A Pulsational Study of a Sample of CoRoT Faint Be Stars

Abstract

We present an intensive study of a sample of 12 Be stars in the first exo-planetary fields of the CoRoT mission. The aim is to understand the short-term variability in Be stars. We use both spectroscopic and photometric data: VLT-GIRAFFE spectra to derive the fundamental parameters and CoRoT light curves to search for low-amplitude frequencies. This allows us to locate the stars in the HR diagram and compare their positions in the instability strip with those of other pulsating B stars. From VLT-GIRAFFE observations we determined the stellar parameters by fitting the observed spectra with non-LTE stellar atmosphere models. The observed spectra were corrected for veiling effects due to circumstellar material and for rotational effects. We estimated the rotational frequency using the corrected fundamental parameters. For the CoRoT light curves, we determined all significant frequencies and compared the main frequencies with the rotational frequency. We also investigated the variation of the frequencies and amplitudes with time and, in particular, during outbursts. This is the first time that a statistical study with space data has been performed for Be stars. Our study suggests that rotational modulation is not the cause of short-term photometric variability in Be stars.