Steve B. Howell

Context. Gas giant planets with orbital periods of P ∼8–200 d, known as warm Jupiters, are thought to be largely unaffected by the tidal interactions that can often erase valuable information on the dynamical histories of hot Jupiters. Their orbital eccentricities ( e ) and stellar obliquities are therefore expected to be preserved, making them valuable probes of giant-planet formation and migration. Aims. Our aim is to identify and characterise transiting warm Jupiters and expand the sample of well-characterised systems and enable further studies of giant-planet formation and migration. Methods. We analysed TESS transit photometry, together with ground-based radial velocity (RV) measurements. We performed a joint fit of the photometric and spectroscopic data from the TS23 and FIES spectrographs to determine the planetary and orbital parameters. Results. We report on the discovery and characterisation of two new, transiting warm Jupiters; TOI-5120 b ( M _p = 1.23 ± 0.05 M _J , R _p = 0.969 ± 0.017 R _J , P = 24.91645 ± 0.00002 d, e = 0.10 ± 0.02) and TOI-5699 b ( M _p = 0.25 ± 0.03 M _J , R _p = 0.996 ± 0.015 R _J , P = 22.01850 ± 0.00004 d, e = 0.30 _−0.08 ^+0.09 ). We also refined the parameters of the known warm Jupiter TOI-2158 b ( M _p = 0.87 ± 0.04 M _J , R = 0.899 ± 0.015 R _J , P = 8.60079 _−0.00001 ^+0.00002 d, e = 0.028 _−0.014 ^+0.013 ). In addition, we detected an outer planetary companion, TOI-2158 c ( M _p sin i = 1.62 ± 0.13 M _J , P = 414.5 _−1.6 ^+1.5 d, e = 0.54 ± 0.04), and identified a long-term RV trend that could indicate another planetary companion on a wide orbit. Conclusions. The diverse architectures of these systems, particularly the presence and absence of outer companions, highlight the range of dynamical pathways leading to warm Jupiters.

Neptune-sized exoplanets appear to be located in three distinct regions when plotted in the period-radius space: the desert, which is an ultra-close-in region nearest to the host star and is typically defined by orbital periods shorter than 3.2 days and is characterised by a scarcity of planets; the savanna, in which planets reside at a safer distance from their hosts and are found in moderate abundance; and an intermediate region called the ridge, which features a surprising statistical overdensity. The formation and evolution pathways by which a planet ends up in one of these three regions are still poorly understood. This makes any new planet that is discovered in these regions, especially in the desert, a key new laboratory. We report the confirmation of the TESS transiting-planet candidate orbiting the metal-rich F8IV-V subgiant star TOI-5646 ( V = 11.38 mag; T _eff = 6136 ± 51 K). The planetary nature of TOI-5646 b was confirmed by means of HARPS-N follow-up radial velocity measurements. We determined that the planet has an orbital period of 2.427702 ± 0.000025 days and an orbital eccentricity compatible with zero. With a mass of 45.9 ± 4.4 M _⊕ , a radius of 6.6 ± 0.3 R _⊕ , and an equilibrium temperature of 1935 ± 29 K, it is one of the hottest super-Neptune exoplanets ever discovered in the Neptune desert. Its density, 0.87 ± 0.15 g cm ⁻³ , is lower than that of most other desert dwellers, but still appears to follow the trend that the desert is populated by dense planets than those in the ridge and savanna. The metallicity of the parent star ([Fe/H] = 0.32 ± 0.06) follows the trend whereby the host stars of Neptune-sized exoplanets in the desert and the ridge are generally richer in metal than those in the savanna. The log g of the parent star, 4.09 ± 0.08, suggests that the host is an evolved star, making this a peculiar system: TOI-5646 is the largest star (∼1.8 R _⊙ ) ever discovered to host a Neptune-sized planet in the desert. Internal structure modelling revealed that TOI-5646 b is highly enriched in metals, with an inferred bulk metallicity between 0.7 and 0.95. Atmospheric evolution simulations indicate that the planet has undergone significant mass loss (6–16%) through intense XUV irradiation from its host star. These results indicate a peculiar formation history (potentially involving early protoplanetary disk dispersal), a planetary collision, or a late tidal destruction event, to explain its current state as a low-density survivor in the Neptune desert.

High-resolution imaging with optical speckle interferometry has revealed that many transiting exoplanet host stars possess close-in stellar companions. The objective of this study is to quantify how the presence of these companions impacts the ability of TESS to detect the transits of small planets. We accomplish this by examining 2052 TESS Objects of Interest (TOIs) that appear to be single-star systems based on speckle interferometric observations as well as 188 TOIs in unresolved ( . ″ 2) stellar binaries. For each planet, we take its transit signal-to-noise ratio (SNR), radius, and orbital period from the TOI catalog and, for planets in stellar binaries, we correct the radius for dilution by the companion. By applying a scaling relation to the measured transit SNR of each TOI in our sample, we determine the detectability of transits in each TOI as a function of both planet radius and orbital period. When applied to the full sample, this procedure elucidates the sensitivity of TESS to transiting planets as a function of binarity, host-star spectral type, planet radius, and planet orbital period. These sensitivity grids quantify the bias against the detection of small planets in unresolved binaries by TESS and show that there is a particularly low sensitivity to planets transiting secondary stars in unresolved binaries, especially as the magnitude difference between the stars increases. These sensitivity grids are available for download to facilitate their use in other studies.

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% of 68 contrast-curve-bearing validated planets would fail validation without their adopted contrast curves. The fraction requiring imaging decreases with increasing planet size, from 100% below 1.7 R _⊕ to 33% above 4 R _⊕ : within our sample and TRICERATOPS -based analysis, the availability of high-resolution imaging directly limits the yield of small-planet validation and the supply of validated targets for atmospheric characterization. Our analysis statistically validates 64 new TESS planets with sizes spanning 0.94 to 7.83 R _⊕ across hosts of spectral types: M through F. Four of these are highly amenable to JWST observations based on the transmission and emission spectroscopy metrics, and each achieves validation only with its imaging constraint.

We characterize the radius-dependent observed transiting eccentricity distribution of 219 warm ( P = 8–50 days) systems with only one transiting planetary candidate identified during Sectors 1–69 of the Transiting Exoplanet Survey Satellite (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 (〈 e _low 〉 = 0.03 9 − 0.038 + 0.018 ) and a secondary dynamically excited mode (〈 e _high 〉 = 0.46 6 − 0.068 + 0.067 ). 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 . 2 − 1.1 + 1.9 R _⊕ . This trend places warm sub-Saturns predominantly on the same low-eccentricity track as sub-Neptunes. In contrast, warm Jovians (8–16 R _⊕ ) are frequently eccentric, with 6 5 − 12 + 13 % of the population in the high-eccentricity mode. Under the assumption of a two-component model, we see tentative evidence for a bimodal Jovian distribution at ∼2.7 σ . Finally, we identify a nonnegligible tail of highly eccentric sub-Neptunes (1–4 R _⊕ ), which comprise 16 . 2 − 6.4 + 5.2 % of the population, consistent with excitation by nontransiting external companions.

Transiting warm Jupiters orbiting bright stars are scarcely known, but a substantial number of these planets have been uncovered by the TESS mission. In this work, we report the discovery and confirmation of a transiting warm Jupiter orbiting the bright ( V = 8.70) subgiant star HD 715 (TOI-6893). HD 715 b was originally identified from a single transit event in TESS Sector 70. We acquired two seasons of radial velocity follow-up using the PFS, TRES, and MINERVA-Australis spectrographs, which clearly detect the planetary orbit. At M _* = 1.60 ± 0.04 M _⊙ , HD 715 thus becomes one of the most massive stars known to host a transiting warm Jupiter. From a joint fit to the TESS transit and our RVs, we find that HD 715 b has a 56.4 0 − 0.23 + 0.19 day orbital period and measure a precise mass and radius of 0.635 ± 0.056 M _J and 1.07 ± 0.04 R _J , rendering it a relatively typical member of the warm Jupiter population. The moderate orbital eccentricity of 0.2 1 − 0.08 + 0.07 contrasts with the higher eccentricities of other similar warm Jupiters orbiting evolved stars, indicating a greater diversity in orbital eccentricities than previously known. The absence of additional transits in preceding TESS observations in Sectors 42 and 43 allows us to further refine the range of possible orbital periods to [56.01, 56.35] days. Though the ephemeris uncertainty remains substantial, future photometric observations may nonetheless allow for recovery of the transit of HD 715 b.

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.

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 3.437312 5 − 0.0000019 + 0.0000020 days 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 0.15 9 − 0.054 + 0.055 g cm ⁻³ . We also characterize the host star, showing that TOI-7169 is ancient (12.3 ± 0.6 Gyr) and α enhanced ([ α /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.

Young planets (R _⊕ planet on a 10.47 day orbit, and report the candidate TIC 150070085 c, a 3.0 R _⊕ planet on a 15.90 day orbit. While we are unable to validate the second signal, the proximity to mean-motion resonance (3:2) and transit timing variations observed in the transits of TIC 150070085 b strongly suggest that the signal is planetary. We confirm the host star as a member of Alessi 84 and combine the group’s color–magnitude diagram, rotation, and variability properties to update the age to 135 ± 10 Myr. We additionally use MAROON-X to observe the Rossiter–McLaughlin signal of TIC 150070085 b and measure the sky projected obliquity angle ( λ ). We find that TIC 150070085 b is consistent with a near-aligned orbit with its host star (∣ λ ∣ = 18° ± 12°), in line with similarly aged transiting planets with measured λ values. Continued discovery and characterization of planets in this age regime are vital to link planetary infancy (1 Gyr).

The number of artificial satellites in low Earth orbit (LEO) has been increasing at an exponential rate since 2019. Satellites are visible to both ground and space telescopes, and their bright emission in optical, infrared, and radio wavelengths contaminates astronomical observations, degrading the data’s scientific value. Recent simulations forecast that if all satellite constellations listed in current launch manifests are deployed to LEO, satellite trails will appear in up to 96% of the images obtained by most space telescopes. In this article, we use the recently launched Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx) space telescope to corroborate these models. SPHEREx observations obtained between 2025 May and September indicate that 73. 3 − 1.2 + 1.3 % of the images already show satellite-trail contamination, with an average number of N = 2.1 8 − 0.09 + 0.11 trails per exposure, providing observational validation of the published light contamination models. The observed satellite trails display highly inclined trajectories in agreement with the simulated ones. We discuss potential data-reduction mitigation methods, and provide an updated satellite light pollution forecast for Hubble and SPHEREx including the newer satellite constellations proposed in early 2026.