Volume 617, September 2018
|Number of page(s)||17|
|Section||Planets and planetary systems|
|Published online||25 September 2018|
The HADES RV Programme with HARPS-N at TNG
VIII. GJ15A: a multiple wide planetary system sculpted by binary interaction★
INAF – Osservatorio Astrofisico di Torino,
Via Osservatorio 20,
Pino Torinese, Italy
2 Dipartimento di Fisica e Astronomia, Università di Padova, Via Marzolo 8, 35131 Padova, Italy
3 INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
4 INAF – Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
5 INAF – Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
6 INAF – Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy
7 Fundación Galileo Galilei – INAF, Ramble José Ana Fernandez Pérez 7, 38712 Breña Baja, TF, Spain
8 Dipartimento di Fisica e Chimica, Università di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
9 INAF – Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate, Italy
10 Instituto de Astrofísica de Canarias (IAC), 38205 La Laguna, Tenerife, Spain
11 Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
12 Institut de Ciències de l’Espai (ICE, CSIC), Campus UAB, C/ de Can Magrans s/n, 08193 Cerdanyola del Vallès, Spain
13 Observatoire Astronomique de l’Université de Genève, 1290 Versoix, Switzerland
14 Institut d’Estudis Espacials de Catalunya (IEEC), C/ Gran Capità 2-4, 08034 Barcelona, Spain
Accepted: 10 April 2018
We present 20 yr of radial velocity (RV) measurements of the M1 dwarf Gl15A, combining five years of intensive RV monitoring with the HARPS-N spectrograph with 15 yr of archival HIRES/Keck RV data. We have carried out an MCMC-based analysis of the RV time series, inclusive of Gaussian Process (GP) approach to the description of stellar activity induced RV variations. Our analysis confirms the Keplerian nature and refines the orbital solution for the 11.44-day period super Earth, Gl15A b, reducing its amplitude to 1.68−0.18+0.17 m s−1 (M sin i = 3.03−0.44+0.46 M⊕), and successfully models a long-term trend in the combined RV dataset in terms of a Keplerian orbit with a period around 7600 days and an amplitude of 2.5−1.0+1.3 m s−1, corresponding to a super-Neptune mass (M sin i = 36−18+25 M⊕) planetary companion. We also discuss the present orbital configuration of Gl15A planetary system in terms of the possible outcomes of Lidov–Kozai interactions with the wide-separation companion Gl15B in a suite of detailed numerical simulations. In order to improve the results of the dynamical analysis, we have derived a new orbital solution for the binary system, combining our RV measurements with astrometric data from the WDS catalogue. The eccentric Lidov–Kozai analysis shows the strong influence of Gl15B on the Gl15A planetary system, which can produce orbits compatible with the observed configuration for initial inclinations of the planetary system between 75° and 90°, and can also enhance the eccentricity of the outer planet well above the observed value, even resulting in orbital instability, for inclinations around 0° and 15°−30°. The Gl15A system is the multi-planet system closest to Earth, at 3.56 pc, and hosts the longest period RV sub-Jovian mass planet discovered so far. Its orbital architecture constitutes a very important laboratory for the investigation of formation and orbital evolution scenarios for planetary systems in binary stellar systems.
Key words: techniques: radial velocities / stars: individual: GJ15A / binaries: visual / instrumentation: spectrographs / planets and satellites: detection / planets and satellites: dynamical evolution and stability
Based on observations made with the Italian Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the INAF – Fundación Galileo Galilei at the Roche de Los Muchachos Observatory of the Instituto de Astrofísica de Canarias (IAC); photometric observations made with the robotic telescope APT2 (within the EXORAP programme) located at Serra La Nave on Mt. Etna.
© ESO 2018
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