problem in cosmological simulations, provided that supernova feedback is modeled in a way that allows it to efficiently regulate star formation in the low-mass progenitor environments of stellar halo outskirts.

Keywords: galaxy stellar halos; astronomical simulations; galaxy structure; galaxy formation; stellar feedback
Precise Ages of Field Stars from White Dwarf Companions in Gaia DR2

We analyze 4050 wide binary star systems involving a white dwarf (WD) and usually a main-sequence (MS) star, drawn from the large sample assembled by Tian et al. Using the modeling code BASE-9, we determine the system's ages, the WD progenitors' zero-age MS masses, the extinction values (AV), and the distance moduli. Discarding the cases with poor age convergences, we obtain ages for 3551 WDs, with a median age precision of στ/τ = 20%, and system ages typically in the range of 1-6 Gyr. We validated these ages against the very few known clusters and through cross validation of 236 WD-WD binaries. Under the assumption that the components are coeval in a binary system, this provides precise age constraints on the usually low-mass MS companions, mostly inaccessible by any other means.

Keywords: stellar ages; wide binary stars; field stars; markov chain monte carlo; bayesian statistics; main sequence stars; white dwarf stars; zero-age main sequence stars; stellar evolutionary tracks; initial mass function; photometry
Cosmic-Ray Convection-Diffusion Anisotropy

Under nonuniform convection, the distribution of diffusive particles can exhibit dipole and quadrupole anisotropy induced by the fluid inertial and shear force, respectively. These convection-related anisotropies, unlike the Compton-Getting effect, typically increase with the cosmic-ray (CR) energy, and are thus candidate contributors for the CR anisotropy. In consideration of the inertial effect, CR observational data can be used to set an upper limit on the average acceleration of the local interstellar medium in the equatorial plane to be on the order of 100 μm s-2. Using Oort constants, the quadrupole anisotropy above 200 TeV may be modeled with the shear effect arising from the Galactic differential rotation.

Keywords: high energy astrophysics; particle astrophysics; cosmic rays; galactic cosmic rays; cosmic ray astronomy; interstellar medium; interstellar dynamics; interstellar plasma; intergalactic gas
Nonlinear Wave-Wave Coupling Related to Whistler-mode and Electron Bernstein Waves Observed by the Parker Solar Probe

We report nonlinear wave-wave coupling related to whistler-mode or electron Bernstein waves in the near-Sun slow solar wind with Parker Solar Probe (PSP) data. Prominent plasma wave power enhancements usually exist near the electron gyrofrequency (fce), identified as electrostatic whistler-mode and electron Bernstein waves (Malaspina et al. 2020). We find that these plasma waves near fce typically have a harmonic spectral structure and further classify them into three types identified by the characteristics of wave frequency and electric power. For short, we will call these type I, type II, and type III waves. The first (type I) is the quasi-electrostatic whistler-mode wave and its second harmonic, which resembles the quasi-electrostatic multiband chorus in the Earth's magnetosphere. The second (type II) is the pure electron Bernstein wave. The last (type III) is an intermixture of whistler-mode and electron Bernstein waves, where the wave mode driven by the coupling between them was also detected. During the first five orbits of PSP, the type III spectra have the largest occurrence rate, then the type I spectra. The type II spectra are the rarest type of wave. Our study reveals that nonlinear wave-wave coupling in the solar wind may be as common as in the Earth's magnetosphere.

Keywords: solar wind
Observational Signatures of Planets in Protoplanetary Disks: Temperature Structures in Spiral Arms

High-resolution imaging of protoplanetary disks has unveiled a rich diversity of spiral structure, some of which may arise from disk-planet interaction. Using 3D hydrodynamics with β cooling to a vertically stratified background, as well as radiative-transfer modeling, we investigate the temperature rise in planet-driven spirals. In rapidly cooling disks, the temperature rise is dominated by a contribution from stellar irradiation, 0.3%-3% inside the planet radius but always < 0.5% outside. When cooling time equals or exceeds dynamical time, however, this is overwhelmed by hydrodynamic PdV work, which introduces a ~10%-20% perturbation within a factor of ~2 from the planet's orbital radius. We devise an empirical fit of the spiral amplitude ${\rm{\Delta }}{(T)=({M}_{p}/{M}_{\mathrm{th}})}^{c}({f}_{{PdV}}{e}^{-{t}_{\mathrm{arm}}/{t}_{c}}+{f}_{\mathrm{rad}})$ to take into account both effects. Where cooling is slow, we find also that temperature perturbations from buoyancy spirals-a strictly 3D, nonisothermal phenomenon-become nearly as strong as those from Lindblad spirals, which are amenable to 2D and isothermal studies. Our findings may help explain observed thermal features in disks like TW Hydrae and CQ Tauri, and underscore that 3D effects have a qualitatively important effect on disk structure.

Keywords: protoplanetary disks; hydrodynamical simulations; exoplanet detection methods
An Oversized Magnetic Sheath Wrapping around the Parsec-scale Jet in 3C 273

In recent studies, several active galactic nuclei (AGNs) have exhibited gradients of the Faraday rotation measure (RM) transverse to their parsec-scale jet direction. Faraday rotation likely occurs as a result of a magnetized sheath wrapped around the jet. In the case of 3C 273, using Very Long Baseline Array multiepoch observations at 5, 8, and 15 GHz in 2009-2010, we observe that the jet RM has changed significantly toward negative values compared with that previously observed. These changes could be explained by a swing of the parsec-scale jet direction, which causes synchrotron emission to pass through different portions of the Faraday screen. We develop a model for the jet-sheath system in 3C 273 where the sheath is wider than the single-epoch narrow relativistic jet. We present our oversized sheath model together with a derived wide-jet full intrinsic opening angle αint = 2°1 and magnetic field strength B∣∣ = 3 μG, and thermal particle density Ne = 125 cm-3 at the wide jet-sheath boundary 230 pc downstream (deprojected) from its beginning. Most of the Faraday rotation occurs within the innermost layers of the sheath. The model brings together the jet direction swing and long-term RM evolution and may be applicable to other AGN jets that exhibit changes in their apparent jet direction.

Keywords: radio loud quasars; polarimetry; very long baseline interferometry; relativistic jets; radio jets; active galactic nuclei; blazars; quasars
Scaling K2. V. Statistical Validation of 60 New Exoplanets From K2 Campaigns 2-18

The NASA K2 mission, salvaged from the hardware failures of the Kepler telescope, has continued Kepler's planet-hunting success. It has revealed nearly 500 transiting planets around the ecliptic plane, many of which are the subject of further study, and over 1000 additional candidates. Here we present the results of an ongoing project to follow-up and statistically validate new K2 planets, in particular to identify promising new targets for further characterization. By analyzing the reconnaissance spectra, high-resolution imaging, centroid variations, and statistical likelihood of the signals of 91 candidates, we validate 60 new planets in 46 systems. These include a number of planets amenable to transmission spectroscopy (K2-384 f, K2-387 b, K2-390 b, K2-403 b, and K2-398 c), emission spectroscopy (K2-371 b, K2-370 b, and K2-399 b), and both (K2-405 b and K2-406 b); several systems with planets in or close to mean motion resonances (K2-381 and K2-398) including a compact, TRAPPIST-1-like system of five small planets orbiting a mid-M dwarf (K2-384); an ultra-short-period sub-Saturn in the hot Saturn desert (K2-399 b); and a super-Earth orbiting a moderately bright (V = 11.93), metal-poor ([Fe/H] = -0.579 ± 0.080) host star (K2-408 b). In total we validate planets around four F stars, 26 G stars, 13 K stars, and three M dwarfs. In addition, we provide a list of 37 vetted planet candidates that should be prioritized for future follow-up observation in order to be confirmed or validated.

Keywords: exoplanet catalogs; exoplanet systems