The GAPS programme with HARPS-N at TNG
IX. The multi-planet system KELT-6: Detection of the planet KELT-6 c and measurement of the Rossiter-McLaughlin effect for KELT-6 b⋆,⋆⋆
INAF–Osservatorio Astrofisico di Torino, via Osservatorio
2 Instituto de Astrofísica de Canarias, C/Via Láctea S/N, 38200, La Laguna, Tenerife, Spain
3 Departamento de Astrofísica, Universidad de La Laguna, 38205, La Laguna, Tenerife, Spain
4 INAF–Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
5 Dip. di Fisica e Astronomia Galileo Galilei – Università di Padova, Vicolo dell’Osservatorio 2, 35122 Padova, Italy
6 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
7 INAF–Osservatorio Astrofisico di Catania, via S.Sofia 78, 95123, Catania, Italy
8 INAF–Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131 Napoli, Italy
9 Dipartimento di Fisica, Universitá di Torino, via P. Giuria 1, 10125 Torino, Italy
10 Landessternwarte Königstuhl, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
11 INAF–Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate ( LC), Italy
12 Department of Astrophysical Sciences, Princeton University, Ivy Lane, Princeton, NJ 08544, USA
13 Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA
14 Department of Physics and Astronomy, University of Louisville, Louisville, KY 40292, USA
15 Fundación Galileo Galilei − INAF, Rambla José Ana Fernandez Pérez 7, 38712 Breña Baja, TF, Spain
16 INAF–Osservatorio Astronomico di Palermo, Piazza del Parlamento, 1, 90134 Palermo, Italy
17 INAF–IASF Milano, via Bassini 15, 20133 Milano, Italy
18 INAF–Osservatorio Astronomico di Trieste, via Tiepolo 11, 34143 Trieste, Italy
19 Universidad de Atacama, Departamento de Fisica, Copayapu 485, Copiapo, Chile
20 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
21 Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
Received: 19 July 2015
Accepted: 26 August 2015
Aims. For more than 1.5 years we spectroscopically monitored the star KELT-6 (BD+31 2447), which is known to host the transiting hot-Saturn KELT-6 b, because a previously observed long-term trend in radial velocity time series suggested that there is an outer companion.
Methods. We collected a total of 93 new spectra with the HARPS-N and TRES spectrographs. A spectroscopic transit of KELT-6 b was observed with HARPS-N, and simultaneous photometry was obtained with the IAC-80 telescope.
Results. We proved the existence of an outer planet with a mininum mass Mpsin i = 3.71 ± 0.21 MJup and a moderately eccentric orbit (e = 0.21-0.036+0.039) of period P ~ 3.5 years. We improved the orbital solution of KELT-6 b and obtained the first measurement of the Rossiter-McLaughlin effect, showing that the planet has a likely circular, prograde, and slightly misaligned orbit with a projected spin-orbit angle of λ = −36 ± 11 degrees. We improved the KELT-6 b transit ephemeris from photometry and provide new measurements of the stellar parameters. KELT-6 appears as an interesting case for studying the formation and evolution of multi-planet systems.
Key words: stars: individual: KELT-6 / planetary systems / techniques: radial velocities / techniques: photometric
Based on observations made with (i) the HARPS-N spectrograph on the Italian Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the INAF − Fundacion Galileo Galilei (Spanish Observatory of Roque de los Muchachos of the IAC); (ii) the Tillinghast Reflector Echelle Spectrograph (TRES) on the 1.5-m Tillinghast telescope, located at the Smithsonian Astrophysical Observatory’s Fred L. Whipple Observatory on Mt. Hopkins in Arizona; (iii) the IAC-80 telescope at the Teide Observatory (Instituto de Astrofísica de Canarias, IAC).
Figure 4 and Tables 2 and 3 are available in electronic form at http://www.aanda.org
© ESO, 2015