TOI-1235 b: A Keystone Super-Earth for Testing Radius Valley Emergence Models around Early M Dwarfs
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Cloutier_2020_AJ_160_22.pdf
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Published version
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2.6 MB
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Author(s)
Cloutier, Ryan
Rodriguez, Joseph E.
Irwin, Jonathan
Charbonneau, David
Stassun, Keivan G.
Mortier, Annelies
Latham, David W.
Isaacson, Howard
Howard, Andrew W.
Udry, Stéphane
Date Issued
June 2020
Journal
Astronomical Journal
Publisher
American Astronomical Society
Citation
Cloutier, Ryan et al. "TOI-1235 b: A Keystone Super-Earth for Testing Radius Valley Emergence Models around Early M Dwarfs." Astronomical Journal 160, 1 (June 2020): dx.doi.org/10.3847/1538-3881/ab9534 © 2020 American Astronomical Society
Version
Final published version
Abstract
Small planets on close-in orbits tend to exhibit envelope mass fractions of either effectively zero or up to a few percent depending on their size and orbital period. Models of thermally driven atmospheric mass loss and of terrestrial planet formation in a gas-poor environment make distinct predictions regarding the location of this rocky/nonrocky transition in period-radius space. Here we present the confirmation of TOI-1235 b (P = 3.44 days, rp1.738-0.076+0.087 R⊕), a planet whose size and period are intermediate between the competing model predictions, thus making the system an important test case for emergence models of the rocky/nonrocky transition around early M dwarfs (R s = 0.630± 0.015 ⊕, M s = 0.640 ± 0.016 ⊙. We confirm the TESS planet discovery using reconnaissance spectroscopy, ground-based photometry, high-resolution imaging, and a set of 38 precise radial velocities (RVs) from HARPS-N and HIRES. We measure a planet mass of 6.91-0.85+0.75M⊕ which implies an iron core mass fraction of 20-12+15% in the absence of a gaseous envelope. The bulk composition of TOI-1235 b is therefore consistent with being Earth-like, and we constrain an H/He envelope mass fraction to be <0.5% at 90% confidence. Our results are consistent with model predictions from thermally driven atmospheric mass loss but not with gas-poor formation, suggesting that the former class of processes remains efficient at sculpting close-in planets around early M dwarfs. Our RV analysis also reveals a strong periodicity close to the first harmonic of the photometrically determined stellar rotation period that we treat as stellar activity, despite other lines of evidence favoring a planetary origin ( = P 21.8+0.9-0.8days,mp sin =13.0+ 3.8-5.3M⊕) that cannot be firmly ruled out by our data.
MIT Department
Massachusetts Institute of Technology. Department of Physics
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
https://doi.org/10.3847/1538-3881/ab9534
