HD 219666 b: a hot-Neptune from TESS Sector 1
Alonso, R.; Bouchy, F.; Deeg, H.; Deleuil, M.; Erikson, A.; Fridlund, M.; Pätzold, M.; Rauer, H.; Pallé, E.; Ribas, I.; Guenther, E. W.; Barragán, O.; Dai, F.; Gandolfi, D.; Hirano, T.; Fossati, L.; Korth, J.; Prieto-Arranz, J.; Nespral, D.; Hjorth, M.; Grziwa, S.; Hatzes, A. P.; Smith, A. M. S.; Cabrera, J.; Narita, N.; Cochran, W. D.; Persson, C. M.; Van Eylen, V.; Nowak, G.; Winn, J. N.; Knudstrup, E.; Lund, M. N.; Adibekyan, V.; Sousa, S. G.; Barrado, D.; Barros, S. C. C.; Esposito, M.; Lam, K. W. F.; Luque, R.; Osborn, H. P.; Pollacco, D.; Redfield, S.; Santos, N. C.; Udry, S.; Lillo-Box, J.; Figueira, P.; Wheatley, P. J.; Mathur, S.; Bonomo, A. S.; Díaz, R. F.; Dumusque, X.; Demangeon, O.; Faedi, F.; Fukui, A.; Hidalgo, D.; Justesen, A. B.; Cubillos, P. E.; Endl, M.; Csizmadia, S.; Beck, P. G.; Hojjatpanah, S.; Nielsen, L. D.; Armstrong, D. J.; Meru, F.; Bayliss, D.; Brown, D. J. A.; Bryant, E.; Niraula, P.; Livingston, J. H.; de Leon, J.; Delgado Mena, E.; Cooke, B.; Musso, M. M.; Eigmüller, P.; Montañés Rodríguez, P.; Tala-Pinto, M.
Germany, United Kingdom, Italy, Portugal, Sweden, Netherlands, Japan, Austria, Chile, Spain, Denmark, Argentina, United States, Switzerland, France
Abstract
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 Mb = 16.6 ± 1.3 M⊕, a radius of Rb = 4.71 ± 0.17 R⊕, and an orbital period of Porb ≃ 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 (Teff = 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.
Based on observations made with the 3.6 m-ESO telescope at La Silla observatory under ESO programmes IDs 1102.C-0923 (PI: Gandolfi) and 1102.C-0249 (PI: Armstrong).