K2-110 b: a massive mini-Neptune exoplanet
Abstract
We report the discovery of the exoplanet K2-110 b (previously EPIC212521166b) from K2 photometry orbiting in a 13.8637d period around an old, metal-poor K3 dwarf star. With a V-band magnitude of 11.9,K2-110 is particularly amenable to RV follow-up. A joint analysis of K2 photometry and high-precision RVs from 28 HARPS and HARPS-N spectra reveal it to have a radius of 2.6 ± 0.1R⊕ and amass of 16.7 ± 3.2M⊕, hence a density of 5.2± 1.2 g cm-3, making it one of the most massive planets yet to be found with a sub-Neptune radius. When accounting for compression, the resulting Earth-like density is best fitted by a 0.2M⊕ hydrogen atmosphere over an 16.5M⊕ Earth-like interior, although the planet could also have significant water content. At 0.1 AU, even taking into account the old stellar age of 8 ± 3 Gyr, the planet is unlikely to have been significantly affected by EUV evaporation. However the planet likely disc-migrated to its current position making the lack of a thick H2 atmosphere puzzling. This analysis has made K2-110 b one of the best-characterised mini-Neptunes with density constrained to less than 30%.
Citation
Osborn , H P , Santerne , A , Barros , S C C , Santos , N C , Dumusque , X , Malavolta , L , Armstrong , D J , Hojjatpanah , S , Demangeon , O , Adibekyan , V , Almenara , J-M , Barrado , D , Bayliss , D , Boisse , I , Bouchy , F , Brown , D J A , Cameron , A C , Charbonneau , D , Deleuil , M , Delgado Mena , E , Díaz , R F , Hébrard , G , Kirk , J , King , G W , Lam , K W F , Latham , D , Lillo-Box , J , Louden , T M , Lovis , C , Marmier , M , McCormac , J , Molinari , E , Pepe , F , Pollacco , D , Sousa , S G , Udry , S & Walker , S R 2017 , ' K2-110 b: a massive mini-Neptune exoplanet ' , Astronomy & Astrophysics , vol. 604 , A19 . https://doi.org/10.1051/0004-6361/201628932
Publication
Astronomy & Astrophysics
Status
Peer reviewed
ISSN
0004-6361Type
Journal article
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