While giant extrasolar planets have been studied for more than two decades now, there are still some open questions as to their dominant formation and migration processes, as well as to their atmospheric evolution in different stellar environments. In this paper, we study a sample of giant transiting exoplanets detected by the Kepler telescope with orbital periods up to 400 days. We first defined a sample of 129 giant-planet candidates that we followed up with the SOPHIE spectrograph (OHP, France) in a 6-year radial velocity campaign. This allowed us to unveil the nature of these candidates and to measure a false-positive rate of 54.6 ± 6.5% for giant-planet candidates orbiting within 400 days of period. Based on a sample of confirmed or likely planets, we then derived the occurrence rates of giant planets in different ranges of orbital periods. The overall occurrence rate of giant planets within 400 days is 4.6 ± 0.6%. We recovered, for the first time in the Kepler data, the different populations of giant planets reported by radial velocity surveys. Comparing these rates with other yields, we find that the occurrence rate of giant planets is lower only for hot Jupiters but not for the longer-period planets. We also derive a first measurement of the occurrence rate of brown dwarfs in the brown-dwarf desert with a value of 0.29 ± 0.17%. Finally, we discuss the physical properties of the giant planets in our sample. We confirm that giant planets receiving moderate irradiation are not inflated, but we find that they are on average smaller than predicted by formation and evolution models. In this regime of low-irradiated giant planets, we find a possible correlation between their bulk density and the iron abundance of the host star, which needs more detections to be confirmed.

Context. Brown-dwarfs (BD) are substellar objects with masses intermediate between planets and stars within about 13-80 M J . While isolated brown-dwarfs are most likely produced by gravitational collapse in molecular clouds down to masses of a few M J , a nonnegligible fraction of low-mass companions might be formed through the planet formation channel in protoplanetary disks. The upper mass limit of objects formed within disks is still observationnally unknown, the main reason being the strong dearth of BD companions at orbital periods shorter than 10 years, a.k.a. the brown-dwarf desert. Aims. We aim at determining the best statistics of secondary companions within the 10-100 M Jup range within ∼10 au from the primary star, while minimising observational bias. This can help determining the mass limit separating planet-formed from star-formed browndwarfs. Moreover, the exact shape of the BD desert in a mass-period space is still underdetermined, and can strongly constrain the companion-star interactions mechanisms at work in close binary systems at small mass ratio. Methods. We made an extensive use of the radial velocity (RV) surveys of FGK stars below 60 pc distance to the Sun and in the northern hemisphere performed with the SOPHIE spectrograph at Observatoire de Haute-Provence. We derived the Keplerian solutions of the RV variations of 54 sources. Public astrometric data of the Hipparcos and Gaia missions allowed deriving direct astrometric solution of orbital motion and constraining the mass of the companion for most sources. We introduce GASTON, a new method to derive inclination combining RVs Keplerian and astrometric excess noise from Gaia DR1. Results. We report the discovery of 12 new BD candidates. For 5 of them, additional astrometric data led to revise their mass in the M-dwarf regime. Among the 7 remaining objects, 4 are confirmed BD companions, and 3 others are likely also in this mass regime. Moreover, we report the detection of 42 objects in the M-dwarf mass regime 90 M J -0.52 M . The resulting M sin i-P distribution of BD candidates shows a clear drop in the detection rate below 80-day orbital period. Above that limit, the BD desert reveals rather wet, with a uniform distribution of the M sin i. We derive a minimum BD-detection frequency around Solar-like stars of 2.0±0.5%.

Radial velocity planet search surveys of nearby solar-type stars have shown a strong scarcity of brown dwarf companions within ∼5 AU. There is presently no comprehensive explanation for this lack of brown dwarf companions; therefore, increasing the sample of such objects is crucial to understand their formation and evolution. Based on precise radial velocities obtained using the SOPHIE spectrograph at Observatoire de Haute-Provence we characterise the orbital parameters of 15 companions to solar-type stars and constrain their true mass using astrometric data from the H space mission. The nine companions not shown to be stellar in nature have minimum masses ranging from ∼13 to 70 M Jup , and are well distributed across the planet/brown dwarf mass regime, making them an important contribution to the known population of massive companions around solar-type stars. We characterise six companions as stellar in nature with masses ranging from a minimum mass of 76 ± 4 M Jup to a mass of 0.35 ± 0.03 M . The orbital parameters of two previously known substellar candidates are improved.