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The two planets of the HAT-P-11 system represent fascinating dynamical puzzles due to their significant eccentricities and orbital misalignments. In particular, HAT-P-11 b is in a close-in orbit in which tides should have circularized well within the age of the system. Here we propose a two-step dynamical process that can reproduce all intriguing aspects of the system. We first invoke planet–planet scattering to generate significant eccentricities and mutual inclinations between the planets. We then propose that this misalignment initiated von-Zeipel-Lidov-Kozai cycles and high-eccentricity migration that ultimately brought HAT-P-11 b to its present-day orbit. We find that this scenario is fully consistent only when significant tidally driven radius inflation is accounted for during the tidal migration. We present a suite of N -body simulations exploring each phase of evolution and show that this scenario is consistent with all observational posteriors and the reported age of the system.

The properties of exoplanet host stars are traditionally characterized through a detailed forward-modeling analysis of high-resolution spectra. However, many exoplanet radial velocity surveys employ iodine-cell-calibrated spectrographs, such that the vast majority of spectra obtained include an imprinted forest of iodine absorption lines. For surveys that use iodine cells, iodine-free “template” spectra must be separately obtained for precise stellar characterization. These template spectra often require extensive additional observing time to obtain, and they are not always feasible to obtain for faint stars. In this paper, we demonstrate that machine-learning methods can be applied to infer stellar parameters and chemical abundances from iodine-imprinted spectra with high accuracy and precision. The methods presented in this work are broadly applicable to any iodine-cell-calibrated spectrograph. We make publicly available our spectroscopic pipeline, the Cannon HIRES Iodine Pipeline, which derives stellar parameters and 15 chemical abundances from iodine-imprinted spectra of FGK stars and which has been set up for ease of use with Keck/HIRES spectra. Our proof of concept offers an efficient new avenue to rapidly estimate a large number of stellar parameters even in the absence of an iodine-free template spectrum.

The stellar obliquity distribution of warm-Jupiter systems is crucial for constraining the dynamical history of Jovian exoplanets, as the warm Jupiters’ tidal detachment likely preserves their primordial obliquity. However, the sample size of warm-Jupiter systems with measured stellar obliquities has historically been limited compared to that of hot Jupiters, particularly in hot-star systems. In this work, we present newly obtained sky-projected stellar obliquity measurements for the warm-Jupiter systems TOI-559, TOI-2025, TOI-2031, TOI-2485, TOI-2524, and TOI-3972, derived from the Rossiter–McLaughlin effect, and show that all six systems display alignment with a median measurement uncertainty of 13°. Combining these new measurements with the set of previously reported stellar obliquity measurements, our analysis reveals that single-star warm-Jupiter systems tend to be aligned, even around hot stellar hosts. This alignment exhibits a 3.4 σ deviation from the T _eff – λ dependency observed in hot-Jupiter systems, where planets around cool stars tend to be aligned, while those orbiting hot stars show considerable misalignment. The current distribution of spin–orbit measurements for Jovian exoplanets indicates that misalignments are neither universal nor primordial phenomena affecting all types of planets. The absence of misalignments in single-star warm-Jupiter systems further implies that many hot Jupiters, by contrast, have experienced a dynamically violent history.

Multiplanet systems face significant challenges to detection. For example, farther-orbiting planets have a reduced signal-to-noise ratio in radial velocity detection methods, and small mutual inclinations between planets can prevent them from all transiting. One mechanism for exciting mutual inclination between planets is secular resonance, where the nodal precession frequencies of the planets align so as to greatly increase the efficiency of the angular momentum transport between planets. These resonances can significantly misalign planets from one another, hindering detection, and typically can only occur when there are three or more planets in the system. Naively, systems can only be in resonance for particular combinations of planet semimajor axes and masses; however, effects that alter the nodal precession frequencies of the planets, such as the decay of stellar oblateness, can significantly expand the region of parameter space where resonances occur. In this work, we explore known three-planet systems, determine whether they are in (or were in) secular resonance due to evolving stellar oblateness, and demonstrate the implications of resonance on their detectability and stability. We show that about 20% of a sample of three-planet transiting systems seem to undergo these resonances early in their lives.

We present a radial velocity (RV) analysis of TOI-1136, a bright Transiting Exoplanet Survey Satellite (TESS) system with six confirmed transiting planets, and a seventh single-transiting planet candidate. All planets in the system are amenable to transmission spectroscopy, making TOI-1136 one of the best targets for intra-system comparison of exoplanet atmospheres. TOI-1136 is young (∼700 Myr), and the system exhibits transit timing variations (TTVs). The youth of the system contributes to high stellar variability on the order of 50 m s ^−1 , much larger than the likely RV amplitude of any of the transiting exoplanets. Utilizing 359 High Resolution Echelle Spectrometer and Automated Planet Finder RVs collected as part of the TESS-Keck Survey, and 51 High-Accuracy Radial velocity Planetary Searcher North RVs, we experiment with a joint TTV-RV fit. With seven possible transiting planets, TTVs, more than 400 RVs, and a stellar activity model, we posit that we may be presenting the most complex mass recovery of an exoplanet system in the literature to date. By combining TTVs and RVs, we minimized Gaussian process overfitting and retrieved new masses for this system: ( m _b−g = ${3.50}_{-0.7}^{+0.8}$ , ${6.32}_{-1.3}^{+1.1}$ , ${8.35}_{-1.6}^{+1.8}$ , ${6.07}_{-1.01}^{+1.09}$ , ${9.7}_{-3.7}^{+3.9}$ , ${5.6}_{-3.2}^{+4.1}$ M _⊕ ). We are unable to significantly detect the mass of the seventh planet candidate in the RVs, but we are able to loosely constrain a possible orbital period near 80 days. Future TESS observations might confirm the existence of a seventh planet in the system, better constrain the masses and orbital properties of the known exoplanets, and generally shine light on this scientifically interesting system.

An intriguing pattern among exoplanets is the lack of detected planets between approximately 1.5 R _⊕ and 2.0 R _⊕ . One proposed explanation for this “radius gap” is the photoevaporation of planetary atmospheres, a theory that can be tested by studying individual planetary systems. Kepler-105 is an ideal system for such testing due to the ordering and sizes of its planets. Kepler-105 is a Sun-like star that hosts two planets straddling the radius gap in a rare architecture with the larger planet closer to the host star ( R _b = 2.53 ± 0.07 R _⊕ , P _b = 5.41 days, R _c = 1.44 ± 0.04 R _⊕ , P _c = 7.13 days). If photoevaporation sculpted the atmospheres of these planets, then Kepler-105b would need to be much more massive than Kepler-105c to retain its atmosphere, given its closer proximity to the host star. To test this hypothesis, we simultaneously analyzed radial velocities and transit-timing variations of the Kepler-105 system, measuring disparate masses of M _b = 10.8 ± 2.3 M _⊕ ( ρ _b = 3.68 ± 0.84 g cm ^−3 ) and M _c = 5.6 ± 1.2 M _⊕ ( ρ _c = 10.4 ± 2.39 g cm ^−3 ). Based on these masses, the difference in gas envelope content of the Kepler-105 planets could be entirely due to photoevaporation (in 76% of scenarios), although other mechanisms like core-powered mass loss could have played a role for some planet albedos.

The Gemini Planet Imager (GPI) has excelled in imaging debris disks in the near-infrared. The GPI Exoplanet Survey imaged 24 debris disks in polarized H -band light, while other programs observed half of these disks in polarized J and/or K 1 bands. Using these data, we present a uniform analysis of the morphology of each disk to find asymmetries suggestive of perturbations, particularly those due to planet–disk interactions. The multiwavelength surface brightness, disk color, and geometry permit the identification of any asymmetries such as warps or disk offsets from the central star. We find that 19 of the disks in this sample exhibit asymmetries in surface brightness, disk color, disk geometry, or a combination of the three, suggesting that for this sample, perturbations, as seen in scattered light, are common. The relationship between these perturbations and potential planets in the system is discussed. We also explore correlations among stellar temperatures, ages, disk properties, and observed perturbations. We find significant trends between the vertical aspect ratio and the stellar temperature, disk radial extent, and the dust grain size distribution power law, q . We also confirm a trend between the disk color and stellar effective temperature, where the disk becomes increasingly red/neutral with increasing temperature. Such results have important implications for the evolution of debris disk systems around stars of various spectral types.

Discovering and characterizing exoplanets at the outer edge of the transit method’s sensitivity has proven challenging owing to geometric biases and the practical difficulties associated with acquiring long observational baselines. Nonetheless, a sample of giant exoplanets on orbits longer than 100 days has been identified by transit hunting missions. We present long-term Doppler spectroscopy for 11 such systems with observation baselines spanning a few years to a decade. We model these radial velocity observations jointly with transit photometry to provide initial characterizations of these objects and the systems in which they exist. Specifically, we make new precise mass measurements for four long-period giant exoplanets (Kepler-111 c, Kepler-553 c, Kepler-849 b, and PH-2 b), we place new upper limits on mass for four others (Kepler-421 b, KOI-1431.01, Kepler-1513 b, and Kepler-952 b), and we show that several confirmed planets are in fact not planetary at all. We present these findings to complement similar efforts focused on closer-in short-period giant planets, and with the hope of inspiring future dedicated studies of cool giant exoplanets.

The current orbital geometries of exoplanet systems offer a fossilized record of the systems’ dynamical histories. A particularly rich set of dynamical mechanisms is available to exoplanets residing in multistar systems, which may have their evolution shaped by the gravitational influence of bound stellar companions. In this work, we examine the joint distribution of stellar obliquities and orbital orientations for transiting exoplanets residing within astrometrically resolved binary and triple-star systems. We leverage existing constraints on stellar obliquities in exoplanet systems, together with astrometric measurements from Gaia DR3, to uncover a set of fully aligned, “orderly” exoplanet systems that exhibit evidence of both spin–orbit and orbit–orbit alignment. We also find evidence that the observed distribution of orbit–orbit orientations in our sample is more strongly peaked toward alignment than an isotropic distribution. Our results may be indicative of efficient viscous dissipation by nodally recessing protoplanetary disks, demonstrating a regime in which stellar companions produce and maintain order in planetary systems, rather than enhancing misalignments.

In order to understand the relationship between planet multiplicity, mass, and composition, we present newly measured masses of five planets in two planetary systems: Kepler-323 and Kepler-104. We used the HIRES instrument at the W.M. Keck Observatory to collect 79 new radial velocity (RV) measurements for Kepler-323, which we combined with 48 literature RVs from TNG/HARPS-N. We also conducted a reanalysis of the Kepler-104 system, using 44 previously published RV measurements. Kepler-323 b and c have masses of ${2.0}_{-1.1}^{+1.2}$ M _⊕ and 6.5±1.6 M _⊕ , respectively, whereas the three Kepler-104 planets are more massive (10.0±2.8 M _⊕ , ${7.1}_{-3.5}^{+3.8}$ M _⊕ , and ${5.5}_{-3.5}^{+4.6}$ M _⊕ for planets b, c, and d, respectively). The Kepler-104 planets have densities consistent with rocky cores overlaid with gaseous envelopes ( ${4.1}_{-1.1}^{+1.2}$ g cc ^−1 , ${2.9}_{-1.5}^{+1.7}$ g cc ^−1 , and ${1.6}_{-1.1}^{+1.5}$ g cc ^−1 respectively), whereas the Kepler-323 planets are consistent with having rocky compositions ( ${4.5}_{-2.4}^{+2.8}$ g cc ^−1 and ${9.9}_{-2.5}^{+2.7}$ g cc ^−1 ). The Kepler-104 system has among the lowest values for gap complexity ( ${ \mathcal C }$ = 0.004) and mass partitioning ( ${ \mathcal Q }$ = 0.03); whereas, the Kepler-323 planets have a mass partitioning similar to that of the Inner Solar System ( ${ \mathcal Q }$ = 0.28 and ${ \mathcal Q }$ = 0.24, respectively). For both exoplanet systems, the uncertainty in the mass partitioning is affected equally by (1) individual mass errors of the planets and (2) the possible existence of undetected low-mass planets, meaning that both improved mass characterization and improved sensitivity to low-mass planets in these systems would better elucidate the mass distribution among the planets.

TOI-677 b is part of an emerging class of “tidally detached” gas giants ( a / R _⋆ ≳ 11) that exhibit large orbital eccentricities and yet low stellar obliquities. Such sources pose a challenge for models of giant planet formation, which must account for the excitation of high eccentricities without large changes in the orbital inclination. In this work, we present a new Rossiter–McLaughlin measurement of the tidally detached warm Jupiter TOI-677 b, obtained using high-precision radial velocity observations with Magellan’s Planet Finder Spectrograph (PFS). Combined with previously published observations from the Very Large Telescope’s ESPRESSO spectrograph, we derive one of the most precisely constrained sky-projected spin–orbit angle measurements to date for an exoplanet. The combined fit offers a refined set of self-consistent parameters, including a low sky-projected stellar obliquity of $\lambda ={3\buildrel{\circ}\over{.} 2}_{-{1.}^{\circ }5}^{+{1.}^{\circ }6}$ and a moderately high eccentricity of $e={0.460}_{-0.018}^{+0.019}$ , which further constrain the puzzling architecture of this system. We examine several potential scenarios that may have produced the current TOI-677 orbital configuration, ultimately concluding that TOI-677 b most likely had its eccentricity excited through disk–planet interactions. This system adds to a growing population of aligned warm Jupiters on eccentric orbits around hot ( T _eff > 6100 K) stars.

We present and confirm TOI-1751 b, a transiting sub-Neptune orbiting a slightly evolved, solar-type, metal-poor star ( T _eff = 5996 ± 110 K, $\mathrm{log}(g)=4.2\pm 0.1$ , V = 9.3 mag, [Fe/H] = −0.40 ± 0.06 dex) every 37.47 days. We use TESS photometry to measure a planet radius of ${2.77}_{-0.07}^{+0.15}\,{R}_{\oplus }$ . We also use both Keck/HIRES and APF/Levy radial velocities (RV) to derive a planet mass of ${14.5}_{-3.14}^{+3.15}\,{M}_{\oplus }$ , and thus a planet density of 3.6 ± 0.9 g cm ^−3 . There is also a long-period (∼400 days) signal that is observed in only the Keck/HIRES data. We conclude that this long-period signal is not planetary in nature and is likely due to the window function of the Keck/HIRES observations. This highlights the role of complementary observations from multiple observatories to identify and exclude aliases in RV data. Finally, we investigate the potential compositions of this planet, including rocky and water-rich solutions, as well as theoretical irradiated ocean models. TOI-1751 b is a warm sub-Neptune with an equilibrium temperature of ∼820 K. As TOI-1751 is a metal-poor star, TOI-1751 b may have formed in a water-enriched formation environment. We thus favor a volatile-rich interior composition for this planet.

JWST has ushered in an era of unprecedented ability to characterize exoplanetary atmospheres. While there are over 5000 confirmed planets, more than 4000 Transiting Exoplanet Survey Satellite (TESS) planet candidates are still unconfirmed and many of the best planets for atmospheric characterization may remain to be identified. We present a sample of TESS planets and planet candidates that we identify as “best-in-class” for transmission and emission spectroscopy with JWST. These targets are sorted into bins across equilibrium temperature T _eq and planetary radius R _p and are ranked by a transmission and an emission spectroscopy metric (TSM and ESM, respectively) within each bin. We perform cuts for expected signal size and stellar brightness to remove suboptimal targets for JWST. Of the 194 targets in the resulting sample, 103 are unconfirmed TESS planet candidates, also known as TESS Objects of Interest (TOIs). We perform vetting and statistical validation analyses on these 103 targets to determine which are likely planets and which are likely false positives, incorporating ground-based follow-up from the TESS Follow-up Observation Program to aid the vetting and validation process. We statistically validate 18 TOIs, marginally validate 31 TOIs to varying levels of confidence, deem 29 TOIs likely false positives, and leave the dispositions for four TOIs as inconclusive. Twenty-one of the 103 TOIs were confirmed independently over the course of our analysis. We intend for this work to serve as a community resource and motivate formal confirmation and mass measurements of each validated planet. We encourage more detailed analysis of individual targets by the community.

We confirm a massive sub-Neptune-sized planet on a P = 22.8 days orbit around the star TOI-1824 ( T _eff = 5200 K, V = 9.7 mag). TESS first identified TOI-1824 b (formerly TOI-1824.01) as an object of interest in 2020 April after two transits in Sector 22 were matched with a single transit in Sector 21. TOI-1824 was subsequently targeted for ground-based Doppler monitoring with Keck-HIRES and APF-Levy. Using a joint model of the TESS photometry, radial velocities, and Ca ii H and K emission measurements as an activity indicator, we find that TOI-1824 b is an unusually dense sub-Neptune. The planet has a radius R _p = 2.63 ± 0.15 R _⊕ and mass M _p = 18.5 ± 3.2 M _⊕ , implying a bulk density of 5.6 ± 1.4 g cm ^−3 . TOI-1824 b's mass and radius situate it near a small group of “superdense sub-Neptunes” ( R _p ≲ 3 R _⊕ and M _p ≳ 20 M _⊕ ). While the formation mechanism of superdense sub-Neptunes is a mystery, one possible explanation is the constructive collision of primordial icy cores; such giant impacts would drive atmospheric escape and could help explain these planets' apparent lack of massive envelopes. We discuss TOI-1824 b in the context of these overdense planets, whose unique location in the exoplanet mass–radius plane make them a potentially valuable tracer of planet formation.

The Transiting Exoplanet Survey Satellite (TESS) has discovered hundreds of new worlds, with TESS planet candidates now outnumbering the total number of confirmed planets from Kepler. Owing to differences in survey design, TESS continues to provide planets that are better suited for subsequent follow-up studies, including mass measurement through radial velocity (RV) observations, compared to Kepler targets. In this work, we present the TESS-Keck Survey’s (TKS) Mass Catalog: a uniform analysis of all TKS RV survey data that has resulted in mass constraints for 126 planets and candidate signals. This includes 58 mass measurements that have reached ≥5 σ precision. We confirm or validate 32 new planets from the TESS mission either by significant mass measurement (15) or statistical validation (17), and we find no evidence of likely false positives among our entire sample. This work also serves as a data release for all previously unpublished TKS survey data, including 9,204 RV measurements and associated activity indicators over our three-year survey. We took the opportunity to assess the performance of our survey and found that we achieved many of our goals, including measuring the mass of 38 small (

Hot Neptunes, gaseous planets smaller than Saturn (∼3–8 R _⊕ ) with orbital periods less than 10 days, are rare. Models predict this is due to high-energy stellar irradiation stripping planetary atmospheres over time, often leaving behind only rocky planetary cores. Using our TESS full-frame-image pipeline giants in conjunction with Keck/HIRES radial velocity measurements, we present the discovery of TIC365102760 b, a 6.2 R _⊕ (0.55 R _J ), 19.2 M _⊕ (0.060 M _J ) planet transiting a red giant star every 4.21285 days. The old age and high equilibrium temperature yet remarkably low density of this planet ( ${\rho }_{p}={0.58}_{-0.20}^{+0.30}{\rho }_{{\rm{J}}}$ ) suggest that its gaseous envelope should have been stripped by high-energy stellar irradiation billions of years ago. The present-day planet mass and radius suggest the atmospheric stripping was slower than predicted. Unexpectedly low stellar activity and/or late-stage planet inflation could be responsible for the observed properties of this system. Further studies of this system with more precise photometry in multiple passbands will be capable of revealing more details of this planet’s atmosphere.

The degree of alignment between a star’s spin axis and the orbital plane of its planets (the stellar obliquity) is related to interesting and poorly understood processes that occur during planet formation and evolution. Hot Jupiters orbiting hot stars (≳6250 K) display a wide range of obliquities, while similar planets orbiting cool stars are preferentially aligned. Tidal dissipation is expected to be more rapid in stars with thick convective envelopes, potentially explaining this trend. Evolved stars provide an opportunity to test the damping hypothesis, particularly stars that were hot on the main sequence and have since cooled and developed deep convective envelopes. We present the first systematic study of the obliquities of hot Jupiters orbiting subgiants that recently developed convective envelopes using Rossiter–McLaughlin observations. Our sample includes two newly discovered systems in the Giants Transiting Giants survey (TOI-6029 b, TOI-4379 b). We find that the orbits of hot Jupiters orbiting subgiants that have cooled below ∼6250 K are aligned or nearly aligned with the spin axis of their host stars, indicating rapid tidal realignment after the emergence of a stellar convective envelope. We place an upper limit for the timescale of realignment for hot Jupiters orbiting subgiants at ∼500 Myr. Comparison with a simplified tidal evolution model shows that obliquity damping needs to be ∼4 orders of magnitude more efficient than orbital period decay to damp the obliquity without destroying the planet, which is consistent with recent predictions for tidal dissipation from inertial waves excited by hot Jupiters on misaligned orbits.

Despite decades of effort, the mechanisms by which the spin axis of a star and the orbital axes of its planets become misaligned remain elusive. In particular, it is of great interest whether the large spin–orbit misalignments observed are driven primarily by high-eccentricity migration—expected to have occurred for short-period, isolated planets—or reflect a more universal process that operates across systems with a variety of present-day architectures. Compact multiplanet systems offer a unique opportunity to differentiate between these competing hypotheses, as their tightly packed configurations preclude violent dynamical histories, including high-eccentricity migration, allowing them to trace the primordial disk plane. In this context, we report measurements of the sky-projected stellar obliquity ( λ ) via the Rossiter–McLaughlin effect for two sub-Saturns in multiple-transiting systems: TOI-5126 b ( λ = 1 ± 48°) and TOI-5398 b ( $\lambda =-{8.1}_{-6.3}^{+5.3}{^\circ} $ ). Both are spin–orbit aligned, joining a fast-growing group of just three other compact sub-Saturn systems, all of which exhibit spin–orbit alignment. In aggregate with archival data, our results strongly suggest that sub-Saturn systems are primordially aligned and become misaligned largely in the postdisk phase, as appears to be the case increasingly for other exoplanet populations.

Exoplanet discoveries have revealed a dramatic diversity of planet sizes across a vast array of orbital architectures. Sub-Neptunes are of particular interest; due to their absence in our own solar system, we rely on demographics of exoplanets to better understand their bulk composition and formation scenarios. Here, we present the discovery and characterization of TOI-1437 b, a sub-Neptune with a 18.84 day orbit around a near-solar analog ( M _⋆ = 1.10 ± 0.10 M _☉ , R _⋆ =1.17 ± 0.12 R _☉ ). The planet was detected using photometric data from the Transiting Exoplanet Survey Satellite (TESS) mission and radial velocity (RV) follow-up observations were carried out as a part of the TESS-Keck Survey using both the HIRES instrument at Keck Observatory and the Levy Spectrograph on the Automated Planet Finder telescope. A combined analysis of these data reveal a planet radius of R _p = 2.24 ± 0.23 R _⊕ and a mass measurement of M _p = 9.6 ± 3.9 M _⊕ ). TOI-1437 b is one of few (∼50) known transiting sub-Neptunes orbiting a solar-mass star that has a RV mass measurement. As the formation pathway of these worlds remains an unanswered question, the precise mass characterization of TOI-1437 b may provide further insight into this class of planet.

Recent observations have demonstrated that some subsets of even moderately wide-separation planet-hosting binaries are preferentially configured such that planetary and binary orbits appear to lie within the same plane. In this work, we explore dissipation during the protoplanetary disk phase, induced by disk warping as the system is forced into nodal recession by an inclined binary companion as a possible avenue of achieving orbit–orbit alignment. We analytically model the coupled evolution of the disk angular momentum vector and stellar spin vector under the influence of a distant binary companion. We find that a population of systems with random initial orientations can appear detectably more aligned after undergoing dissipative precession, and that this process can simultaneously produce an obliquity distribution that is consistent with observations. While dissipative precession proceeds efficiently in close binaries, favorable system properties (e.g., r _out ≳ 100 au, α ≳ 0.05, and/or M _b / M _* ≳ 1) are required to reproduce observed alignment trends at wider binary separations a _b ≳ 450 au. Our framework further predicts that circum-primary planets in systems with high stellar mass ratios should be preferentially less aligned than planets in equal mass stellar binary systems. We discover tentative evidence for this trend in Gaia DR3 and Transiting Exoplanet Survey Satellite data. Our findings suggest that dissipative precession may play a significant role in sculpting orbital configurations in a subset of moderately wide planet-hosting binaries, but is likely not solely responsible for their observed population-level alignment.

Brown dwarfs occupy a middle ground in mass space between gaseous giant planets and ultracool dwarf stars, and the characterisation of their orbital orientations may shed light on how these neighbouring objects form. We present an analysis of the Rossiter–McLaughlin effect across the transit of TOI-2533 b , a brown dwarf on a moderately eccentric ( e _b = 0.2476 ± 0.0090) and wide-separation ( a _b / R _⋆ = 13.34 ± 0.30) orbit around an F8-type star, using data from the NEID/WIYN spectrograph in combination with archival photometry and radial velocity observations. Spin-orbit analyses of brown dwarfs are relatively rare, and TOI-2533 stands out as the fifth brown dwarf system with a measured spin–orbit constraint. We derive a sky-projected stellar obliquity of λ = −7° ± 14° for TOI-2533 b , finding that the brown dwarf is consistent with spin–orbit alignment. Our joint model also indicates that TOI-2533 b falls near the lower bound of the hydrogen-burning minimum mass range ( M _b = 74.9 ± 5.3 M _Jup ). Ultimately, we find that TOI-2533 b is consistent with formation from disc fragmentation in a primordially spin–orbit aligned orientation, although we cannot rule out the possibility that the system has been tidally realigned during its lifetime.

The extreme environments of ultra-short-period planets (USPs) make excellent laboratories to study how exoplanets obtain, lose, retain, and/or regain gaseous atmospheres. We present the confirmation and characterization of the USP TOI-1347 b, a 1.8 ± 0.1 R _⊕ planet on a 0.85 day orbit that was detected with photometry from the TESS mission. We measured radial velocities of the TOI-1347 system using Keck/HIRES and HARPS-N and found the USP to be unusually massive at 11.1 ± 1.2 M _⊕ . The measured mass and radius of TOI-1347 b imply an Earth-like bulk composition. A thin H/He envelope (>0.01% by mass) can be ruled out at high confidence. The system is between 1 and 1.8 Gyr old; therefore, intensive photoevaporation should have concluded. We detected a tentative phase-curve variation (3 σ ) and a secondary eclipse (2 σ ) in TESS photometry, which, if confirmed, could indicate the presence of a high-mean-molecular-weight atmosphere. We recommend additional optical and infrared observations to confirm the presence of an atmosphere and investigate its composition.

We present optical spectroscopy of 710 solar neighborhood stars collected over 20 years to catalog chromospheric activity and search for stellar activity cycles. The California Legacy Survey stars are amenable to exoplanet detection using precise radial velocities, and we present their Ca ii H and K time series as a proxy for stellar and chromospheric activity. Using the High Resolution Echelle Spectrometer at Keck Observatory, we measured stellar flux in the cores of the Ca ii H and K lines to determine S -values on the Mount Wilson scale and the $\mathrm{log}({R}_{\mathrm{HK}}^{{\prime} })$ metric, which is comparable across a wide range of spectral types. From the 710 stars, with 52,372 observations, 285 stars were sufficiently sampled to search for stellar activity cycles with periods of 2–25 yr, and 138 stars showed stellar cycles of varying length and amplitude. S -values can be used to mitigate stellar activity in the detection and characterization of exoplanets. We used them to probe stellar dynamos and to place the Sun's magnetic activity into context among solar neighborhood stars. Using precise stellar parameters and time-averaged activity measurements, we found tightly constrained cycle periods as a function of stellar temperature between $\mathrm{log}({R}_{\mathrm{HK}}^{{\prime} })$ of −4.7 and −4.9, a range of activity in which nearly every star has a periodic cycle. These observations present the largest sample of spectroscopically determined stellar activity cycles to date.

Warm Jupiters are close-in giant planets with relatively large planet–star separations (i.e., 10 < a / R _⋆ < 100). Given their weak tidal interactions with their host stars, measurements of stellar obliquity may be used to probe the initial obliquity distribution and dynamical history for close-in gas giants. Using spectroscopic observations, we confirm the planetary nature of TOI-1859b and determine the stellar obliquity of TOI-1859 to be λ = 38.9 ${}_{-2.7}^{+2.8}$ ° relative to its planetary companion using the Rossiter–McLaughlin effect. TOI-1859b is a 64 day warm Jupiter orbiting around a late F dwarf and has an orbital eccentricity of 0.57 ${}_{-0.16}^{+0.12}$ inferred purely from transit light curves. The eccentric and misaligned orbit of TOI-1859b is likely an outcome of dynamical interactions, such as planet–planet scattering and planet–disk resonance crossing.

The mechanisms responsible for generating spin–orbit misalignments in exoplanetary systems are still not fully understood. It is unclear whether these misalignments are related to the migration of hot Jupiters or are a consequence of general star and planet formation processes. One promising method to address this question is to constrain the distribution of spin–orbit angle measurements for a broader range of planets beyond hot Jupiters. In this work, we present the sky-projected obliquity ( $\lambda =-68\buildrel{\circ}\over{.} {1}_{-14.7}^{+21.2}$ ) for the warm sub-Saturn TOI-1842b, obtained through a measurement of the Rossiter–McLaughlin effect using WIYN/NEID. From this, we determine the resulting 3D obliquity ( ψ ) to be $\psi =73\buildrel{\circ}\over{.} {3}_{-12.9}^{+16.3}$ . As the first spin–orbit angle determination made for a sub-Saturn-mass planet around a massive ( M _* = 1.45 M _☉ ) star, our result presents an opportunity to examine the orbital geometries for new regimes of planetary systems. When combined with archival measurements, our observations of TOI-1842b support the hypothesis that the previously established prevalence of misaligned systems around hot, massive stars may be driven by planet–planet dynamical interactions. In massive stellar systems, multiple gas giants are more likely to form and can then dynamically interact with each other to excite spin–orbit misalignments.

We report the measurement of the sky-projected obliquity angle λ of the warm Jovian exoplanet TOI-1670 c via the Rossiter–McLaughlin effect. We observed the transit window during UT 2023 April 20 for 7 continuous hours with NEID on the 3.5 m WIYN Telescope at Kitt Peak National Observatory. TOI-1670 hosts a sub-Neptune ( P ∼ 11 days; planet b) interior to the warm Jovian ( P ∼ 40 days; planet c), which presents an opportunity to investigate the dynamics of a warm Jupiter with an inner companion. Additionally, TOI-1670 c is now among the longest-period planets to date to have its sky-projected obliquity angle measured. We find planet c is well aligned to the host star, with λ = − 0.°3 ± 2.°2. TOI-1670 c joins a growing census of aligned warm Jupiters around single stars and aligned planets in multiplanet systems.

The fate of planets around rapidly evolving stars is not well understood. Previous studies have suggested that, relative to the main-sequence population, planets transiting evolved stars ( P < 100 days) tend to have more eccentric orbits. Here we present the discovery of TOI-4582 b, a ${0.94}_{-0.12}^{+0.09}$ R _J , 0.53 ± 0.05 M _J planet orbiting an intermediate-mass subgiant star every 31.034 days. We find that this planet is also on a significantly eccentric orbit ( e = 0.51 ± 0.05). We then compare the population of planets found transiting evolved (log g < 3.8) stars to the population of planets transiting main-sequence stars. We find that the rate at which median orbital eccentricity grows with period is significantly higher for evolved star systems than for otherwise similar main-sequence systems. In general, we observe that mean planet eccentricity 〈 e 〉 = a + b log _10 ( P ) for the evolved population with significant orbital eccentricity where a = −0.18 ± 0.08 and b = 0.38 ± 0.06, significantly distinct from the main-sequence planetary system population. This trend is seen even after controlling for stellar mass and metallicity. These systems do not appear to represent a steady evolution pathway from eccentric, long-period planetary orbits to circular, short-period orbits, as orbital model comparisons suggest that inspiral timescales are uncorrelated with orbital separation or eccentricity. Characterization of additional evolved planetary systems will distinguish effects of stellar evolution from those of stellar mass and composition.

TOI-561 is a galactic thick-disk star hosting an ultra-short-period (0.45-day-orbit) planet with a radius of 1.37 R _⊕ , making it one of the most metal-poor ([Fe/H] = −0.41) and oldest (≈10 Gyr) sites where an Earth-sized planet has been found. We present new simultaneous radial velocity (RV) measurements from Gemini-N/MAROON-X and Keck/HIRES, which we combined with literature RVs to derive a mass of M _b = 2.24 ± 0.20 M _⊕ . We also used two new sectors of TESS photometry to improve the radius determination, finding R _b = 1.37 ± 0.04 R _⊕ and confirming that TOI-561 b is one of the lowest-density super-Earths measured to date ( ρ _b = 4.8 ± 0.5 g cm ^−3 ). This density is consistent with an iron-poor rocky composition reflective of the host star’s iron and rock-building element abundances; however, it is also consistent with a low-density planet with a volatile envelope. The equilibrium temperature of the planet (∼2300 K) suggests that this envelope would likely be composed of high mean molecular weight species, such as water vapor, carbon dioxide, or silicate vapor, and is likely not primordial. We also demonstrate that the composition determination is sensitive to the choice of stellar parameters and that further measurements are needed to determine whether TOI-561 b is a bare rocky planet, a rocky planet with an optically thin atmosphere, or a rare example of a nonprimordial envelope on a planet with a radius smaller than 1.5 R _⊕ .

The first discovered extrasolar worlds—giant, “hot Jupiter” planets on short-period orbits—came as a surprise to solar system–centric models of planet formation, prompting the development of new theories for planetary system evolution. The near absence of observed nearby planetary companions to hot Jupiters has been widely quoted as evidence in support of high-eccentricity tidal migration, a framework in which hot Jupiters form further out in their natal protoplanetary disks before being thrown inward with extremely high eccentricities, stripping systems of any close-in planetary companions. In this work, we present new results from a search for transit timing variations across the full 4 yr Kepler data set, demonstrating that at least 12% ± 6% of hot Jupiters have a nearby planetary companion. This subset of hot Jupiters is expected to have a quiescent dynamical history such that the systems could retain their nearby companions. We also demonstrate a ubiquity of nearby planetary companions to warm Jupiters (≥70% ± 16%), indicating that warm Jupiters typically form quiescently. We conclude by combining our results with existing observational constraints to propose an “eccentric migration” framework for the formation of short-period giant planets through postdisk dynamical sculpting in compact multiplanet systems. Our framework suggests that hot Jupiters constitute the natural end stage for giant planets spanning a wide range of eccentricities, with orbits that reach small enough periapses—either from their final orbital configurations in the disk phase or from eccentricity excitation in the postdisk phase—to trigger efficient tidal circularization.

The evolutionary history of an extrasolar system is, in part, fossilized through its planets’ orbital orientations relative to the host star’s spin axis. However, spin–orbit constraints for warm Jupiters—particularly in binary star systems, which are amenable to a wide range of dynamical processes—are relatively scarce. We report a measurement of the Rossiter–McLaughlin effect, observed with the Keck/HIRES spectrograph, across the transit of Qatar-6 A b—a warm Jupiter orbiting one star within a binary system. From this measurement, we obtain a sky-projected spin–orbit angle λ = 0.°1 ± 2.°6. Combining this new constraint with the stellar rotational velocity of Qatar-6 A that we measure from TESS photometry, we derive a true obliquity $\psi ={21.82}_{-18.36}^{+8.86\circ} $ —consistent with near-exact alignment. We also leverage astrometric data from Gaia DR3 to show that the Qatar-6 binary star system is edge-on ( ${i}_{B}={90.17}_{-1.06}^{+1.07\circ} $ ), such that the stellar binary and the transiting exoplanet orbit exhibit line-of-sight orbit–orbit alignment. Ultimately, we demonstrate that all current constraints for the three-body Qatar-6 system are consistent with both spin–orbit and orbit–orbit alignment. High-precision measurements of the projected stellar spin rate of the host star and the sky-plane geometry of the transit relative to the binary plane are required to conclusively verify the full 3D configuration of the system.

The HR 2562 system is a rare case where a brown dwarf companion resides in a cleared inner hole of a debris disk, offering invaluable opportunities to study the dynamical interaction between a substellar companion and a dusty disk. We present the first ALMA observation of the system as well as the continued Gemini Planet Imager monitoring of the companion’s orbit with six new epochs from 2016 to 2018. We update the orbital fit, and in combination with absolute astrometry from GAIA, place a 3 σ upper limit of 18.5 M _J on the companion’s mass. To interpret the ALMA observations, we used radiative transfer modeling to determine the disk properties. We find that the disk is well resolved and nearly edge-on. While the misalignment angle between the disk and the orbit is weakly constrained, due to the short orbital arc available, the data strongly support a (near) coplanar geometry for the system. Furthermore, we find that the models that describe the ALMA data best have inner radii that are close to the companion’s semimajor axis. Including a posteriori knowledge of the system’s SED further narrows the constraints on the disk’s inner radius and places it at a location that is in reasonable agreement with (possibly interior to) predictions from existing dynamical models of disk truncation by an interior substellar companion. HR 2562 has the potential over the next few years to become a new test bed for dynamical interaction between a debris disk and a substellar companion.

We present the stellar and planetary properties for 85 TESS Objects of Interest (TOIs) hosting 108 planet candidates that compose the TESS-Keck Survey (TKS) sample. We combine photometry, high-resolution spectroscopy, and Gaia parallaxes to measure precise and accurate stellar properties. We then use these parameters as inputs to a light-curve processing pipeline to recover planetary signals and homogeneously fit their transit properties. Among these transit fits, we detect significant transit-timing variations among at least three multiplanet systems (TOI-1136, TOI-1246, TOI-1339) and at least one single-planet system (TOI-1279). We also reduce the uncertainties on planet-to-star radius ratios R _p / R _⋆ across our sample, from a median fractional uncertainty of 8.8% among the original TOI Catalog values to 3.0% among our updated results. With this improvement, we are able to recover the Radius Gap among small TKS planets and find that the topology of the Radius Gap among our sample is broadly consistent with that measured among Kepler planets. The stellar and planetary properties presented here will facilitate follow-up investigations of both individual TOIs and broader trends in planet properties, system dynamics, and the evolution of planetary systems.

With JWST’s successful deployment and unexpectedly high fuel reserves, measuring the masses of sub-Neptunes transiting bright, nearby stars will soon become the bottleneck for characterizing the atmospheres of small exoplanets via transmission spectroscopy. Using a carefully curated target list and observations from more than 2 yr of APF-Levy and Keck-HIRES Doppler monitoring, the TESS-Keck Survey is working toward alleviating this pressure. Here we present mass measurements for 11 transiting planets in eight systems that are particularly suited to atmospheric follow-up with JWST. We also report the discovery and confirmation of a temperate super-Jovian-mass planet on a moderately eccentric orbit. The sample of eight host stars, which includes one subgiant, spans early-K to late-F spectral types ( T _eff = 5200–6200 K). We homogeneously derive planet parameters using a joint photometry and radial velocity modeling framework, discuss the planets’ possible bulk compositions, and comment on their prospects for atmospheric characterization.

In this study, we performed a homogeneous analysis of the planets around FGK dwarf stars observed by the Kepler and K2 missions, providing spectroscopic parameters for 310 K2 targets —including 239 Scaling K2 hosts—observed with Keck/HIRES. For orbital periods less than 40 days, we found that the distribution of planets as a function of orbital period, stellar effective temperature, and metallicity was consistent between K2 and Kepler, reflecting consistent planet formation efficiency across numerous ∼1 kpc sight-lines in the local Milky Way. Additionally, we detected a 3× excess of sub-Saturns relative to warm Jupiters beyond 10 days, suggesting a closer association between sub-Saturn and sub-Neptune formation than between sub-Saturn and Jovian formation. Performing a joint analysis of Kepler and K2 demographics, we observed diminishing super-Earth, sub-Neptune, and sub-Saturn populations at higher stellar effective temperatures, implying an inverse relationship between formation and disk mass. In contrast, no apparent host-star spectral-type dependence was identified for our population of Jupiters, which indicates gas-giant formation saturates within the FGK mass regimes. We present support for stellar metallicity trends reported by previous Kepler analyses. Using Gaia DR3 proper motion and radial velocity measurements, we discovered a galactic location trend; stars that make large vertical excursions from the plane of the Milky Way host fewer super-Earths and sub-Neptunes. While oscillation amplitude is associated with metallicity, metallicity alone cannot explain the observed trend, demonstrating that galactic influences are imprinted on the planet population. Overall, our results provide new insights into the distribution of planets around FGK dwarf stars and the factors that influence their formation and evolution.

As next-generation imaging instruments and interferometers search for planets closer to their stars, they must contend with increasing orbital motion and longer integration times. These compounding effects make it difficult to detect faint planets but also present an opportunity. Increased orbital motion makes it possible to move the search for planets into the orbital domain, where direct images can be freely combined with the radial velocity and proper motion anomaly, even without a confirmed detection in any single epoch. In this paper, we present a fast and differentiable multimethod orbit-modeling and planet detection code called Octofitter. This code is designed to be highly modular and allows users to easily adjust priors, change parameterizations, and specify arbitrary function relations between the parameters of one or more planets. Octofitter further supplies tools for examining model outputs including prior and posterior predictive checks and simulation-based calibration. We demonstrate the capabilities of Octofitter on real and simulated data from different instruments and methods, including HD 91312, simulated JWST/NIRISS aperture masking interferometry observations, radial velocity curves, and grids of images from the Gemini Planet Imager. We show that Octofitter can reliably recover faint planets in long sequences of images with arbitrary orbital motion. This publicly available tool will enable the broad application of multiepoch and multimethod exoplanet detection, which could improve how future targeted ground- and space-based surveys are performed. Finally, its rapid convergence makes it a useful addition to the existing ecosystem of tools for modeling the orbits of directly imaged planets.

Although close-orbiting, massive exoplanets—known as hot and warm Jupiters—are among the most observationally accessible known planets, their formation pathways are still not universally agreed upon. One method to constrain the possible dynamical histories of such planets is to measure the systems’ sky-projected spin–orbit angles using the Rossiter–McLaughlin effect. By demonstrating whether planets orbit around the stellar equator or on offset orbits, Rossiter–McLaughlin observations offer clues as to whether the planet had a quiescent or violent formation history. Such measurements are, however, only a reliable window into the history of the system if the planet in question orbits sufficiently far from its host star; otherwise, tidal interactions with the host star can erase evidence of past dynamical upheavals. We present a WIYN/NEID Rossiter–McLaughlin measurement of the tidally detached ( ${\boldsymbol{a}}/{R}_{* }={13.18}_{-0.37}^{+0.35}$ ) warm Jupiter WASP-106 b, which orbits a star along the Kraft break ( T _eff = 6002 ± 164 K). We find that WASP-106 b is consistent with a low spin–orbit angle ( $\lambda ={6}_{-16}^{+17}\,^\circ $ and $\psi ={26}_{-17}^{+12}\,^\circ $ ), suggesting a relatively quiescent formation history for the system. We conclude by comparing the stellar obliquities of hot and warm Jupiter systems, with the WASP-106 system included, to gain insight into the possible formation routes of these populations of exoplanets.

The geometries of near-resonant planetary systems offer a relatively pristine window into the initial conditions of exoplanet systems. Given that near-resonant systems have likely experienced minimal dynamical disruptions, the spin–orbit orientations of these systems inform the typical outcomes of quiescent planet formation, as well as the primordial stellar obliquity distribution. However, few measurements have been made to constrain the spin–orbit orientations of near-resonant systems. We present a Rossiter–McLaughlin measurement of the near-resonant warm Jupiter TOI-2202 b, obtained using the Carnegie Planet Finder Spectrograph on the 6.5 m Magellan Clay Telescope. This is the eighth result from the Stellar Obliquities in Long-period Exoplanet Systems survey. We derive a sky-projected 2D spin–orbit angle $\lambda ={26}_{-15}^{+12}{^\circ} $ and a 3D spin–orbit angle $\psi ={31}_{-11}^{+13}{^\circ} $ , finding that TOI-2202 b—the most massive near-resonant exoplanet with a 3D spin–orbit constraint to date—likely deviates from exact alignment with the host star’s equator. Incorporating the full census of spin–orbit measurements for near-resonant systems, we demonstrate that the current set of near-resonant systems with period ratios P _2 / P _1 ≲ 4 is generally consistent with a quiescent formation pathway, with some room for low-level (≲20°) protoplanetary disk misalignments or post-disk-dispersal spin–orbit excitation. Our result constitutes the first population-wide analysis of spin–orbit geometries for near-resonant planetary systems.