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Abstract We present the discovery and characterization of TOI-4364b, a young mini-Neptune in the tidal tails of the Hyades cluster, identified through TESS transit observations and ground-based follow-up photometry. The planet orbits a bright M dwarf (K= 9.1 mag) at a distance of 44 pc, with an orbital period of 5.42 days and an equilibrium temperature of $488_{-7}^{+9}$K. The host star's well-constrained age of 710 Myr makes TOI-4364b an exceptional target for studying early planetary evolution around low-mass stars. We determined a planetary radius of $2.01_{-0.08}^{+0.10}{R}_{\oplus }$, indicating that this planet is situated near the upper edge of the radius valley. This suggests that the planet retains a modest H/He envelope. As a result, TOI-4364b provides a unique opportunity to explore the transition between rocky super-Earths and gas-rich mini-Neptunes at the early stages of evolution. Its radius, which may still evolve as a result of ongoing atmospheric cooling, contraction, and photoevaporation, further enhances its significance for understanding planetary development. Furthermore, TOI-4364b’s moderately high transmission spectroscopy metric of 44.2 positions it as a viable candidate for atmospheric characterization with instruments such as JWST. This target has the potential to offer crucial insights into atmospheric retention and loss in young planetary systems. 

Abstract We present the discovery of 11 new transiting brown dwarfs (BDs) and low-mass M dwarfs from NASA’s Transiting Exoplanet Survey Satellite (TESS) mission: TOI-2844, TOI-3122, TOI-3577, TOI-3755, TOI-4462, TOI-4635, TOI-4737, TOI-4759, TOI-5240, TOI-5467, and TOI-5882. They consist of five BD companions and six very-low-mass stellar companions ranging in mass from 25M_Jto 128M_J. We used a combination of photometric time-series, spectroscopic, and high-resolution imaging follow-up as a part of the TESS Follow-up Observing Program (or TFOP) to characterize each system. With over 50 transiting BDs confirmed, we now have a large enough sample to directly test different formation and evolutionary scenarios. We provide a renewed perspective on the transiting “brown dwarf desert” and its role in differentiating between planetary and stellar formation mechanisms. Our analysis of the eccentricity distribution for the transiting BD sample does not support previous claims of a transition between planetary and stellar formation at ∼42M_J. We also contribute a first look into the metallicity distribution of transiting companions in the range 7–150M_J, showing that this does not support a ∼42M_Jtransition too. Finally, we also detect a significant lithium absorption feature in one of the BD hosts (TOI-5882). However, we determine that the host star is likely old based on rotation, kinematic, and photometric mdeasurements. We therefore claim that TOI-5882 may be a candidate for planetary engulfment. 

Astronomers have found more than a dozen planets transiting stars that are 10–40 million years old1, but younger transiting planets have remained elusive. The lack of such discoveries may be because planets have not fully formed at this age or because our view is blocked by the protoplanetary disk. However, we now know that many outer disks are warped or broken2; provided the inner disk is depleted, transiting planets may thus be visible. Here we report observations of the transiting planet IRAS 04125+2902 b orbiting a 3-million-year-old, 0.7-solar-mass, pre-main-sequence star in the Taurus Molecular Cloud. The host star harbours a nearly face-on (30 degrees inclination) transitional disk3 and a wide binary companion. The planet has a period of 8.83 days, a radius of 10.7 Earth radii (0.96 Jupiter radii) and a 95%-confidence upper limit on its mass of 90 Earth masses (0.3 Jupiter masses) from radial-velocity measurements, making it a possible precursor of the super-Earths and sub-Neptunes frequently found around main-sequence stars. The rotational broadening of the star and the orbit of the wide (4 arcseconds, 635 astronomical units) companion are both consistent with edge-on orientations. Thus, all components of the system are consistent with alignment except the outer disk; the origin of this misalignment is unclear. 

ABSTRACT Transit timing variations (TTVs) can be induced by a range of physical phenomena, including planet–planet interactions, planet–moon interactions, and stellar activity. Recent work has shown that roughly half of moons would induce fast TTVs with a short period in the range of 2–4 orbits of its host planet around the star. An investigation of the Kepler TTV data in this period range identified one primary target of interest, Kepler-1513 b. Kepler-1513 b is a $$8.05^{+0.58}_{-0.40}$$ R⊕ planet orbiting a late G-type dwarf at $$0.53^{+0.04}_{-0.03}$$ au. Using Kepler photometry, this initial analysis showed that Kepler-1513 b’s TTVs were consistent with a moon. Here, we report photometric observations of two additional transits nearly a decade after the last Kepler transit using both ground-based observations and space-based photometry with TESS. These new transit observations introduce a previously undetected long period TTV, in addition to the original short period TTV signal. Using the complete transit data set, we investigate whether a non-transiting planet, a moon, or stellar activity could induce the observed TTVs. We find that only a non-transiting perturbing planet can reproduce the observed TTVs. We additionally perform transit origami on the Kepler photometry, which independently applies pressure against a moon hypothesis. Specifically, we find that Kepler-1513 b’s TTVs are consistent with an exterior non-transiting ∼Saturn mass planet, Kepler-1513 c, on a wide orbit, $$\sim 5~{{\ \rm per \, cent}}$$ outside a 5:1 period ratio with Kepler-1513 b. This example introduces a previously unidentified cause for planetary interlopers in the exomoon corridor, namely an insufficient baseline of observations. 

Abstract We report the validation of multiple planets transiting the nearby (d= 12.8 pc) K5V dwarf HD 101581 (GJ 435, TOI–6276, TIC 397362481). This system consists of at least two Earth-size planets whose orbits are near a mutual 4:3 mean-motion resonance, HD 101581 b ( $R_p={0.956}_{-0.061}^{+0.063}{R}_{\oplus }$,P= 4.47 days) and HD 101581c ( $R_p={0.990}_{-0.070}^{+0.070}{R}_{\oplus }$,P= 6.21 days). Both planets were discovered in Sectors 63 and 64 TESS observations and statistically validated with supporting ground-based follow-up. We also identify a signal that probably originates from a third transiting planet, TOI-6276.03 ( $R_p={0.982}_{-0.098}^{+0.114}{R}_{\oplus }$,P= 7.87 days). These planets are remarkably uniform in size and their orbits are evenly spaced, representing a prime example of the “peas-in-a-pod” architecture seen in other compact multiplanet systems. AtV= 7.77, HD 101581 is the brightest star known to host multiple transiting planets smaller than 1.5R_⊕. HD 101581 is a promising system for atmospheric characterization and comparative planetology of small planets. 

Abstract Young (<500 Myr) planets are critical to studying how planets form and evolve. Among these young planetary systems, multiplanet configurations are particularly useful, as they provide a means to control for variables within a system. Here, we report the discovery and characterization of a young planetary system, TOI-1224. We show that the planet host resides within a young population we denote as MELANGE-5. By employing a range of age-dating methods—isochrone fitting, lithium abundance analysis, gyrochronology, and Gaia excess variability—we estimate the age of MELANGE-5 to be 210 ± 27 Myr. MELANGE-5 is situated in close proximity to previously identified younger (80–110 Myr) associations, Crius 221 and Theia 424/Volans-Carina, motivating further work to map out the group boundaries. In addition to a planet candidate detected by the TESS pipeline and alerted as a TESS object of interest, TOI-1224 b, we identify a second planet, TOI-1224 c, using custom search tools optimized for young stars (NotchandLOCoR). We find that the planets are 2.10 ± 0.09R_⊕and 2.88 ± 0.10R_⊕and orbit their host star every 4.18 and 17.95 days, respectively. With their bright (K= 9.1 mag), small (R_*= 0.44R_⊙), and cool (T_eff= 3326 K) host star, these planets represent excellent candidates for atmospheric characterization with JWST. 

Abstract 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’sTESSmission 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 GaiaG-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 (0.55M_J<M_P< 3.88M_J) and sizes (0.967R_J<R_P< 1.438R_J) and orbit stars that have an effective temperature in the range of 5360 K <T_eff< 6860 K with GaiaG-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. 

We report the confirmation and characterisation of TOI-1820 b, TOI-2025 b, and TOI-2158 b, three Jupiter-sized planets on short-period orbits around G-type stars detected by TESS. Through our ground-based efforts using the FIES and Tull spectrographs, we have confirmed these planets and characterised their orbits, and find periods of around 4.9 d, 8.9 d, and 8.6 d for TOI-1820 b, TOI-2025 b, and TOI-2158 b, respectively. The sizes of the planets range from 0.96 to 1.14 Jupiter radii, and their masses are in the range from 0.8 to 4.4 Jupiter masses. For two of the systems, namely TOI-2025 and TOI-2158, we see a long-term trend in the radial velocities, indicating the presence of an outer companion in each of the two systems. For TOI-2025 we furthermore find the star to be well aligned with the orbit, with a projected obliquity of 9 −31 +33 °. As these planets are all found in relatively bright systems ( V ~ 10.9–11.6 mag), they are well suited for further studies, which could help shed light on the formation and migration of hot and warm Jupiters. 

Abstract 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 temperatureT_eqand planetary radiusR_pand 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. 

Abstract We present the Transiting Exoplanet Survey Satellite (TESS) discovery of the LHS 1678 (TOI-696) exoplanet system, comprised of two approximately Earth-sized transiting planets and a likely astrometric brown dwarf orbiting a bright ( V J = 12.5, K s = 8.3) M2 dwarf at 19.9 pc. The two TESS-detected planets are of radius 0.70 ± 0.04 R ⊕ and 0.98 ± 0.06 R ⊕ in 0.86 day and 3.69 day orbits, respectively. Both planets are validated and characterized via ground-based follow-up observations. High Accuracy Radial Velocity Planet Searcher RV monitoring yields 97.7 percentile mass upper limits of 0.35 M ⊕ and 1.4 M ⊕ for planets b and c, respectively. The astrometric companion detected by the Cerro Tololo Inter-American Observatory/Small and Moderate Aperture Telescope System 0.9 m has an orbital period on the order of decades and is undetected by other means. Additional ground-based observations constrain the companion to being a high-mass brown dwarf or smaller. Each planet is of unique interest; the inner planet has an ultra-short period, and the outer planet is in the Venus zone. Both are promising targets for atmospheric characterization with the James Webb Space Telescope and mass measurements via extreme-precision radial velocity. A third planet candidate of radius 0.9 ± 0.1 R ⊕ in a 4.97 day orbit is also identified in multicycle TESS data for validation in future work. The host star is associated with an observed gap in the lower main sequence of the Hertzsprung–Russell diagram. This gap is tied to the transition from partially to fully convective interiors in M dwarfs, and the effect of the associated stellar astrophysics on exoplanet evolution is currently unknown. The culmination of these system properties makes LHS 1678 a unique, compelling playground for comparative exoplanet science and understanding the formation and evolution of small, short-period exoplanets orbiting low-mass stars.