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

Esposito, M.; Armstrong, D. J.; Gandolfi, D.; Adibekyan, V.; Fridlund, M.; Santos, N. C.; Livingston, J. H.; Delgado Mena, E.; Fossati, L.; Lillo-Box, J.; Barragán, O.; Barrado, D.; Cubillos, P. E.; Cooke, B.; Justesen, A. B.; Meru, F.; Díaz, R. F.; Dai, F.; Nielsen, L. D.; Persson, C. M.; Wheatley, P. J.; Hatzes, A. P.; Van Eylen, V.; Musso, M. M.; Alonso, R.; Beck, P. G.; Barros, S. C. C.; Bayliss, D.; Bonomo, A. S.; Bouchy, F.; Brown, D. J. A.; Bryant, E.; Cabrera, J.; Cochran, W. D.; Csizmadia, S.; Deeg, H.; Demangeon, O.; Deleuil, M.; Dumusque, X.; Eigmüller, P.; Endl, M.; Erikson, A.; Faedi, F.; Figueira, P.; Fukui, A.; Grziwa, S.; Guenther, E. W.; Hidalgo, D.; Hjorth, M.; Hirano, T.; Hojjatpanah, S.; Knudstrup, E.; Korth, J.; Lam, K. W. F.; de Leon, J.; Lund, M. N.; Luque, R.; Mathur, S.; Montañés Rodríguez, P.; Narita, N.; Nespral, D.; Niraula, P.; Nowak, G.; Osborn, H. P.; Pallé, E.; Pätzold, M.; Pollacco, D.; Prieto-Arranz, J.; Rauer, H.; Redfield, S.; Ribas, I.; Sousa, S. G.; Smith, A. M. S.; Tala-Pinto, M.; Udry, S.; Winn, J. N.
Bibliographical reference

Astronomy and Astrophysics, Volume 623, id.A165, 11 pp.

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3
2019
Number of authors
76
IAC number of authors
12
Citations
31
Refereed citations
29
Description
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).
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