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We provide a database of transit times and updated ephemerides for 382 planets based on data from the NASA Transiting Exoplanet Survey Satellite (TESS) and previously reported transit times, which were scraped from the literature in a semiautomated fashion. In total, our database contains 8667 transit-timing measurements for 382 systems. About 240 planets in the catalog are hot Jupiters (i.e., planets with mass >0.3 M Jup and period <10 days) that have been observed by TESS. The new ephemerides are useful for scheduling follow-up observations and searching for long-term period changes. WASP-12 remains the only system for which a period change is securely detected. We remark on other cases of interest, such as a few systems with suggestive (but not yet convincing) evidence for period changes, and the detection of a second transiting planet in the NGTS-11 system. The compilation of light curves, transit times, ephemerides, and timing residuals are made available online, along with the Python code that generated them (visit https://transit-timing.github.io).

HD 110067 is the brightest star known to have six transiting planets. Each adjacent pair of planets has a period ratio that is nearly equal to a ratio of small integers, suggesting the planets are in a chain of mean-motion resonances, but the limited time span of the available data has prevented firm conclusions. Here, we show that the requirement of long-term dynamical stability implies that all six planets are very likely to form a resonant chain. Dynamical simulations of nonresonant systems with initial conditions compatible with the available data almost always suffer an instability within 25 Myr (∼0.3% of the system’s age). Assuming the system is in resonance, we place upper limits on the planets’ eccentricities and lower limits on the masses of the planets that have not yet been measured. We also predict the characteristics of transit timing variations and the values of the three-body libration centers.

Misalignments between planetary orbits and the equatorial planes of their host stars are clues about the formation and evolution of planetary systems. Earlier work found evidence for a peak near 90° in the distribution of stellar obliquities, based on frequentist tests. We performed hierarchical Bayesian inference on a sample of 174 planets for which either the full three-dimensional stellar obliquity has been measured (72 planets) or for which only the sky-projected stellar obliquity has been measured (102 planets). We investigated whether the obliquities are best described by a Rayleigh distribution or by a mixture of a Rayleigh distribution representing well-aligned systems and a different distribution representing misaligned systems. The mixture models are strongly favored over the single-component distribution. For the misaligned component, we tried an isotropic distribution and a distribution peaked at 90° and found the evidence to be essentially the same for both models. Thus, our Bayesian inference engine did not find strong evidence favoring a “perpendicular peak,” unlike the frequentist tests. We also investigated selection biases that affect the inferred obliquity distribution, such as the bias of the gravity-darkening method against obliquities near 0° or 180°. Further progress in characterizing the obliquity distribution will probably require the construction of a more homogeneous and complete sample of measurements.

Super-puffs are low-density planets of unknown origin and composition. If they form by accreting nebular gas through a circumplanetary disk, one might expect super-puffs to be spinning quickly. Here, we derive upper limits on the rotational oblateness of the super-puff Kepler-51d, based on precise transit observations with the NIRSpec instrument on board the James Webb Space Telescope. The absence of detectable oblateness-related anomalies in the light curve leads to an upper limit of about 0.15 on the planet's sky-projected oblateness. Assuming the sky-projected oblateness to be representative of the true oblateness, the rotation period of Kepler-51d is ≳40 hr, or equivalently, its rotation speed is ≲42% of the breakup speed. Alternatively, if the apparently low density of Kepler-51d is due to an opaque planetary ring, the ring must be oriented within 30∘ of face on and have an inner radius smaller than 1.2 times the planet's radius. Separately, the lack of anomalies exceeding 0.01% in the ingress and egress portions of the light curve places a constraint on the model of Wang & Dai, in which the planet's apparently low density is due to a dusty outflowing atmosphere.

Nontransiting planets can reveal themselves through transit timing variations (TTVs), but inferring the properties of the perturbing planet is a highly degenerate inverse problem. We present a systematic reassessment of all 12 published cases in which a nontransiting planet was claimed to have been uniquely characterized using TTVs. Two systems (KOI-142 and Kepler-419) stand out clearly with compelling evidence for unique solutions. Two other systems (KOI-872 and KOI-884) exhibit complex degeneracies, but the data are just precise enough to single out a best solution. Six systems (Kepler-82, Kepler-411, Kepler-725, KOI-134, Kepler-138, and TOI-4562) admit multiple viable solutions involving very different perturbing planets. In the remaining two systems (WASP-18 and WASP-126), the evidence for any perturbing planet is weak. We find that a necessary (but not sufficient) condition for a unique solution is the detection of short-timescale TTV structure associated with conjunctions, either in the near-resonant “chopping” regime or in eccentric systems with phase-dependent close approaches. In some systems, aliasing of the synodic period leads to ambiguities in associating observed TTV timescales with physical timescales, threatening uniqueness. Our results highlight the difficulty of achieving unique solutions in TTV inversions and underscore the need for long time baselines, accurate timing uncertainties, and complementary constraints from radial velocities or other observations when characterizing nontransiting planets.

A handful of stars are known to host both an inner system of multiple transiting planets and an outer giant planet. These systems all feature a prominent gap between the orbits of two of the transiting planets, distinguishing them from typical multiplanet systems with more uniform orbital spacings. The reason for the association between inner gaps and outer giants is unknown. In this paper, we assess whether undiscovered planets might occupy these gaps in systems with outer giants. For each of the four relevant systems—Kepler-48, Kepler-65, Kepler-90, and Kepler-139—we found that a typical small planet (∼1–20 M⊕) could reside in the gap without inducing dynamical instability. However, in each case the gravitational influence of the outer giant planet is insufficient to tilt the orbit of the hypothetical planet by enough to prevent transits, strongly disfavoring a proposed theory for the observed gap–giant association. The gaps might instead contain smaller, undetected planets (≲ 1 R⊕), or be entirely devoid of planets.

The retrograde orbit of the hot Jupiter HAT-P-7b is suggestive of high-eccentricity (high-e) migration caused by dynamical interactions with a massive companion. However, the only other known body in the system is an M dwarf located ∼103 au away, too distant to cause high-e migration without fine-tuning. Here, we present transit-timing and radial-velocity evidence for an additional stellar companion with a semimajor axis of 32−11+16 au, eccentricity 0.76−0.26+0.12 , and minimum mass of 0.19−0.06+0.11 M⊙. We investigate several dynamical routes by which this nearby companion star could have played a role in converting a cold Jupiter into the retrograde hot Jupiter that is observed today. Of particular interest is a novel “eccentricity cascade” mechanism involving both of the companion stars: the outer companion periodically excites the eccentricity of the inner companion through von Zeipel–Lidov–Kozai cycles, and this eccentricity excitation is slowly transferred to the cold Jupiter via successive close encounters, eventually triggering its high-e migration. The plausibility of this mechanism in explaining HAT-P-7b shows that stellar companions traditionally considered too distant to cause hot Jupiter formation might nevertheless be responsible, with the aid of closer-orbiting massive companions. With these developments, HAT-P-7b is one of the few hot Jupiters for which a complete high-e migration history can be simulated based only on observed bodies, rather than invoking bodies that are beneath detection limits or that are no longer in the system.

We present an estimate of the occurrence rate of hot Jupiters (7 R ⊕ ≤ R p ≤ 2 R J, 0.8 ≤ P b ≤ 10 days) around early-type M dwarfs based on stars observed by the Transiting Exoplanet Survey Satellite (TESS) during its primary mission. We adopt stellar parameters from the TESS Input Catalog and construct a sample of 60,819 M dwarfs with 10.5 ≤ T mag ≤ 13.5, effective temperatures 2900 ≤ T eff ≤ 4000 K, and stellar masses 0.45 ≤ M * ≤ 0.65 M ⊙. We conduct a uninformed transit search using a detection pipeline based on the box least square search and characterize the searching completeness through an injection and recovery experiment. We combine a series of vetting steps including light centroid measurement, odd/even and secondary eclipse analysis, rotation and transit period synchronization tests as well as inspecting the ground-based photometric, spectroscopic, and imaging observations. Finally, we find a total of nine planet candidates, all of which are known TESS objects of interest. We obtain an occurrence rate of 0.27% ± 0.09% for hot Jupiters around early-type M dwarfs that satisfy our selection criteria. Compared with previous studies, the occurrence rate of hot Jupiters around early-type M dwarfs is smaller than all measurements for FGK stars, although they are consistent within 1σ–2σ. There is a trend that the occurrence rate of hot Jupiters has a peak at G dwarfs and falls toward both hotter and cooler stars. Combining results from transit, radial velocity, and microlensing surveys, we find that hot Jupiters around early-type M dwarfs possibly show a steeper decrease in the occurrence rate per logarithmic semimajor axis bin ( dN/dlog10a ) when compared with FGK stars.

Stellar activity interferes with precise radial velocity measurements and limits our ability to detect and characterize planets, in particular Earth-like planets. We introduce AESTRA (Auto-Encoding STellar Radial-velocity and Activity), a deep-learning method for precise radial velocity measurements. It combines a spectrum autoencoder, which learns to create realistic models of the star’s rest-frame spectrum, and a radial-velocity estimator, which learns to identify true Doppler shifts in the presence of spurious shifts due to line-profile variations. Being self-supervised, AESTRA does not need “ground truth” radial velocities for training, making it applicable to exoplanet host stars for which the truth is unknown. In tests involving 1000 simulated spectra, AESTRA can detect planetary signals as low as 0.1 m s−1 even in the presence of 3 m s−1 of activity-induced noise and 0.3 m s−1 of photon noise per spectrum.

In 2017, the California-Kepler Survey (CKS) published its first data release (DR1) of high-resolution optical spectra of 1305 planet hosts. Refined CKS planet radii revealed that small planets are bifurcated into two distinct populations, super-Earths (smaller than 1.5 R ⊕) and sub-Neptunes (between 2.0 and 4.0 R ⊕), with few planets in between (the “radius gap”). Several theoretical models of the radius gap predict variation with stellar mass, but testing these predictions is challenging with CKS DR1 due to its limited M ⋆ range of 0.8–1.4 M ⊙. Here we present CKS DR2 with 411 additional spectra and derived properties focusing on stars of 0.5–0.8 M ⊙. We found that the radius gap follows R p ∝ P m with m = −0.10 ± 0.03, consistent with predictions of X-ray and ultraviolet- and core-powered mass-loss mechanisms. We found no evidence that m varies with M ⋆. We observed a correlation between the average sub-Neptune size and M ⋆. Over 0.5–1.4 M ⊙, the average sub-Neptune grows from 2.1 to 2.6 R ⊕, following Rp∝M⋆α with α = 0.25 ± 0.03. In contrast, there is no detectable change for super-Earths. These M ⋆–R p trends suggest that protoplanetary disks can efficiently produce cores up to a threshold mass of M c , which grows linearly with stellar mass according to M c ≈ 10 M ⊕(M ⋆/M ⊙). There is no significant correlation between sub-Neptune size and stellar metallicity (over −0.5 to +0.5 dex), suggesting a weak relationship between planet envelope opacity and stellar metallicity. Finally, there is no significant variation in sub-Neptune size with stellar age (over 1–10 Gyr), which suggests that the majority of envelope contraction concludes after ∼1 Gyr.