Characterization of the L 98-59 multiplanetary system with HARPS. Mass characterization of a hot super-Earth, a sub-Neptune, and a mass upper limit on the third planet
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aa35957-19.pdf
Description
Published version
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4.55 MB
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Adobe PDF
Checksum (MD5)
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Author(s)
Seager, Sara
Date Issued
September 2019
Journal
Astronomy and astrophysics
Publisher
EDP Sciences
Citation
Cloutier, R. et al. “Characterization of the L 98-59 multiplanetary system with HARPS. Mass characterization of a hot super-Earth, a sub-Neptune, and a mass upper limit on the third planet” Astronomy and astrophysics, vol. 629, 2019, Article 111 © 2019 The Author(s)
Version
Final published version
Abstract
Aims.L 98-59 (TIC 307210830, TOI-175) is a nearby M3 dwarf around which TESS revealed three small transiting planets (0.80,1.35, 1.57 Earth radii) in a compact configuration with orbital periods shorter than 7.5 days. Here we aim to measure the masses of theknown transiting planets in this system using precise radial velocity (RV) measurements taken with the HARPS spectrograph.Methods.We considered both trained and untrained Gaussian process regression models of stellar activity, which are modeled simul-taneously with the planetary signals. Our RV analysis was then supplemented with dynamical simulations to provide strong constraintson the planets’ orbital eccentricities by requiring long-term stability.Results.We measure the planet masses of the two outermost planets to be2.42±0.35and2.31±0.46Earth masses, which confirmsthe bulk terrestrial composition of the former and eludes to a significant radius fraction in an extended gaseous envelope for the latter.We are able to place an upper limit on the mass of the smallest, innermost planet of<1.01Earth masses with 95% confidence. OurRV plus dynamical stability analysis places strong constraints on the orbital eccentricities and reveals that each planet’s orbit likely hase<0.1.Conclusions.L 98-59 is likely a compact system of two rocky planets plus a third outer planet with a lower bulk density possiblyindicative of the planet having retained a modest atmosphere. The system offers a unique laboratory for studies of planet formation,dynamical stability, and comparative atmospheric planetology as the two outer planets are attractive targets for atmospheric character-ization through transmission spectroscopy. Continued RV monitoring will help refine the characterization of the innermost planet andpotentially reveal additional planets in the system at wider separations.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
Massachusetts Institute of Technology. Department of Aeronautics and Astronautics
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1051/0004-6361/201935957
