Karen A. Collins

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.

We report the discovery of two planets, a hot Jupiter (HJ) and a nearby outer sub-Neptune, orbiting the star TOI-4468. This system is unique among the current exoplanet census in that it features a close outer companion to a HJ without an accompanying inner companion. By jointly fitting radial velocity (RV) measurements taken with the NEID spectrograph and transit photometry from the Transiting Exoplanet Survey Satellite (TESS) and several ground-based observatories, we constrain the orbital periods, masses, and radii of these two planets. We confirm the planetary nature of the HJ TOI-4468 b ( R = 1.01 R _J , m = 0.54 M _J , P = 2.77 days). We also validate the outer planet TOI-4468 c ( R = 0.28 R _J , P = 7.01 days) statistically, incorporating constraints from ground-based observations. We also identify, but cannot confirm, an additional RV signal that may be due to an outer giant in this system with an orbital period of 624 days. From the observed geometry of this system, we argue that it must never have encountered an early secular resonance that is thought to excite the mutual inclination of other HJ/outer companion systems. We discuss the possibility of an undetected inner companion, as well as potential implications for HJ formation.

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.

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.

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.

It is inherently challenging to characterize long-period transiting exoplanets because the transit events are rare and last long. 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, however. 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, confirming it as the longest-period exoplanet known to exhibit measurable TTVs. By combining this new precise measurement with the transit timings of the two outer planets in the system (HIP 41378 d and HIP 41378 e), we performed a dynamical modeling of the system using the N -body integrator TRADES , refined the ephemeris of HIP 41378 f, and predict future transit events for all three outer transiting 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 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.