Preliminary results on γ Dor and δ Sct-γ Dor hybrid s in the CoRoT exo-field of LRa01

Abstract

The 131 days long, high-precision light curves observed in the CoRoT exo-field during LRa01 were investigated for γ Dor and δ Sct-γ Dor hybrid stars. In total 418 γ Dor and 274 δ Sct-γ Dor hybrid candidates were identified. For a fraction of these candidates spectra are available obtained at the Anglo-Australian Observatory. Effective temperatures and surface gravity were derived by fitting synthetic spectra of three Balmer lines, i.e. Hα, Hβ, and Hγ, as well as of the Ca K line at 3933 Å. The bona fide γ Dor and hybrid stars were plotted in an T_eff - log g diagram that shows the expected concentration of γ Dor stars at the cool border of the δ Sct strip. In contrast, the hybrids fill the whole δ Sct instability strip without a noticeable concentration. Remarkably, the fraction of constant stars, with no signal above 3 times the noise level, is smallest in the same temperature regime.

The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain.