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High-resolution spectroscopy has opened the way for new, detailed study of exoplanet atmospheres. There is evidence that this technique can be sensitive to the complex, three-dimensional (3D) atmospheric structure of these planets. In this work, we perform cross-correlation analysis of high-resolution (R ∼ 100,000) CRIRES/VLT emission spectra of the hot Jupiter HD 209458b. We generate template emission spectra from a 3D atmospheric circulation model of the planet, accounting for temperature structure and atmospheric motions—winds and planetary rotation—missed by spectra calculated from one-dimensional models. In this first-of-its-kind analysis, we find that using template spectra generated from a 3D model produces a more significant detection (6.9σ) of the planet's signal than any of the hundreds of one-dimensional models we tested (maximum of 5.1σ). We recover the planet's thermal emission, its orbital motion, and the presence of CO in its atmosphere at high significance. Additionally, we analyzed the relative influences of 3D temperature and chemical structures in this improved detection, including the contributions from CO and H₂O, as well as the role of atmospheric Doppler signatures from winds and rotation. This work shows that the hot Jupiter's 3D atmospheric structure has a first-order influence on its emission spectra at high resolution and motivates the use of multidimensional atmospheric models in high-resolution spectral analysis.

Planets around young stars trace the early evolution of planetary systems. We report the discovery and validation of two planetary systems with ages ≲300 Myr from observations by the Transiting Exoplanet Survey Satellite (TESS). The $40\mbox{--}320$ Myr old G star TOI-251 hosts a ${2.74}_{-0.18}^{+0.18}\,{R}_{\oplus }$ mini-Neptune with a $4.94$ day period. The $20\mbox{--}160$ Myr old K star TOI-942 hosts a system of inflated Neptune-sized planets, with TOI-942b orbiting in a period of $4.32$ days with a radius of ${4.81}_{-0.20}^{+0.20}\,{R}_{\oplus }$ and TOI-942c orbiting in a period of $10.16$ days with a radius of ${5.79}_{-0.18}^{+0.19}\,{R}_{\oplus }$. Though we cannot place either host star into a known stellar association or cluster, we can estimate their ages via their photometric and spectroscopic properties. Both stars exhibit significant photometric variability due to spot modulation, with measured rotation periods of ∼3.5 days. These stars also exhibit significant chromospheric activity, with age estimates from the chromospheric calcium emission lines and X-ray fluxes matching that estimated from gyrochronology. Both stars also exhibit significant lithium absorption, similar in equivalent width to well-characterized young cluster members. TESS has the potential to deliver a population of young planet-bearing field stars, contributing significantly to tracing the properties of planets as a function of their age.

We announce the public release of 141,531 moderate-dispersion optical spectra of 72,247 objects acquired over the past 25 yr with the FAST Spectrograph on the Fred L. Whipple Observatory 1.5 m Tillinghast telescope. We describe the data acquisition and processing so that scientists can understand the spectra. We highlight some of the largest FAst Spectrograph for the Tillinghast Telescope (FAST) survey programs, and make recommendations for use. The spectra have been placed in a Virtual Observatory–accessible archive and ready for download.

The study of exoplanetary atmospheres relies on detecting minute changes in the transit depth at different wavelengths. To date, a number of ground- and space-based instruments have been used to obtain transmission spectra of exoplanets in different spectral bands. One common practice is to combine observations from different instruments in order to achieve a broader wavelength coverage. We present here two inconsistent observations of WASP-96 b, one by the Hubble Space Telescope (HST) and the other by the Very Large Telescope (VLT). We present two key findings in our investigation: (1) a strong water signature is detected via the HST WFC3 observations and (2) a notable offset in transit depth (>1100 ppm) can be seen when the ground-based and space-based observations are combined. The discrepancy raises the question of whether observations from different instruments could indeed be combined. We attempt to align the observations by including an additional parameter in our retrieval studies but are unable to definitively ascertain that the aligned observations are indeed compatible. The case of WASP-96 b signals that compatibility of instruments should not be assumed. While wavelength overlaps between instruments can help, it should be noted that combining data sets remains risky business. The difficulty of combining observations also strengthens the need for next-generation instruments that possess broader spectral coverage.

We present new near-infrared Gemini Planet Imager (GPI) spectroscopy of HD 206893 B, a substellar companion orbiting within the debris disk of its F5V star. The J, H, K1, and K2 spectra from GPI demonstrate the extraordinarily red colors of the object, confirming it as the reddest substellar object observed to date. The significant flux increase throughout the infrared presents a challenging atmosphere to model with existing grids. Best-fit values vary from 1200 to 1800 K for effective temperature and from 3.0 to 5.0 for log(g), depending on which individual wavelength band is fit and which model suite is applied. The extreme redness of the companion can be partially reconciled by invoking a high-altitude layer of submicron dust particles, similar to dereddening approaches applied to the peculiar red field L dwarf population. However, reconciling the HD 206893 B spectra with even those of the reddest low-gravity L dwarf spectra still requires the contribution of additional atmospheric dust, potentially due to the debris disk environment in which the companion resides. Orbit fitting from 4 yr of astrometric monitoring is consistent with a ∼30 yr period, an orbital inclination of 147°, and a semimajor axis of 10 au, well within the estimated disk inner radius of ∼50 au. As one of a very few substellar companions imaged interior to a circumstellar disk, the properties of this system offer important dynamical constraints on companion–disk interaction and provide a benchmark for substellar and planetary atmospheric study.

We use the Gaia DR2 catalog to improve the astrometric accuracy of about 1.7 billion objects in Pan-STARRS1 Data Release 2 (PS1 DR2). We also obtain proper motions for these PS1 objects. The cross-match between Gaia and PS1 reveals residuals that are correlated on a scale of about 1'. We apply a spatially adaptive correction algorithm for all PS1 objects having more than two detections to reduce these residuals and align the object positions to Gaia. For point-like PS1 objects that cross-match to Gaia, the algorithm reduces PS1/Gaia residuals by 33% in position (median value of 13.5 mas reduced to 9.0 mas) and by 24% in proper motion (median value of 6.3 mas yr⁻¹ reduced to 4.8 mas yr⁻¹). The residuals for the corrected positions are smallest for objects with the most point-like morphologies and with intermediate magnitudes of about 17 mag. The residual errors in decl. are systematically larger than those in R.A.; the decl. errors increase with zenith angle in proportion to the air mass of the observations. The decl. positional residuals at a given decl. generally vary with color and are consistent with the effects of differential atmospheric refraction. In principle, these residuals could be reduced further by taking into account object color.

In the globular cluster NGC 3201, we study subpopulations (SPs) of red giants (RGs) distinguished by their characteristics. In its central part, we make use of multicolor Hubble Space Telescope (HST) photometry coupled with spectroscopy of RGs spread out over a larger cluster face. In the color index CI $=\,({m}_{{\rm{F}}275{\rm{W}}}-{m}_{{\rm{F}}336{\rm{W}}})\,-({m}_{{\rm{F}}336{\rm{W}}}-{m}_{{\rm{F}}439{\rm{W}}})$, RGs commonly referred to as first generation, SPI, are separated from the counterparts of the second generation, SPII. The latter are more concentrated than the former at a confidence level of P = 93%, within the field covered by the HST photometry. Their minor portion (∼28%, SPIIm) located in the middle of the δCI range spanned across the split RG branch relative to the splitting edge is more centrally concentrated at a higher confidence level of 96%. We found, from the [Na/Fe]−δCI plot for RGs in common between the photometry and spectroscopy, that SPI and SPII are mostly overlapped within 0.0 < [Na/Fe] < 0.3. RGs with [Na/Fe] < 0.0 (mostly SPI) keep their lower concentration to the cluster center over larger radial distance as compared to SPII RGs with [Na/Fe] > 0.3 at a confidence level of P = 88%. It is increased up to 95% if a restriction on [O/Fe] is imposed. The obtained result, particularly in the central part, is a clue that SPIIm RGs are the descendants of more massive progenitors. Of these RGs approximately one-third probably originate from recent (within the past 1.5 Gyr) blue stragglers with M_BS > 1.1M_☉, and the other two-thirds could be accounted for by older collision products of primordial MS stars.

We identify 1325 member candidates of the open cluster (OC) Stock 2 using data from Gaia DR2. We use the algorithms Clusterix 2.0 and HDBSCAN to select cluster candidates and further refine the final cluster membership by defining neighbors in 5D phase space (X_cp, Y_cp, ${Z}_{\mathrm{cp}},\kappa \cdot {\mu }_{\alpha }^{* }$/ϖ, κ · μ_δ/ϖ). Among these candidates, less than half have G, G_BP, and G_RP extinctions from Gaia. When Gaia extinctions are unavailable, we compute extiction using empirical formulas and E(B − V) = 0.350. We analyze the spatial distribution and mass profile of Stock 2. Our results reveal Stock 2 is still a bound OC and we find evidence of mass segregation. By comparing initial mass functions, the present-day mass function indicates that Stock 2 is a massive stellar cluster with a mass of 4000 M_⊙. The core radius and tidal radius, calculated via the radial density profile and total mass, are 3.97 pc and 22.65 pc, respectively. Common stars between our selected member candidates and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope DR7 medium-resolution catalog give a metalliclity of [Fe/H] = −0.040 ± 0.147.

We analyze the oxygen abundances of a stellar sample representative of the two major Galactic populations: the thin and thick disks. The aim is to investigate the differences between members of the Galactic disks and contribute to the understanding of the origin of oxygen chemical enrichment in the Galaxy. The analysis is based on the [O i] = 6300.30 Å oxygen line in high-resolution spectra (R ∼ 52,500) obtained from the Gaia-ESO public spectroscopic Survey (GES). By comparing the observed spectra with a theoretical data set computed in LTE with the SPECTRUM synthesis and ATLAS12 codes, we derive the oxygen abundances of 516 FGK dwarfs for which we have previously measured carbon abundances. Based on kinematic, chemical, and dynamical considerations, we identify 20 thin and 365 thick disk members. We study the potential trends of both subsamples in terms of their chemistry ([O/H], [O/Fe], [O/Mg], and [C/O] versus [Fe/H] and [Mg/H]), age, and position in the Galaxy. The main results are that (a) [O/H] and [O/Fe] ratios versus [Fe/H] show systematic differences between thin and thick disk stars with an enhanced O abundance of thick disk stars with respect to thin disk members and a monotonic decrement of [O/Fe] with increasing metallicity, even at metal-rich regime; (b) there is a smooth correlation of [O/Mg] with age in both populations, suggesting that this abundance ratio can be a good proxy of stellar ages within the Milky Way; and (c) thin disk members with [Fe/H] ≃ 0 display a [C/O] ratio smaller than the solar value, suggesting a possibly outward migration of the Sun from lower Galactocentric radii.

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 M_pl = 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 M_pl = 10.26 ± 0.99 M_⊕, while for HD 216520 c, P = 154.43 days, K = 1.29 ± 0.22 m s⁻¹, and M_pl = 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 M_pl = 12.214 ± 1.05 M_⊕. For GJ 686 b, we find P = 15.53 days and M_pl = 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.

The Voyager 1 (V1) and Voyager 2 (V2) spacecraft were launched in 1977 on a mission to explore the outer planets and reach the heliopause, the boundary between the hot solar plasma and the relatively cool interstellar plasma. V1 reached the heliopause on 2012 August 25, at 121.6 au, and V2 reached the heliopause on 2018 November 5, at 119.0 au. One of their remarkable discoveries was the detection of shocks propagating into the interstellar plasma from energetic solar events. These shocks are typically preceded by electron plasma oscillations excited by electron beams streaming along interstellar magnetic field lines ahead of the shocks. The frequencies of the plasma oscillations have now provided radial electron density profiles in the outer heliosphere and in the interstellar medium to radial distances of more than 145 au. The oscillations are typically preceded by bursts of high-energy ∼5–100 MeV electrons. These electron bursts are interpreted as being due to the reflection (and acceleration) of cosmic-ray electrons by the shock at the time the shock first contacts the magnetic field line that passes through the spacecraft. Relative timing between the cosmic rays reflected by the shock and the onset of the plasma oscillations allow us, for the first time, to estimate the energy, ∼20–100 eV, of the electron beams responsible for the plasma oscillations. These observations are combined into a self-consistent model called the foreshock model that describes the interaction of shocks of solar origin with the interstellar plasma.

The legacy imaging surveys for the Dark Energy Spectroscopic Instrument project provides multiple-color photometric data, which are about 2 mag deeper than those from the SDSS. In this study, we redetermine the fundamental properties for an old halo globular cluster of Palomar 5 based on these new imaging data, including structure parameters, stellar population parameters, and luminosity and mass functions. These characteristics, together with its tidal tails, are key for dynamical studies of the cluster and constraining the mass model of the Milky Way. By fitting the King model to the radial surface density profile of Palomar 5, we derive the core radius of ${r}_{c}=2\buildrel{\,\prime}\over{.} 96\pm 0\buildrel{\,\prime}\over{.} 11$, tidal radius of ${r}_{t}=17\buildrel{\,\prime}\over{.} 99\pm 1\buildrel{\,\prime}\over{.} 49$, and concentration parameter of c = 0.78 ± 0.04. We apply a Bayesian analysis method to derive the stellar population properties and get an age of 11.508 ± 0.027 Gyr, metallicity of [Fe/H]  =   −1.798 ± 0.014, reddening of E(B − V) = 0.0552 ± 0.0005, and distance modulus of ${\left(m-M\right)}_{0}\,=\,16.835\pm 0.006$. The main-sequence luminosity and mass functions for both the cluster center and tidal tails are investigated. The luminosity and mass functions at different distances from the cluster center suggest that there is obvious spatial mass segregation. Many faint low-mass stars have been evaporated at the cluster center, and the tidal tails are enhanced by low-mass stars. Both the concentration and relaxation times suggest that Palomar 5 is a totally relaxed system.

We report the discovery and validation of TOI 122b and TOI 237b, two warm planets transiting inactive M dwarfs observed by the Transiting Exoplanet Survey Satellite (TESS). Our analysis shows that TOI 122b has a radius of 2.72 ± 0.18 R_⊕ and receives 8.8 ± 1.0 times  Earth's bolometric insolation, and TOI 237b has a radius of 1.44±0.12 R_⊕ and receives 3.7 ± 0.5 times Earth's insolation, straddling the 6.7 × Earth insolation that Mercury receives from the Sun. This makes these two of the cooler planets yet discovered by TESS, even on their 5.08 and 5.43 day orbits. Together, they span the small-planet radius valley, providing useful laboratories for exploring volatile evolution around M dwarfs. Their relatively nearby distances (62.23 ± 0.21 pc and 38.11 ± 0.23 pc, respectively) make them potentially feasible targets for future radial velocity follow-up and atmospheric characterization, although such observations may require substantial investments of time on large telescopes.

This paper presents the results of the largest very long baseline interferometry (VLBI) absolute astrometry campaign to date of 13,645 radio source observations with the Very Long Baseline Array. Of these, 7220 have been detected, including 6755 target sources that have never been observed with VLBI before. This makes the present VLBI catalog the largest ever published. The positions of the target sources have been determined with the median uncertainty of 1.7 mas, and 15,542 images of 7171 sources have been generated. Unlike previous absolute radio astrometry campaigns, observations were made at 4.3 and 7.6 GHz simultaneously using a single wide-band receiver. Because of the fine spectral and time resolutions, the field of view was 4'–8'—much greater than the 10''–20'' in previous surveys. This made possible the use of input catalogs with low position accuracy and the detection of a compact component in extended sources. Unlike previous absolute astrometry campaigns, both steep- and flat-spectrum sources were observed. The observations were scheduled in the so-called filler mode to fill the gaps between other high-priority programs. This was achieved by the development of the totally automatic scheduling procedure.

The ongoing Zwicky Transient Facility (ZTF) survey is generating a massive alert rate from a variety of optical transients and variable stars, which are being filtered down to subsets meeting user-specified criteria by broker systems such as the Arizona-NOIRLab Temporal Analysis and Response to Events System (ANTARES). In a beta implementation of the algorithm of Soraisam et al. on ANTARES, we flagged AT 2020iko from the ZTF real-time alert stream as an anomalous source. This source is located close to a red extended Sloan Digital Sky Survey source. In the first few epochs of detection, it exhibited a V-shaped brightness profile, preceded by nondetections both in ZTF and in the All-Sky Automated Survey for Supernovae extending to 2014. Its full light curve shows a precursor event, followed by a main superoutburst and at least two rebrightenings. A low-resolution spectrum of this source points to a dwarf nova (DN) nature. Although some of the features of AT 2020iko indicate an SU UMa-type DN, its large amplitude, presence of rebrightenings, and inferred supercycle period of ≥6 yr are in favor of AT 2020iko being a new WZ Sge-type DN candidate, a subset of rare DNe consisting of extreme mass-ratio (<0.1) binaries with an orbital period around the period minimum. The precusor event of AT 2020iko brightened by 6.5 mag, while its decay spanned 3–5 mag. We speculate this superoutburst is associated with a less expanded accretion disk than in typical superoutbursts in WZ Sge systems, with the large depth of the precursor decay implying an extremely small mass ratio. To the best of our knowledge, such a precursor event has not been recorded for any DN. This result serves to demonstrate the efficacy of our real-time anomaly search algorithm.

The Kepler mission observed thousands of transiting exoplanet candidates around hundreds of thousands of FGK dwarf stars. He et al. applied forward modeling to infer the distribution of intrinsic architectures of planetary systems, developed a clustered Poisson point process model for exoplanetary systems (SysSim) to reproduce the marginal distributions of the observed Kepler population, and they showed that orbital periods and planet radii are clustered within a given planetary system. Here, we extend the clustered model to explore correlations between planetary systems and their host-star properties. We split the sample of Kepler FGK dwarfs into two halves and model the fraction of stars with planets (0.5–10R_⊕ and 3–300 days), f_swpa, as a linear function of the Gaia DR2 color. We confirm previous findings that the occurrence of these planetary systems rises significantly toward later-type (redder) stars. The fraction of stars with planets increases from ${f}_{\mathrm{swpa}}={0.32}_{-0.11}^{+0.12}$ for F2V dwarfs to ${f}_{\mathrm{swpa}}={0.96}_{-0.19}^{+0.04}$ for mid-K dwarfs. About half (${f}_{\mathrm{swpa}}={0.57}_{-0.10}^{+0.14}$) of all solar-type (G2V) dwarfs harbor a planetary system between 3 and 300 days. This simple model can closely match the observed multiplicity distributions of both the bluer and redder halves in our sample, suggesting that the architectures of planetary systems around stars of different spectral types may be similar aside from a shift in the overall fraction of planet-hosting stars.

τ Ceti is the closest single Sun-like star to the solar system and hosts a multiplanet system with four confirmed planets. The possible presence of additional planets, especially potentially habitable worlds, remains of great interest. We analyze the structure of the τ Ceti planetary system via the DYNAMITE algorithm, combining information from exoplanet population statistics and orbital dynamics with measurements of this specific system. We also expand DYNAMITE to incorporate radial velocity information. Our analysis suggests the presence of four additional planets, three of which match closely with the periods of three tentative planet candidates reported previously. We also predict at least one more planet candidate with an orbital period between ∼270 and 470 days, in the habitable zone for τ Ceti. Based on the measured $m\sin i$ values of the confirmed planets, we also assess the possible masses and nature of the detected and undetected planets. The least massive planets and candidates are likely to be rocky, while the other planets and candidates could either be rocky or contain a significant gaseous envelope. The radial velocity observable signature from the predicted habitable zone planet candidate would likely be at or just above the noise level in current data, but should be detectable in future extremely high-precision radial velocity and direct-imaging studies.

We present a transmission spectrum for the warm (500−600 K) sub-Neptune HD 3167c obtained using the Hubble Space Telescope Wide Field Camera 3 infrared spectrograph. We combine these data, which span the 1.125–1.643 μm wavelength range, with broadband transit measurements made using Kepler/K2 (0.6–0.9 μm) and Spitzer/IRAC (4–5 μm). We find evidence for absorption by at least one of H₂O, HCN, CO₂, and CH₄ (Bayes factor 7.4; 2.5σ significance), although the data precision does not allow us to unambiguously discriminate between these molecules. The transmission spectrum rules out cloud-free hydrogen-dominated atmospheres with metallicities ≤100× solar at >5.8σ confidence. In contrast, good agreement with the data is obtained for cloud-free models assuming metallicities >700× solar. However, for retrieval analyses that include the effect of clouds, a much broader range of metallicities (including subsolar) is consistent with the data, due to the degeneracy with cloud-top pressure. Self-consistent chemistry models that account for photochemistry and vertical mixing are presented for the atmosphere of HD 3167c. The predictions of these models are broadly consistent with our abundance constraints, although this is primarily due to the large uncertainties on the latter. Interior structure models suggest that the core mass fraction is >40%, independent of a rock or water core composition, and independent of atmospheric envelope metallicity up to 1000× solar. We also report abundance measurements for 15 elements in the host star, showing that it has a very nearly solar composition.

We present an atmospheric characterization study of two medium-sized planets bracketing the radius of Neptune: HD 106315c (R_P = 4.98 ± 0.23 R_⊕) and HD 3167c (${R}_{{\rm{P}}}={2.740}_{-0.100}^{+0.106}$R_⊕). We analyze spatially scanned spectroscopic observations obtained with the G141 grism (1.125–1.650 μm) of the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope. We use the publicly available Iraclis pipeline and TauREx3 atmospheric retrieval code and detect water vapor in the atmosphere of both planets, with an abundance of ${\mathrm{log}}_{10}[{{\rm{H}}}_{2}{\rm{O}}]=-{2.1}_{-1.3}^{+0.7}$ (∼5.68σ) and ${\mathrm{log}}_{10}[{{\rm{H}}}_{2}{\rm{O}}]=-{4.1}_{-0.9}^{+0.9}$ (∼3.17σ) for HD 106315c and HD 3167c, respectively. The transmission spectrum of HD 106315c also shows possible evidence of ammonia absorption (${\mathrm{log}}_{10}[{\mathrm{NH}}_{3}]=-{4.3}_{-2.0}^{+0.7},\sim 1.97\sigma$, even if it is not significant), while carbon dioxide absorption features may be present in the atmosphere of HD 3167c in the ∼1.1–1.6 μm wavelength range (${\mathrm{log}}_{10}[{\mathrm{CO}}_{2}]=-{2.4}_{-1.0}^{+0.7}$, ∼3.28σ). However, the CO₂ detection appears significant, and it must be considered carefully and put into perspective. Indeed, CO₂ presence is not explained by 1D equilibrium chemistry models, and it could be due to possible systematics. The additional contributions of clouds, CO, and CH₄ are discussed. HD 106315c and HD 3167c will be interesting targets for upcoming telescopes such as the James Webb Space Telescope and the Atmospheric Remote-sensing Infrared Exoplanet Large-survey.

We describe a new instrument capable of high-precision (10⁻⁵) polarimetric observations simultaneously in three passbands (BVR). The instrument utilizes electron-multiplying charge-coupled device (EM CCD) cameras for high efficiency and fast image readout. The key features of the Double Image Polarimeter—Ultra Fast (DIPol-UF) are: (i) the optical design with high throughput and inherent stability; (ii) great versatility, which makes the instrument optimally suitable for observations of bright and faint targets; and (iii) a control system, which allows the use of the polarimeter remotely. Examples are given of the first results obtained from high signal-to-noise observations of bright nearby stars and of fainter sources such as X-ray binaries in their quiescent states.

The Kepler mission and subsequent ground-based follow-up observations have revealed a number of exoplanet host stars with nearby stellar companions. This study presents speckle observations of 57 Kepler objects of interest (KOIs) that are also double stars, each observed over a 3–8 yr period, which has allowed us to track their relative motions with high precision. Measuring the position angle and separation of the companion with respect to the primary can help determine if the pair exhibits common proper motion, indicating it is likely to be a bound binary system. We report on the motions of 34 KOIs that have close stellar companions, three of which are triple stars, for a total of 37 companions studied. Eighteen of the 34 systems are confirmed exoplanet hosts, including one triple star, while four other systems have been subsequently judged to be false positives and twelve are yet to be confirmed as planet hosts. We find that 21 are most likely to be common proper motion pairs, 4 are line-of-sight companions, and 12 are of an uncertain disposition at present. The fraction of the confirmed exoplanet host systems that are common proper motion pairs is approximately 86% in this sample. In this subsample, the planets are exclusively found with periods of less than 110 days, so that in all cases the stellar companion is found at a much larger separation from the planet host star than the planet itself. A preliminary period–radius relation for the confirmed planets in our sample suggests no obvious differences at this stage with the full sample of known exoplanets.

HD 106906 is a 15 Myr old short-period (49 days) spectroscopic binary that hosts a wide-separation (737 au) planetary-mass ($\sim 11\,{M}_{\mathrm{Jup}}$) common proper motion companion, HD 106906 b. Additionally, a circumbinary debris disk is resolved at optical and near-infrared wavelengths that exhibits a significant asymmetry at wide separations that may be driven by gravitational perturbations from the planet. In this study we present the first detection of orbital motion of HD 106906 b using Hubble Space Telescope images spanning a 14 yr period. We achieve high astrometric precision by cross-registering the locations of background stars with the Gaia astrometric catalog, providing the subpixel location of HD 106906 that is either saturated or obscured by coronagraphic optical elements. We measure a statistically significant 31.8 ± 7.0 mas eastward motion of the planet between the two most constraining measurements taken in 2004 and 2017. This motion enables a measurement of the inclination between the orbit of the planet and the inner debris disk of either ${36}_{-14}^{+27}$ deg or ${44}_{-14}^{+27}$ deg, depending on the true orientation of the orbit of the planet. There is a strong negative correlation between periastron and mutual inclination; orbits with smaller periastra are more misaligned with the disk plane. With a periastron of ${510}_{-320}^{+480}$ au, HD 106906 b is likely detached from the planetary region within 100 au radius, showing that a Planet Nine–like architecture can be established very early in the evolution of a planetary system.

We present the discovery of TOI 540 b, a hot planet slightly smaller than Earth orbiting the low-mass star 2MASS J05051443-4756154. The planet has an orbital period of P = 1.239149 days (±170 ms) and a radius of $r=0.903\pm 0.052{R}_{\oplus }$, and is likely terrestrial based on the observed mass–radius distribution of small exoplanets at similar insolations. The star is 14.008 pc away and we estimate its mass and radius to be $M=0.159\pm 0.014$${M}_{\odot }$ and $R=0.1895\pm 0.0079{R}_{\odot }$, respectively. The star is distinctive in its very short rotational period of ${P}_{\mathrm{rot}}=17.4264\pm 0.0094$ hr and correspondingly small Rossby number of 0.007 as well as its high X-ray-to-bolometric luminosity ratio of ${L}_{{\rm{X}}}/{L}_{\mathrm{bol}}=0.0028$ based on a serendipitous XMM-Newton detection during a slew operation. This is consistent with the X-ray emission being observed at a maximum value of ${L}_{{\rm{X}}}/{L}_{\mathrm{bol}}\simeq {10}^{-3}$ as predicted for the most rapidly rotating M dwarfs. TOI 540 b may be an alluring target to study atmospheric erosion due to the strong stellar X-ray emission. It is also among the most accessible targets for transmission and emission spectroscopy and eclipse photometry with the James Webb Space Telescope, and may permit Doppler tomography with high-resolution spectroscopy during transit. This discovery is based on precise photometric data from the Transiting Exoplanet Survey Satellite and ground-based follow-up observations by the MEarth team.

We present TRICERATOPS, a new Bayesian tool that can be used to vet and validate TESS Objects of Interest (TOIs). We test the tool on 68 TOIs that have been previously confirmed as planets or rejected as astrophysical false positives. By looking in the false-positive probability (FPP)−nearby false-positive probability (NFPP) plane, we define criteria that TOIs must meet to be classified as validated planets (FPP < 0.015 and NFPP < 10⁻³), likely planets (FPP < 0.5 and NFPP < 10⁻³), and likely nearby false positives (NFPP > 10⁻¹). We apply this procedure on 384 unclassified TOIs and statistically validate 12, classify 125 as likely planets, and classify 52 as likely nearby false positives. Of the 12 statistically validated planets, 9 are newly validated. TRICERATOPS is currently the only TESS vetting and validation tool that models transits from nearby contaminant stars in addition to the target star. We therefore encourage use of this tool to prioritize follow-up observations that confirm bona fide planets and identify false positives originating from nearby stars.

We describe a fast, approximate method to characterize the orbits of satellites around a central binary in numerical simulations. A goal is to distinguish the free eccentricity—the random motion of a satellite relative to a dynamically cool orbit—from oscillatory modes driven by the central binary's time-varying gravitational potential. We assess the performance of the method using the Kepler-16, Kepler-47, and Pluto–Charon systems. We then apply the method to a simulation of orbital damping in a circumbinary environment, resolving relative speeds between small bodies that are slow enough to promote mergers and growth. These results illustrate how dynamical cooling can set the stage for the formation of Tatooine-like planets around stellar binaries and the small moons around the Pluto–Charon binary planet.

By controlling instrumental errors to below 10 cm s⁻¹, the EXtreme PREcision Spectrograph (EXPRES) allows for a more insightful study of photospheric velocities that can mask weak Keplerian signals. Gaussian processes (GP) have become a standard tool for modeling correlated noise in radial velocity data sets. While GPs are constrained and motivated by physical properties of the star, in some cases they are still flexible enough to absorb unresolved Keplerian signals. We apply GP regression to EXPRES radial velocity measurements of the 3.5 Gyr old chromospherically active Sun-like star, HD 101501. We obtain tight constraints on the stellar rotation period and the evolution of spot distributions using 28 seasons of ground-based photometry, as well as recent Transiting Exoplanet Survey Satellite data. Light-curve inversion was carried out on both photometry data sets to reveal the spot distribution and spot evolution timescales on the star. We find that the >5 m s⁻¹ rms radial velocity variations in HD 101501 are well modeled with a GP stellar activity model without planets, yielding a residual rms scatter of 45 cm s⁻¹. We carry out simulations, injecting and recovering signals with the GP framework, to demonstrate that high-cadence observations are required to use GPs most efficiently to detect low-mass planets around active stars like HD 101501. Sparse sampling prevents GPs from learning the correlated noise structure and can allow it to absorb prospective Keplerian signals. We quantify the moderate to high-cadence monitoring that provides the necessary information to disentangle photospheric features using GPs and to detect planets around active stars.

In this paper, we analyze the light variations of KIC 10975348 using photometric data delivered from the Kepler mission. This star is exceptionally faint (K_p = 18.6 mag) compared to most well-studied δ Scuti stars. The Fourier analysis of the short-cadence data (i.e., Q14, Q15, and Q16, spanning 220 days) reveals that the variations are dominated by the strongest mode with a frequency of F0 = 10.231899 day⁻¹, which is compatible with that obtained from RATS–Kepler. The other two independent modes with F1 (=13.4988 day⁻¹) and F2 (=19.0002 day⁻¹) are newly detected and have amplitudes two orders of magnitude smaller than F0. We note that, for the first time, this star is identified to be a high-amplitude δ Sct (HADS) star with an amplitude of about 0.7 mag, and the lower ratio of F0/F1 = 0.758 suggests that it might be a metal-rich variable star. The frequency F2 may be a third overtone mode, suggesting that this target might be a new radial triple-mode HADS star. We perform an O − C analysis using 1018 newly determined times of maximum light and derive an ephemeris formula of T_max = 2456170.241912(0)+0.097734(1) × E. The O − C diagram shows that the pulsation period of KIC 10975348 seems to show no obvious change, which is in contrast to that of the majority of HADS stars. The possible cause of that may be due to the current short time span of the observations. To verify its possible period variations, regular observation from space with a longer time span in the future is needed.

Herbig Ae/Be stars represent the early outcomes of star formation and the initial stages of planet formation at intermediate stellar masses. Understanding both of these processes requires detailed characterization of their disk structures and companion frequencies. We present new 3.7 μm imaging of the Herbig Be star MWC 297 from nonredundant masking observations on the phase-controlled, 23 m Large Binocular Telescope Interferometer. The images reveal complex disk structure on the scales of several au, as well as a companion candidate. We discuss physical interpretations for these features and demonstrate that the imaging results are independent of choices such as priors, regularization hyperparameters, and error-bar estimates. With an angular resolution of ∼17 mas, these data provide the first robust Extremely Large Telescope–resolution view of a distant young star.

The mid-infrared spectrum contains rich diagnostics to probe the physical properties of galaxies, among which the pervasive emission features from polycyclic aromatic hydrocarbons (PAHs) offer promising means of estimating the star formation rate (SFR) relatively immune from dust extinction. This paper investigates the effectiveness of PAH emission as a SFR indicator on subkiloparsec scales by studying the Spitzer/IRS mapping-mode observations of the nearby grand-design spiral galaxy M51. We present a new approach of analyzing the spatial elements of the spectral data cube that simultaneously maximizes spatial resolution and spatial coverage, while yielding reliable measurements of the total, integrated 5–20 μm PAH emission. We devise a strategy of extracting robust PAH emission using spectra with only partial spectral coverage, complementing missing spectral regions with properly combined mid-infrared photometry. We find that in M51 the PAH emission correlates tightly with the extinction-corrected far-ultraviolet, near-ultraviolet, and Hα emission, from scales of ∼0.4 kpc close to the nucleus to 6 kpc out in the disk of the galaxy, indicating that PAH serves as an excellent tracer of SFR over a wide range of galactic environments. But regional differences exist. Close to the active nucleus of M51 the 6.2 μm feature is weaker, and the overall level of PAH emission is suppressed. The spiral arms and the central star-forming region of the galaxy emit stronger 7.7 and 8.6 μm PAH features than the inter-arm regions.

We present a novel population-based Bayesian inference approach to model the average and population variance of the spatial distribution of a set of observables from ensemble analysis of low signal-to-noise-ratio measurements. The method consists of (1) inferring the average profile using Gaussian processes and (2) computing the covariance of the profile observables given a set of independent variables. Our model is computationally efficient and capable of inferring average profiles of a large population size from noisy measurements, without stacking data or parameterizing the shape of the mean profile. We demonstrate the performance of our method using dark matter, gas, and stellar profiles extracted from hydrodynamical cosmological simulations of galaxy formation. Population Profile Estimator is publicly available in a GitHub repository. Our new method should be useful for measuring the spatial distribution and internal structure of a variety of astrophysical systems using large astronomical surveys.

The discovery of terrestrial exoplanets is uncovering increasingly diverse architectures. Of particular interest are those systems that contain exoplanets at a variety of star–planet separations, allowing direct comparison of exoplanet evolution (comparative planetology). The Kepler-1649 system contains two terrestrial planets similar both in size and insolation flux to Venus and Earth, although their eccentricities remain largely unconstrained. Here we present results of dynamical studies of the system and the potential effects on climate. The eccentricities of the Kepler-1649 system are poorly constrained, and we show that there are dynamically viable regions for further terrestrial planets in between the two known planets for a limited range of eccentricities. We investigate the effect of eccentricity of the outer planet on the dynamics of both planets and show that this results in high-frequency (1000–3000 years) eccentricity oscillations in long-term stable configurations. We calculate the resulting effect of these eccentricity variations on insolation flux and present the results of 3D climate simulations for the habitable zone planet. Our simulations demonstrate that, despite large eccentricity variations, the planet can maintain stable climates with relatively small temperature variations on the substellar hemisphere for a variety of initial climate configurations. Such systems thus provide key opportunities to explore alternative Venus/Earth climate evolution scenarios.

CW Cep is an early B-type eclipsing binary with mass measurement precisions better than 1%. We report the discovery of pulsation signatures in the Transiting Exoplanet Survey Satellite time-series data of the system observed during Sectors 17 and 18. Our binary modeling indicates that the target star is a partially eclipsing detached system with masses of 12.95 M_⊙ and 11.88 M_⊙ and radii of 5.52 R_⊙ and 5.09 R_⊙ in an eccentric orbit of e = 0.0305. The distance to the eclipsing system, 928 ± 36 pc, is much more precise than the Gaia distance of 962 ± 453 pc. Applying multifrequency analyses to the residual light curve in the outside-eclipse part, we detected 13 significant signals in two frequency regions. Six frequencies below 1 day⁻¹ appeared to be mostly orbital harmonic and combination terms, or sidelobes due to insufficient removal of the binary effects. In contrast, seven frequencies clustered around 2.73 day⁻¹ and 5.34 day⁻¹ could be considered β Cep–type pulsations. Our results represent the second discovery of β Cep pulsations present in double-lined eclipsing binaries with precise masses and, hence, CW Cep serves as an important test bed for the asteroseismic modeling of high-mass stars.

Protoplanetary disks with large inner dust cavities are thought to host massive planetary or substellar companions. These disks show asymmetries and rings in the millimeter continuum caused by dust trapping in pressure bumps and potentially vortices or horseshoes. The origin of the asymmetries and their diversity remains unclear. We present a comprehensive study of 16 disks for which the gas surface density profile has been constrained by CO isotopologue data. First, we compare the azimuthal extents of the dust continuum profiles with the local gas surface density in each disk and find that the asymmetries correspond to higher Stokes numbers or low gas surface density. We discuss which asymmetric structures can be explained by a horseshoe, a vortex, or spiral density waves. Second, we reassess the gas gap radii from the ¹³CO maps, which are about a factor of 2 smaller than the dust ring radii, suggesting that the companions in these disks are in the brown dwarf (∼15–50 M_Jup) or super-Jovian (∼3–15 M_Jup) mass regime on eccentric orbits. This is consistent with the estimates from contrast curves on companion mass limits. These curves rule out (sub)stellar companions (q > 0.05) for the majority of the sample at the gap location, but it remains possible at even smaller radii. Third, we find that spiral arms in scattered-light images are primarily detected around high-luminosity stars with disks with wide gaps, which can be understood by the dependence of the spiral arm pitch angle on disk temperature and companion mass.

In this paper, we investigate portions of the Kepler K2 Short Cadence light curve of the dwarf nova (DN) TW Vir at quiescence, using light-curve modeling. The light curve was separated into 24 sections, each with a data length of ∼0.93 days, comprising 4 sections before, and 20 after a superoutburst (SO). Due to morphological differences, the quiescent orbital modulation is classified into three types. Using a fixed disk radius and the two component stellar parameters, all 24 synthetic disk models from these sections show a consistent configuration, consisting of a disk and two hotspots: one at the vertical side of the edge of the disk and the other on the surface of the disk. Before the SO, the disk and a ringlike surface-hotspot are suddenly enhanced, triggering a precursor, and then the SO. At the end of the quiescent period following the SO and before the first normal outburst, the edge-hotspot becomes hotter, while the surface-hotspot switches into a "coolspot" with a coverage of nearly half of the disk's surface. During quiescence, the surface-hotspot is always located at the outer part of the disk, with a constant radial width. A flat radial temperature distribution of the disk is found, and appears flatter when approaching the outburst. Like many U Gem-type DN with orbital periods of 3–5 hr, the mass transfer rate is significantly lower than the predictions of the standard/revised models of CV evolution.

Using the Kepler Eclipsing Binary Catalog, we found seven EW-type eclipsing binaries within the tidal radius of the intermediate-aged open cluster NGC 6819 (about 40'). These seven EW eclipsing binaries are all confirmed to be contact binaries by light curve analysis with the 2015 version Wilson–Devinney program. Using the parameter characteristics of contact binaries, we found that only KIC 4937217 could be a member of NGC 6819. Moreover, KIC 5199489 should be a shallow, unity-mass-ratio contact binary implying an early contact stage or a mass-ratio reverse stage. Nevertheless, KIC 5198934 and KIC 5374883 should be deep, low mass ratio contact binaries (DLMRCBs), which are usually considered as premergers.

We present the occurrence rates for rocky planets in the habitable zones (HZs) of main-sequence dwarf stars based on the Kepler DR25 planet candidate catalog and Gaia-based stellar properties. We provide the first analysis in terms of star-dependent instellation flux, which allows us to track HZ planets. We define η_⊕ as the HZ occurrence of planets with radii between 0.5 and 1.5 R_⊕ orbiting stars with effective temperatures between 4800 and 6300 K. We find that η_⊕ for the conservative HZ is between ${0.37}_{-0.21}^{+0.48}$ (errors reflect 68% credible intervals) and ${0.60}_{-0.36}^{+0.90}$ planets per star, while the optimistic HZ occurrence is between ${0.58}_{-0.33}^{+0.73}$ and ${0.88}_{-0.51}^{+1.28}$ planets per star. These bounds reflect two extreme assumptions about the extrapolation of completeness beyond orbital periods where DR25 completeness data are available. The large uncertainties are due to the small number of detected small HZ planets. We find similar occurrence rates between using Poisson likelihood Bayesian analysis and using Approximate Bayesian Computation. Our results are corrected for catalog completeness and reliability. Both completeness and the planet occurrence rate are dependent on stellar effective temperature. We also present occurrence rates for various stellar populations and planet size ranges. We estimate with 95% confidence that, on average, the nearest HZ planet around G and K dwarfs is ∼6 pc away and there are ∼4 HZ rocky planets around G and K dwarfs within 10 pc of the Sun.

We present a study based on Gaia DR2 of the population of blue straggler stars in the open clusters Trumpler 5, Trumpler 20, and NGC 2477. All candidates were selected according to their position in the color–magnitude diagram, their proper motion components, and their parallax. We also looked for yellow stragglers, i.e., possible evolved blue stragglers. We found that Trumpler 5 hosts a large blue straggler star population, which allowed us to analyze their radial distribution as a probe of the cluster's dynamical status. The blue straggler star distribution was compared with that of red giant branch stars to evaluate mass segregation. Our results indicate that blue straggler stars are not more centrally concentrated than red giant branch stars stars in any of the clusters. The radial distribution of blue straggler stars in Trumpler 5 is flat. Additionally, using a multi-epoch radial velocity survey conducted with the high-resolution spectrograph FLAMES/GIRAFFE at the Very Large Telescope, we measured the radial velocities of a sample of stragglers to compare with the mean radial velocity and velocity dispersion of the clusters. Based on the radial velocity variations for different epochs, we roughly classified these stars as possible close or long-period binaries.

Molecular D/H ratios are frequently used to probe the chemical past of solar system volatiles. Yet it is unclear which parts of the solar nebula hosted an active deuterium fractionation chemistry. To address this question, we present 02–04 Atacama Large Millimeter/submillimeter Array (ALMA) observations of DCO⁺ and DCN 2–1, 3–2, and 4–3 toward the nearby protoplanetary disk around TW Hya, taken as part of the TW Hya Rosetta Stone project, augmented with archival data. DCO⁺ is characterized by an excitation temperature of ∼40 K across the 70 au radius pebble disk, indicative of emission from a warm, elevated molecular layer. Tentatively, DCN is present at even higher temperatures. Both DCO⁺ and DCN present substantial emission cavities in the inner disk, while in the outer disk the DCO⁺ and DCN morphologies diverge: most DCN emission originates from a narrow ring peaking around 30 au, with some additional diffuse DCN emission present at larger radii, while DCO⁺ is present in a broad structured ring that extends past the pebble disk. Based on a set of simple parametric disk abundance models, these emission patterns can be explained by a near-constant DCN abundance exterior to the cavity, and an increasing DCO⁺ abundance with radius. In conclusion, the ALMA observations reveal an active deuterium fractionation chemistry in multiple disk regions around TW Hya, but not in the cold planetesimal-forming midplane and in the inner disk. More observations are needed to explore whether deuterium fractionation is actually absent in these latter regions, and if its absence is a common feature or something peculiar to the old TW Hya disk.

As our ability to undertake searches for extraterrestrial intelligence (SETI) grows, so does interest in the controversial endeavor of messaging extraterrestrial intelligence (METI). METI proponents point to the SETI Paradox—if all civilizations refrain from METI then SETI is futile. I introduce mutual detectability as a game-theoretic strategy to increase the success potential of targeted SETI. Mutual detectability comprises four laws that establish how SETI participants can engage each other based on mutual evidence of mutual existence. I argue that the party whom both SETI participants can judge to have better quality evidence, or common denominator information (CDI), has an onus to transmit to avoid the SETI Paradox. Transiting exoplanets within the Earth Transit Zone form a target subset that satisfies mutual detectability requirements. I identify the intrinsic time-integrated transit signal strength, which for Earth is 10³ L_⊙ ppm hours yr⁻¹, as suitable CDI. Civilizations on habitable-zone planets of radius ${R}_{{\rm{p}}}/{R}_{\oplus }\lesssim {({L}_{* }/{L}_{\odot })}^{-1/7}$ have superior CDI on us, and so under the mutual detectability framework have game-theory incentive (onus) to transmit. While the onus to transmit falls on us for habitable planets around L_* > L_⊙ stars, considerations of relative stellar frequency, main-sequence lifetime and planet occurrence rates mean that such systems are likely to be in a small minority. Surveys of the Earth Transit Zone for Earth-analog transiting planets around subsolar luminosity hosts would facilitate targeted SETI programs for civilizations who have game-theory incentive to transmit signals to us. A choice to remain silent, by not engaging in METI toward such systems, does not in this case fuel concerns of a SETI Paradox.

Ground-based optical long-baseline interferometry has the power to measure the orbits of close binary systems at ∼10 μas precision. This precision makes it possible to detect "wobbles" in the binary motion due to the gravitational pull from additional short-period companions. We started the ARrangement for Micro-Arcsecond Differential Astrometry (ARMADA) survey with the Michigan Infra-Red Combiner (MIRC)/MIRC-X instrument at the Center for High Angular Resoloution Astronomy (CHARA) array for the purpose of detecting giant planets and stellar companions orbiting individual stars in binary systems. We describe our observations for the survey, and introduce the wavelength calibration scheme that delivers precision at the tens of microarcseconds level for <02 binaries. We test our instrument performance on a known triple system, κ Peg, and show that our survey is delivering a factor of 10 better precision than previous similar surveys. We present astrometric detections of tertiary components to two B-type binaries: a 30 day companion to α Del, and a 50 day companion to ν Gem. We also collected radial velocity data for α Del with the Tennessee State University Automated Spectroscopic Telescope at Fairborn Observatory. We are able to measure the orbits and masses of all three components in these systems. We find that the previously published radial velocity orbit for the inner pair of ν Gem is not consistent with our visual orbit. The precision achieved for these orbits suggests that our ARMADA survey will be successful at discovering new compact triple systems to A/B-type binary systems, leading to better statistics of hierarchical system architectures and formation history.

This study constitutes part of a larger effort aimed at better characterizing the Galactic globular clusters (GGCs) located toward the inner Milky Way bulge and disk. Here, we focus on internal kinematics of nine GGCs, obtained from space-based imaging over time baselines of >9 yr. We exploit multiple avenues to assess the dynamical state of the target GGCs, constructing radial profiles of projected stellar density, proper motion dispersion, and anisotropy. We posit that two-thirds (6/9) of our target GGCs are in an advanced dynamical state, and are close to (or have recently undergone) core-collapse, supported by at least two lines of evidence. First, we find relatively steep proper motion dispersion profiles, in accord with literature values for core-collapsed GGCs. Second, we find that our sample is, in the mean, isotropic even out to their half-light radii, although one of our target clusters (NGC 6380) is tangentially anisotropic at >1σ beyond its half-light radius, in accord with theoretical predictions for clusters evolving in strong tidal fields. Our proper motion dispersion and anisotropy profiles are made publicly available.

We present a new volume-limited sample of L0–T8 dwarfs out to 25 pc defined entirely by parallaxes, using our recent measurements from UKIRT/WFCAM along with Gaia DR2 and literature parallaxes. With 369 members, our sample is the largest parallax-defined volume-limited sample of L and T dwarfs to date, yielding the most precise space densities for such objects. We find the local L0–T8 dwarf population includes $5.5 \% \pm 1.2 \%$ young objects (≲200 Myr) and $2.6 \% \pm 1.6 \%$ subdwarfs, as expected from recent studies favoring representative ages ≲4 Gyr for the ultracool field population. This is also the first volume-limited sample to comprehensively map the transition from L to T dwarfs (spectral types ≈L8–T4). After removing binaries, we identify a previously unrecognized, statistically significant (>4.4σ) gap ≈0.5 mag wide in ${(J-K)}_{\mathrm{MKO}}$ colors in the L/T transition, i.e., a lack of such objects in our volume-limited sample, implying a rapid phase of atmospheric evolution. In contrast, the most successful models of the L/T transition to date—the "hybrid" models of Saumon & Marley—predict a pileup of objects at the same colors where we find a deficit, demonstrating the challenge of modeling the atmospheres of cooling brown dwarfs. Our sample illustrates the insights to come from even larger parallax-selected samples from the upcoming Legacy Survey of Space and Time by the Vera Rubin Obsevatory.

The hierarchical three-body problem is one of the classical issues of celestial mechanics, but recently it has regained importance due to its applications to new scenarios, like compact objects and exoplanets. In this paper we realize a computational study of this problem using the TIDES software package, which is applied not only to a set of theoretical cases but also to actual stellar systems. The characteristics of the Taylor series integration method, used by TIDES, permit the confirmation of the appearance of the Lidov–Kozai cycles in the case of high mutual inclinations. In addition, a historical review of this problem is included.

Atmospheric characterization of temperate, rocky planets is the holy grail of exoplanet studies. These worlds are at the limits of our capabilities with current instrumentation in transmission spectroscopy and challenge our state-of-the-art statistical techniques. Here we present the transmission spectrum of the temperate super-Earth LHS 1140b using the Hubble Space Telescope (HST). The Wide Field Camera 3 (WFC3) G141 grism data of this habitable-zone (T_eq = 235 K) super-Earth (R = 1.7 R_⊕) shows tentative evidence of water. However, the signal-to-noise ratio, and thus the significance of the detection, is low and stellar contamination models can cause modulation over the spectral band probed. We attempt to correct for contamination using these models and find that, while many still lead to evidence for water, some could provide reasonable fits to the data without the need for molecular absorption although most of these cause features in the visible ground-based data which are nonphysical. Future observations with the James Webb Space Telescope would be capable of confirming, or refuting, this atmospheric detection.

We present and make publicly available the third data release (DR3) of the Keck Observatory Database of Ionized Absorption toward Quasars (KODIAQ) survey. KODIAQ DR3 consists of a fully reduced sample of 727 quasars at 0.1 < z_em < 6.4 observed with the Echellette Sepctrograph and Imager at moderate resolution (4000 ≤ R ≤ 10,000). DR3 contains 872 spectra available in flux calibrated form, representing a sum total exposure time of ∼2.8 megaseconds. These coadded spectra arise from a total of 2753 individual exposures of quasars taken from the Keck Observatory Archive (KOA) in raw form and uniformly processed using a data reduction package made available through the XIDL distribution. DR3 is publicly available to the community, housed as a higher level science product at the KOA and in the igmspec database.

The continuous and unbroken time-series photometry data of Kepler and the Transiting Exoplanet Survey Satellite (TESS) provide a good opportunity to study the continuous variations in the light curve of binary stars. This paper reports the discoveries of the correlation between the two maxima on the light curve of KIC 06852488 and the correlation between the O'Connell effect and the O − C curve. The Max I and Max II vary with a same cycle length of ∼2000 days and a 180° phase difference, and the variation of the Max II coincides with the O − C curve of the primary light minima. After analyzing the Kepler and TESS light curves, it is detected that this binary is a semi-detached system with a mass ratio of 0.4622(±0.0036). The secondary component is filling its critical Roche lobe, while the primary component is only filling 12.25(±0.10)% of the lobe volume that contributes more than 85% luminosity of the total system. The variation of the O'Connell effect could be explained by an evolving hot spot on the primary component and an evolving cool spot on the secondary component. It is found that their positions are symmetrical with the inner Lagrange L1 point. After subtracting the binary brightness changes, six optical flares are detected that come from the cool secondary. We calculated the energy of flares and found that all of the flares are superflares. Both the flares and an evolving dark spot on the lobe-filling secondary component make the system a very interesting source to investigate the effects of binary interaction on the magnetic activities.

HD 106315 and GJ 9827 are two bright, nearby stars that host multiple super-Earths and sub-Neptunes discovered by K2 that are well suited for atmospheric characterization. We refined the planets' ephemerides through Spitzer transits, enabling accurate transit prediction required for future atmospheric characterization through transmission spectroscopy. Through a multiyear high-cadence observing campaign with Keck/High Resolution Echelle Spectrometer and Magellan/Planet Finder Spectrograph, we improved the planets' mass measurements in anticipation of Hubble Space Telescope transmission spectroscopy. For GJ 9827, we modeled activity-induced radial velocity signals with a Gaussian process informed by the Calcium II H&K lines in order to more accurately model the effect of stellar noise on our data. We measured planet masses of M_b = 4.87 ± 0.37 M_⊕, M_c = 1.92 ± 0.49 M_⊕, and M_d = 3.42 ± 0.62 M_⊕. For HD 106315, we found that such activity radial velocity decorrelation was not effective due to the reduced presence of spots and speculate that this may extend to other hot stars as well (T_eff > 6200 K). We measured planet masses of M_b = 10.5 ± 3.1 M_⊕ and M_c = 12.0 ± 3.8 M_⊕. We investigated all of the planets' compositions through comparison of their masses and radii to a range of interior models. GJ 9827 b and GJ 9827 c are both consistent with a 50/50 rock-iron composition, GJ 9827 d and HD 106315 b both require additional volatiles and are consistent with moderate amounts of water or hydrogen/helium, and HD 106315 c is consistent with a ∼10% hydrogen/helium envelope surrounding an Earth-like rock and iron core.

Three-body interactions are ubiquitous in astrophysics. For instance, Kozai–Lidov oscillations in hierarchical triple systems have been studied extensively and applied to a wide range of astrophysical systems. However, mildly hierarchical triples also play an important role, but they are less explored. In this work, we consider the secular dynamics of a test particle in a mildly hierarchical configuration. We find the limit within which the secular approximation is reliable when the outer perturber is in a circular orbit. In addition, we present resonances and chaotic regions using surface-of-section plots, and characterize regions of phase space that allow large eccentricity and inclination variations. Finally, we apply the secular results to the outer Solar System. We focus on the distribution of extreme trans-Neptunian objects (eTNOs) under the perturbation of a possible outer planet (Planet 9), and find that in addition to a low-inclination Planet 9, a polar or a counter-orbiting one could also produce pericenter clustering of eTNOs, while the polar one leads to a wider spread of eTNO inclinations.

We present new measurements of the clustering of stellar-mass-complete samples of ∼40,000 SDSS galaxies at z ∼ 0.03 as a joint function of stellar mass and specific star formation rate (sSFR). Our results confirm what Coil et al. find at z ∼ 0.7: galaxy clustering is a stronger function of sSFR at fixed stellar mass than of stellar mass at fixed sSFR. We also find that galaxies above the star-forming main sequence (SFMS) with higher sSFR are less clustered than galaxies below the SFMS with lower sSFR, at a given stellar mass. A similar trend is present for quiescent galaxies. This confirms that main-sequence scatter, and scatter within the quiescent sequence, is physically connected to the large-scale cosmic density field. We compare the resulting galaxy bias versus sSFR, and relative bias versus sSFR ratio, for different galaxy samples across 0 < z < 1.2 to mock galaxy catalogs based on the empirical galaxy evolution model of Behroozi et al. This model fits PRIMUS and DEEP2 clustering data well at intermediate redshift, but agreement with SDSS is not as strong. We show that increasing the correlation between galaxy SFR and halo accretion rate at z ∼ 0 in the model substantially improves agreement with SDSS data. Mock catalogs suggest that central galaxies contribute substantially to the dependence of clustering on sSFR at a given stellar mass and that the signal is not simply an effect of satellite galaxy fraction differences with sSFR. Our results are highly constraining for galaxy evolution models and show that the stellar-to-halo mass relation depends on sSFR.