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Kepler-539: A young extrasolar system with two giant planets on wide orbits and in gravitational interaction

Mancini, L.; Lillo-Box, J.; Southworth, J.; Borsato, L.; Gandolfi, D.; Ciceri, S.; Barrado, D.; Brahm, R.; Th. Henning

Kepler-539: A young extrasolar system with two giant planets on wide orbits and in gravitational interaction Thumbnail


L. Mancini

J. Lillo-Box

L. Borsato

D. Gandolfi

S. Ciceri

D. Barrado

R. Brahm

Th. Henning


We confirm the planetary nature of Kepler-539?b (aka Kepler object of interest K00372.01), a giant transiting exoplanet orbiting a solar-analogue G2?V star. The mass of Kepler-539?b was accurately derived thanks to a series of precise radial velocity measurements obtained with the CAFE spectrograph mounted on the CAHA 2.2-m telescope. A simultaneous fit of the radial-velocity data and Kepler photometry revealed that Kepler-539?b is a dense Jupiter-like planet with a mass of Mp = 0.97 ± 0.29 MJup and a radius of Rp = 0.747 ± 0.018 RJup, making a complete circular revolution around its parent star in 125.6 days. The semi-major axis of the orbit is roughly 0.5?au, implying that the planet is at ˜0.45?au from the habitable zone. By analysing the mid-transit times of the 12 transit events of Kepler-539?b recorded by the Kepler spacecraft, we found a clear modulated transit time variation (TTV), which is attributable to the presence of a planet c in a wider orbit. The few timings available do not allow us to precisely estimate the properties of Kepler-539?c and our analysis suggests that it has a mass between 1.2 and 3.6 MJup, revolving on a very eccentric orbit (0.4 <e = 0.6) with a period larger than 1000?days. The high eccentricity of planet c is the probable cause of the TTV modulation of planet b. The analysis of the CAFE spectra revealed a relatively high photospheric lithium content, A(Li) = 2.48 ± 0.12?dex, which, together with both a gyrochronological and isochronal analysis, suggests that the parent star is relatively young.

Journal Article Type Article
Acceptance Date Apr 19, 2016
Online Publication Date May 25, 2016
Publication Date 2016-06
Journal Astronomy & Astrophysics
Print ISSN 0004-6361
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 590
Article Number A112
Keywords planetary systems, stars, fundamental parameters, individual, Kepler-539
Publisher URL