H. Le Coroller

The SOPHIE search for northern extrasolar planets - I. A companion around HD 16760 with mass close to the planet/brown-dwarf transition

We report on the discovery of a substellar companion or a massive Jupiter orbiting the G5V star HD 16760 using the spectrograph SOPHIE installed on the OHP 1.93-m telescope. Characteristics and performances of the spectrograph are presented, as well as the SOPHIE exoplanet consortium program. With a minimum mass of 14.3 MJup, an orbital period of 465 days and an eccentricity of 0.067, HD 16760b seems to be located just at the end of the mass distribution of giant planets, close to the planet/brown-dwarf transition. Its quite circular orbit supports a formation in a gaseous protoplanetary disk.

The SOPHIE spectrograph: design and technical key-points for high throughput and high stability

SOPHIE is a new fiber-fed echelle spectrograph in operation since October 2006 at the 1.93-m telescope of Observatoire de Haute-Provence. Benefiting from experience acquired on HARPS (3.6-m ESO), SOPHIE was designed to obtain accurate radial velocities (~3 m/s over several months) with much higher optical throughput than ELODIE (by a factor of 10). These enhanced capabilities have actually been achieved and have proved invaluable in asteroseismology and exoplanetology. We present here the optical concept, a double-pass Schmidt echelle spectrograph associated with a high efficiency coupling fiber system, and including simultaneous wavelength calibration. Stability of the projected spectrum has been obtained by the encapsulation of the dispersive components in a constant pressure tank. The main characteristics of the instrument are described. We also give some technical details used in reaching this high level of performance.

First images of R aquarii and its asymmetric H2O shell

We report imaging observations of the symbiotic long-period Mira variable R Aquarii (R Aqr) at near-infrared and radio wavelengths. The near-infrared observations were made with the IOTA imaging interferometer in three narrowband filters centered at 1.51, 1.64, and 1.78 μm, which sample mainly water, continuum, and water features, respectively. Our near-infrared fringe visibility and closure phase data are analyzed using three models. (1) A uniform disk model with wavelength-dependent sizes fails to fit the visibility data, and is inconsistent with the closure phase data. (2) A three-component model, consisting of a Mira star, water shell, and an off-axis point source, provide a good fit to all data. (3) A model generated by a constrained image reconstruction analysis provides more insight, suggesting that the water shell is highly nonuniform, i.e., clumpy. The VLBA observations of SiO masers in the outer molecular envelope show evidence of turbulence, with jetlike features containing velocity gradients.

The pulsation of χ cygni imaged by optical interferometry: A novel technique to derive distance and mass of mira stars

We present infrared interferometric imaging of the S-type Mira star χ Cygni. The object was observed at four different epochs in 2005-2006 with the Infrared-Optical Telescope Array optical interferometer (H band). Images show up to 40% variation in the stellar diameter, as well as significant changes in the limb darkening and stellar inhomogeneities. Model fitting gave precise time-dependent values of the stellar diameter, and reveals presence and displacement of a warm molecular layer. The star radius, corrected for limb darkening, has a mean value of 12.1 mas and shows a 5.1 mas amplitude pulsation. Minimum diameter was observed at phase 0.94 ± 0.01. Maximum temperature was observed several days later at phase 1.02 ± 0.02. We also show that combining the angular acceleration of the molecular layer with CO (Δ_v = 3) radial velocity measurements yields a 5.9 ± 1.5 mas parallax. The constant acceleration of the CO molecules—during 80% of the pulsation cycle—lead us to argument for a free-falling layer. The acceleration is compatible with a gravitational field produced by a 2.1^(+1.5)_(–0.7) solar mass star. This last value is in agreement with fundamental mode pulsator models. We foresee increased development of techniques consisting in combining radial velocity with interferometric angular measurements, ultimately allowing total mapping of the speed, density, and position of the diverse species in pulsation-driven atmospheres.

The structure of radiative shock waves - IV. Effects of electron thermal conduction

We consider the structure of steady–state radiative shock waves propagating in partially ionized hydrogen gas with density

The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs at wide orbits. IV. Gravitational instability rarely forms wide, giant planets

\rho_1 = 10^{-10}~{\rm gm}~{\rm cm}^{-3}

Spectral and atmospheric characterization of 51 Eridani b using VLT/SPHERE

and temperature

Non-linear radiative models of post-AGB stars: Application to HD 56126

3000~{\rm K}\le T_1\le 8000~{\rm K}

Tests with a Carlina-type diluted telescope - Primary coherencing

. The radiative shock wave models with electron thermal conduction in the vicinity of the viscous jump are compared with pure radiative models. The threshold shock wave velocity above which effects of electron thermal conduction become perceptible is found to be

RESOLVING THE PLANET-HOSTING INNER REGIONS OF THE LkCa 15 DISK

U_1^*\approx 70~{\rm km}~{\rm s}^{-1}