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1. Kepler-102: Masses and Compositions for a Super-Earth and Sub-Neptune Orbiting an Active Star

   https://doi.org/10.3847/1538-3881/aca64d  

   Brinkman, Casey L. ; Cadman, James ; Weiss, Lauren ; Gaidos, Eric ; Rice, Ken ; Huber, Daniel ; Claytor, Zachary R. ; Bonomo, Aldo S. ; Buchhave, Lars A. ; Cameron, Andrew Collier ; et al ( January 2023 , The Astronomical Journal)

   Radial velocity (RV) measurements of transiting multiplanet systems allow us to understand the densities and compositions of planets unlike those in the solar system. Kepler-102, which consists of five tightly packed transiting planets, is a particularly interesting system since it includes a super-Earth (Kepler-102d) and a sub-Neptune-sized planet (Kepler-102e) for which masses can be measured using RVs. Previous work found a high density for Kepler-102d, suggesting a composition similar to that of Mercury, while Kepler-102e was found to have a density typical of sub-Neptune size planets; however, Kepler-102 is an active star, which can interfere with RV mass measurements. To better measure the mass of these two planets, we obtained 111 new RVs using Keck/HIRES and Telescopio Nazionale Galileo/HARPS-N and modeled Kepler-102's activity using quasiperiodic Gaussian process regression. For Kepler-102d, we report a mass upper limitM_d< 5.3M_⊕(95% confidence), a best-fit massM_d= 2.5 ± 1.4M_⊕, and a densityρ_d= 5.6 ± 3.2 g cm⁻³, which is consistent with a rocky composition similar in density to the Earth. For Kepler-102e we report a massM_e= 4.7 ± 1.7M_⊕and a densityρ_e= 1.8 ± 0.7 g cm⁻³. These measurements suggest that Kepler-102e has a rocky core with a thick gaseous envelope comprising 2%–4% of themore »planet mass and 16%–50% of its radius. Our study is yet another demonstration that accounting for stellar activity in stars with clear rotation signals can yield more accurate planet masses, enabling a more realistic interpretation of planet interiors.

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2. Sub-stellar companions of intermediate-mass stars with CoRoT: CoRoT–34b, CoRoT–35b, and CoRoT–36b

   https://doi.org/10.1093/mnras/stac2131  

   Sebastian, D. ; Guenther, E. W. ; Deleuil, M. ; Dorsch, M. ; Heber, U. ; Heuser, C. ; Gandolfi, D. ; Grziwa, S. ; Deeg, H. J. ; Alonso, R. ; et al ( August 2022 , Monthly Notices of the Royal Astronomical Society)

   Theories of planet formation give contradicting results of how frequent close-in giant planets of intermediate mass stars (IMSs; $1.3\le M_{\star }\le 3.2\, \mathrm{M}_{\odot }$) are. Some theories predict a high rate of IMSs with close-in gas giants, while others predict a very low rate. Thus, determining the frequency of close-in giant planets of IMSs is an important test for theories of planet formation. We use the CoRoT survey to determine the absolute frequency of IMSs that harbour at least one close-in giant planet and compare it to that of solar-like stars. The CoRoT transit survey is ideal for this purpose, because of its completeness for gas-giant planets with orbital periods of less than 10 d and its large sample of main-sequence IMSs. We present a high precision radial velocity follow-up programme and conclude on 17 promising transit candidates of IMSs, observed with CoRoT. We report the detection of CoRoT–34b, a brown dwarf close to the hydrogen burning limit, orbiting a 1.1 Gyr A-type main-sequence star. We also confirm two inflated giant planets, CoRoT–35b, part of a possible planetary system around a metal-poor star, and CoRoT–36b on a misaligned orbit. We find that $0.12 \pm 0.10\, {{\ \rm per\ cent}}$ of IMSsmore »between $1.3\le M_{\star }\le 1.6\, \mathrm{M}_{\odot }$ observed by CoRoT do harbour at least one close-in giant planet. This is significantly lower than the frequency ($0.70 \pm 0.16\, {{\ \rm per\ cent}}$) for solar-mass stars, as well as the frequency of IMSs harbouring long-period planets ($\sim 8\, {{\ \rm per\ cent}}$).

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3. Measuring the Obliquities of the TRAPPIST-1 Planets with MAROON-X

   https://doi.org/10.3847/1538-3881/acb5f7  

   Brady, Madison ; Bean, Jacob L. ; Seifahrt, Andreas ; Kasper, David ; Luque, Rafael ; Reiners, Ansgar ; Benneke, Björn ; Stefánsson, Gudmundur ; Stürmer, Julian ( February 2023 , The Astronomical Journal)

   A star’s obliquity with respect to its planetary system can provide us with insight into the system’s formation and evolution, as well as hinting at the presence of additional objects in the system. However, M dwarfs, which are the most promising targets for atmospheric follow-up, are underrepresented in terms of obliquity characterization surveys due to the challenges associated with making precise measurements. In this paper, we use the extreme-precision radial velocity (RV) spectrograph MAROON-X to measure the obliquity of the late M dwarf TRAPPIST-1. With the Rossiter–McLaughlin effect, we measure a system obliquity of$-2{°}_{-{19}^{◦}}^{+{17}^{◦}}$and a stellar rotational velocity of 2.1 ± 0.3 km s⁻¹. We were unable to detect stellar surface differential rotation, and we found that a model in which all planets share the same obliquity was favored by our data. We were also unable to make a detection of the signatures of the planets using Doppler tomography, which is likely a result of the both the slow rotation of the star and the low signal-to-noise ratio of the data. Overall, TRAPPIST-1 appears to have a low obliquity, which could imply that the system has a low primordial obliquity. It also appears to be amore »slow rotator, which is consistent with past characterizations of the system and estimates of the star’s rotation period. The MAROON-X data allow for a precise measurement of the stellar obliquity through the Rossiter–McLaughlin effect, highlighting the capabilities of MAROON-X and its ability to make high-precision RV measurements around late, dim stars.

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4. Kepler-167e as a Probe of the Formation Histories of Cold Giants with Inner Super-Earths

   https://doi.org/10.3847/1538-4357/ac3ed6  

   Chachan, Yayaati ; Dalba, Paul A. ; Knutson, Heather A. ; Fulton, Benjamin J. ; Thorngren, Daniel ; Beichman, Charles ; Ciardi, David R. ; Howard, Andrew W. ; Van Zandt, Judah ( February 2022 , The Astrophysical Journal)

   Abstract The observed correlation between outer giant planets and inner super-Earths is emerging as an important constraint on planet formation theories. In this study, we focus on Kepler-167, which is currently the only system known to contain both inner transiting super-Earths and a confirmed outer transiting gas giant companion beyond 1 au. Using long-term radial velocity monitoring, we measure the mass of the gas giant Kepler-167e ( P = 1071 days) to be 1.01 − 0.15 + 0.16 M J , thus confirming it as a Jupiter analog. We refit the Kepler photometry to obtain updated radii for all four planets. Using a planetary structure model, we estimate that Kepler-167e contains 66 ± 19 M ⊕ of solids and is significantly enriched in metals relative to its solar-metallicity host star. We use these new constraints to explore the broader question of how systems like Kepler-167 form in the pebble accretion framework for giant planet core formation. We utilize simple disk evolution models to demonstrate that more massive and metal-rich disks, which are the most favorable sites for giant planet formation, can also deliver enough solids to the inner disk to form systems of super-Earths. We use these same models tomore »constrain the nature of Kepler-167's protoplanetary disk and find that it likely contained ≳300 M ⊕ of dust and was ≳40 au in size. These values overlap with the upper end of the observed dust mass and size distributions of Class 0 and I disks and are also consistent with the observed occurrence rate of Jupiter analogs around Sun-like stars.« less
5. The McDonald Accelerating Stars Survey: Architecture of the Ancient Five-planet Host System Kepler-444

   https://doi.org/10.3847/1538-3881/aca88c  

   Zhang, Zhoujian ; Bowler, Brendan P. ; Dupuy, Trent J. ; Brandt, Timothy D. ; Brandt, G. Mirek ; Cochran, William D. ; Endl, Michael ; MacQueen, Phillip J. ; Kratter, Kaitlin M. ; Isaacson, Howard T. ; et al ( January 2023 , The Astronomical Journal)

   We present the latest and most precise characterization of the architecture for the ancient (≈11 Gyr) Kepler-444 system, which is composed of a K0 primary star (Kepler-444 A) hosting five transiting planets and a tight M-type spectroscopic binary (Kepler-444 BC) with an A–BC projected separation of 66 au. We have measured the system’s relative astrometry using the adaptive optics imaging from Keck/NIRC2 and Kepler-444 A’s radial velocities from the Hobby-Eberly Telescope and reanalyzed relative radial velocities between BC and A from Keck/HIRES. We also include the Hipparcos-Gaia astrometric acceleration and all published astrometry and radial velocities in an updated orbit analysis of BC’s barycenter. These data greatly extend the time baseline of the monitoring and lead to significant updates to BC’s barycentric orbit compared to previous work, including a larger semimajor axis ($a={52.2}_{-2.7}^{+3.3}$au), a smaller eccentricity (e= 0.55 ± 0.05), and a more precise inclination ($i=85.°4_{-0.°4}^{+0.°3}$). We have also derived the first dynamical masses of B and C components. Our results suggest that Kepler-444 A’s protoplanetary disk was likely truncated by BC to a radius of ≈8 au, which resolves the previously noticed tension between Kepler-444 A’s disk mass and planet masses. Kepler-444more »BC’s barycentric orbit is likely aligned with those of A’s five planets, which might be primordial or a consequence of dynamical evolution. The Kepler-444 system demonstrates that compact multiplanet systems residing in hierarchical stellar triples can form at early epochs of the universe and survive their secular evolution throughout cosmic time.

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