The TESS-Keck Survey. XVII. Precise Mass Measurements in a Young, High-multiplicity Transiting Planet System Using Radial Velocities and Transit Timing Variations

Beard, Corey; Robertson, Paul; Dai, Fei; Holcomb, Rae; Lubin, Jack; Akana Murphy, Joseph M.; Batalha, Natalie M.; Blunt, Sarah; Crossfield, Ian; Dressing, Courtney; Fulton, Benjamin; Howard, Andrew W.; Huber, Dan; Isaacson, Howard; Kane, Stephen R.; Nowak, Grzegorz; Petigura, Erik A; Roy, Arpita; Rubenzahl, Ryan A.; Weiss, Lauren M.; Barrena, Rafael; Behmard, Aida; Brinkman, Casey L.; Carleo, Ilaria; Chontos, Ashley; Dalba, Paul A.; Fetherolf, Tara; Giacalone, Steven; Hill, Michelle L.; Kawauchi, Kiyoe; Korth, Judith; Luque, Rafael; MacDougall, Mason G.; Mayo, Andrew W.; Močnik, Teo; Morello, Giuseppe; Murgas, Felipe; Orell-Miquel, Jaume; Palle, Enric; Polanski, Alex S.; Rice, Malena; Scarsdale, Nicholas; Tyler, Dakotah; Van Zandt, Judah

doi:10.3847/1538-3881/ad1330

Cited by 4 publications

(1 citation statement)

References 117 publications

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“…If a model is overfitting, the evaluation data residuals should have systematically higher scatter than the training data residuals and/or be offset from zero. For examples, see Figure 5 in Blunt et al (2023) and Figure 8 in Beard et al (2024).…”

Section: Cross-validation To Assess Overfittingmentioning

confidence: 99%

The TESS-Keck Survey. VII. A Superdense Sub-Neptune Orbiting TOI-1824*

Lange,

Murphy,

Batalha

et al. 2024

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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.

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Section: Cross-validation To Assess Overfittingmentioning

confidence: 99%

The TESS-Keck Survey. VII. A Superdense Sub-Neptune Orbiting TOI-1824*

Lange,

Murphy,

Batalha

et al. 2024

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HD 110067 c has an aligned orbit

Zak,

Boffin,

Sedaghati

et al. 2024

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Planetary systems in mean motion resonances hold a special place among the planetary population. They allow us to study planet formation in great detail as dissipative processes are thought to have played an important role in their existence. Additionally, planetary masses in bright resonant systems can be independently measured via both radial velocities and transit timing variations. In principle, they also allow us to quickly determine the inclination of all planets in the system since, for the system to be stable, they are likely all in coplanar orbits. To describe the full dynamical state of the system, we also need the stellar obliquity, which provides the orbital alignment of a planet with respect to the spin of its host star and can be measured thanks to the Rossiter-McLaughlin effect. It was recently discovered that HD 110067 harbors a system of six sub-Neptunes in resonant chain orbits. We here analyze an ESPRESSO high-resolution spectroscopic time series of HD 110067 during the transit of planet c. We find the orbit of HD 110067 c to be well aligned, with a sky-projected obliquity of $ $\,deg. This result indicates that the current architecture of the system was reached through convergent migration without any major disruptive events. Finally, we report transit-timing variation in this system as we find a significant offset of 19 pm 4 minutes in the center of the transit compared to the published ephemeris.

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Utilizing Photometry from Multiple Sources to Mitigate Stellar Variability in Precise Radial Velocities: A Case Study of Kepler-21

Beard,

Robertson,

Giovinazzi

et al. 2024

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We present a new analysis of Kepler-21, the brightest (V = 8.5) Kepler system with a known transiting exoplanet, Kepler-21 b. Kepler-21 b is a radius valley planet (R = 1.6 ± 0.2R ⊕) with an Earth-like composition (8.38 ± 1.62 g cm–3), though its mass and radius fall in the regime of possible “water worlds.” We utilize new Keck/High-Resolution Echelle Spectrometer and WIYN/NEID radial velocity (RV) data in conjunction with Kepler and Transiting Exoplanet Survey Satellite (TESS) photometry to perform a detailed study of activity mitigation between photometry and RVs. We additionally refine the system parameters, and we utilize Gaia astrometry to place constraints on a long-term RV trend. Our activity analysis affirms the quality of Kepler photometry for removing correlated noise from RVs, despite its temporal distance, though we reveal some cases where TESS may be superior. Using refined orbital parameters and updated composition curves, we rule out a water world scenario for Kepler-21 b, and we identify a long-period super-Jupiter planetary candidate, Kepler-21 (c).

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The TESS-Keck Survey. XVII. Precise Mass Measurements in a Young, High-multiplicity Transiting Planet System Using Radial Velocities and Transit Timing Variations

Cited by 4 publications

References 117 publications

The TESS-Keck Survey. VII. A Superdense Sub-Neptune Orbiting TOI-1824*

The TESS-Keck Survey. VII. A Superdense Sub-Neptune Orbiting TOI-1824*

HD 110067 c has an aligned orbit

Utilizing Photometry from Multiple Sources to Mitigate Stellar Variability in Precise Radial Velocities: A Case Study of Kepler-21

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