adsabs/SciX_UAT_keywords huggingface dataset:
Around Which Stars Can TESS Detect Earth-like Planets? The Revised TESS Habitable Zone Catalog

In the search for life in the cosmos, NASA's Transiting Exoplanet Survey Satellite (TESS) mission has already monitored about 74% of the sky for transiting extrasolar planets, including potentially habitable worlds. However, TESS only observed a fraction of the stars long enough to be able to find planets like Earth. We use the primary mission data—the first two years of observations—and identify 4239 stars within 210 pc that TESS observed long enough to see three transits of an exoplanet that receives similar irradiation to Earth: 738 of these stars are located within 30 pc. We provide reliable stellar parameters from the TESS Input Catalog that incorporates Gaia DR2 and also calculate the transit depth and radial velocity semiamplitude for an Earth-analog planet. Of the 4239 stars in the Revised TESS HZ Catalog, 9 are known exoplanet hosts—GJ1061, GJ1132, GJ3512, GJ685, Kepler-42, LHS1815, L98-59, RRCae, and TOI700—around which TESS could identify additional Earth-like planetary companions. Thirty-seven additional stars host yet unconfirmed TESS Objects of Interest: three of these orbit in the habitable zone—TOI203, TOI715, and TOI2298. For a subset of 614 of the 4239 stars, TESS has observed the star long enough to be able to observe planets throughout the full temperate, habitable zone out to the equivalent of Mars' orbit. Thus, the Revised TESS Habitable Zone Catalog provides a tool for observers to prioritize stars for follow-up observation to discover life in the cosmos. These stars are the best path toward the discovery of habitable planets using the TESS mission data.

Keywords: exoplanet catalogs; exoplanet astronomy; exoplanet detection methods; transits; astrobiology; sky surveys; habitable planets; observational astronomy; biosignatures; exoplanets
Understanding the Velocity Distribution of the Galactic Bulge with APOGEE and Gaia

We revisit the stellar velocity distribution in the Galactic bulge/bar region with Apache Point Observatory Galactic Evolution Experiment DR16 and Gaia DR2, focusing in particular on the possible high-velocity (HV) peaks and their physical origin. We fit the velocity distributions with two different models, namely with Gauss-Hermite polynomials and Gaussian mixture models (GMMs). The result of the fit using Gauss-Hermite polynomials reveals a positive correlation between the mean velocity ( $\,\overline{V}$ ) and the "skewness" (h3) of the velocity distribution, possibly caused by the Galactic bar. The n = 2 GMM fitting reveals a symmetric longitudinal trend of ∣μ2∣ and σ2 (the mean velocity and the standard deviation of the secondary component), which is inconsistent with the x2 orbital family predictions. Cold secondary peaks could be seen at ∣l∣ ∼ 6°. However, with the additional tangential information from Gaia, we find that the HV stars in the bulge show similar patterns in the radial-tangential velocity distribution (VR-VT), regardless of the existence of a distinct cold HV peak. The observed VR-VT (or VGSR-μl) distributions are consistent with the predictions of a simple Milky Way bar model. The chemical abundances and ages inferred from ASPCAP and CANNON suggest that the HV stars in the bulge/bar are generally as old as, if not older than, the other stars in the bulge/bar region.

Keywords: milky way dynamics; galactic bulge
Bayesian Evidence for a Nonlinear Damping Model for Coronal Loop Oscillations

Recent observational and theoretical studies indicate that the damping of solar coronal loop oscillations depends on the oscillation amplitude. We consider two mechanisms: linear resonant absorption and a nonlinear damping model. We confront theoretical predictions from these models with observed data in the plane of observables defined by the damping ratio and the oscillation amplitude. The structure of the Bayesian evidence in this plane displays a clear separation between the regions where each model is more plausible relative to the other. There is qualitative agreement between the regions of high marginal likelihood and Bayes factor for the nonlinear damping model and the arrangement of observed data. A quantitative application to 101 loop oscillation cases observed with Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) results in the marginal likelihood for the nonlinear model being larger in the majority of them. The cases with conclusive evidence for the nonlinear damping model outnumber considerably those in favor of linear resonant absorption.

Keywords: magnetohydrodynamics; solar coronal loops; solar coronal seismology; bayesian statistics; bayes factor
The Dusty Heart of NGC 4151 Revealed by λ ∼ 1-40 μm Reverberation Mapping and Variability: A Challenge to Current Clumpy Torus Models

We probe the dusty environment of the archetypical Type 1 active galactic nucleus (AGN) in NGC 4151 with comprehensive IR reverberation mapping over several decades, in the J (∼1.22 μm), H (∼1.63 μm), K (∼2.19 μm), L (∼3.45 μm), and N bands (∼10.6 μm), plus multiple measurements at 20-40 μm. At 1-4 μm, the hot dust reverberation signals come from two distinct dust populations at separate radii (∼0.033 pc and ∼0.076 pc), with temperatures of ∼1500-2500 K and ∼900-1000 K, consistent with the expected properties of sublimating graphite and silicate dust grains. The domination of the torus infrared output by carbon and silicate grains near their sublimation temperatures and radii may account for the general similarity of AGN near-IR spectral energy distributions. The torus inner edge defined by the hottest dust remains at roughly the same radius independent of the AGN optical luminosity over ∼25 yr. The emission by hot dust warmed directly by the optical/UV AGN output has increased gradually by ∼4% yr-1, indicating a possibly growing torus. A third dust component at ∼700 K does not seem to participate directly in the IR reverberation behavior, and its emission may originate deep in the circumnuclear torus. We find a reverberation signal at ∼10 μm with an inferred radius for the warm dust of ∼2.2-3.1 pc. The lack of variability at 20-40 μm indicates that the far-IR emission comes from even more extended regions. The torus properties revealed by dust reverberation analysis are inconsistent with predictions from pure clumpy torus models. Instead, the longer-wavelength emission possibly originates in a flared torus or the polar wind.

Keywords: active galactic nuclei; dust continuum emission; reverberation mapping; galaxy nuclei; interstellar dust; extragalactic astronomy; seyfert galaxies
Self-organized Criticality in Stellar Flares

Power-law size distributions are the hallmarks of nonlinear energy dissipation processes governed by self-organized criticality (SOC). Here we analyze 75 data sets of stellar flare size distributions, mostly obtained from the Extreme-Ultraviolet Explorer and the Kepler mission. We aim to answer the following questions for size distributions of stellar flares. (i) What are the values and uncertainties of power-law slopes? (ii) Do power-law slopes vary with time? (iii) Do power-law slopes depend on the stellar spectral type? (iv) Are they compatible with solar flares? (v) Are they consistent with SOC models? We find that the observed size distributions of stellar flare fluences (or energies) exhibit power-law slopes of αE = 2.09 ± 0.24 for optical data sets observed with Kepler. The observed power-law slopes do not show much time variability and do not depend on the stellar spectral type (M, K, G, F, A, giants). In solar flares, we find that background subtraction lowers the uncorrected value of αE = 2.20 ± 0.22 to αE = 1.57 ± 0.19. Furthermore, most of the stellar flares are temporally not resolved in low-cadence (30 minutes) Kepler data, which causes an additional bias. Taking these two biases into account, the stellar flare data sets are consistent with the theoretical prediction $N(x)\propto {x}^{-{\alpha }_{x}}$ of SOC models, i.e., αE = 1.5. Thus, accurate power-law fits require automated detection of the inertial range and background subtraction, which can be modeled with the generalized Pareto distribution, finite-system size effects, and extreme event outliers.

Keywords: stellar activity; stellar flares; solar flares; astrostatistics
Modeling Stochastic Variability in Multiband Time-series Data

In preparation for the era of time-domain astronomy with upcoming large-scale surveys, we propose a state-space representation of a multivariate damped random walk process as a tool to analyze irregularly-spaced multifilter light curves with heteroscedastic measurement errors. We adopt a computationally efficient and scalable Kalman filtering approach to evaluate the likelihood function, leading to maximum $O({k}^{3}n)$ complexity, where k is the number of available bands and n is the number of unique observation times across the k bands. This is a significant computational advantage over a commonly used univariate Gaussian process that can stack up all multiband light curves in one vector with maximum $O({k}^{3}{n}^{3})$ complexity. Using such efficient likelihood computation, we provide both maximum likelihood estimates and Bayesian posterior samples of the model parameters. Three numerical illustrations are presented: (i) analyzing simulated five-band light curves for a comparison with independent single-band fits; (ii) analyzing five-band light curves of a quasar obtained from the Sloan Digital Sky Survey Stripe 82 to estimate short-term variability and timescale; (iii) analyzing gravitationally lensed g- and r-band light curves of Q0957+561 to infer the time delay. Two R packages, Rdrw and timedelay, are publicly available to fit the proposed models.

Keywords: astrostatistics; interdisciplinary astronomy; astrostatistics tools
A Wide-orbit Exoplanet OGLE-2012-BLG-0838Lb

We present the discovery of a planet on a very wide orbit in the microlensing event OGLE-2012-BLG-0838. The signal of the planet is well separated from the main peak of the event and the planet-star projected separation is found to be twice the Einstein ring radius, which corresponds to a projected separation of ≈4 au. Similar planets around low-mass stars are very hard to find using any technique other than microlensing. We discuss microlensing model fitting in detail and discuss the prospects for measuring the mass and distance of the lens system directly.

Keywords: exoplanet detection methods; extrasolar ice giants
Rapid Dust Growth during Hydrodynamic Clumping due to Streaming Instability

Streaming instability is considered to be one of the dominant processes in promoting planetesimal formation by the gravitational collapse of dust clumps. The development of streaming instability is expected to form dust clumps in which the local dust density is strongly enhanced and even greater than the Roche density. The resulting clumps can collapse to form planetesimals. Recent simulations showed that such strong clumping occurs in a wider parameter space than previously expected. However, the indicated timescale for strong clumping can be on the order of tens to hundreds of Keplerian periods. In this paper, we estimate the growth time of dust grains during the pre-clumping phase. We find that the dust growth proceeds considerably before the strong clumping because even the moderate clumping due to streaming instability increases the local dust-to-gas ratio to ≳10. Depending on the sound speed, the dust collision velocity can be kept below ~1 m s-1 once sufficiently strong dust clumping occurs. Thus, even silicate grains might have the potential to grow safely toward the size whose Stokes number is unity during the clumping. Our results demonstrate the importance of local dust coagulation during dust clumping due to streaming instability.

Keywords: protoplanetary disks; planetesimals
Temporal and Spectral Properties of the Persistent Radio Source Associated with FRB 20190520B with the VLA

Among more than 800 known fast radio bursts (FRBs), only two, namely FRB 20121102A and FRB 20190520B, are confirmed to be associated with persistent radio sources (PRSs). Here, we report evidence of apparent temporal variability in the PRS associated with the bursting FRB 20190520B based on Karl G. Jansky Very Large Array observations taken in 2020 and 2021. Based on the analysis of the epoch-to-epoch variability of the PRS at the L, S, C, and X bands (1-12 GHz), we detected not only overall marginal variability, but also a likely radio flux decrease (σ ~ 3.2) between the observations taken in 2020 and 2021 at 3 GHz. Assuming no spectral variation in the PRS during these observations, we found evidence for an overall broadband radio flux decrease by about 20% between the 2020 and the 2021 observations, suggesting that the PRS probably evolves on a yearly timescale. If we attribute the marginal variability at 3 GHz as intrinsic or due to scintillation, the size of the potential variable component of the PRS is constrained to be subparsec. On the other hand, the size of the PRS can be also constrained to ≳0.22 pc from the time-averaged radio spectrum and the integrated radio luminosity in the 1-12 GHz band, based on equipartition and self-absorption arguments. We discuss the potential origins of the PRS and suggest that an accreting compact object origin might be able to explain the PRS's temporal and spectral properties. Confirmation of the variability or flux decline of the PRS will be critical for our understanding of the PRS and its relation to the bursting source.

Keywords: radio transient sources; radio bursts
Retrieving Internal Kinematics of Galaxies with Deep Learning Using Single-band Optical Images

Using deep machine learning we show that the internal velocities of galaxies can be retrieved from optical images trained using 4596 systems observed with the SDSS-MaNGA survey. Using only i-band images we show that the velocity dispersions and the rotational velocities of galaxies can be measured to an accuracy of 29 km s-1 and 69 km s-1 respectively, close to the resolution limit of the spectroscopic data. This shows that galaxy structures in the optical holds important information concerning the internal properties of galaxies, and that the internal kinematics of galaxies are quantitatively reflected in their stellar light distributions.

Keywords: galaxy classification systems; convolutional neural networks; galaxy structure
Sunspot Shearing and Sudden Retraction Motion Associated with the 2013 August 17 M3.3 Flare

In this Letter, we give a detailed analysis of the M3.3 class flare that occurred on 2013 August 17 (SOL2013-08-17T18:16). It presents a clear picture of mutual magnetic interaction initially from the photosphere to the corona via the abrupt rapid shearing motion of a small sunspot before the flare, and then suddenly from the corona back to the photosphere via the sudden retraction motion of the same sunspot during the flare's impulsive phase. About 10 hr before the flare, a small sunspot in the active region NOAA 11818 started to move northeast along a magnetic polarity inversion line (PIL), creating a shearing motion that changed the quasi-static state of the active region. A filament right above the PIL was activated following the movement of the sunspot and then got partially erupted. The eruption eventually led to the M3.3 flare. The sunspot was then suddenly pulled back to the opposite direction upon the flare onset. During the backward motion, the Lorentz force underwent a simultaneous impulsive change both in magnitude and direction. Its directional change is found to be conformable with the retraction motion. The observation provides direct evidence for the role of the shearing motion of the sunspot in powering and triggering the flare. It especially confirms that the abrupt motion of a sunspot during a solar flare is the result of a backreaction caused by the reconfiguration of the coronal magnetic field. *Released on May 10, 2022.

Keywords: solar flares; sunspots
Chemistry Along Accretion Streams in a Viscously Evolving Protoplanetary Disk

The composition of a protoplanetary disk is set by a combination of interstellar inheritance and gas and grain surface chemical reactions within the disk. The survival of inherited molecules, as well as the disk in situ chemistry depends on the local temperature, density and irradiation environment, which can change over time due to stellar and disk evolution, as well as transport in the disk. We address one aspect of this coupling between the physical and chemical evolution in disks by following accretion streamlines of gas and small grains in the disk midplane, while simultaneously taking the evolving star into account. This approach is computationally efficient and enables us to take into account changing physical conditions without reducing the chemical network. We find that many species are enhanced in the inner disk midplane in the dynamic model due to inward transport of cosmic-ray driven chemical products, resulting in, e.g., orders of magnitude hydrocarbon enhancements at 1 au, compared to a static disk. For several other chemical families, there is no difference between the static and dynamic models, indicative of a robust chemical reset, while yet others show differences between static and dynamic models that depend on complex interactions between physics and chemistry during the inward track. The importance of coupling dynamics and chemistry when modeling the chemical evolution of protoplanetary disks thus depends on what chemistry is of interest.

Keywords: protoplanetary disks; stellar accretion disks; astrochemistry
Influence of Jets on [O III] Extensions in Green Pea/Bean Galaxies

We present a study investigating the influence of jets on galaxies exhibiting strong [O III]λ5007 emission, known as Green Peas and Green Beans. Our sample comprised 12 nearby sources (z ~ 0.04-0.1, six with jets and six without jets) with high [O III] luminosity (L ~ 1040 erg s-1), selected from a radio-selected galaxy sample observed with the Sloan Digital Sky Survey and Radio Sky at Twenty-centimeters survey. We perform Large Binocular Telescope-Multi-Object Double Spectrograph long-slit spectroscopy at two position angles for each galaxy: one aligned with the jet direction and another perpendicular to it. By tracing the [O III] emission along these slits, we aimed to assess the extension of the narrow line region and examine the impact of jets. Surprisingly, our analysis revealed no preferred direction for the extension of the [O III] emission, indicating that jets have a limited influence on the extended emission line regions (EELRs). This also suggests the possibility of missed detection of conical-shaped EELRs aligned with the jets, attributable to our slit orientations. Furthermore, we compared the extension of [O II] emission, which traces star-forming regions, with that of [O III]. We observed a significant difference, with [O II] exhibiting a considerably greater extension along the galactic plane. This suggests a stronger association of [O II] emission with stellar processes.

Keywords: extragalactic astronomy; emission line galaxies; active galaxies
The Properties of Fast Yellow Pulsating Supergiants: FYPS Point the Way to Missing Red Supergiants

Fast yellow pulsating supergiants (FYPS) are a recently discovered class of evolved massive pulsators. As candidate supergiant objects, and one of the few classes of pulsating evolved massive stars, these objects have incredible potential to change our understanding of the structure and evolution of massive stars. Here we examine the lightcurves of a sample of 126 cool supergiants in the Magellanic Clouds observed by the Transiting Exoplanet Survey Satellite in order to identify pulsating stars. After making quality cuts and filtering out contaminant objects, we examine the distribution of pulsating stars in the Hertzprung-Russel (HR) diagram, and find that FYPS occupy a region above $\mathrm{log}L/{L}_{\odot }\gtrsim 5.0$ . This luminosity boundary corresponds to stars with initial masses of ~18-20 M ⊙, consistent with the most massive red supergiant progenitors of supernovae (SNe) II-P, as well as the observed properties of SNe IIb progenitors. This threshold is in agreement with the picture that FYPS are post-RSG stars. Finally, we characterize the behavior of FYPS pulsations as a function of their location in the HR diagram. We find low-frequency pulsations at higher effective temperatures, and higher-frequency pulsations at lower temperatures, with a transition between the two behaviors at intermediate temperatures. The observed properties of FYPS make them fascinating objects for future theoretical study.

Keywords: massive stars; stellar evolution; asteroseismology; stellar pulsations; stellar mass loss; type ii supernovae; red supergiant stars; late-type supergiant stars; yellow hypergiant stars; hertzsprung russell diagram
Evolution of the Radius Valley around Low-mass Stars from Kepler and K2

We present calculations of the occurrence rate of small close-in planets around low-mass dwarf stars using the known planet populations from the Kepler and K2 missions. Applying completeness corrections clearly reveals the radius valley in the maximum a posteriori occurrence rates as a function of orbital separation and planet radius. We measure the slope of the valley to be ${r}_{p,\mathrm{valley}}\propto {F}^{-0.060\pm 0.025}, which bears the opposite sign from that measured around Sun-like stars, thus suggesting that thermally driven atmospheric mass loss may not dominate the evolution of planets in the low stellar mass regime or that we are witnessing the emergence of a separate channel of planet formation. The latter notion is supported by the relative occurrence of rocky to non-rocky planets increasing from 0.5 ± 0.1 around mid-K dwarfs to 8.5 ± 4.6 around mid-M dwarfs. Furthermore, the center of the radius valley at 1.54 ± 0.16 R⊕ is shown to shift to smaller sizes with decreasing stellar mass, in agreement with physical models of photoevaporation, core-powered mass loss, and gas-poor formation. Although current measurements are insufficient to robustly identify the dominant formation pathway of the radius valley, such inferences may be obtained by the Transiting Exoplanet Survey Satellite with ${ \mathcal O } (85,000) mid-to-late M dwarfs observed with 2 minutes cadence. The measurements presented herein also precisely designate the subset of planetary orbital periods and radii that should be targeted in radial velocity surveys to resolve the rocky to non-rocky transition around low-mass stars.

Keywords: transits; radial velocity; exoplanets; low mass stars; exoplanet formation; exoplanet evolution; astrostatistics
The Relationship between Chirality, Sense of Rotation, and Hemispheric Preference of Solar Eruptive Filaments

The orientation, chirality, and dynamics of solar eruptive filaments are key to our understanding of the magnetic field of coronal mass ejections (CMEs), and therefore to predicting the geoeffectiveness of CMEs arriving at Earth. However, confusion and contention remain over the relationship between the filament chirality, magnetic helicity, and the sense of rotation during eruption. To resolve the ambiguity in observations, in this paper we used stereoscopic observations to determine the rotation direction of filament apex and the method proposed by Chen et al. to determine the filament chirality. Our sample of 12 eruptive active-region filaments establishes a strong one-to-one relationship, I.e., during the eruption, sinistral/dextral filaments (located in the southern/northern hemisphere) rotate clockwise/counterclockwise when viewed from above, and corroborates a weak hemispheric preference, I.e., a filament and related sigmoid both exhibit a forward (reverse) S shape in the southern (northern) hemisphere, which suggests that the sigmoidal filament is associated with a low-lying magnetic flux rope with its axis dipped in the middle. As a result of rotation, the projected S shape of a filament is anticipated to be reversed during eruption.

Keywords: solar filament eruptions; solar filaments