Luque, R;
Nowak, G;
Hirano, T;
Kossakowski, D;
Pallé, E;
Nixon, MC;
Morello, G;
... Osorio, MR Zapatero; + view all
(2022)
Precise mass determination for the keystone sub-Neptune planet transiting the mid-type M dwarf G 9-40.
Astronomy & Astrophysics
, 666
, Article A154. 10.1051/0004-6361/202244426.
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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.
| Type: | Article |
|---|---|
| Title: | Precise mass determination for the keystone sub-Neptune planet transiting the mid-type M dwarf G 9-40 |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1051/0004-6361/202244426 |
| Publisher version: | https://doi.org/10.1051/0004-6361/202244426 |
| Language: | English |
| Additional information: | © R. Luque et al. 2022. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0). |
| Keywords: | planetary systems, techniques: photometric, techniques: radial velocities, stars: low-mass, stars: individual: G 9–40 |
| UCL classification: | UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics UCL > Provost and Vice Provost Offices > UCL BEAMS UCL |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10155677 |
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