David W. Latham

Planetary transits require a fortuitous alignment between a planet’s orbit and our line of sight, but dynamical interactions can render this geometric coincidence only temporary. We report the discovery of the hot Jupiter TOI-2535b, the first confirmed planet orbiting a single star whose transits have been directly observed to disappear. Over 7 yr of photometry from NASA’s Transiting Exoplanet Survey Satellite (TESS), the planet’s transit chord traversed and eventually moved off the stellar disk entirely, with an impact parameter changing at the rate of b ̇ = 0.16 yr − 1 . The transit midtimes also show significant departures of ±6 hr from a linear ephemeris. Joint modeling of the transit timing and duration variations (TTVs and TDVs) and NEID radial-velocity data indicates the presence of a nearby, mutually inclined ( i _mut ≳ 5 ^∘ ) planetary perturber, with the TDV being primarily due to precession of the planets’ orbital planes. Our dynamical modeling reveals that the perturber is likely of Saturn-mass or greater and in a mean-motion resonance with TOI-2535b, making this an unusual system that contains two short-period giant planets. The TDVs measured for TOI-2535b represent one of the most extreme examples of planet–planet interactions driving orbital evolution on human timescales.

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.

Aims. We are striving to better understand the stellar and orbital properties of compact and tight triple star systems with large dynamical interactions. Methods. We analyze TESS photometric data, radial velocity measurements, and eclipse timing variation curves for the triple star system, TIC 366240660, with a photodynamical code to infer the properties of all three stars and orbital motions. Results. With an outer orbital period of only 30.5 d, this is the second most compact triple reported in the literature. We have determined the masses and T _eff values of the three stars with an accuracy of about 1% and the radii to about 2%. The inclination angles of the two planes, and the mutual inclination angle are found with an accuracy of better than 1/3°. The system is determined to be quite flat (to within 1/2°), but with an outer eccentricity of e _out ≃ 0.33. We find that the properties of the secondary star of the inner binary are completely inconsistent with the evolution of a single star in isolation, and it must have transferred most of its envelope to the current primary star in the inner binary during a prior episode of mass transfer. The eclipse timing variation (ETV) curve derived from the TESS photometric data shows that, in addition to a typical dynamical delay curve at the period of the outer orbit, there is also a much larger amplitude anomalous sinusoidal-like delay with a period of 840 d. This latter feature in the ETV curve is not yet describable in simple analytic terms, but it appears certain that it can be explained by the near integer (≃13:1) ratio of the outer to the inner orbital periods. Conclusions. We have extensively explored the exotic and anomalous ETVs of this highly compact triple system and found that they can exceed hours for the inner binary eclipses, and several days for the outer orbital eclipses. We provide a preliminary explanation for how these are related to the 13:1 mean motion resonance of the outer to inner orbits.

The γ Cephei system hosts one of the first exoplanets discovered and is orbited by one of the closest known stellar companions to a planet-hosting star. In this work, we derive updated orbital fits for γ Cep AB, the stellar binary, and Ab, the planet, by combining literature data with Hipparcos–Gaia astrometry, new radial velocities (RVs), and adaptive optics imaging. We acquired 328 RVs of γ Cep A with Keck/HIRES, AFP/Levy, McDonald/Tull, and Whipple/TRES, and eight adaptive optics imaging epochs with Keck/NIRC2, including the earliest spatially resolved image of γ Cep B in 2003. These observations extend the precision RV baseline of γ Cep to 45 yr and the direct imaging baseline to 23 yr, improving the inferred orbital parameter precision by a factor of 2–10 compared to previous work. For γ Cep B, we derive a semimajor axis of a _B = 20.07 ± 0.06 au, a mass of M _B = 415 ± 2 M _Jup (0.396 ± 0.002 M _⊙ ), an eccentricity of e _B = 0.422 ± 0.002, and an inclination of i _B = 119 . ° 8 ± 0 . ° 1. For γ Cep Ab, we find a semimajor axis of a _Ab = 1.978 ± 0.007 au, a minimum mass of M A b sin i = 1.6 2 − 0.04 + 0.04 M Jup , and an eccentricity of e A b = 0.0 7 − 0.03 + 0.03 . The system is dynamically compact, and its orbital architecture is consistent with von Zeipel–Lidov–Kozai (vZLK) oscillations, although the planet’s orbital inclination remains insufficiently constrained to determine whether the vZLK mechanism is active. Using the RV residuals and dynamical constraints, we rule out additional Jovian companions between 2.5 and 20 au, and companions more massive than Neptune for a < 1 au, both at >90% confidence. The absence of additional giant planets over a broad range of orbital separations is consistent with a dynamically sculpted system in which the close stellar companion has strongly limited the formation or long-term survival of other long-period giant companions.

Context . Hot Jupiters are key targets for understanding planet formation, migration, and atmospheres. Yet most of the ground-based observational resources for the follow-up of the TESS mission are focused on the confirmation of low-mass planet candidates. This leaves the more massive planets, such as hot Jupiters, without mass determinations and definitive confirmations. Aims . We used the CAFE ₂ spectrograph at the Calar Alto Observatory to monitor the radial velocity of stars with hot-Jupiter candidates that have been left behind by follow-up efforts with the goal of confirming their planetary nature. Here, we present the results for seven candidates. Methods . We monitored the radial velocity of the seven candidate host stars TOI-603, TOI-1137, TOI-1837, TOI-2114, TOI-4492, TOI-5806, and TOI-5811. Each hosts a hot-Jupiter candidate detected by the TESS mission. We characterized these stars and jointly modeled the CAFE ₂ RVs and the TESS photometric data to unravel the nature of the transiting objects and to infer their properties. Results . The objects we confirmed to be new planets are TOI-603 b (mass 33.0 ^+6.5 _−6.2 M _⊕ , period 16.2 d); TOI-2114 b (1.01 ^+0.14 _−0.12 M _Jup , 6.2 d); TOI-4492 b (5.92 ^+0.67 _−0.64 M _Jup , 4.4 d); TOI-5806 b (2.77 ^+0.34 _−0.32 M _Jup , 3.2 d); and TOI-5811 B b (0.81 ^+0.11 _−0.10 M _Jup , 6.3 d). Based on their masses and periods, TOI-603 b is a member of the “Neptune savanna”, while TOI-2114 b, TOI-4492 b, TOI-5806 b, and TOI-5811 B b are hot Jupiters orbiting slightly evolved stars. We found the candidate TOI-5811.01 to actually be a planet orbiting the nearby bound companion TOI-5811 B. We also identified a bound stellar companion to TOI-5806 at a projected separation of 248 au, thus both form satellite-type planetary systems. As for the two remaining candidates, TOI-1837.01 is definitely an eclipsing binary, while the nature of TOI-1137.01 remains indeterminate. Conclusions . The five newly confirmed planets orbit relatively bright stars (G = 8.6–10.2 mag), and four of them are excellent candidates for atmospheric studies (with transmission spectroscopy metrics exceeding 90 for TOI-603 b, TOI-2114 b, TOI-5806 b, and TOI-5811 B b). The complex configurations of all of these systems underscore the need for intensive follow-up efforts to clarify the nature of transiting planet candidates.

Planet formation in the Galactic thick disk is expected to be inefficient—low solid reservoirs, short disk lifetimes, and harsh irradiation environments should conspire to inhibit the assembly of planetary bodies—yet, planets are there, and they are stranger than we expected. Here, we present a homogeneous characterization of 32 exoplanetary systems orbiting chemically and kinematically confirmed thick disk stars, combining new detections with a systematic reassessment of archival systems, increasing the total number of exoplanets orbiting thick disk stars to 66. When planets form in the thick disk, a notable fraction are giants and move on more eccentric orbits than their thin disk counterparts—two results that challenge standard disk-evolution models. However, this should be interpreted with caution given detection biases and sample size. We also report TOI-1927 b and TOI-2643 b, the first puffy, low-density giant planets known to orbit thick disk stars, unexpected in old, metal-poor environments where planets should cool and contract efficiently. Together, these findings reveal an early Milky Way far more hospitable to planetary diversity than its harsh conditions would initially suggest.

Context. The architecture of planetary systems hosting ultra-short-period (USP) planets is a key diagnostic for understanding formation and migration scenarios. The presence of outer giant companions in these systems is of particular interest to test theories regarding dynamical effects and pebble accretion. Aims. We present an extended radial velocity (RV) monitoring of the bright star K2-312≡HD 80653, known to host a rocky USP super-Earth ( P _b = 0.720 d). Previous studies identified a long-term trend and subsequently a Keplerian signal due to an outer highly eccentric giant planet, K2-312 c. We aim to refine the orbital parameters of K2-312 c by precisely monitoring its periastron passage and to model the formation and dynamical evolution of the system. Methods. We analyzed a set of 237 HARPS-N high-resolution spectra, extending the observation baseline of previous literature by almost 4 years. We performed a joint analysis of the RVs together with K2 and TESS photometry to refine the ephemerides and properties of the two planets. To account for stellar activity, we coupled the Keplerian models with a Gaussian processes regression. Results. K2-312 c is a cold Jupiter on a wide orbit (orbital period refined to P _c = 871.32 d), with a minimum mass of M _c sin i ~5 M _Jup and a refined eccentricity of e _c ~ 0.85. It is among the most eccentric cold Jupiters known in multi-planet systems, and the only one that is highly eccentric and has a USP planet companion. Our simulations suggest that planet-planet scattering between two giant planets could have driven K2-312 c to its current high eccentricity, ejected the other giant, and still allowed for the survival of K2-312 b. The extended observation baseline further allowed us to identify the stellar rotation period and a long activity cycle, while a new K2 reduction improved the significance of the secondary eclipse detection for K2-312 b.

Of the >500 confirmed transiting hot Jupiters and ≈2000 additional candidates today, only 10 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 5 yr of TESS data. Accounting for observational completeness and detection efficiency, we arrive at an occurrence rate of ( 7.6 − 3.8 + 5.5 ) % , 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.

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.