adsabs/SciX_UAT_keywords huggingface dataset:
BASS. XXX. Distribution Functions of DR2 Eddington Ratios, Black Hole Masses, and X-Ray Luminosities

We determine the low-redshift X-ray luminosity function, active black hole mass function (BHMF), and Eddington ratio distribution function (ERDF) for both unobscured (Type 1) and obscured (Type 2) active galactic nuclei (AGNs), using the unprecedented spectroscopic completeness of the BAT AGN Spectroscopic Survey (BASS) data release 2. In addition to a straightforward 1/V max approach, we also compute the intrinsic distributions, accounting for sample truncation by employing a forward-modeling approach to recover the observed BHMF and ERDF. As previous BHMFs and ERDFs have been robustly determined only for samples of bright, broad-line (Type 1) AGNs and/or quasars, ours are the first directly observationally constrained BHMF and ERDF of Type 2 AGNs. We find that after accounting for all observational biases, the intrinsic ERDF of Type 2 AGNs is significantly more skewed toward lower Eddington ratios than the intrinsic ERDF of Type 1 AGNs. This result supports the radiation-regulated unification scenario, in which radiation pressure dictates the geometry of the dusty obscuring structure around an AGN. Calculating the ERDFs in two separate mass bins, we verify that the derived shape is consistent, validating the assumption that the ERDF (shape) is mass-independent. We report the local AGN duty cycle as a function of mass and Eddington ratio, by comparing the BASS active BHMF with the local mass function for all supermassive black holes. We also present the of the Swift/BAT 70 month sources.

Keywords: supermassive black holes; quasars; active galactic nuclei; high energy astrophysics; active galaxies; x-ray active galactic nuclei; x-ray surveys; luminosity function; accretion
The Influence of Tidal Heating on the Habitability of Planets Orbiting White Dwarfs

In recent years, there have been a growing number of observations indicating the presence of rocky material in short-period orbits around white dwarfs. In this Letter, we revisit the prospects for habitability around these post-main-sequence star systems. In addition to the typically considered radiative input luminosity, potentially habitable planets around white dwarfs are also subjected to significant tidal heating. The combination of these two heating sources can, for a narrow range of planetary properties and orbital parameters, continuously maintain surface temperatures amenable for habitability for planets around white dwarfs over timescales up to 10 Gyr. We show that for a specific locus of orbital parameter space, tidal heating can substantially extend the timescale of continuous habitability for a planet around a white dwarf.

Keywords: white dwarf stars; exoplanet dynamics; habitable zone
GeV Signatures of Short Gamma-Ray Bursts in Active Galactic Nuclei

The joint detection of gravitational waves and the gamma-ray counterpart of a binary neutron star merger event, GW170817, unambiguously validates the connection between short gamma-ray bursts and compact binary object (CBO) mergers. We focus on a special scenario where short gamma-ray bursts produced by CBO mergers are embedded in disks of active galactic nuclei (AGNs), and we investigate the γ-ray emission produced in the internal dissipation region via synchrotron, synchrotron self-Compton, and external inverse Compton (EIC) processes. In this scenario, isotropic thermal photons from the AGN disks contribute to the EIC component. We show that a low-density cavity can be formed in the migration traps, leading to the embedded mergers producing successful GRB jets. We find that the EIC component would dominate the GeV emission for typical CBO mergers with an isotropic-equivalent luminosity of L j,iso = 1048.5 erg s-1 that are located close to the central supermassive black hole. Considering a long-lasting jet of duration T dur ~ 102-103 s, we find that the future Cherenkov Telescope Array (CTA) will be able to detect its 25-100 GeV emission out to a redshift z = 1.0. In the optimistic case, it is possible to detect the on-axis extended emission simultaneously with GWs within one decade using MAGIC, H.E.S.S., VERITAS, CTA, and LHAASO-WCDA. Early diagnosis of prompt emissions with Fermi-GBM and HAWC can provide valuable directional information for the follow-up observations.

Keywords: gamma-ray bursts; active galactic nuclei; non-thermal radiation sources; compact binary stars
Simulating the Photospheric to Coronal Plasma Using Magnetohydrodynamic Characteristics. I. Data-driven Boundary Conditions

We develop a general description of how information propagates through a magnetohydrodynamic (MHD) system based on the method of characteristics and use that to formulate numerical boundary conditions that are intrinsically consistent with the MHD equations. Our formulation includes two major advances for simulations of the Sun. First, we derive data-driven boundary conditions that optimally match the state of the plasma inferred from a time series of observations of a boundary (e.g., the solar photosphere). Second, our method directly handles random noise and systematic bias in the observations, and finds a solution for the boundary evolution that is strictly consistent with MHD and maximally consistent with the observations. We validate the method against a Ground Truth (GT) simulation of an expanding spheromak. The data-driven simulation can reproduce the GT simulation above the photosphere with high fidelity when driven at high cadence. Errors progressively increase for lower driving cadence until a threshold cadence is reached and the driven simulation can no longer accurately reproduce the GT simulation. However, our characteristic formulation of the boundary conditions still requires adherence of the boundary evolution to the MHD equations even when the driven solution departs from the true solution in the driving layer. That increasing departure clearly indicates when additional information at the boundary is needed to fully specify the correct evolution of the system. The method functions even when no information about the evolution of some variables on the lower boundary is available, albeit with a further decrease in fidelity.

Keywords: solar physics; solar magnetic fields; magnetohydrodynamical simulations; solar photosphere; solar corona; solar chromosphere; magnetohydrodynamics; solar magnetic flux emergence; emerging flux tubes
Monte-Carlo Neutrino Transport in Neutron Star Merger Simulations

Gravitational waves and electromagnetic signals from merging neutron star binaries provide valuable information about the the properties of dense matter, the formation of heavy elements, and high-energy astrophysics. To fully leverage observations of these systems, we need numerical simulations that provide reliable predictions for the properties of the matter unbound in these mergers. An important limitation of current simulations is the use of approximate methods for neutrino transport that do not converge to a solution of the transport equations as numerical resolution increases, and thus have errors that are impossible to quantify. Here, we report on a first simulation of a binary neutron star merger that uses Monte-Carlo techniques to directly solve the transport equations in low-density regions. In high-density regions, we use approximations inspired by implicit Monte-Carlo to greatly reduce the cost of simulations, while only introducing errors quantifiable through more expensive convergence studies. We simulate an unequal mass neutron star binary merger up to 5 ms past merger, and report on the properties of the matter and neutrino outflows. Finally, we compare our results to the output of our best approximate "M1" transport scheme, demonstrating that an M1 scheme that carefully approximates the neutrino energy spectrum only leads to ∼10% uncertainty in the composition and velocity of the ejecta, and ∼20% uncertainty in the νe and ${\bar{\nu }}_{e}$ luminosities and energies. The most significant disagreement found between M1 and Monte-Carlo results is a factor of ∼2 difference in the luminosity of heavy-lepton neutrinos.

Keywords: r-process; neutron stars; gravitational wave sources; computational methods; computational astronomy
OGLE-2015-BLG-1771Lb: A Microlens Planet Orbiting an Ultracool Dwarf?

We report the discovery and the analysis of the short ( ${t}_{{\rm{E}}}\lt 5$ days) planetary microlensing event, OGLE-2015-BLG-1771. The event was discovered by the Optical Gravitational Lensing Experiment, and the planetary anomaly (at I ∼ 19) was captured by The Korea Microlensing Telescope Network. The event has three surviving planetary models that explain the observed light curves, with planet-host mass ratio q ∼ 5.4 × 10-3, 4.5 × 10-3 and 4.5 × 10-2, respectively. The first model is the best-fit model, while the second model is disfavored by Δχ2 ∼ 3. The last model is strongly disfavored by Δχ2 ∼ 15 but not ruled out. A Bayesian analysis using a Galactic model indicates that the first two models are probably composed of a Saturn-mass planet orbiting a late M dwarf, while the third one could consist of a super-Jovian planet and a mid-mass brown dwarf. The source-lens relative proper motion is μrel ∼ 9 mas yr-1, so the source and lens could be resolved by current adaptive-optics instruments in 2020 if the lens is luminous.

Keywords: gravitational microlensing exoplanet detection
A Study of Particle Acceleration in Blazar Jets

The particle acceleration of blazar jets is crucial to high-energy astrophysics, yet the acceleration mechanism division in blazar subclasses and the underlying nature of these mechanisms remain elusive. In this work, we utilized the synchrotron spectral information (synchrotron peak frequency, $\mathrm{log}{\nu }_{\mathrm{sy}}$ , and corresponding curvature, b sy) of 2705 blazars from the literature and studied the subject of particle acceleration in blazar jets by analyzing the correlation between $\mathrm{log}{\nu }_{\mathrm{sy}}$ and 1/b sy. Our results suggested that the entire sample follows an energy-dependent probability acceleration (EDPA). Specifically, the low inverse Compton peak sources (LCPs) follow the mechanism of fluctuations of fractional gain acceleration (FFGA), while the high inverse Compton peak sources (HCPs) follow an acceleration mechanism of EDPA. Our results indicated that the separation between LCPs and HCPs results from the electron peak Lorentz factor (γ p), and the differentiation should originate from different acceleration mechanisms. Moreover, our study revealed a transition in the acceleration mechanism from FFGA to EDPA around $\mathrm{log}{\nu }_{\mathrm{sy}}\sim 15$ through a detailed analysis of binned- $\mathrm{log}{\nu }_{\mathrm{sy}}$ . The mechanism of FFGA dominates the particle acceleration in LCP jets because of stronger jets and the EDPA dominates the particle energy gain in the HCPs due to a more efficient acceleration process.

Keywords: blazars; relativistic jets
The Evolution of Accreting Binaries: From Brown Dwarfs to Supermassive Black Holes

Circumbinary accretion occurs throughout the universe, from the formation of stars and planets to the aftermath of major galactic mergers. We present an extensive investigation of circumbinary accretion disks, studying circular binaries with mass ratios (q ≡ M 2/M 1) from 0.01 to 1 and at each mass ratio probing the effects of disk thickness and viscosity. We study disks with aspect ratios H/r ∈ {0.1, 0.05, 0.03} and vary both the magnitude and spatial dependence of viscosity. Although thin accretion disks have previously been found to promote rapid inspirals of equal-mass binaries, we find that gravitational torques become weaker at lower mass ratios and most binaries with 0.01 ≤ q ≤ 0.04 outspiral, which may delay the coalescence of black hole binaries formed from minor mergers and cause high-mass exoplanets to migrate outward. However, in a number of cases, the disks accreting onto binaries with mass ratios ∼0.07 fail to develop eccentric modes, leading to extremely rapid inspirals. Variability in black hole accretion correlates with disk eccentricity, and we observe variability above the ∼10% level even for mass ratios of 0.01. We demonstrate that the spatial dependence of the viscosity (e.g., α vs. constant ν) significantly affects the degree of preferential accretion onto the secondary, resolving discrepancies between previous studies. Colder circumbinary disks remain eccentric even at q ∼ 0.01 and sustain deep, asymmetric cavities.

Keywords: active galactic nuclei; accretion; supermassive black holes; hydrodynamical simulations; binary stars; exoplanet migration
A Collage of Small Planets from the Lick-Carnegie Exoplanet Survey: Exploring the Super-Earth and Sub-Neptune Mass Regime

Analysis of new precision radial velocity (RV) measurements from the Lick Automated Planet Finder and Keck HIRES has yielded the discovery of three new exoplanet candidates orbiting the nearby stars HD 190007 and HD 216520. We also report new velocities from the APF and the Planet Finder Spectrograph and updated orbital fits for the known exoplanet host stars GJ 686 and HD 180617. Of the newly discovered planets, HD 190007 b has a period of P = 11.72 days, an RV semiamplitude of K = 5.64 ± 0.55 m s-1, a minimum mass of Mpl = 16.46 ± 1.66 M⊕, and orbits the slightly metal-rich, active K4V star HD 190007. For HD 216520 b, we find P = 35.45 days, K = 2.28 ± 0.20 m s-1, and Mpl = 10.26 ± 0.99 M⊕, while for HD 216520 c, P = 154.43 days, K = 1.29 ± 0.22 m s-1, and Mpl = 9.44 ± 1.63 M⊕. Both planets orbit the slightly metal-poor, inactive K0V star HD 216520. Our updated best-fit models for HD 180617 b and GJ 686 b are in good agreement with the published results. For HD 180617 b, we obtain P = 105.91 days and Mpl = 12.214 ± 1.05 M⊕. For GJ 686 b, we find P = 15.53 days and Mpl = 6.624 ± 0.432 M⊕. Using an injection-recovery exercise, we find that HD 190007 b and HD 216520 b are unlikely to have additional planets with masses and orbital periods within a factor of 2, in marked contrast to ∼85% of planets in this mass and period range discovered by Kepler. * This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: exoplanet astronomy; exoplanet detection methods; exoplanets; radial velocity; mini neptunes
Flashlights: Properties of Highly Magnified Images Near Cluster Critical Curves in the Presence of Dark Matter Subhalos

Dark matter subhalos with extended profiles and density cores, and globular star clusters of mass 106–108 M ⊙ that live near the critical curves in galaxy cluster lenses can potentially be detected through their lensing magnification of stars in background galaxies. In this work, we study the effect such subhalos have on lensed images, and compare to the case of more well-studied microlensing by stars and black holes near critical curves. We find that the cluster density gradient and the extended mass distribution of subhalos are important in determining image properties. Both lead to an asymmetry between the image properties on the positive- and negative-parity sides of the cluster that is more pronounced than in the case of microlensing. For example, on the negative-parity side, subhalos with cores larger than about 50 pc do not generate any images with magnification above ∼100 outside of the immediate vicinity of the cluster critical curve. We discuss these factors using analytical and numerical analysis, and exploit them to identify observable signatures of subhalos: Subhalos create pixel-to-pixel flux variations of ≳0.1 mag on the positive-parity side of clusters. These pixels tend to cluster around (otherwise invisible) subhalos. Unlike in the case of microlensing, signatures of subhalo lensing can be found up to 1″ away from the critical curves of massive clusters.

Keywords: galaxy clusters; gravitational lensing
A Model of Rotating Convection in Stellar and Planetary Interiors. II. Gravito-inertial Wave Generation

Gravito-inertial waves are excited at the interface of convective and radiative regions and by the Reynolds stresses in the bulk of the convection zones of rotating stars and planets. Such waves have notable asteroseismic signatures in the frequency spectra of rotating stars, particularly among rapidly rotating early-type stars, which provides a means of probing their internal structure and dynamics. They can also transport angular momentum, chemical species, and energy from the excitation region to where they dissipate in radiative regions. To estimate the excitation and convective parameter dependence of the amplitude of those waves, a monomodal model for stellar and planetary convection as described in Paper I is employed, which provides the magnitude of the rms convective velocity as a function of rotation rate. With this convection model, two channels for wave driving are considered: excitation at a boundary between convectively stable and unstable regions and excitation due to Reynolds stresses. Parameter regimes are found where the sub-inertial waves may carry a significant energy flux, depending upon the convective Rossby number, the interface stiffness, and the wave frequency. The super-inertial waves can also be enhanced, but only for convective Rossby numbers near unity. Interfacially excited waves have a peak energy flux near the lower cutoff frequency when the convective Rossby number of the flows that excite them are below a critical Rossby number that depends upon the stiffness of the interface, whereas that flux decreases when the convective Rossby number is larger than this critical Rossby number.

Keywords: stellar convective zones; stellar oscillations; stellar dynamics; stellar physics; stellar rotation
On the Hubble Constant Tension in the SNe Ia Pantheon Sample

The Hubble constant (H0) tension between Type Ia supernovae (SNe Ia) and Planck measurements ranges from 4 to 6σ. To investigate this tension, we estimate H0 in the ΛCDM and ${w}_{0}{w}_{a}$ CDM (cold dark matter) models by dividing the Pantheon sample, the largest compilation of SNe Ia, into 3, 4, 20, and 40 bins. We fit the extracted H0 values with a function mimicking the redshift evolution: $g{(z)={H}_{0}(z)={\tilde{H}}_{0}/(1+z)}^{\alpha }$ , where α indicates an evolutionary parameter and ${\tilde{H}}_{0}={H}_{0}$ at z = 0. We set the absolute magnitude of SNe Ia so that ${H}_{0}\,=73.5\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ , and we fix fiducial values for ${{\rm{\Omega }}}_{0m}^{{\rm{\Lambda }}\mathrm{CDM}}=0.298$ and ${{\rm{\Omega }}}_{0m}^{{w}_{0}{w}_{a}\mathrm{CDM}}=0.308$ . We find that H0 evolves with redshift, showing a slowly decreasing trend, with α coefficients consistent with zero only from 1.2 to 2.0σ. Although the α coefficients are compatible with zero in 3σ, this however may affect cosmological results. We measure locally a variation of ${H}_{0}(z=0)-{H}_{0}(z=1)=0.4\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ in three and four bins. Extrapolating ${H}_{0}(z)$ to z = 1100, the redshift of the last scattering surface, we obtain values of H0 compatible in 1σ with Planck measurements independent of the cosmological models and number of bins we investigated. Thus, we have reduced the H0 tension in the range from 54% to 72% for both cosmological models. If the decreasing trend of ${H}_{0}(z)$ is real, it could be due to astrophysical selection effects or to modified gravity.

Keywords: type ia supernovae
Polytropic Index of the Solar Wind Ions Near the Earth Calculated Using a Homogeneous Magnetohydrodynamic Bernoulli Integral

This paper, using the data of Cluster during 2001-2010, studies the polytropic processes of solar wind ions near the Earth. We calculate the polytropic index of ions for different outward electromagnetic energy ratios δE×B and entropy parameter changes δentropy based on the approach of the homogeneous magnetohydrodynamic Bernoulli integral (MBI). Solar wind ions have a broad distribution of polytropic indices with multiple peaks in the range of [-7.0, 6.0]. The median polytropic indices are 1.264, 1.321, and 1.418 at δentropy = 5% for δE×B ≤ 5%, 3%, and 1% and 1.241 and 1.097 at δE×B ≤ 5% for δentropy ≤ 3% and 1%. In most of the dayside, the median polytropic index of the solar wind basically increases with increasing geocentric distance and has an obvious dawn-dusk asymmetry because of the solar wind-magnetosphere interaction. The polytropic indices near the bow shock are basically within the range from ∼-1.0 to ∼3.0, and their median values are between 0.5 and 1.3. Those polytropic indices of solar wind ions far away from the bow shock are basically in the range from ∼-2.0 to ∼6.0 and have median values between 1.6 and 2.2. Near the terminator, the median polytropic index has no obvious radial distribution, but it has an obvious dawn-dusk asymmetry. The above results suggest that polytropic indices in the solar wind become smaller after being scattered or rebounded by a fast shock wave. It is also found that the polytropic processes in the solar wind near the Earth are closely related to those in the magnetosheath.

Keywords: solar wind; plasma physics; solar physics
Mercury's Circumsolar Dust Ring as an Imprint of a Recent Impact

A circumsolar dust ring has been recently discovered close to the orbit of Mercury. There are currently no hypotheses for the origin of this ring in the literature, so we explore four different origin scenarios here: the dust originated from (1) the sporadic meteoroid complex that comprises the major portion of the Zodiacal Cloud, (2) recent asteroidal/cometary activity, (3) hypothetical dust-generating bodies locked in mean-motion resonances beyond Mercury, and (4) bodies co-orbiting with Mercury. We find that only scenario (4) reproduces the observed structure and location of Mercury's dust ring. However, the lifetimes of Mercury's co-orbitals (<20 Ma) preclude a primordial origin of the co-orbiting source population due to dynamical instabilities and meteoroid bombardment, demanding a recent event feeding the observed dust ring. We find that an impact on Mercury can eject debris into the co-orbital resonance. We estimate the ages of six candidate impacts that formed craters larger than 40 km in diameter using high-resolution spacecraft data from MESSENGER and find two craters with estimated surface ages younger than 50 Ma. We find that the amount of mass transported from Mercury's surface into the co-orbital resonance from these two impacts is several orders of magnitude smaller than what is needed to explain the magnitude of Mercury's ring inferred from remote sensing. Therefore we suggest that numerous younger, smaller impacts collectively contributed to the origin of the ring. We conclude that the recent impact hypothesis for the origin of Mercury's dust ring is a viable scenario, whose validity can be constrained by future inner solar system missions.

Keywords: meteoroid dust clouds; interplanetary dust; zodiacal cloud; mercury (planet); asteroids; impact phenomena; planetary surfaces; craters; orbital resonances
Oscillations of Hypermassive Compact Stars with Gravitational Radiation and Viscosity

Binary neutron star mergers, such as the multimessenger GW170817 event, may produce hypermassive compact objects that are supported against collapse by the internal circulation of the fluid within the star. We compute their unstable modes of oscillations driven by gravitational-wave radiation and shear viscosity, modeling them as triaxial Riemann ellipsoids. We work in a perturbative regime, where the gravitational radiation-reaction force is taken into account at 2.5-post-Newtonian order and find unstable modes with dissipation timescales ≳1 ms that are relevant to the transient state of a hypermassive remnant of a merger. We show that the secular instabilities are dominated by gravitational-wave radiation. If the shear viscosity is included, it can increase the growth times or even stabilize the unstable modes, but it must have values several orders of magnitude larger than predicted for cold neutron stars.

Keywords: neutron stars; stellar oscillations; gravitational waves