Sazuna/UAT_keywords huggingface dataset:
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, Exoplanets, Astrostatistics, Exoplanet evolution, Low mass stars, Radial velocity, Exoplanet formation
Detection and Classification of Astronomical Targets with Deep Neural Networks in Wide-field Small Aperture Telescopes. Wide-field small aperture telescopes are widely used for optical transient observations. Detection and classification of astronomical targets in observed images are the most important and basic step. In this paper, we propose an astronomical target detection and classification framework based on deep neural networks. Our framework adopts the concept of the Faster R-CNN and uses a modified Resnet-50 as a backbone network and a feature pyramid network to extract features from images of different astronomical targets. To increase the generalization ability of our framework, we use both simulated and real observation images to train the neural network. After training, the neural network could detect and classify astronomical targets automatically. We test the performance of our framework with simulated data and find that our framework has almost the same detection ability as that of the traditional method for bright and isolated sources and our framework has two times better detection ability for dim targets, albeit all celestial objects detected by the traditional method can be classified correctly. We also use our framework to process real observation data and find that our framework can improve 25% detection ability than that of the traditional method when the threshold of our framework is 0.6. Rapid discovery of transient targets is quite important and we further propose to install our framework in embedded devices such as the Nvidia Jetson Xavier to achieve real-time astronomical targets detection and classification abilities.

Keywords: Astrostatistics techniques, Convolutional neural networks, Transient detection, Classification
Fourth-order Coronagraph for High-contrast Imaging of Exoplanets with Off-axis Segmented Telescopes. We propose a coronagraphic system with fourth-order null for off-axis segmented telescopes, which is sufficiently insensitive to the telescope pointing errors and finite angular diameter of the host star to enable high-contrast imaging of potentially habitable planets. The inner working angle of the coronagraphic system is close to 1λ/D, and there is no outer limit. The proposed coronagraphic system is made up of a new focal plane mask and an optimized Lyot stop with the second-order null. The new focal plane mask is an extension of the band-limited masks with a phase modulation. We construct a coronagraphic system with fourth-order null by placing two of the new coronagraph systems in succession to be orthogonal to each other. The proposed system is limited to narrow-band usage. The characteristics of the proposed coronagraph system are derived analytically, which includes (1) the leak of stellar lights due to the finite stellar diameter and pointing jitter of a telescope, and (2) the peak throughput. We achieve the performance simulations of this coronagraphic system based on these analytical expressions, considering a monochromatic light of 0.75 μm and an off-axis primary mirror with a diameter of 8.5 m. Thanks to the wide working area of the mask, the result shows that terrestrial planets orbiting K and G dwarfs can be detected under the condition that the telescope pointing jitter is less than 0.01λ/D ≈ 240 as. The proposed coronagraphic system is promising for the detection of potentially habitable planets with future space off-axis hexagonally segmented telescopes.

Keywords: Observational astronomy, Pointing error, Pointing accuracy, Exoplanets, Exoplanet astronomy, Coronagraphic imaging, Astronomical techniques, Astrobiology, Direct imaging, Exoplanet detection methods, Biosignatures, Habitable planets
A Multiwavelength Search for Intrinsic Linear Polarization in Wolf-Rayet Winds. Wolf-Rayet stars have strong, hot winds, with mass-loss rates at least a factor of 10 greater than their O-star progenitors, although their terminal wind speeds are similar. In this paper, we use the technique of multiband linear polarimetry to extract information on the global asymmetry of the wind in a sample of 47 bright Galactic WR stars. Our observations also include time-dependent observations of 17 stars in the sample. The path to our goal includes removing the dominating component of wavelength-dependent interstellar polarization (ISP), which normally follows the well-known Serkowski law. We include a wavelength-dependent ISP position angle parameter in our ISP law and find that 15 stars show significant results for this parameter. We detect a significant component of wavelength-independent polarization due to electron scattering in the wind for 10 cases, with most WR stars showing none at the ∼0.05% level precision of our data. The intrinsically polarized stars can be explained with binary interaction, large-scale wind structure, and clumping. We also found that 5 stars out of 19 observed with the Strömgren b filter (probing the complex λ4600-4700 emission-line region) have significant residuals from the ISP law and propose that this is due to wind asymmetries. We provide a useful catalog of ISP for 47 bright Galactic WR stars and upper limits on the possible level of intrinsic polarization.

Keywords: Binary stars, Surveys, Massive stars, Astronomical reference materials, Wolf-Rayet stars, Polarimetry
Disk-integrated Thermal Properties of Ceres Measured at Millimeter Wavelengths. We observed Ceres at three epochs in 2015 November and 2017 September and October with Atacama Large Millimeter/submillimeter Array (ALMA) 12 m array and in 2017 October with the ALMA Compact Array (ACA), all at ∼265 GHz continuum (wavelengths of ∼1.1 mm) to map the temperatures of Ceres over a full rotation at each epoch. We also used 2017 October ACA observations to search for HCN. The disk-averaged brightness temperature of Ceres is measured to be between 170 and 180 K during our 2017 observations. The rotational light curve of Ceres shows a double-peaked shape with an amplitude of about 4%. Our HCN search returns a negative result with an upper limit production rate of ∼2 × 1024 molecules s-1, assuming globally uniform production and a Haser model. A thermophysical model suggests that Ceres's top layer has higher dielectric absorption than lunar-like materials at a wavelength of 1 mm. However, previous observations showed that the dielectric absorption of Ceres decreases toward longer wavelengths. Such distinct dielectric properties might be related to the hydrated phyllosilicate composition of Ceres and possibly abundant micrometer-sized grains on its surface. The thermal inertia of Ceres is constrained by our modeling as likely being between 40 and 160 thermal inertia units, much higher than previous measurements at infrared wavelengths. Modeling also suggests that Ceres's light curve is likely dominated by spatial variations in its physical or compositional properties that cause changes in Ceres's observed thermal properties and dielectric absorption as it rotates.

Keywords: Ceres, Main belt asteroids, Asteroids, Small Solar System bodies
Low-mass Group Environments Have No Substantial Impact on the Circumgalactic Medium Metallicity. We explore how environment affects the metallicity of the circumgalactic medium (CGM) using 13 low-mass galaxy groups (two to five galaxies) at $\langle {z}_{\mathrm{abs}}\rangle =0.25 identified near background quasars. Using quasar spectra from the Hubble Space Telescope/COS and from Keck/HIRES or the Very Large Telescope/UVES, we measure column densities of or determine limits on CGM absorption lines. We use a Markov Chain Monte Carlo approach with Cloudy to estimate metallicities of cool (T ∼ 104 K) CGM gas within groups and compare them to CGM metallicities of 47 isolated galaxies. Both group and isolated CGM metallicities span a wide range (-2 &lt; [Si/H] &lt; 0), where the mean group (-0.54 ± 0.22) and isolated (-0.77 ± 0.14) CGM metallicities are similar. Group and isolated environments have similar distributions of ${\rm{H}}\,{\rm{I}} column densities as a function of impact parameter. However, contrary to isolated galaxies, we do not find an anticorrelation between ${\rm{H}}\,{\rm{I}} column density and the nearest group galaxy impact parameter. We additionally divided the groups by member luminosity ratios (i.e., galaxy-galaxy and galaxy-dwarf groups). While there was no significant difference in their mean metallicities, a modest increase in sample size should allow one to statistically identify a higher CGM metallicity in galaxy-dwarf groups compared to galaxy-galaxy groups. We conclude that either environmental effects have not played an important role in the metallicity of the CGM at this stage and expect that this may only occur when galaxies are strongly interacting or merging or that some isolated galaxies have higher CGM metallicities due to past interactions. Thus, environment does not seem to be the cause of the CGM metallicity bimodality.

Keywords: Galaxy environments, Metallicity, Quasar absorption line spectroscopy, Circumgalactic medium
Nodal Precession in Closely Spaced Planet Pairs. Planet-planet perturbations can cause planets' orbital elements to change on secular timescales. Previous work has evaluated the nodal precession rate for planets in the limit of low α (semimajor axis ratio; 0 &lt; α ≤ 1). Our simulations show that systems at high α (or low period ratio), similar to multiplanet systems found in the Kepler survey, have a nodal precession rate that is more strongly dependent on eccentricity and inclination. We present a complete expansion of the nodal precession rate to fourth order in the disturbing function and show that this analytical solution much better describes the simulated N-body behavior of high-α planet pairs; at α ≈ 0.5, the higher-order solution, on average, reduces the median analytical error by a factor of 7.5 from linear theory and 6.2 from a similar expansion assuming low α. We set limits on eccentricity and inclination where the theory is precisely validated by N-body integrations, which can be useful in future secular treatments of planetary systems.

Keywords: Exoplanet dynamics, Orbits, Exoplanet systems, Ascending node, Analytical mathematics, Celestial mechanics, Three-body problem, N-body simulations
Faint and Fading Tails: The Fate of Stripped H I Gas in Virgo Cluster Galaxies. Although many galaxies in the Virgo cluster are known to have lost significant amounts of H I gas, only about a dozen features are known where the H I extends significantly outside its parent galaxy. Previous numerical simulations have predicted that H I removed by ram pressure stripping should have column densities far in excess of the sensitivity limits of observational surveys. We construct a simple model to try and quantify how many streams we might expect to detect. This accounts for the expected random orientation of the streams in position and velocity space as well as the expected stream length and mass of stripped H I. Using archival data from the Arecibo Galaxy Environment Survey, we search for any streams that might previously have been missed in earlier analyses. We report the confident detection of 10 streams as well as 16 other less-certain detections. We show that these well match our analytic predictions for which galaxies should be actively losing gas; however, the mass of the streams is typically far below the amount of missing H I in their parent galaxies, implying that a phase change and/or dispersal renders the gas undetectable. By estimating the orbital timescales, we estimate that dissolution rates of 1-10 M ${}_{\odot } yr-1 are able to explain both the presence of a few long, massive streams and the greater number of shorter, less-massive features.

Keywords: Galaxy clusters, Virgo Cluster, Galaxy dynamics, Galaxy evolution, Intracluster medium
Securing the Legacy of TESS through the Care and Maintenance of TESS Planet Ephemerides. Much of the science from the exoplanets detected by the Transiting Exoplanet Survey Satellite (TESS) mission relies on precisely predicted transit times that are needed for many follow-up characterization studies. We investigate ephemeris deterioration for simulated TESS planets and find that the ephemerides of 81% of those will have expired (i.e., 1σ mid-transit time uncertainties greater than 30 minutes) 1 yr after their TESS observations. We verify these results using a sample of TESS planet candidates as well. In particular, of the simulated planets that would be recommended as James Webb Space Telescope (JWST) targets by Kempton et al., ∼80% will have mid-transit time uncertainties &gt;30 minutes by the earliest time JWST would observe them. This rapid deterioration is driven primarily by the relatively short time baseline of TESS observations. We describe strategies for maintaining TESS ephemerides fresh through follow-up transit observations. We find that the longer the baseline between the TESS and the follow-up observations, the longer the ephemerides stay fresh, and that 51% of simulated primary mission TESS planets will require space-based observations. The recently approved extension to the TESS mission will rescue the ephemerides of most (though not all) primary mission planets, but the benefits of these new observations can only be reaped 2 yr after the primary mission observations. Moreover, the ephemerides of most primary mission TESS planets (as well as those newly discovered during the extended mission) will again have expired by the time future facilities such as the ELTs, Ariel, and the possible LUVOIR/Origins Space Telescope missions come online, unless maintenance follow-up observations are obtained.

Keywords: Surveys, Ephemerides, Transits, Exoplanets
WIYN Open Cluster Study LXXIX. M48 (NGC 2548) I. Radial Velocities, Rotational Velocities, and Metallicities of Stars in the Open Cluster M48 (NGC 2548). WIYN/Hydra spectra (R ∼ 13,500, signal-to-noise pixel-1 = 50-1000) of a 400 Å region around Li 6708 Å are used to determine radial and rotational velocities for 287 photometrically selected candidate members of the open cluster M48. The sample ranges from turnoff A stars to late-K dwarfs and eight giants. We combine our VRAD measurements and power spectrum analysis with parallax and proper motion data from Gaia DR2 to evaluate membership and multiplicity. We classify 152 stars as single cluster members, 11 as binary members, 16 as members of uncertain multiplicity, 56 as single nonmembers, 28 as single "likely" nonmembers, two as single "likely" members, one as a binary "likely" member, five as binary nonmembers, 10 as "likely" members of uncertain multiplicity, three as nonmembers of uncertain multiplicity, and three as "likely" nonmembers of uncertain multiplicity. From a subsample of 95 single members, we derive VRAD = 8.512 ± 0.087 km s-1 (σμ, and σ = 0.848 km s-1). Using 16 isolated Fe I lines for a subsample of 99 single members (that have ${\sigma }_{{T}_{\mathrm{eff}}}\lt 75 K (from 10 colors from UBVRI), v sin i &lt; 25 km s-1, and well-behaved Fe I lines), [Fe/H]M48 = -0.063 ± 0.007 dex (σμ). [Fe/H] is independent of Teff over an unprecedentedly large range of 2500 K. The minimum cluster binary fraction is 11%-21%. M48 exhibits a clear but modest broadening of the main-sequence turnoff, and there is no correlation between color and v sin i.

Keywords: Stellar abundances, Stellar effective temperatures, Radial velocity, Open star clusters, Metallicity
Chandra Resolves the Double FU Orionis System RNO 1B/1C in X-Rays. We present new Chandra X-ray observations of the close pair of young stars RNO 1B and 1C (6″ separation) located in the L1287 cloud. RNO 1B erupted in 1978-1990 and is classified as an FU Orionis star (FUor). RNO 1C also shows most of the properties of an FUor but no eruption has been seen yet. Only a few dozen FUors are known and the presence of two such objects with a small angular separation is rare, suggesting a common origin. Both stars were faintly detected by Chandra and we summarize their X-ray properties within the framework of other previously detected FUors. We also report other X-ray detections in L1287 including the deeply embedded young star RNO 1G, the jet-like radio source VLA 3, and an enigmatic hard flaring source with no Two Micron All Sky Survey counterpart that was only detected in the second of the two Chandra exposures.

Keywords: T Tauri stars, Young stellar objects, FU Orionis stars
Accretion Properties of PDS 70b with MUSE. We report a new evaluation of the accretion properties of PDS 70b obtained with the Very Large Telescope/Multi Unit Spectroscopic Explorer. The main difference from the previous studies of Haffert et al. and Aoyama &amp; Ikoma is in the mass accretion rate. Simultaneous multiple line observations, such as Hα and Hβ, can better constrain the physical properties of an accreting planet. While we clearly detected Hα emissions from PDS 70b, no Hβ emissions were detected. We estimate the line flux of Hβ with a 3σ upper limit to be 2.3 × 10-16 erg s-1 cm-2. The flux ratio FHβ/FHα for PDS 70b is &lt;0.28. Numerical investigations by Aoyama et al. suggest that FHβ/FHα should be close to unity if the extinction is negligible. We attribute the reduction of the flux ratio to the extinction, and estimate the extinction of Hα (AHα) for PDS 70b to be &gt;2.0 mag using the interstellar extinction value. By combining with the Hα linewidth and the dereddening line luminosity of Hα, we derive the PDS 70b mass accretion rate to be ≳5 × 10-7 MJup yr-1. The PDS 70b mass accretion rate is an order of magnitude larger than that of PDS 70. We found that the filling factor ff (the fractional area of the planetary surface emitting Hα) is ≳0.01, which is similar to the typical stellar value. The small value of ff indicates that the Hα emitting areas are localized at the surface of PDS 70b.

Keywords: Accretion, Exoplanet formation, Direct imaging
Robustly Detecting Changes in Warm Jupiters' Transit Impact Parameters. Torques from a mutually inclined perturber can change a transiting planet's impact parameter, resulting in variations in the transit shape and duration. Detection of and upper limits on changes in impact parameter yield valuable constraints on a planetary system's three-dimensional architecture. Constraints for warm Jupiters are particularly interesting because they allow us to test origins theories that invoke a mutually inclined perturber. Because of warm Jupiters' high signal-to-noise ratio transits, it is feasible to detect changes in impact parameter. However, here we show that allowing the impact parameter to vary uniformly and independently from transit to transit leads to incorrect inferences about the change, propagating to incorrect inferences about the perturber. We demonstrate that an appropriate prior on the change in impact parameter mitigates this problem. We apply our approach to eight systems from the literature and find evidence for changes in impact parameter for warm Jupiter Kepler-46b. We conclude with our recommendations for light-curve fitting, including when to fit impact parameters versus transit durations.

Keywords: Transit photometry, Transit duration variation method, Extrasolar gaseous giant planets, Exoplanets
Kepler Data Analysis: Non-Gaussian Noise and Fourier Gaussian Process Analysis of Stellar Variability. We develop a statistical analysis model of Kepler stellar flux data in the presence of planet transits, non-Gaussian noise, and stellar variability. We first develop a model for the Kepler noise probability distribution in the presence of outliers, which make the noise probability distribution non-Gaussian. We develop a signal likelihood analysis based on this probability distribution, in which we model the signal as a sum of the star variability and planetary transits. We argue that these components need to be modeled together if optimal signal is to be extracted from the data. For the stellar variability model we develop an optimal Gaussian process analysis using a Fourier-based Wiener filter approach, where the power spectrum is non-parametric and learned from the data. We develop high dimensional optimization of the objective function, where we jointly optimize all the model parameters, including thousands of star variability modes, and planet transit parameters. We apply the method to Kepler-90 data and show that it gives a better match to the stellar variability than the existing methods, and robustly handles noise outliers. As a consequence, the planet radii have a higher value than what the existing methods give, including splines and celerite.

Keywords: Astronomy data modeling, Astronomy data analysis, Exoplanet astronomy, Non-Gaussianity, Exoplanet detection methods
Smaller than Expected Bright-spot Offsets in Spitzer Phase Curves of the Hot Jupiter Qatar-1b. We present Spitzer full-orbit thermal phase curves of the hot Jupiter Qatar-1b, a planet with the same equilibrium temperature -- and intermediate surface gravity and orbital period -- as the well-studied planets HD 209458b and WASP-43b. We measure secondary eclipse depths of 0.21 ± 0.02% at 3.6 μm and 0.30 ± 0.02% at 4.5 μm, corresponding to dayside brightness temperatures of ${1542}_{-31}^{+32} K and ${1557}_{-36}^{+35} K, respectively, consistent with a vertically isothermal dayside. The respective nightside brightness temperatures are ${1117}_{-71}^{+76} and ${1167}_{-74}^{+69} K, in line with a trend that hot Jupiters all have similar nightside temperatures. We infer a Bond albedo of ${0.12}_{-0.16}^{+0.14} and a moderate day-night heat recirculation efficiency, similar to HD 209458b. General circulation models for HD 209458b and WASP-43b predict that their bright spots should be shifted east of the substellar point by tens of degrees, and these predictions were previously confirmed with Spitzer full-orbit phase curve observations. The phase curves of Qatar-1b are likewise expected to exhibit eastward offsets. Instead, the observed phase curves are consistent with no offset: 11° ± 7° at 3.6 μm and -4° ± 7° at 4.5 μm. The discrepancy in circulation patterns between these three otherwise similar planets points to the importance of secondary parameters like rotation rate and surface gravity, and the presence or absence of clouds, in determining atmospheric conditions on hot Jupiters.

Keywords: Light curves, Extrasolar gaseous giant planets, Hot Jupiters, Exoplanet atmospheres