Earths are not Super-Earths, Saturns are not Jupiters: Imprints of pressure-bump planet formation on planetary architectures

In protoplanetary disks, sufficiently massive planets excite pressure bumps, which can then be preferred locations for forming new planet cores. We discuss how this loop may affect the architecture of multi-planet systems, and compare our predictions with observation. Our main prediction is that low-mass planets and giant planets can each be divided into two subpopulations with different levels of mass uniformity. Low-mass planets that can and cannot reach the pebble isolation mass (the minimum mass required to produce a pressure bump) develop into intra-similar "Super-Earths" and more diverse "Earths", respectively. Gas giants that do and do not accrete envelope quickly develop into intra-similar "Jupiters" and more diverse "Saturns", respectively. Super-Earths prefer to form long chains via repeated pressure-bump planet formation, while Jupiter formation is usually terminated at pairs or triplets due to dynamical instability. These predictions are broadly consistent with observations. In particular, we discover a previously overlooked mass uniformity dichotomy among the observed populations of both low-mass planets (Earths vs. Super-Earths) and gas giants (Saturns vs. Jupiters). For low-mass planets, planets well below the pebble isolation mass ($\lesssim 3M_\oplus$ or $\lesssim 1.5 R_\oplus$ for sun-like stars) show significantly higher intra-system pairwise mass difference than planets around the pebble isolation mass. For gas giants, the period ratios of intra-system pairs show a bimodal distribution, which can be interpreted as two subpopulations with different levels of mass uniformity. These findings suggest that pressure-bump planet formation could be an important ingredient in shaping planetary architectures.Comment: 15 pages, 6 figures. Accepted for publication in ApJ

Evidence for Hidden Nearby Companions to Hot Jupiters

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 four-year Kepler dataset, demonstrating that at least $12\pm6\%$ 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 ($\geq70\pm{16}\%$), 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 post-disk dynamical sculpting in compact multi-planet 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 post-disk phase -- to trigger efficient tidal circularization.Comment: 19 pages, 5 figures, Accepted for publication in the Astronomical Journa

The Spin-Orbit Misalignment of TOI-1842b: The First Measurement of the Rossiter-McLaughlin Effect for a Warm Sub-Saturn around a Massive Star

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=-68.1_{-14.7}^{+21.2} \,^{\circ}) for the warm sub-Saturn TOI-1842b, obtained through a measurement of the Rossiter-McLaughlin effect using WIYN/NEID. Using the projected obliquity, the stellar rotation period obtained from the TESS light curve, and the projected rotation velocity from spectral analysis, we infer the 3D spin-orbit angle ($\psi$) to be \psi=73.3^{+16.3}_{-12.9} \,^{\circ}. As the first spin-orbit angle determination made for a sub-Saturn-mass planet around a massive ($M_{\rm *}=1.45 \,{\rm M_\odot}$) 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.Comment: 8 pages, 2 tables, 2 figures, accepted for publication in ApJ

SOLES VII: The Spin-Orbit Alignment of WASP-106 b, a Warm Jupiter Along the Kraft Break

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 warm Jupiter WASP-106 b, which orbits a star along the Kraft break ($T_{\mathrm{eff}}=6002\pm164$ K). We find that WASP-106 b is consistent with a low spin-orbit angle (\lambda=6^{+17}_{-16}\,^{\circ} and \psi = 26^{+12}_{-17}\,^{\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.Comment: 9 pages, 2 figures. Submitted to AAS journals 8/7/2

Enhanced Size Uniformity for Near-resonant Planets

Super-Earths within the same close-in, compact planetary system tend to exhibit a striking degree of uniformity in their radius, mass, and orbital spacing, and this 'peas-in-a-pod' phenomenon itself serves to provide one of the strongest constrains on planet formation at large. While it has been recently demonstrated from independent samples that such planetary uniformity occurs for both configurations near and distant from mean motion resonance, the question thus remains if the strength of this uniformity itself differs between near-resonant and nonresonant configurations such that the two modes may be astrophysically distinct in their evolution. We thus provide in this work a novel comparative size uniformity analysis for 48 near-resonant and 251 nonresonant multi-planet systems from the California Kepler Survey catalog, evaluating uniformity both across systems and between planetary pairs within the same system. We find that while multiplanet configurations exhibit strong peas-in-a-pod size uniformity regardless of their proximity to resonance, near-resonant configurations display enhanced intra-system size uniformity as compared to their analogous nonresonant counterparts at the level of both entire systems and subsystem planetary pairs and chains. These results are broadly consistent with a variety of formation paradigms for multiplanet systems, such as convergent migration within a turbulent protoplanetary disk or planet-planet interactions incited by postnebular dynamical instabilities. Nevertheless, further investigation is necessary to ascertain whether the nonresonant and near-resonant planetary configurations respectively evolve via a singular process or mechanisms that are dynamically distinct.Comment: 15 pages, 6 figures. Accepted to ApJ July 202