The TESS–Keck Survey. VI. Two Eccentric Sub-Neptunes Orbiting HIP-97166
Name
2110.05628.pdf
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Accepted version
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3.16 MB
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Adobe PDF
Checksum (MD5)
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Author(s)
Seager, Sara
Date Issued
2021
Journal
Astronomical Journal
Publisher
American Astronomical Society
Citation
Seager, Sara. 2021. "The TESS–Keck Survey. VI. Two Eccentric Sub-Neptunes Orbiting HIP-97166." Astronomical Journal, 162 (6).
Version
Author's final manuscript
Abstract
We report the discovery of HIP-97166b (TOI-1255b), a transiting sub-Neptune on a 10.3 day orbit around a K0 dwarf 68 pc from Earth. This planet was identified in a systematic search of TESS Objects of Interest for planets with eccentric orbits, based on a mismatch between the observed transit duration and the expected duration for a circular orbit. We confirmed the planetary nature of HIP-97166b with ground-based radial-velocity measurements and measured a mass of Mb = 20 ± 2 M⊕ along with a radius of Rb = 2.7 ± 0.1 R⊕ from photometry. We detected an additional nontransiting planetary companion with Mc sini = 10 ± 2 M⊕ on a 16.8 day orbit. While the short transit duration of the inner planet initially suggested a high eccentricity, a joint RV-photometry analysis revealed a high impact parameter b = 0.84 ± 0.03 and a moderate eccentricity. Modeling the dynamics with the condition that the system remain stable over >105 orbits yielded eccentricity constraints eb = 0.16 ± 0.03 and ec < 0.25. The eccentricity we find for planet b is above average for the small population of sub-Neptunes with well-measured eccentricities. We explored the plausible formation pathways of this system, proposing an early instability and merger event to explain the high density of the inner planet at 5.3 ± 0.9 g cc−1 as well as its moderate eccentricity and proximity to a 5:3 mean-motion resonance.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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Creative Commons Attribution-Noncommercial-Share Alike
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DOI of Published Version
https://doi.org/10.3847/1538-3881/AC295E
