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 Hipparcos space mission. The nine companions not shown to be stellar in nature have minimum masses ranging from ~13 to 70 M sub(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 + or - 4 M sub(Jup) to a mass of 0.35 + or - 0.03 M sub(middot in circle). The orbital parameters of two previously known substellar candidates are improved.
We present the radial-velocity follow-up of two Kepler planetary transiting candidates (KOI-189 and KOI-686) carried out with the SOPHIE spectrograph at the Observatoire de Haute Provence. These data ...promptly discard these objects as viable planet candidates and show that the transiting objects are in the regime of very low-mass stars, where a strong discrepancy between observations and models persists for the mass and radius parameters. By combining the SOPHIE spectra with the Kepler light curve and photometric measurements found in the literature, we obtain a full characterization of the transiting companions, their orbits, and their host stars. The two companions are in significantly eccentric orbits with relatively long periods (30 days and 52.5 days), which makes them suitable objects for a comparison with theoretical models, since the effects invoked to understand the discrepancy with observations are weaker for these orbital distances. KOI-189 b has a mass M = 0:0745 + or - 0:0033 M sub(middot in circle) and a radius R = 0:1025 + or - 0:0024 R sub(middot in circle). The density of KOI-189 b is significantly lower than expected from theoretical models for a system of its age. We explore possible explanations for this difference. KOI-189 b is the smallest hydrogen-burning star with such a precise determination of its fundamental parameters. KOI-686 b is larger and more massive (M = 0:0915 + or - 0:0043 M sub(middot in circle); R = 0:1201 + or - 0:0033 R sub(middot in circle)), and its position in the mass-radius diagram agrees well with theoretical expectations.
We present the detection and characterization of the transiting warm Jupiter KOI-12b, first identified with Kepler with an orbital period of 17.86 days. We combine the analysis of Kepler photometry ...with Doppler spectroscopy and line-profile tomography of time-series spectra obtained with the SOPHIE spectrograph to establish its planetary nature and derive its properties. To derive reliable estimates for the uncertainties on the tomographic model parameters, we devised an empirical method of calculating statistically independent error bars on the time-series spectra. KOI-12b has a radius of 1.43 + or - 0.13 R sub(Jup) and a 3sigma upper mass limit of 10 M sub(Jup). It orbits a fast-rotating star (vsinilow * = 60.0 + or - 0.9 km s super(-1)) with mass and radius of 1.45 + or - 0.09 M sub(middot in circle) and 1.63 + or -0.15 R sub(middot in circle), located at 426 + or - 40 pc from the Earth. Doppler tomography allowed higher precision on the obliquity to be reached by comparison with analysis of the Rossiter-McLaughlin radial velocity anomaly, and we find that KOI-12b lies on a prograde, slightly misaligned orbit with low sky-projected obliquity lambda = (ProQuest: Formulae and/or non-USASCII text omitted). The properties of this planetary system, with a 11.4 mag host star, make of KOI-12b a precious target for future atmospheric characterization.
We report the discovery of a long-period brown-dwarf transiting companion of the solar-type star KOI-415. The transits were detected by the Kepler space telescope. We conducted Doppler measurements ...using the SOPHIE spectrograph at the Observatoire de Haute-Provence. The photometric and spectroscopic signals allow us to characterize a 62.14 + or - 2.69 M sub(Jup) brown-dwarf companion of an evolved 0.94 + or - 0.06 Mmiddot in circle star in a highly eccentric orbit of P= 166.78805 + or - 0.00022 days and e = 0.698 + or - 0.002. The radius of KOI-415 b is 0.79 sub(-0.07) super(+0.12)R sub(Jup) , a value that is compatible with theoretical predictions for a 10 Gyr, low-metallicity and non-irradiated object.
Context. Hot Jupiters are still a fascinating exoplanet population that presents a diversity we are still far from understanding. High-precision photometric observations combined with radial velocity ...measurements give us a unique opportunity to constrain their properties better, on both their internal structure and their atmospheric bulk properties. Aims. We initiated a follow-up program of Kepler-released planet candidates with the goal of confirming the planetary nature of a number of them through radial velocity measurements. For those that successfully passed the radial velocity screening, we furthermore performed a detailed exploration of their properties to characterize the systems. As a byproduct, these systematic observations allow us to consolidate the exoplanets’ occurrence rate. Methods. We performed a complete analysis of the Kepler-412 system, listed as planet candidate KOI-202 in the Kepler catalog, by combining the Kepler observations from Q1 to Q15, to ground-based spectroscopic observations that allowed us to derive radial velocity measurements, together with the host-star parameters and properties. We also analyzed the light curve to derive the star’s rotation period and the phase function of the planet, including the secondary eclipse. Results. We secured the planetary nature of Kepler-412b. We found the planet has a mass of 0.939 ± 0.085MJup and a radius of 1.325 ± 0.043RJup, which makes it a member of the bloated giant subgroup. It orbits its G3 V host star in 1.72 days. The system has an isochronal age of 5.1 Gyr, consistent with its moderate stellar activity as observed in the Kepler light curve and the rotation of the star of 17.2 ± 1.6 days. From the detected secondary we derived the day-side temperature as a function of the geometric albedo. We estimated that the geometrical albedo Ag should be between 0.094 ± 0.015 and 0.013+0.017-0.013 and the brightness of the day side 2380 ± 40 K. The measured night-side flux corresponds to a night-side brightness temperature of 2154 ± 83 K, much greater than what is expected for a planet with homogeneous heat redistribution. From the comparison to star and planet evolution models, we found that dissipation should operate in the deep interior of the planet. This modeling also shows that despite its inflated radius, the planet presents a noticeable amount of heavy elements, which accounts for a mass fraction of 0.11 ± 0.04.
We report the discovery of a transiting brown dwarf companion to KOI-205, a K0 main-sequence star, in a 11.720125-day period orbit. The transits were detected by the Kepler space telescope, and the ...reflex motion of the star was measured using radial velocity observations obtained with the SOPHIE spectrograph. The atmospheric parameters of the host stars were determined from the analysis of high-resolution, high signal-to-noise ratio ESPaDOns spectra obtained for this purpose. Together with spectrophotometric measurements recovered from the literature, these spectra indicate that the star is a mildly metallic K0 dwarf with T sub(eff)5237 + or - 60 K. The mass of the companion is 39.9 + or - 1.0 M sub(Jup)and its radius is 0.81 + or - 0.02 /R sub(Jup), in agreement with current theoretical predictions. This is the first time a bona fide brown dwarf companion is detected in orbit around a star of this type. The formation and orbital evolution of brown dwarf companions is briefly discussed in the light of this new discovery.
We present the detection and characterization of the two new transiting, close-in, giant extrasolar planets KOI-200 b and KOI-889 b. They were first identified by the Kepler team as promising ...candidates from photometry of the Kepler satellite; we then established their planetary nature thanks to the radial velocity follow-up jointly secured with the spectrographs SOPHIE and HARPS-N. Combined analyses of the whole datasets allow the two planetary systems to be characterized. The planet KOI-200 b has mass and radius of 0.68 ± 0.09 MJup and 1.32 ± 0.14 RJup; it orbits in 7.34 days a F8V host star with mass and radius of 1.40-0.11+0.14 M⊙ and 1.51 ± 0.14 R⊙. The planet KOI-889 b is a massive planet with mass and radius of 9.9 ± 0.5 MJup and 1.03 ± 0.06 RJup; it orbits in 8.88 days an active G8V star with a rotation period of 19.2 ± 0.3 days, and mass and radius of 0.88 ± 0.06 M⊙ and 0.88 ± 0.04 R⊙. Both planets lie on eccentric orbits and are located just at the frontier between regimes where tides can explain circularization and where tidal effects are negligible. The two planets are among the first detected and characterized thanks to observations secured with HARPS-N, the new spectrograph recently mounted at the Telescopio Nazionale Galileo. These results illustrate the benefits that could be obtained from joint studies using two spectrographs as SOPHIE and HARPS-N.
As part of our follow-up campaign of Kepler planets, we observed Kepler-117 with the SOPHIE spectrograph at the Observatoire de Haute-Provence. This F8-type star hosts two transiting planets in ...non-resonant orbits. The planets, Kepler-117 b and c, have orbital periods 18.8 and 50.8 days, and show transit-timing variations (TTVs) of several minutes. We performed a combined Markov chain Monte Carlo (MCMC) fit on transits, radial velocities, and stellar parameters to constrain the characteristics of the system. We included the fit of the TTVs in the MCMC by modeling them with dynamical simulations. In this way, consistent posterior distributions were drawn for the system parameters. According to our analysis, planets b and c have notably different masses (0.094 + or - 0.033 and 1.84 + or - 0.18M sub(J)) and low orbital eccentricities (0.0493 + or - 0.0062 and 0.0323 + or - 0.0033). The uncertainties on the derived parameters are strongly reduced if the fit of the TTVs is included in the combined MCMC. The TTVs allow measuring the mass of planet b although its radial velocity amplitude is poorly constrained. Finally, we checked that the best solution is dynamically stable.
Context. The impact of stellar mass on the properties of giant planets is still not fully understood. Main-sequence (MS) stars more massive than the Sun remain relatively unexplored in radial ...velocity (RV) surveys, due to their characteristics which hinder classical RV measurements. Aims. Our aim is to characterize the close (up to ~2 au) giant planet (GP) and brown dwarf (BD) population around AF MS stars and compare this population to stars with different masses. Methods. We used the SOPHIE spectrograph located on the 1.93 m telescope at Observatoire de Haute-Provence to observe 125 northern, MS AF dwarfs. We used our dedicated SAFIR software to compute the RV and other spectroscopic observables. We characterized the detected substellar companions and computed the GP and BD occurrence rates combining the present SOPHIE survey and a similar HARPS survey. Results. We present new data on two known planetary systems around the F5-6V dwarfs HD 16232 and HD 113337. For the latter, we report an additional RV variation that might be induced by a second GP on a wider orbit. We also report the detection of 15 binaries or massive substellar companions with high-amplitude RV variations or long-term RV trends. Based on 225 targets observed with SOPHIE and/or HARPS, we constrain the BD frequency within 2–3 au around AF stars to be below 4% (1σ). For Jupiter-mass GPs within 2–3 au (periods ≤103 days), we find the occurrence rate to be 3.7−1+3 $3.7_{-1}^{+3}$3.7−1+3% around AF stars with masses <1.5 M⊙, and to be ≤6% (1σ) around AF stars with masses >1.5 M⊙. For periods shorter than 10 days, we find the GP occurrence rate to be below 3 and 4.5% (1σ), respectively. Our results are compatible with the GP frequency reported around FGK dwarfs and are compatible with a possible increase in GP orbital periods with stellar mass as predicted by formation models.
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