Sazuna/UAT_keywords huggingface dataset:
OGLE-2018-BLG-0567Lb and OGLE-2018-BLG-0962Lb: Two Microlensing Planets through the Planetary-caustic Channel. We present the analyses of two microlensing events, OGLE-2018-BLG-0567 and OGLE-2018-BLG-0962. In both events, the short-lasting anomalies were densely and continuously covered by two high-cadence surveys. The light-curve modeling indicates that the anomalies are generated by source crossings over the planetary caustics induced by planetary companions to the hosts. The estimated planet/host separation (scaled to the angular Einstein radius θE) and mass ratio are (s, q × 103) = (1.81 ± 0.02, 1.24 ± 0.07) and (s, q × 103) = (1.25 ± 0.03, 2.38 ± 0.08), respectively. From Bayesian analyses, we estimate the host and planet masses as $({M}_{{\rm{h}}},{M}_{{\rm{p}}})=({0.25}_{-0.13}^{+0.27}\,{M}_{\odot },{0.32}_{-0.17}^{+0.34}\,{M}_{{\rm{J}}})$ and $({M}_{{\rm{h}}},{M}_{{\rm{p}}})=({0.54}_{-0.28}^{+0.33}\,{M}_{\odot },{1.34}_{-0.70}^{+0.82}\,{M}_{{\rm{J}}})$ , respectively. These planetary systems are located at a distance of ${7.06}_{-1.15}^{+0.93}\,\mathrm{kpc}$ for OGLE-2018-BLG-0567 and ${6.50}_{-1.75}^{+1.06}\,\mathrm{kpc}$ for OGLE-2018-BLG-0962, suggesting that they are likely to be near the Galactic bulge. The two events prove the capability of current high-cadence surveys for finding planets through the planetary-caustic channel. We find that most published planetary-caustic planets are found in Hollywood events in which the source size strongly contributes to the anomaly cross-section relative to the size of the caustic.

Keywords: Gravitational microlensing, Gravitational microlensing exoplanet detection
An Empirical Bayesian Approach to Limb Darkening in Modeling WASP-121b Transit Light Curves. We present a novel, iterative method using an empirical Bayesian approach for modeling the limb-darkened WASP-121b transit from the TESS light curve. Our method is motivated by the need to improve Rp/R* estimates for exoplanet atmosphere modeling and is particularly effective with the limb-darkening (LD) quadratic law requiring no prior central value from stellar atmospheric models. With the nonlinear LD law, the method has all the advantages of not needing atmospheric models but does not converge. The iterative method gives a different Rp/R* for WASP-121b at a significance level of 1σ when compared with existing noniterative methods. To assess the origins and implications of this difference, we generate and analyze light curves with known values of the LD coefficients (LDCs). We find that noniterative modeling with LDC priors from stellar atmospheric models results in an inconsistent Rp/R* at a 1.5σ level when the known LDC values are the same as those previously found when modeling real data by the iterative method. In contrast, the LDC values from the iterative modeling yield the correct value of Rp/R* to within 0.25σ. For more general cases with different known inputs, Monte Carlo simulations show that the iterative method obtains unbiased LDCs and correct Rp/R* to within a significance level of 0.3σ. Biased LDC priors can cause biased LDC posteriors and lead to bias in the Rp/R* of up to 0.82%, 2.5σ for the quadratic law and 0.32%, 1.0σ for the nonlinear law. Our improvement in Rp/R* estimation is important when analyzing exoplanet atmospheres.

Keywords: Exoplanet detection methods, Transit photometry, Exoplanet systems, Exoplanet atmospheres
Observations with the Differential Speckle Survey Instrument. X. Preliminary Orbits of K-dwarf Binaries and Other Stars. This paper details speckle observations of binary stars taken at the Lowell Discovery Telescope, the WIYN telescope, and the Gemini telescopes between 2016 January and 2019 September. The observations taken at Gemini and Lowell were done with the Differential Speckle Survey Instrument (DSSI), and those done at WIYN were taken with the successor instrument to DSSI at that site, the NN-EXPLORE Exoplanet Star and Speckle Imager (NESSI). In total, we present 378 observations of 178 systems, and we show that the uncertainty in the measurement precision for the combined data set is ∼2 mas in separation, ∼1°-2° in position angle depending on the separation, and ∼0.1 mag in magnitude difference. Together with data already in the literature, these new results permit 25 visual orbits and one spectroscopic-visual orbit to be calculated for the first time. In the case of the spectroscopic-visual analysis, which is done on the ternary star HD 173093, we calculate masses with a precision of better than 1% for all three stars in that system. Twenty-one of the visual orbits calculated have a K dwarf as the primary star; we add these to the known orbits of K-dwarf primary stars and discuss the basic orbital properties of these stars at this stage. Although incomplete, the data that exist so far indicate that binaries with K-dwarf primaries tend not to have low-eccentricity orbits at separations of one to a few tens of astronomical units, that is, on solar system scales.

Keywords: Spectroscopic binary stars, K dwarf stars, Speckle interferometry, Interferometric binary stars, Visual binary stars
Searching for Interstellar Quantum Communications. The modern search for extraterrestrial intelligence began with the seminal publications of Cocconi &amp; Morrison and Schwartz &amp; Townes, who proposed searching for narrowband signals in the radio spectrum and optical laser pulses. Over the last six decades, more than 100 dedicated search programs have targeted these wavelengths, all with null results. All of these campaigns searched for classical communications, that is, for a significant number of photons above a noise threshold, with the assumption of a pattern encoded in time and/or frequency space. I argue that future searches should also target quantum communications. They are preferred over classical communications with regard to security and information efficiency, and they would have escaped detection in all previous searches. The measurement of Fock state photons or squeezed light would indicate the artificiality of a signal. I show that quantum coherence is feasible over interstellar distances and explain for the first time how astronomers can search for quantum transmissions sent by ETI to Earth using commercially available telescopes and receiver equipment.

Keywords: Search for extraterrestrial intelligence, Astronomical detectors, Astronomy data analysis
Multifilter Observations of the Complex Periodic Variations in the M-dwarf Star RIK 90. The star RIK 90 is a member of a group of recently discovered young T Tauri stars showing complex periodic modulations of their light output, which have been difficult to explain. As one of the brightest, and having a relatively short period, RIK 90 is of particular interest. Thirty-three hours of contemporaneous BVRCIC photometry of the star are presented in this paper. An independent secondary periodicity was removed and the remainder of the data phased with the primary 0.25955 day period and smoothed to reveal the detailed structure of the light curves. The ratios of the amplitude in B to those in VRCIC are 1.2, 1.5, and 1.8. It is found that a collection of five cool starspots with temperatures in the range 2230-2550 K provides an excellent match to almost all observations, small-scale features in the IC-band light curve being the notable exception. Starspot modeling of K2 observations of RIK 90 was also attempted. The morphology of the K2 light curve is entirely different from that discussed in this paper but could be accurately modeled by four dark starspots. In order to put these results into context, 15 other distinct K2 light curves belonging to 10 similarly variable T Tauri stars were also studied. Excellent fits were obtained to some of these with models consisting of large cool starspots. The majority of the remaining light curves could be modeled with a combination of hot and cold starspots.

Keywords: Starspots, Peculiar variable stars, T Tauri stars, Pre-main sequence stars, Variable stars, Late-type dwarf stars
Dynamical Avenues for Mercury's Origin. II. In Situ Formation in the Inner Terrestrial Disk. Modern terrestrial-planet formation models are highly successful at consistently generating planets with masses and orbits analogous to those of Earth and Venus. In stark contrast to classic theoretical predictions and inferred demographics of multiplanet systems of rocky exoplanets, the mass (≳10) and orbital period (≳2) ratios between Venus and Earth and the neighboring Mercury and Mars are not common outcomes in numerically generated systems. While viable solutions to the small-Mars problem are abundant in the literature, Mercury's peculiar origin remains rather mysterious. In this paper, we investigate the possibility that Mercury formed in a mass-depleted, inner region of the terrestrial disk (a &lt; 0.5 au). This regime is often ignored in terrestrial-planet formation models because of the high computational cost of resolving hundreds of short-period objects over ∼100 Myr timescales. By testing multiple disk profiles and mass distributions, we identify several promising sets of initial conditions that lead to remarkably successful analog systems. In particular, our most successful simulations consider moderate total masses of Mercury-forming material (0.1-0.25 Earth masses). While larger initial masses tend to yield disproportionate Mercury analogs, smaller values often inhibit the planets' formation as the entire region of material is easily accreted by Venus. Additionally, we find that shallow surface density profiles and larger inventories of small planetesimals moderately improve the likelihood of adequately reproducing Mercury.

Keywords: Mercury (planet), Solar system formation, Solar system planets, Solar system terrestrial planets, Planetary system formation, Protoplanetary disks, Planetary science, Planetesimals
Analysis of Hybrid Gas-Dust Outbursts Observed at 67P/Churyumov-Gerasimenko. Cometary outbursts offer a valuable window into the composition of comet nuclei with their forceful ejection of dust and volatiles in explosive events, revealing the interior components of the comet. Understanding how different types of outbursts influence the dust properties and volatile abundances, to better interpret what signatures can be attributed to primordial composition and what features are the result of processing, is an important task best undertaken with a multi-instrument approach. The European Space Agency Rosetta mission to 67P/Churyumov-Gerasimenko carried a suite of instruments capable of carrying out this task in the near-nucleus coma with unprecedented spatial and spectral resolution. In this work, we discuss two outbursts that occurred 2015 November 7 and were observed by three instruments on board: the Alice ultraviolet spectrograph, the Visual Infrared and Thermal Imaging Spectrometer, and the Optical, Spectroscopic, and Infrared Remote Imaging System. Together, the observations show that mixed gas and dust outbursts can have different spectral signatures representative of their initiating mechanisms, with the first outburst showing indicators of a cliff collapse origin and the second more representative of fresh volatiles being exposed via a deepening fracture. This analysis opens up the possibility of remote spectral classification of cometary outbursts with future work.

Keywords: Ultraviolet astronomy, Neutral coma gases, Comets, Small Solar System bodies
Spatial Distribution of Ultraviolet Emission from Cometary Activity at 67P/Churyumov-Gerasimenko. The Alice ultraviolet spectrograph on board the Rosetta orbiter provided the first near-nucleus ultraviolet observations of a cometary coma from arrival at comet 67P/Churyumov-Gerasimenko in 2014 August through 2016 September. The characterization of atomic and molecular emissions in the coma revealed the unexpected contribution of dissociative electron impact emission at large heliocentric distances and during some outbursts. This mechanism also proved useful for compositional analysis, and Alice observed many cases that suggested elevated levels of the supervolatile O2, identifiable in part to their emissions resulting from dissociative electron impact. In this paper, we present the first two-dimensional UV maps constructed from Alice observations of atomic emission from 67P during an increase in cometary activity on 2015 November 7-8. Comparisons to observations of the background coma and an earlier collimated jet are used to describe possible changes to the near-nucleus coma and plasma. To verify the mapping method and place the Alice observations in context, comparisons to images derived from the MIRO and VIRTIS-H instruments are made. The spectra and maps we present show an increase in dissociative electron impact emission and an O2/H2O ratio of ∼0.3 for the activity; these characteristics have been previously identified with cometary outbursts seen in Alice data. Further, UV maps following the increases in activity show the spatial extent and emission variation experienced by the near-nucleus coma, informing future UV observations of comets that lack the same spatial resolution.

Keywords: Neutral coma gases, Comets, Comet volatiles , Small Solar System bodies
A New Method for Aerosol Measurement Using Wide-field Photometry. We present a new method to measure the vertical aerosol optical depth (VAOD) during clear nights using a wide-field imager—a CCD camera with a photographic lens on an equatorial mount. A series of 30 s exposures taken at different altitudes above the horizon can be used to measure the VAOD with a precision better than 0.008 optical depths within a few minutes. Such a measurement does not produce any light and is thus suitable for use at sites where other astronomical instruments are located. The precision of the VAOD measurement depends on the laboratory calibration of spectral properties of the system and of the response of the camera electronics to varying illumination levels, as well as careful considerations of the details of stellar photometry and modeling of the dependence of the measured stellar flux, the star color, and the position within the field of view. The results obtained with robotic setups at the future sites of the Cerenkov Telescope Array show good internal consistency and agreement with simultaneous measurements from a Sun/Moon photometer located at the same sites.

Keywords: CCD photometry, Atmospheric extinction
HAT-P-58b-HAT-P-64b: Seven Planets Transiting Bright Stars. We report the discovery and characterization of seven transiting exoplanets from the HATNet survey. The planets, which are hot Jupiters and Saturns transiting bright Sun-like stars, include: HAT-P-58b (with mass Mp = 0.37 MJ, radius Rp = 1.33 RJ, and orbital period P = 4.0138 days), HAT-P-59b (Mp = 1.54 MJ, Rp = 1.12 RJ, P = 4.1420 days), HAT-P-60b (Mp = 0.57 MJ, Rp = 1.63 RJ, P = 4.7948 days), HAT-P-61b (Mp = 1.06 MJ, Rp = 0.90 RJ, P = 1.9023 days), HAT-P-62b (Mp = 0.76 MJ, Rp = 1.07 RJ, P = 2.6453 days), HAT-P-63b (Mp = 0.61 MJ, Rp = 1.12 RJ, P = 3.3777 days), and HAT-P-64b (Mp = 0.58 MJ, Rp = 1.70 RJ, P = 4.0072 days). The typical errors on these quantities are 0.06 MJ, 0.03 RJ, and 0.2 s, respectively. We also provide accurate stellar parameters for each of the host stars. With V = 9.710 ± 0.050 mag, HAT-P-60 is an especially bright transiting planet host, and an excellent target for additional follow-up observations. With Rp = 1.703 ± 0.070 RJ, HAT-P-64b is a highly inflated hot Jupiter around a star nearing the end of its main-sequence lifetime, and is among the largest known planets. Five of the seven systems have long-cadence observations by TESS which are included in the analysis. Of particular note is HAT-P-59 (TOI-1826.01) which is within the northern continuous viewing zone of the TESS mission, and HAT-P-60, which is the TESS candidate TOI-1580.01. * Based on observations of the Hungarian-made Automated Telescope Network and observations obtained at the following observatories: W. M. Keck Observatory, the 1.5 m and the 1.2 m telescopes at the Fred Lawrence Whipple Observatory of the Smithsonian Astrophysical Observatory, the Kitt Peak National Observatory, the 1.93 m telescope at Observatoire de Haute-Provence, the Subaru Telescope of the National Astronomical Observatory of Japan, the Nordic Optical Telescope in the Spanish Observatorio del Roque de los Muchachos of the Intituto de Astrofísica de Canarias, and the Apache Point Observatory 3.5 m telescope.

Keywords: Exoplanet astronomy, Hot Jupiters, Astronomical instrumentation, Exoplanets
Limiting Behavior of Asteroid Obliquity and Spin Using a Semi-analytic Thermal Model of the YORP Effect. The Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect governs the spin evolution of small asteroids. The axial component of YORP, which alters the rotation rate of the asteroid, is mostly independent of its thermal inertia, while the obliquity component is very sensitive to the thermal model of the asteroid. Here, we develop a semi-analytic theory for the obliquity component of YORP. We integrate an approximate thermal model over the surface of an asteroid, and find an analytic expression for the obliquity component in terms of two YORP coefficients. This approach allows us to investigate the overall evolution of asteroid rotation state, and to generalize the results previously obtained in the case of zero thermal inertia. The proposed theory also explains how a nonzero obliquity component of YORP originates even for a symmetric asteroid, due to its finite thermal inertia. In many cases, this causes equatorial planes of asteroids to align with their orbital planes. The studied nontrivial behavior of YORP as a function of thermal model allows for a new kind of rotational equilibria, which can have important evolutionary consequences for asteroids.

Keywords: Asteroid rotation, Asteroid dynamics
Direct Imaging of Exoplanets beyond the Radial Velocity Limit: Application to the HD 134987 System. Future direct imaging missions will primarily observe planets that have been previously detected, mostly via the radial velocity (RV) technique, to characterize planetary atmospheres. In the meantime, direct imaging may discover new planets within existing planetary systems that have bright enough reflected flux but insufficient signals for other methods to detect. Here we investigate the parameter space within which planets are unlikely to be detected by RV in the near future due to precision limitations but could be discovered through reflected light with future direct imaging missions. We use the HD 134987 system as a working example, combine RV and direct imaging detection limit curves in the same parameter space through various assumptions, and insert a fictitious planet into the system while ensuring that it lies between the RV and imaging detection limits. Planet validity tested through dynamical simulations and retrieval tests revealed that the planet could indeed be detected by imaging while remaining hidden from RV surveys. Direct imaging retrieval was carried out using starshade simulations for two mission concepts: the Starshade Rendezvous Probe, which could be coupled with the Nancy Grace Roman Space Telescope, and the Habitable Exoplanet Observatory. This method is applicable to all other systems and high-contrast direct imaging instruments and could help inform future imaging observations and data analysis on the discovery of new exoplanets.

Keywords: Exoplanet detection methods, Exoplanets, Exoplanet systems, Direct imaging, Radial velocity
The High-energy Spectrum of the Nearby Planet-hosting Inactive Mid-M Dwarf LHS 3844. To fully characterize the atmospheres, or lack thereof, of terrestrial exoplanets, we must include the high-energy environments provided by their host stars. The nearby mid-M dwarf LHS 3844 hosts a terrestrial world that lacks a substantial atmosphere. We present a time-series UV spectrum of LHS 3844 from 1131 to 3215 Å captured by HST/COS. We detect one flare in the FUV that has an absolute energy of 8.96 ± 0.77 × 1028 erg and an equivalent duration of 355 ± 31 s. We extract the flare and quiescent UV spectra separately. For each spectrum, we estimate the Lyα flux using correlations between UV line strengths. We use Swift-XRT to place an upper limit on the soft X-ray flux and construct a differential emission model to estimate flux that is obscured by the interstellar medium. We compare the differential emission model flux estimates in the XUV to other methods that rely on scaling from the Lyα, Si iv, and N v lines in the UV. The XUV, FUV, and NUV flux of LHS 3844 relative to its bolometric luminosity is log10(Lband/LBol) =-3.65, -4.16, and -4.48, respectively, for the quiescent state. These values agree with trends in high-energy flux as a function of stellar effective temperature found by the MUSCLES survey for a sample of early-M dwarfs. Many of the most spectroscopically accessible terrestrial exoplanets orbit inactive mid-to-late M dwarfs like LHS 3844. Measurements of M dwarf high-energy spectra are preferable for exoplanet characterization but are not always possible. The spectrum of LHS 3844 is a useful proxy for the current radiation environment for these worlds.

Keywords: M dwarf stars, Hubble Space Telescope, Ultraviolet observatories, Ultraviolet astronomy, Space observatories, Stellar flares, Exoplanet atmospheres
EDEN: Flare Activity of the Nearby Exoplanet-hosting M Dwarf Wolf 359 Based on K2 and EDEN Light Curves. We report the flare activity of Wolf 359, the fifth closest star to the Sun and a candidate exoplanet-hosting M dwarf. The star was a target of the Kepler/K2 mission and was observed by the EDEN project, a global network of 1-2 m class telescopes for detection and characterization of rocky exoplanets in the habitable zones of late-M dwarfs within 50 light year from the solar system. In the combination of the archived K2 data and our EDEN observations, a total of 872 flares have been detected, 861 with the K2 (860 in the short-cadence and 18 in the long-cadence data, with 17 long-cadence events having short-cadence counterparts) and 11 with EDEN. Wolf 359 has relatively strong flare activity even among flaring M dwarfs, in terms of the flare activity indicator (FA) defined as the integrated flare energy relative to the total stellar bolometric energy, where FA = ∑Ef/∫Lbol dt ∼ 8.93 × 10-5 for the long-cadence flares, whereas for K2 short cadence and EDEN flares, the FA values are somewhat larger, FA ≈ 6.67 × 10-4 and FA ≈ 5.25 × 10-4, respectively. Such a level of activity, in accordance with the rotation period (Prot), suggests the star to be in the saturation phase. The size of the starspots is estimated to be at least 1.87% ± 0.59% of the projected disk area of Wolf 359. We find no correlation of FA with the stellar rotational phase. Our analysis indicates a flare frequency distribution in a power-law form of ${dN}/{dE}\propto {E}^{-\alpha }$ with α = 2.13 ± 0.14, equivalent to an occurrence rate of flares Ef ≥ 1031 erg about once per day and of superflares with Ef ≥ 1033 erg approximately 10 times per year. These superflares may impact the habitability of system in multiple ways, the details of which are topics for future investigations.

Keywords: Exoplanets, Stellar phenomena, Exoplanet systems, Flare stars, Exoplanet astronomy, Stellar flares, Planet hosting stars