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A short observing run with the spectrometer Harps at the ESO 3.6-m telescope was conducted in order to continue exploring the asteroseismic properties of F type stars. In fact, Doppler observations of F type on the main sequence are demanding and remain currently limited to a single case (HD 49933). Comparison with photometric results obtained with the CoRoT mission on similar stars will be possible with an enhanced set of observations. We selected the 4th magnitude F8V star HD 203608, in order to investigate the oscillating properties of a low-metallicity star of the old galactic disk. A 5-night asteroseismic observation program has been conducted in August 2006 with Harps. Spectra were reduced with the on-line data reduction software provided by the instrument. A new statistical approach has been developed for extracting the significant peaks in the Fourier domain. The oscillation spectrum shows a significant excess power in the frequency range [1.5, 3.0 mHz]. It exhibits a large spacing about 120.4 $mu$Hz at 2.5 mHz. Variations of the large spacing with frequency are clearly identified, which require an adapted asymptotic development. The modes identification is based on the unambiguous signature of 15 modes with $ell = 0$ and 1. This observation shows the potential diagnostic of asteroseismic constraints. Including them in the stellar modeling enhances significantly the precision on the physical parameters of cible, resulting in a much more precise position in the HR diagram. The age of the star is now determined in the range $7.25pm0.07$ Gyr.
The satellite CoRoT (Convection, Rotation, and planetary Transits) has provided high-quality data for almost six years. We show here the asteroseismic analysis and modeling of HD169392A, which belongs to a binary system weakly gravitationally bound a
We present the mid-infrared spectrum, obtained with the Spitzer Infrared Spectrograph (IRS), of HD 98800, a quadruple star system located in the 10-Myr-old TW Hydrae association. It has a known mid-infrared excess that arises from a circumbinary disk
New photometric material is presented for 6 outer disk supposedly old, Galact ic star clusters: Berkeley 76, Haffner 4, Ruprecht 10, Haffner 7, Haffner 11, and Haffner 15, that are projected against the rich and complex Canis Major overde nsity at $2
The frequency ratios and of HD 49933 exhibit an increase at high frequencies. This behavior also exists in the ratios of other stars, which is considered to result from the low signal-to-noise ratio and the larger line width at the high-frequency end
The detection and analysis of oscillations in binary star systems is critical in understanding stellar structure and evolution. This is partly because such systems have the same initial chemical composition and age. Solar-like oscillations have been