Francois Bouchy

High-precision spectrographs play a key role in exoplanet searches and Doppler asteroseismology using the radial velocity technique. The 1 m s-1level of precision requires very high stability and uniformity of the illumination of the spectrograph. In fiber-fed spectrographs such as SOPHIE, the fiber-link scrambling properties are one of the main conditions for high precision. To significantly improve the radial velocity precision of the SOPHIE spectrograph, which was limited to 5–6 m s-1, we implemented a piece of octagonal-section fiber in the fiber link. We present here the scientific validation of the upgrade of this instrument, demonstrating a real improvement. The upgraded instrument, renamed SOPHIE+, reaches radial velocity precision in the range of 1–2 m s-1. It is now fully efficient for the detection of low-mass exoplanets down to 5–10 M ⊕ and for the identification of acoustic modes down to a few tens of cm s-1.

High-precision spectrographs play a key role in exoplanet searches and Doppler asteroseismology using the radial velocity technique. The 1 m/s level of precision requires very high stability and uniformity of the illumination of the spectrograph. In fiber-fed spectrographs such as SOPHIE, the fiber-link scrambling properties are one of the main conditions for high precision. To significantly improve the radial velocity precision of the SOPHIE spectrograph, which was limited to 5-6 m/s, we implemented a piece of octagonal-section fiber in the fiber link. We present here the scientific validation of the upgrade of this instrument, demonstrating a real improvement. The upgraded instrument, renamed SOPHIE+, reaches radial velocity precision in the range of 1-2 m/s. It is now fully efficient for the detection of low-mass exoplanets down to 5-10 Earth mass and for the identification of acoustic modes down to a few tens of cm/s.

We report the strategy and results of our radial velocity follow-up campaign with the SOPHIE spectrograph (1.93-m OHP) of four transiting planetary candidates discovered by the Kepler space mission. We discuss the selection of the candidates KOI-428, KOI-410, KOI-552, and KOI-423. KOI-428 was established as a hot Jupiter transiting the largest and the most evolved star discovered so far and is described by Santerne et al. (2011, A&A, 528, A63). KOI-410 does not present radial velocity change greater than 120 m s-1, which allows us to exclude at 3σ a transiting companion heavier than 3.4 M Jup. KOI-552b appears to be a transiting low-mass star with a mass ratio of 0.15. KOI-423b is a new transiting companion in the overlapping region between massive planets and brown dwarfs. With a radius of 1.22 ± 0.11 R Jup and a mass of 18.0 ± 0.92 M Jup, KOI-423b is orbiting an F7IV star with a period of 21.0874 ± 0.0002 days and an eccentricity of 0.12 ± 0.02. From the four selected Kepler candidates, at least three of them have a Jupiter-size transiting companion, but two of them are not in the mass domain of Jupiter-like planets. KOI-423b and KOI-522b are members of a growing population of known massive companions orbiting close to an F-type star. This population currently appears to be absent around G-type stars, possibly due to their rapid braking and the engulfment of their companions by tidal decay.

We report the detection of WASP-35b, a planet transiting a metal-poor ([Fe/H] = –0.15) star in the Southern hemisphere, WASP-48b, an inflated planet which may have spun-up its slightly evolved host star of 1.75 R _☉ in the Northern hemisphere, and the independent discovery of HAT-P-30b/WASP-51b, a new planet in the Northern hemisphere. Using WASP, RISE, Faulkes Telescope South, and TRAPPIST photometry, with CORALIE, SOPHIE, and NOT spectroscopy, we determine that WASP-35b has a mass of 0.72 ± 0.06 M_J and radius of 1.32 ± 0.05R_J , and orbits with a period of 3.16 days, WASP-48b has a mass of 0.98 ± 0.09 M_J , radius of 1.67 ± 0.10 R_J , and orbits in 2.14 days, while HAT-P-30b/WASP-51b, with an orbital period of 2.81 days, is found to have a mass of 0.76 ± 0.05 M_J and radius of 1.42 ± 0.03 R_J , agreeing with values of 0.71 ± 0.03 M_J and 1.34 ± 0.07 R_J reported for HAT-P-30b.

We report the strategy and results of our radial velocity follow-up campaign with the SOPHIE spectrograph (1.93-m OHP) of four transiting planetary candidates discovered by the Kepler space mission. We discuss the selection of the candidates KOI-428, KOI-410, KOI-552, and KOI-423. KOI-428 was established as a hot Jupiter transiting the largest and the most evolved star discovered so far and is described by Santerne et al. (2011a). KOI-410 does not present radial velocity change greater than 120 m/s, which allows us to exclude at 3 sigma a transiting companion heavier than 3.4 Mjup. KOI-552b appears to be a transiting low-mass star with a mass ratio of 0.15. KOI-423b is a new transiting companion in the overlapping region between massive planets and brown dwarfs. With a radius of 1.22 +- 0.11 Rjup and a mass of 18.0 +- 0.92 Mjup, KOI-423b is orbiting an F7IV star with a period of 21.0874 +- 0.0002 days and an eccentricity of 0.12 +- 0.02. From the four selected Kepler candidates, at least three of them have a Jupiter-size transiting companion, but two of them are not in the mass domain of Jupiter-like planets. KOI-423b and KOI-522b are members of a growing population of known massive companions orbiting close to an F-type star. This population currently appears to be absent around G-type stars, possibly due to their rapid braking and the engulfment of their companions by tidal decay.

From WASP photometry and SOPHIE radial velocities we report the discovery of WASP-40b (HAT-P-27b), a 0.6 M_Jup planet that transits its 12th magnitude host star every 3.04 days. The host star is of late G-type or early K-type and likely has a metallicity greater than solar ([Fe/H] = 0.14 ± 0.11). The planet's mass and radius are typical of the known hot Jupiters, thus adding another system to the apparent pileup of transiting planets with periods near 3–4 days. Our parameters match those of the recent HATnet announcement of the same planet, thus giving confidence in the techniques used. We report a possible indication of stellar activity in the host star.

Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics

The Kepler mission has detected transits and occultations of a hot compact object around an early-type star, the Kepler Object of Interest KOI 74. The mass of this transiting object was photometrically assessed in a previous study using the presence of the relativistic beaming effect (so-called “Doppler boosting”) in the light curve. Our aim was to provide a spectroscopic validation of this pioneering approach. We measured the radial velocity variations of the A1V star KOI 74 with the SOPHIE spectrograph at the 1.93-m telescope of the Observatoire de Haute-Provence (France). Radial velocity measurements of this star are challenging because of the high level of stellar pulsations and the few available spectral lines. Using a technique dedicated to early-type main-sequence stars, we measured radial velocity variations compatible with a companion of mass 0.252 ± 0.025 M ⊙, in good agreement with the value derived from the Kepler light curve. This work strengthens the scenario suggesting that KOI 74 is a blue straggler orbited by a stellar core despoiled of its envelope, the low-mass white dwarf KOI 74b.