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A comprehensive infrared spectroscopic study of star TRAPPIST-1 is a crucial step toward the detailed examination of its planets. While the presence of Earth’s atmosphere has limited the spectral extent of such a study up to now, the Near Infrared Imager and Slitless Spectrograph (NIRISS) and the Near Infrared Spectrograph instruments aboard the James Webb Space Telescope (JWST) can now yield the 0.6–5 μ m spectral energy distribution (SED) of the star. Here we translate TRAPPIST-1's SED into tight constraints on its luminosity ( L _bol = 0.000566 ± 0.000022 L _⊙ ), effective temperature ( T _eff = 2569 ± 28 K), and metallicity ([Fe/H] = 0.052 ± 0.073) and investigate the behavior of its gravity-sensitive indices. Through band-by-band comparisons of the NIRISS and ground-based spectra, TRAPPIST-1 exhibits a blend of both field source and intermediate-gravity spectral characteristics, suggesting that the star is likely a field-age source with spectral features reminiscent of young objects. We also employ photospheric modeling incorporating theoretical and JWST spectra to constrain stellar surface heterogeneities, finding that the limited fidelity of current stellar spectral models precludes definitive constraints on the physical parameters of the distinct spectral components giving rise to TRAPPIST-1's photospheric heterogeneity and variability. In addition, we find intermodel differences in the inferences of properties (e.g., the effective temperature) over one order of magnitude larger than the instrument-driven uncertainties (∼100 K vs. ∼4 K), pointing toward a model-driven accuracy wall. Our findings call for a new generation of stellar models to support the optimal mining of JWST data and further constraining stellar—and ultimately planetary—properties.

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Hot Jupiters were many of the first exoplanets discovered in the 1990s, but in the decades since their discovery the mysteries surrounding their origins have remained. Here we present nine new hot Jupiters (TOI-1855 b, TOI-2107 b, TOI-2368 b, TOI-3321 b, TOI-3894 b, TOI-3919 b, TOI-4153 b, TOI-5232 b, and TOI-5301 b) discovered by NASA’s TESS mission and confirmed using ground-based imaging and spectroscopy. These discoveries are the first in a series of papers named the Migration and Evolution of giant ExoPlanets survey and are part of an ongoing effort to build a complete sample of hot Jupiters orbiting FGK stars, with a limiting Gaia G -band magnitude of 12.5. This effort aims to use homogeneous detection and analysis techniques to generate a set of precisely measured stellar and planetary properties that is ripe for statistical analysis. The nine planets presented in this work occupy a range of masses (0.55 M _J < M _P < 3.88 M _J ) and sizes (0.967 R _J < R _P < 1.438 R _J ) and orbit stars that have an effective temperature in the range of 5360 K < T _eff < 6860 K with Gaia G -band magnitudes ranging from 11.1 to 12.7. Two of the planets in our sample have detectable orbital eccentricity: TOI-3919 b ( $e={0.259}_{-0.036}^{+0.033}$ ) and TOI-5301 b ( $e={0.33}_{-0.10}^{+0.11}$ ). These eccentric planets join a growing sample of eccentric hot Jupiters that are consistent with high-eccentricity tidal migration, one of the three most prominent theories explaining hot Jupiter formation and evolution.

Sub-Neptunes with radii of 2–3 R _⊕ are intermediate in size between rocky planets and Neptune-sized planets. The orbital properties and bulk compositions of transiting sub-Neptunes provide clues to the formation and evolution of close-in small planets. In this paper, we present the discovery and follow-up of four sub-Neptunes orbiting M dwarfs (TOI-782, TOI-1448, TOI-2120, and TOI-2406), three of which were newly validated by ground-based follow-up observations and statistical analyses. TOI-782 b, TOI-1448 b, TOI-2120 b, and TOI-2406 b have radii of ${R}_{{\rm{p}}}={2.740}_{-0.079}^{+0.082}\,{R}_{\oplus }$ , ${2.769}_{-0.068}^{+0.073}\,{R}_{\oplus }$ , 2.120 ± 0.067 R _⊕ , and ${2.830}_{-0.066}^{+0.068}\,{R}_{\oplus }$ and orbital periods of P = 8.02, 8.11, 5.80, and 3.08 days, respectively. Doppler monitoring with the Subaru/InfraRed Doppler instrument led to 2 σ upper limits on the masses of

JWST has ushered in an era of unprecedented ability to characterize exoplanetary atmospheres. While there are over 5000 confirmed planets, more than 4000 Transiting Exoplanet Survey Satellite (TESS) planet candidates are still unconfirmed and many of the best planets for atmospheric characterization may remain to be identified. We present a sample of TESS planets and planet candidates that we identify as “best-in-class” for transmission and emission spectroscopy with JWST. These targets are sorted into bins across equilibrium temperature T _eq and planetary radius R _p and are ranked by a transmission and an emission spectroscopy metric (TSM and ESM, respectively) within each bin. We perform cuts for expected signal size and stellar brightness to remove suboptimal targets for JWST. Of the 194 targets in the resulting sample, 103 are unconfirmed TESS planet candidates, also known as TESS Objects of Interest (TOIs). We perform vetting and statistical validation analyses on these 103 targets to determine which are likely planets and which are likely false positives, incorporating ground-based follow-up from the TESS Follow-up Observation Program to aid the vetting and validation process. We statistically validate 18 TOIs, marginally validate 31 TOIs to varying levels of confidence, deem 29 TOIs likely false positives, and leave the dispositions for four TOIs as inconclusive. Twenty-one of the 103 TOIs were confirmed independently over the course of our analysis. We intend for this work to serve as a community resource and motivate formal confirmation and mass measurements of each validated planet. We encourage more detailed analysis of individual targets by the community.

The first James Webb Space Telescope observations of TRAPPIST-1 c showed a secondary eclipse depth of 421 ± 94 ppm at 15 μ m, which is consistent with a bare rock surface or a thin, O _2 -dominated, low-CO _2 atmosphere. Here we further explore potential atmospheres for TRAPPIST-1 c by comparing the observed secondary eclipse depth to synthetic spectra of a broader range of plausible environments. To self-consistently incorporate the impact of photochemistry and atmospheric composition on atmospheric thermal structure and predicted eclipse depth, we use a two-column climate model coupled to a photochemical model and simulate O _2 -dominated, Venus-like, and steam atmospheres. We find that a broader suite of plausible atmospheric compositions are also consistent with the data. For lower-pressure atmospheres (0.1 bar), our O _2 –CO _2 atmospheres produce eclipse depths within 1 σ of the data, consistent with the modeling results of Zieba et al. However, for higher-pressure atmospheres, our models produce different temperature–pressure profiles and are less pessimistic, with 1–10 bar O _2 , 100 ppm CO _2 models within 2.0 σ –2.2 σ of the measured secondary eclipse depth and up to 0.5% CO _2 within 2.9 σ . Venus-like atmospheres are still unlikely. For thin O _2 atmospheres of 0.1 bar with a low abundance of CO _2 (∼100 ppm), up to 10% water vapor can be present and still provide an eclipse depth within 1 σ of the data. We compared the TRAPPIST-1 c data to modeled steam atmospheres of ≤3 bars, which are 1.7 σ –1.8 σ from the data and not conclusively ruled out. More data will be required to discriminate between possible atmospheres or more definitively support the bare rock hypothesis.

We present the discovery of TOI-3235 b, a short-period Jupiter orbiting an M dwarf with a stellar mass close to the critical mass at which stars transition from partially to fully convective. TOI-3235 b was first identified as a candidate from TESS photometry and confirmed with radial velocities from ESPRESSO and ground-based photometry from HATSouth, MEarth-South, TRAPPIST-South, LCOGT, and ExTrA. We find that the planet has a mass of 0.665 ± 0.025 M _J and a radius of 1.017 ± 0.044 R _J . It orbits close to its host star, with an orbital period of 2.5926 days but has an equilibrium temperature of ≈ 604 K, well below the expected threshold for radius inflation of hot Jupiters. The host star has a mass of 0.3939 ± 0.0030 M _☉ , a radius of 0.3697 ± 0.0018 R _☉ , an effective temperature of 3389 K, and a J -band magnitude of 11.706 ± 0.025. Current planet formation models do not predict the existence of gas giants such as TOI-3235 b around such low-mass stars. With a high transmission spectroscopy metric, TOI-3235 b is one of the best-suited giants orbiting M dwarfs for atmospheric characterization.

The geometries of near-resonant planetary systems offer a relatively pristine window into the initial conditions of exoplanet systems. Given that near-resonant systems have likely experienced minimal dynamical disruptions, the spin–orbit orientations of these systems inform the typical outcomes of quiescent planet formation, as well as the primordial stellar obliquity distribution. However, few measurements have been made to constrain the spin–orbit orientations of near-resonant systems. We present a Rossiter–McLaughlin measurement of the near-resonant warm Jupiter TOI-2202 b, obtained using the Carnegie Planet Finder Spectrograph on the 6.5 m Magellan Clay Telescope. This is the eighth result from the Stellar Obliquities in Long-period Exoplanet Systems survey. We derive a sky-projected 2D spin–orbit angle $\lambda ={26}_{-15}^{+12}{^\circ} $ and a 3D spin–orbit angle $\psi ={31}_{-11}^{+13}{^\circ} $ , finding that TOI-2202 b—the most massive near-resonant exoplanet with a 3D spin–orbit constraint to date—likely deviates from exact alignment with the host star’s equator. Incorporating the full census of spin–orbit measurements for near-resonant systems, we demonstrate that the current set of near-resonant systems with period ratios P _2 / P _1 ≲ 4 is generally consistent with a quiescent formation pathway, with some room for low-level (≲20°) protoplanetary disk misalignments or post-disk-dispersal spin–orbit excitation. Our result constitutes the first population-wide analysis of spin–orbit geometries for near-resonant planetary systems.

We present the discovery from the TESS mission of two giant planets transiting M-dwarf stars: TOI 4201 b and TOI 5344 b. We also provide precise radial velocity measurements and updated system parameters for three other M dwarfs with transiting giant planets: TOI 519, TOI 3629, and TOI 3714. We measure planetary masses of 0.525 ± 0.064 M _J , 0.243 ± 0.020 M _J , 0.689 ± 0.030 M _J , 2.57 ± 0.15 M _J , and 0.412±0.040 M _J for TOI 519 b, TOI 3629 b, TOI 3714 b, TOI 4201 b, and TOI 5344 b, respectively. The corresponding stellar masses are 0.372 ± 0.018 M _☉ , 0.635 ± 0.032 M _☉ , 0.522 ± 0.028 M _☉ , 0.626 ± 0.033 M _☉ , and 0.612 ± 0.034 M _☉ . All five hosts have supersolar metallicities, providing further support for recent findings that, like for solar-type stars, close-in giant planets are preferentially found around metal-rich M-dwarf host stars. Finally, we describe a procedure for accounting for systematic errors in stellar evolution models when those models are included directly in fitting a transiting planet system.

Observations and statistical studies have shown that giant planets are rare around M dwarfs compared with Sun-like stars. The formation mechanism of these extreme systems has remained under debate for decades. With the help of the TESS mission and ground-based follow-up observations, we report the discovery of TOI-4201b, the most massive and densest hot Jupiter around an M dwarf known so far with a radius of 1.22 ± 0.04 R _J and a mass of 2.48 ± 0.09 M _J , about 5 times heavier than most other giant planets around M dwarfs. It also has the highest planet-to-star mass ratio ( q ∼ 4 × 10 ^−3 ) among such systems. The host star is an early M dwarf with a mass of 0.61 ± 0.02 M _⊙ and a radius of 0.63 ± 0.02 R _⊙ . It has significant supersolar iron abundance ([Fe/H] = 0.52 ± 0.08 dex). However, interior structure modeling suggests that its planet TOI-4201b is metal-poor, which challenges the classical core-accretion correlation of stellar−planet metallicity, unless the planet is inflated by additional energy sources. Building on the detection of this planet, we compare the stellar metallicity distribution of four planetary groups: hot/warm Jupiters around G/M dwarfs. We find that hot/warm Jupiters show a similar metallicity dependence around G-type stars. For M-dwarf host stars, the occurrence of hot Jupiters shows a much stronger correlation with iron abundance, while warm Jupiters display a weaker preference, indicating possible different formation histories.

NASA’s Transiting Exoplanet Survey Satellite (TESS) is an all-sky survey mission designed to find transiting exoplanets orbiting nearby bright stars. It has identified more than 329 transiting exoplanets, and almost 6000 candidates remain unvalidated. In this manuscript, we discuss the findings from the ongoing Validation of Transiting Exoplanets using Statistical Tools (VaTEST) project, which aims to validate new exoplanets for further characterization. We validated 11 new exoplanets by examining the light curves of 24 candidates using the LATTE and TESS-Plot tools and computing the false-positive probabilities using the statistical validation tool TRICERATOPS . These include planets suitable for atmospheric characterization using transmission spectroscopy (TOI-2194b), emission spectroscopy (TOI-3082b and TOI-5704b) and for both transmission and emission spectroscopy (TOI-672b, TOI-1694b, and TOI-2443b). Our validated planets have one super-Earth (TOI-2194b) orbiting a bright ( V = 8.42 mag), metal-poor ([Fe/H] = −0.3720 ± 0.1) star, and one short-period Neptune-like planet (TOI-5704) in the hot-Neptune desert. In total, we validated one super-Earth, seven sub-Neptunes, one Neptune-like, and two sub-Saturn or super-Neptune-like exoplanets. Additionally, we identify five likely planet candidates (TOI-323, TOI-1180, TOI-2200, TOI-2408, and TOI-3913), which can be further studied to establish their planetary nature.

NASA’s Transiting Exoplanet Survey Satellite (TESS) mission promises to improve our understanding of hot Jupiters by providing an all-sky, magnitude-limited sample of transiting hot Jupiters suitable for population studies. Assembling such a sample requires confirming hundreds of planet candidates with additional follow-up observations. Here we present 20 hot Jupiters that were detected using TESS data and confirmed to be planets through photometric, spectroscopic, and imaging observations coordinated by the TESS Follow-up Observing Program. These 20 planets have orbital periods shorter than 7 days and orbit relatively bright FGK stars (10.9 < G < 13.0). Most of the planets are comparable in mass to Jupiter, although there are four planets with masses less than that of Saturn. TOI-3976b, the longest-period planet in our sample ( P = 6.6 days), may be on a moderately eccentric orbit ( e = 0.18 ± 0.06), while observations of the other targets are consistent with them being on circular orbits. We measured the projected stellar obliquity of TOI-1937A b, a hot Jupiter on a 22.4 hr orbit with the Rossiter–McLaughlin effect, finding the planet’s orbit to be well aligned with the stellar spin axis (∣ λ ∣ = 4.°0 ± 3.°5). We also investigated the possibility that TOI-1937 is a member of the NGC 2516 open cluster but ultimately found the evidence for cluster membership to be ambiguous. These objects are part of a larger effort to build a complete sample of hot Jupiters to be used for future demographic and detailed characterization work.

We present a volume-limited, spectroscopically verified sample of M7−L5 ultracool dwarfs (UCDs) within 25 pc. The sample contains 410 sources, of which 93% have trigonometric distance measurements (80% from Gaia DR2) and 81% have low-resolution (R ∼ 120), near-infrared (NIR) spectroscopy. We also present an additional list of 60 sources that may be M7−L5 dwarfs within 25 pc when distance or spectral-type uncertainties are taken into account. The spectra provide NIR spectral and gravity classifications, and we use these to identify young sources, red and blue J − KS color outliers, and spectral binaries. We measure very low gravity and intermediate-gravity fractions of and , respectively; fractions of red and blue color outliers of and , respectively; and a spectral binary fraction of . We present an updated luminosity function for M7−L5 dwarfs continuous across the hydrogen-burning limit that agrees with previous studies. We estimate our completeness to range between 69% and 80% when compared to an isotropic model. However, we find that the literature late-M sample is severely incomplete compared to L dwarfs, with completeness of and , respectively. This incompleteness can be addressed with astrometric-based searches of UCDs with Gaia to identify objects previously missed by color- and magnitude-limited surveys. [ABSTRACT FROM AUTHOR]

We report the discovery of the transiting hot Jupiter KPS-1b. This exoplanet orbits a V = 13.0 K1-type main-sequence star every 1.7 days, has a mass of MJup and a radius of RJup. The discovery was made by the prototype Kourovka Planet Search (KPS) project, which used wide-field CCD data gathered by an amateur astronomer using readily available and relatively affordable equipment. Here we describe the equipment and observing technique used for the discovery of KPS-1b, its characterization with spectroscopic observations by the SOPHIE spectrograph and with high-precision photometry obtained with 1 m class telescopes. We also outline the KPS project evolution into the Galactic Plane eXoplanet survey. The discovery of KPS-1b represents a new major step of the contribution of amateur astronomers to the burgeoning field of exoplanetology. [ABSTRACT FROM AUTHOR]

TRAPPIST-1 is an ultracool dwarf star transited by seven Earth-sized planets, for which thorough characterization of atmospheric properties, surface conditions encompassing habitability, and internal compositions is possible with current and next-generation telescopes. Accurate modeling of the star is essential to achieve this goal. We aim to obtain updated stellar parameters for TRAPPIST-1 based on new measurements and evolutionary models, compared to those used in discovery studies. We present a new measurement for the parallax of TRAPPIST-1, 82.4 ± 0.8 mas, based on 188 epochs of observations with the TRAPPIST and Liverpool Telescopes from 2013 to 2016. This revised parallax yields an updated luminosity of , which is very close to the previous estimate but almost two times more precise. We next present an updated estimate for TRAPPIST-1 stellar mass, based on two approaches: mass from stellar evolution modeling, and empirical mass derived from dynamical masses of equivalently classified ultracool dwarfs in astrometric binaries. We combine them using a Monte-Carlo approach to derive a semi-empirical estimate for the mass of TRAPPIST-1. We also derive estimate for the radius by combining this mass with stellar density inferred from transits, as well as an estimate for the effective temperature from our revised luminosity and radius. Our final results are , , and 2516 ± 41 K. Considering the degree to which the TRAPPIST-1 system will be scrutinized in coming years, these revised and more precise stellar parameters should be considered when assessing the properties of TRAPPIST-1 planets. [ABSTRACT FROM AUTHOR]

K2-19 (EPIC201505350) is an interesting planetary system in which two transiting planets with radii ∼7 R⊕ (inner planet b) and ∼4 R⊕ (outer planet c) have orbits that are nearly in a 3:2 mean-motion resonance. Here, we present results of ground-based follow-up observations for the K2-19 planetary system. We have performed high-dispersion spectroscopy and high-contrast adaptive-optics imaging of the host star with the HDS and HiCIAO on the Subaru 8.2 m telescope. We find that the host star is a relatively old (≥8 Gyr) late G-type star (Teff ∼ 5350 K, Ms ∼ 0.9 M⊙, and Rs ∼ 0.9 R⊙). We do not find any contaminating faint objects near the host star that could be responsible for (or dilute) the transit signals. We have also conducted transit follow-up photometry for the inner planet with KeplerCam on the FLWO 1.2 m telescope, TRAPPISTCAM on the TRAPPIST 0.6 m telescope, and MuSCAT on the OAO 1.88 m telescope. We confirm the presence of transit timing variations (TTVs), as previously reported by Armstrong and coworkers. We model the observed TTVs of the inner planet using the synodic chopping formulae given by Deck & Agol. We find two statistically indistinguishable solutions for which the period ratios (Pc/Pb) are located slightly above and below the exact 3:2 commensurability. Despite the degeneracy, we derive the orbital period of the inner planet Pb ∼ 7.921 days and the mass of the outer planet Mc ∼ 20 M⊕. Additional transit photometry (especially for the outer planet) as well as precise radial-velocity measurements would be helpful to break the degeneracy and to determine the mass of the inner planet. [ABSTRACT FROM AUTHOR]