High-resolution imaging is widely used to constrain false-positive scenarios in exoplanet validation, but it is a finite follow-up resource that reaches only a subset of candidates, and its population-level impact on validation outcomes has not been quantified through controlled removal experiments. Using an automated pipeline built on TRICERATOPS, we compute the false-positive probability (FPP) of 443 TESS planet candidates. For the 264 planet candidates with high-resolution imaging observations, we compute FPP with and without the corresponding contrast curves, allowing us to quantify the impact of the additional data. We find that 72

Binary stars are ubiquitous; yet it remains unclear how wide-orbit stellar companions influence the formation of hot Jupiters, particularly around M dwarfs. Here, we first report the discovery of TOI-5628Ab, a giant planet transiting a midtype M dwarf ( M _* = 0.36 ± 0.02 M _⊙ ) every 4.34 days, accompanied by an associated white dwarf TOI-5628B ( M _WD = 0.59 ± 0.16 M _⊙ ) at a projected distance of about 2500 au. Using TESS, ground-based photometry, and SPIRou radial velocities, we constrain the planet radius to 0.74 ± 0.04 R _J and mass to 0.09 ± 0.04 M _J , with a 3 σ upper limit of 0.22 M _J . Building on this system, we further conduct a homogeneous systematic search for comoving stellar companions with projected semimajor axes between 100 and 10,000 au around all M dwarfs with confirmed giant planets with periods smaller than 10 days and radii larger than 0.7 R _J , as well as a group of field M stars with stellar properties similar to the planet sample, based on the stellar kinematics from Gaia DR3. We measure a stellar multiplicity of 34.2% ± 9.5% for M dwarfs hosting short-period giant planets, which is substantially higher than the fraction of 5.3% ± 3.7% for the field M stars by approximately a factor of 6. Our results suggest that wide-orbit stellar companions tend to promote the formation of short-period gas giants around M stars with masses 0.21 ≤ M _* ≤ 0.64 M _⊙ , and high-eccentricity migration may play an important role in producing such systems.

Hot Jupiters orbiting hot stars (T_eff > 7000 K) are suggested to have experienced high-eccentricity migration, often evidenced by the tendency for misaligned orbits, despite their circular orbits. In this paper, we present the discovery of TOI-1355 b: an eccentric (e∼0.22) hot Jupiter with a mass of m_p∼5.8M_J and a radius of R_p∼ 1.4R_J orbiting an A-type star with a period of about 2.17 days, identified from the TESS transit survey and subsequent follow-up observations. We measured the stellar parameters using the data from the high-resolution spectrograph Seimei/GAOES-RV and obtained the planetary parameters from the photometric data acquired by TESS and ground-based telescopes. This is one of the rare eccentric hot Jupiters around hot stars. This system could be undergoing high-eccentricity migration. We detected nodal precession by measuring the change in its impact parameter. This implies that its transit will no longer be observable from the middle of 2033. Nevertheless, TOI-1355 b is anticipated to be a compelling target for future atmospheric observations, given the hint of atmospheric variability detected in this study.

Context. The structure and evolution of close-in exoplanets are shaped by atmospheric loss and migration processes, which give rise to key population features such as the hot Neptune desert, ridge, and savanna – regions of the period-radius space whose boundaries offer critical insights into planetary formation and survival. Aims. As part of the KESPRINT collaboration, we selected the TESS transiting planet candidate TOI-3862.01 for radial velocity follow-up to confirm its planetary nature and characterize its mass and bulk properties. This planet candidate is of particular interest due to its position in the middle of the hot Neptune desert, making it a valuable probe for testing theories of planet migration and atmospheric loss. Methods. We confirmed the planetary nature and determined the mass of TOI-3862.01 (hereinafter TOI-3862 b) by performing a joint fit with both transit and radial velocity data, precisely characterizing the bulk properties of this planet. Results. TOI-3862b is a super-Neptune on a 1.56-day orbit around a Sun-like star with an effective temperature of 5300±50 K. It has a mass of 53.7−2.9+2.8 M⊕ and a radius of 5.53 ± 0.18 R⊕, corresponding to a density of 1.7±0.2 g/cm3. This places it among the rare population of hot and dense super-Neptune desert planets. Conclusions. TOI-3862b, residing deep in the hot Neptune desert, represents a rare occurrence in an otherwise sparsely populated region, offering a valuable opportunity to probe the processes that may allow planets to survive in such environments.

We characterize the radius-dependent eccentricity distribution of 347 warm (P = 8-200 days) systems with only one transiting planetary candidate identified during Sectors 1-69 of the TESS mission. Using the “photoeccentric effect” in a hierarchical Bayesian framework, we first model the population using discrete planetary size bins (sub-Neptunes, sub-Saturns, and Jovians). We then develop a continuous mixture model with weights governed by a logistic sigmoid function of radius. We find that the warm-single population is best described by two components: a dominant low-eccentricity mode ( = 0.070-0.068+0.026) and a secondary dynamically excited mode ( = 0.616-0.075+0.091). The fraction of planets belonging to this high-eccentricity component increases strongly with planet radius, characterized by a transition at a break radius of R_br = 9.8-1.1+1.4 R_e. This trend places warm sub-Saturns predominantly on the same low-eccentricity track as sub-Neptunes. In contrast, warm Jovians (8–16 R_e) are frequently eccentric, with 59+-13

The radii of small exoplanets form two populations, super-Earths and sub-Neptunes, separated by a gap known as the radius valley. This feature could be produced by the removal of atmospheres by stellar or internal heating or by the lack of an initial envelope. We used transit photometry and radial velocity measurements to detect and characterize four exoplanets orbiting LHS 1903, a red dwarf star in the Milky Way's thick disk. These four planets have orbital periods ranging from 2.2 to 29.3 days and span the radius valley within a single planetary system. The derived densities indicate that LHS 1903 b is rocky, whereas LHS 1903 c and LHS 1903 d have extended atmospheres. The most distant planet from the host star, LHS 1903 e, has no gaseous envelope, indicating that it formed from gas-depleted material.

As part of the KESPRINT collaboration, we present the discovery and characterization of three exoplanets in the sub-Neptune to super-Neptune regime, spanning key regions of the exo-Neptunian landscape. TOI-1472c and TOI-1648b are newly discovered sub-Neptunes, while TOI-1472b is a previously known super-Neptune for which we provide an improved mass measurement. These planets have orbital periods of 6–15 days and radii of 2.5–4.1 R_⊕, probing regions where planet formation and atmospheric evolution remain poorly understood. We combine TESS transit photometry with ground-based radial velocities to determine precise masses, radii, and orbital properties. TOI-1472b has a mass of 18.0^+0.84_-0.85 M_⊕ and a radius of 4.06 ± 0.10 R_⊕, TOI-1472c has a mass of 21.1^+0.96_-0.99 M_⊕ and a radius of 3.33 ± 0.08 R_⊕, and TOI-1648b has a mass of 7.4^+1.1_-1.3 M_⊕ and a radius of 2.54^+0.14_-0.12 R_⊕. The planets exhibit a range of eccentricities (0.041–0.178), indicating diverse evolutionary histories. TOI-1648b, with a high Transmission Spectroscopy Metric (TSM ∼59), is a promising target for atmospheric characterization. Together, these three planets provide precise constraints on the structure, composition, and dynamical evolution of small to intermediate-sized exoplanets, enriching our understanding of the exo-Neptunian landscape.

Despite decades of research on hot Jupiters, there are still several theories for their formation. Perhaps hot Jupiters form in several ways. Atmospheric and dynamical studies have the capability to constrain the formation scenarios. However, potential targets have to be well characterized before these observations can further constrain the theories. We present the confirmation and characterization of five hot and warm Jupiters discovered by the TESS space mission. Using TESS data combined with ground-based observations, we determine the masses, radii, and other parameters of TOI-2040 b, TOI-2049 b, TOI-2578 b, TOI-4427 b, and TOI-4458 b. Three of the planets have equilibrium temperatures of about 1800 K while two have temperatures of about 1000 K. Particularly interesting for future atmospheric characterizations are TOI-2578 b and TOI-4427 b, because of their low density and large transmission spectroscopy metric. TOI-4458 b is of special interest because it is in the northern PLATO field. It appears that TOI-2040 b has a small, but measurable eccentricity.

The Galaxy's most common known planetary systems have several Earth-to-Neptune-size planets in compact orbits1. At small orbital separations, larger planets are less common than their smaller counterparts by an order of magnitude. The young star V1298 Tau hosts one such compact planetary system, albeit with four planets that are uncommonly large (5 to 10 Earth radii)2,3. The planets form a chain of near-resonances that result in transit-timing variations of several hours. Here we present a multi-year campaign to characterize this system with transit-timing variations, a method insensitive to the intense magnetic activity of the star. Through targeted observations, we first resolved the previously unknown orbital period of the outermost planet. The full 9-year baseline from these and archival data then enabled robust determination of the masses and orbital parameters for all four planets. We find the planets have low, sub-Neptune masses and nearly circular orbits, implying a dynamically tranquil history. Their low masses and large radii indicate that the inner planets underwent a period of rapid cooling immediately after dispersal of the protoplanetary disk. Still, they are much less dense than mature planets of comparable size. We predict the planets will contract to 1.5-4.0 Earth radii and join the population of super-Earths and sub-Neptunes that nature produces in abundance.

Characterizing long-period transiting exoplanets is inherently challenging due to the rarity and long duration of transit events. Yet, these systems provide unique insights into planetary formation, migration, the detection of exomoons, and primordial atmospheres by occupying a sparsely populated region of the exoplanet parameter space. The complexity increases further for long-period planets near mean-motion resonances, where transit timing variations (TTVs) can reach amplitudes of several hours to days. We present a coordinated space- and ground-based observing campaign, using photometry from NEOSSat, multiple LCOGT sites, MuSCAT, MuSCAT3, Tierras and NGTS, to capture the 19-hour transit of the long-period giant exoplanet HIP 41378 f (P = 542 d, R = 9.5 R_⊕) on 31 October 2025. Our transit analysis constrains the time of inferior conjunction to T_C = 2460980.888 ± 0.029 BJD_TDB, occurring ∼ 7 hours earlier than predicted from its linear ephemeris. This significant offset is consistent with the previously reported TTVs of HIP 41378 f, making it the longest-period exoplanet known to exhibit measurable TTVs. By combining this new precise measurement to the transit timings of the two outer planets in the system (HIP 41378 d and HIP 41378 e), we perform a dynamical modeling of the system, using the N-body integrator TRADES, refine the ephemeris of HIP 41378 f, and predict future transit events for all three outer transiting planets.

In this paper, we describe Japan's possible contributions for coronagraph of the Habitable Worlds Observatory (HWO) based on our independent study. We are considering to contribute to the HOW coronagraph by science and hardware, based on Japan's experience for the SPICA coronagraph instrument, contributions to the Nancy Grace Roman Space Telescope, and SCExAO for the Subaru telescope. Currently, hardware contributions of various scales, from large-scale to small components, are considered. As an example of the large-scale hardware case, the optical and mechanical layout of the entire infrared coronagraph is presented. Several individual high-contrast technologies are also briefly introduced, for which research is ongoing in Japan. In discussions, it is pointed out that both the inner working angle (IWA) and sensitivity are particularly critical for the NIR coronagraph. In this situation, dedicated observations of a small number of targets close to the solar system can be one of key science program in this situation, and designing consolidating science objectives, requirements, observation targets, and survey plans is important. It is essential to push the development of advanced coronagraphs that provide small IWAs. On the other hand, it is also necessary to prepare solutions that adopt more robust coronagraphs in parallel. How to coexist visible and NIR coronagraphs within constraints of volume, mass, budget etc. is an important issue. The international sharing for the coronagraph development should be carefully decided by international agreement. Although all of our studies may not be realized in contributions to the first generation of HWO instruments, we are considering Japan's multigenerational participation in the HWO to maximize outcomes of the HWO.

Most known planets are found around metal-rich host stars, which has made it difficult to determine whether a lower metallicity limit for planet formation exists and how the properties of planets born in low-metallicity environments may differ from those with metal-rich origins. We present the discovery and characterization of TOI-7169 b (TIC 372048733 b), a hot Jupiter that is orbiting a spectroscopically-confirmed metal-poor ([Fe/H] = -0.72 +/- 0.05) host star. Based on photometry from TESS and follow-up ground-based imaging, we measure an orbital period of 3.4373125 d and a planetary radius of 1.475 +/- 0.029 R_Jup. We use TRES spectroscopy to determine a mass for TOI-7169 b of 0.41 +/- 0.14 M_Jup. The planet is therefore inflated, with a low density of 0.159 +0.055/-0.054 g/cm^3. We also characterize the host star, showing that TOI-7169 is ancient (12.3 +/- 0.6 Gyr) and alpha-enhanced ([alpha/Fe] 0.3), but with a Galactocentric orbit that is confined to the thin disk. TOI-7169 is perhaps the oldest and most metal-poor star currently known to host a transiting giant planet. Future transmission spectroscopy probing the atmosphere of TOI-7169 b may provide insight into the effect of metallicity on the physical properties of giant planets.

Binary stars are ubiquitous, yet it remains unclear how wide-orbit stellar companions influence the formation of hot Jupiters, particularly around M dwarfs. Here, we first report the discovery of TOI-5628Ab, a giant planet transiting a mid-type M dwarf (M_∗=0.36±0.02 M_⊙) every 4.34 days, accompanied by an associated white dwarf TOI-5628B (M_ WD=0.59±0.16 M_⊙) at a projected distance of about 2,500 AU. Using TESS, ground-based photometry and SPIRou RVs, we constrain the planet radius to 0.74±0.04 R_J and mass to 0.09±0.04 M_J, with a 3σ upper limit of 0.22 M_J. Building on this system, we further conduct a homogeneous systematic search for co-moving stellar companions with projected semi-major axis between 100 and 10,000 AU around all M dwarfs with confirmed giant planets with periods smaller than 10 days and radii larger than 0.7 R_J, as well as a group of field M stars with stellar properties similar to the planet sample, based on the stellar kinematics from Gaia DR3. We measure a stellar multiplicity of 34.2±9.5% for M dwarfs hosting short-period giant planets, which is substantially higher than the fraction of 5.3±3.7% for the field M stars by approximately a factor of 6. Our results suggest that wide-orbit stellar companions tend to promote the formation of short-period giant planets around M stars with masses 0.21 ≤ M_∗≤ 0.64 M_⊙, and high-eccentricity migration may play an important role in producing such systems.

Earth-sized planets transiting M dwarf stars present one of the best opportunities with current facilities for studying the atmospheric and bulk compositions of terrestrial worlds. Here, we statistically validate five new transiting Earth and super-Earth sized planets orbiting M dwarf stars using a combination of light curves from the Transiting Exoplanet Survey Satellite, multicolor observations from Palomar and Las Cumbres Observatory, high-resolution imaging, and stellar spectroscopy. The sample includes TOI-5716 b, an Earth-sized planet ( R _p = 0.96 ± 0.05 R _⊕ ) with a 6.766 day orbit around a metal-poor thin-disk star ([Fe/H] = −0.54 ± 0.10); TOI-5728 b, a super-Earth ( R _p = 1.31 ± 0.05 R _⊕ ) on an 11.497 day orbit; and TOI-5736 b, a larger planet ( R _p = 1.56 ± 0.07 R _⊕ ) with an ultrashort period of just 0.649 days. We also statistically validate a multiplanet system, TOI-5489, hosting two similarly sized super-Earths: TOI-5489 b ( R _p = 1.40 ± 0.05 R _⊕ ) and TOI-5489 c ( R _p = 1.28 ± 0.07 R _⊕ ) with orbital periods of 3.152 and 4.921 days, respectively. Due to their longer orbital periods, TOI-5716 b and TOI-5728 b both have equilibrium temperatures ≤ 400 K, making them useful test cases for studies of atmospheric mass loss. If TOI-5728 b is confirmed to have an Earth-like bulk composition, it would join the very small sample of rocky planets orbiting mid-to-late M dwarfs that lie below the cosmic shoreline and therefore may have retained high mean molecular weight atmospheres.

We report the discovery of a low-mass transiting brown dwarf orbiting TOI-6884 (TIC 156514476, T-mag = 11.4) from NASA's Transiting Exoplanet Survey Satellite (TESS) mission. The TESS light curves initially suggested an orbital period of similar to 14.42 days; however, our high-precision ground-based radial velocity measurements and multi-epoch time-series photometry reveal this to be a harmonic alias. We determine the true orbital period to be 4.808264(-0.000014)(+0.000015) days and confirm the substellar nature of the companion. TOI-6884b has a mass of 26.32(-0.93)(+0.98)MJ, a radius of 0.927(-0.52)(+0.51)RJ, and resides on a nearly circular orbit (e=0.067(-0.012)(+0.010)). Its host star is a late F-type slightly evolved star with M-* =1.410(-0.069)(+0.075)M(circle dot), R-* =1.840(-0.073)(+0.072) R-circle dot, log g=4.057(-0.039)(+0.045), [Fe/H]=0.094(-0.068)(+0.073) dex, and T-eff=6330(-160)(+180) K. TOI-6884b is a key addition to the small population of well-characterized transiting brown dwarfs orbiting host stars that have left the main sequence. The detection of such systems will contribute to our understanding of dynamical histories and structural evolution of short-period substellar companions around evolved stars.

As the diversity of exoplanets continues to grow, it is important to revisit assumptions about habitability and classical habitable zone definitions. In this work, we introduce an expanded 'temperate' zone, defined by instellation fluxes in the range 0.1 < S/S-circle plus < 5, thus encompassing a broader range of potentially habitable worlds. We also introduce the TEMPOS survey, which aims to produce a catalogue of precise radii for temperate planets orbiting M dwarfs with T-eff <= 3400 K. This work reports the discovery and characterization of two planets in this temperate regime orbiting mid-type M dwarfs: TOI-6716 b, a R-b = 0.98 +/- 0.07 R-circle plus planet orbiting its M4 host star (R-star = 0.231 +/- 0.015R(circle plus), M-star = 0.223 +/- 0.011 M-circle plus, T-eff = 3110 +/- 80 K) with a period P = 4.7185898(+0.0000054) (-0.0000041 )d, and TOI-7384 b, a R-b = 3.56 +/- 0.21 R-circle plus planet orbiting an M4 (R-star = 0.319 +/- 0.018R(circle plus), M-star = 0.318 +/- 0.016 M-circle plus, T-eff = 3185 +/- 75 K) star every P = 6.2340258(-0.0000036)(+0.0000034 ) d. The radii of TOI-6716 b and TOI-7384 b have precisions of 6.8 per cent and 5.9 per cent, respectively. We validate these planets with multiband ground-based photometric observations, high-resolution imaging, and statistical analyses. We find these planets to have instellation fluxes close to the inner (hotter) edge of the temperate zone, with S-b = 4.4 +/- 1.1 S-circle plus and S-b = 4.9 +/- 1.1 S-circle plus for TOI-6716 b and TOI-7384 b, respectively. Also, with a predicted transmission spectroscopy metric similar to the TRAPPIST-1 planets, TOI-6716 b islikely to be a good rocky-world James Webb Space Telescope target,should it have retained its atmosphere

Of the > 500 confirmed transiting hot jupiters and approximately 2000 additional candidates today, only ten are known to have nearby companion planets. The survival of nearby companions means that these hot jupiters cannot have migrated to their present location via dynamically disruptive high-eccentricity migration but instead have undergone disk migration or formed in situ. The occurrence rate for these nearby companions, therefore, constrains the relative efficiency of different hot jupiter formation pathways. Here, we perform a uniform box least-squares search for nearby transiting companions to hot jupiters in the first five years of TESS data. Accounting for observational completeness and detection efficiency, we arrive at an occurrence rate of (7.6^+5.5_-3.8)%, which is a lower limit on the fraction of hot jupiters that underwent disk migration or in situ formation. Comparing this rate with that derived from transit-timing variation searches suggests that hot jupiters are likely mostly aligned with their nearby companions, but their apparently higher incidence of grazing transits may point to a slight preferential misalignment. We also synthesize evidence that hot jupiters with nearby companions may have cold companions at a rate similar to that of other hot jupiters. Comprehensive transit, radial velocity, and stellar obliquity measurements in hot jupiter systems with nearby companions will be necessary to fully account for the relative prevalence of proposed hot jupiter formation pathways.

Recent large-scale transit surveys conducted by space telescopes such as Kepler and TESS have revealed a vast number of exoplanets, uncovering the diversity of their population. One of the remarkable findings is the presence of a deficiency region in the period-radius distribution of short-period ( < 10 d) Neptune-sized planets ( 4-8 R-circle plus). This region is classified into the Neptune desert ( < 3.2 d) , the ridge ( 3.2-5.7 d) , and the savanna ( > 5.7 d) based on orbital period, each likely reflecting distinct evolutionary pathways. In this study, we used the InfraRed Doppler (IRD) instrument on the Subaru Telescope to determine the mass of the super-Neptune TOI-1883 b, which resides in the ridge region ( P similar to 4.51 d ) orbiting an M dwarf. We measured a planetary mass of M-p = 13.7(-6.5)(+6.8) M-circle plus and a mean density of rho(p) = 0.4(-0.2)(+0.3) g cm(-3), with 3 6 upper limits of 34 . 1 M-circle plus, and 5 6 upper limits of 47 . 7 M-circle plus. These results suggest that TOI-1883 b is likely a low-density super-Neptune. We also find that the boundary of the Neptune desert defined by planets orbiting FGK-type stars exhibits a similar distribution for planets around M-type stars. According to the population-based argument of Bourrier et al. ( 2025 , A&A, 701, A190) , this suggests that TOI-1883 b may have undergone disk-driven migration to reach its current orbit and experienced early atmospheric photoevaporation driven by strong stellar XUV irradiation. The derived planetary mass is comparable to or exceeds the conventional critical core mass. We suggest that the high metallicity of the host star ( [Fe / H ] = 0 . 32 +/- 0 . 18 ) may have suppressed the onset of runaway gas accretion. Furthermore, TOI-1883 b has a high Transmission Spectroscopy Metric (TSM > 140) , making it an excellent target for future atmospheric characterization via transmission spectroscopy.

Complex periodic variables (CPVs) are young low-mass stars whose light curves show periodic dips indicative of transiting corotating material. The origin and composition of this material are unclear. Here we present new optical and near-infrared spectroscopy and photometry of four CPVs from Magellan, Keck, Hale, MuSCAT1, MuSCAT2, Tierras, KeplerCam, and TESS. The spectra imply that CPVs host magnetically bound circumstellar plasma clumps, on the basis of sinusoidal-in-time Balmer emission out of transit, and Balmer dimming during transit. Yet large night-to-night changes in circumstellar hydrogen emissivity occur without clear changes in light curve morphology, suggesting that the sharp flux dips are caused not by circumstellar plasma but by dust. Optical chromaticities (depth proportional to λ^-β, with β = 0.79 ± 0.16) support this, but the power law breaks in the near-infrared, where a single power law under-predicts the depths observed at 2.1 microns. We therefore favor dips caused by dusty plasma clumps with opaque cores and optically thin halos, though we cannot rule out models in which the dust properties vary per-star or per-epoch. Observations at wavelengths greater than 2 microns and less than 0.4 microns would test this interpretation and clarify the dust's origin.