HD 219666 b: a hot-Neptune from TESS Sector 1

ARMSTRONG, D.J.; FRIDLUND, M.; DELGADO MENA, E.; BARRAGÁN, O.; COOKE, B.; DÍAZ, R.F.; PERSSON, C.M.; VAN EYLEN, V.; BECK, P.G.; BONOMO, A.S.; BRYANT, E.; CSIZMADIA, S.; DELEUIL, M.; ENDL, M.; FIGUEIRA, P.; GUENTHER, E.W.; HIRANO, T.; KORTH, J.; LUND, M.N.; MONTAÑÉS RODRÍGUEZ, P.; NIRAULA, P.; PALLÉ, E.; GANDOLFI, D.; PRIETO-ARRANZ, J.; SANTOS, N.C.; RIBAS, I.; FOSSATI, L.; TALA-PINTO, M.; BARRADO, D.; JUSTESEN, A.B.; DAI, F.; WHEATLEY, P.J.; MUSSO, M.M.; BARROS, S.C.C.; BOUCHY, F.; CABRERA, J.; DEEG, H.; DUMUSQUE, X.; ERIKSON, A.; FUKUI, A.; HIDALGO, D.; HOJJATPANAH, S.; LAM, K.W.F.; LUQUE, R.; NARITA, N.; NOWAK, G.; PÄTZOLD, M.; RAUER, H.; SOUSA, S.G.; UDRY, S.; ESPOSITO, M.; ADIBEKYAN, V.; LIVINGSTON, J.H.; LILLO-BOX, J.; CUBILLOS, P.E.; MERU, F.; NIELSEN, L.D.; HATZES, A.P.; ALONSO, R.; BAYLISS, D.; BROWN, D.J.A.; COCHRAN, W.D.; DEMANGEON, O.; EIGMÜLLER, P.; FAEDI, F.; GRZIWA, S.; HJORTH, M.; KNUDSTRUP, E.; DE LEON, J.; MATHUR, S.; NESPRAL, D.; OSBORN, H.P.; POLLACCO, D.; REDFIELD, S.; SMITH, A.M.S.; WINN,

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Año: 2019 vol. 623

0004-6361

We report on the confirmation and mass determination of a transiting planet orbiting the old and inactive G7 dwarf star HD 219666 (M ∗ = 0.92 ± 0.03 M ⊙ , R ∗ = 1.03 ± 0.03 R ⊙ , τ ∗ = 10 ± 2 Gyr). With a mass of M b = 16.6 ± 1.3 M ⊙ , a radius of R b = 4.71 ± 0.17 R ⊙ , and an orbital period of P orb ≃ 6 days, HD 219666 b is a new member of a rare class of exoplanets: the hot-Neptunes. The Transiting Exoplanet Survey Satellite (TESS) observed HD 219666 (also known as TOI-118) in its Sector 1 and the light curve shows four transit-like events, equally spaced in time. We confirmed the planetary nature of the candidate by gathering precise radial-velocity measurements with the High Accuracy Radial velocity Planet Searcher (HARPS) at ESO 3.6 m. We used the co-added HARPS spectrum to derive the host star fundamental parameters (T eff = 5527 ± 65 K, log g ∗ = 4.40 ± 0.11 (cgs), [Fe/H]= 0.04 ± 0.04 dex, log R ′ HK = -5.07 ± 0.03), as well as the abundances of many volatile and refractory elements. The host star brightness (V = 9.9) makes it suitable for further characterisation by means of in-transit spectroscopy. The determination of the planet orbital obliquity, along with the atmosphericmetal-to-hydrogen content and thermal structure could provide us with important clues on the formation mechanisms of this class of objects.