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Precise mass determination for the keystone sub-Neptune planet transiting the mid-type M dwarf G 9-40
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(2022) Precise mass determination for the keystone sub-Neptune planet transiting the mid-type M dwarf G 9-40. Astronomy & Astrophysics, 666 . A154. doi:10.1051/0004-6361/202244426 ISSN 0004-6361.
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Official URL: http://dx.doi.org/10.1051/0004-6361/202244426
Abstract
Context. Despite being a prominent subset of the exoplanet population discovered in the past three decades, the nature and provenance of sub-Neptune-sized planets is still one of the open questions in exoplanet science.
Aims. For planets orbiting bright stars, precisely measuring the orbital and planet parameters of the system is the best approach to distinguish between competing theories regarding their formation and evolution.
Methods. We obtained 69 new radial velocity observations of the mid-M dwarf G 9–40 with the CARMENES instrument to measure for the first time the mass of its transiting sub-Neptune planet, G 9–40 b, discovered in data from the K2 mission.
Results. Combined with new observations from the TESS mission during Sectors 44, 45, and 46, we are able to measure the radius of the planet to an uncertainty of 3.4% (Rb = 1.900 ± 0.065 R⊕) and determine its mass with a precision of 16% (Mb = 4.00 ± 0.63 M⊕). The resulting bulk density of the planet is inconsistent with a terrestrial composition and suggests the presence of either a water-rich core or a significant hydrogen-rich envelope.
Conclusions. G 9–40 b is referred to as a keystone planet due to its location in period-radius space within the radius valley. Several theories offer explanations for the origin and properties of this population and this planet is a valuable target for testing the dependence of those models on stellar host mass. By virtue of its brightness and small size of the host, it joins L 98-59 d as one of the two best warm (Teq ~ 400 K) sub-Neptunes for atmospheric characterization with JWST, which will probe cloud formation in sub-Neptune-sized planets and break the degeneracies of internal composition models.
Item Type: | Journal Article | ||||||||||||||||||||||||||||||
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Subjects: | Q Science > QB Astronomy | ||||||||||||||||||||||||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||||||||||||||||||||||||
Library of Congress Subject Headings (LCSH): | Planetary systems , Astronomical photometry, Low mass stars , M stars -- Motion in line of sight | ||||||||||||||||||||||||||||||
Journal or Publication Title: | Astronomy & Astrophysics | ||||||||||||||||||||||||||||||
Publisher: | EDP Sciences | ||||||||||||||||||||||||||||||
ISSN: | 0004-6361 | ||||||||||||||||||||||||||||||
Official Date: | 21 October 2022 | ||||||||||||||||||||||||||||||
Dates: |
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Volume: | 666 | ||||||||||||||||||||||||||||||
Number of Pages: | 15 | ||||||||||||||||||||||||||||||
Article Number: | A154 | ||||||||||||||||||||||||||||||
DOI: | 10.1051/0004-6361/202244426 | ||||||||||||||||||||||||||||||
Status: | Peer Reviewed | ||||||||||||||||||||||||||||||
Publication Status: | Published | ||||||||||||||||||||||||||||||
Access rights to Published version: | Open Access (Creative Commons) | ||||||||||||||||||||||||||||||
Date of first compliant deposit: | 12 December 2022 | ||||||||||||||||||||||||||||||
Date of first compliant Open Access: | 12 December 2022 | ||||||||||||||||||||||||||||||
RIOXX Funder/Project Grant: |
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