Stellar parameters of Be targets for Corot

1. Stellar parameters of Be targets for Corot C. Neiner1,2, Y.Frémat3, A.-M. Hubert2, M. Floquet2, E. Janot-Pacheco4, J. Fabregat5 , J. Zorec6 1RSSD, ESTEC / ESA, Netherlands 2GEPI, Observatoire de Paris-Meudon, France 3Observatoire Royal de Bruxelles, Belgium 4University of Sao Paulo, Brazil 5University of Valencia, Spain 6IAP, France Contact: cneiner@rssd.esa.int Abstract We determine the stellar parameters of the Be stars in the cones of Corot, to allow a selection of the most interesting targets to be observed with Corot. The spectra were collected from GAUDI for the brightest stars. For the faintest objects, data have been obtained in Brazil or will be obtained in France in January. The stellar parameters are determined by fitting observed hydrogen and helium spectral lines with theoretical NLTE line profiles. The model has already been applied to all the spectra extracted from GAUDI.The FASTROT code is then used to study the effects of fast rotation: stellar flattening and gravitational darkening. Stellar parameters The temperature (Teff in K), gravity (log g in dex) and projected velocity (vsini in km/s) of the Be stars observed for GAUDI are summarized in Tables 1 and 2, for the galactic anticentre and centre respectively. Among those are new Be stars, discovered in GAUDI and presented in the bottom part of the Tables. Depending on the quality of the spectrum, the error bars are between 800 and 3000 K for Teff, around 0.1 dex for log g and between 5 and 30 km/s for vsini. Be stars which are close to a primary target of Corot are indicated in boldface in the Tables. The other Be stars can be chosen as targets for the short runs. Figures Figure 1 shows two examples of line fits (red line) computed with FASTROT on GAUDI data (black dots) to determine the stellar parameters. The fitting procedure only takes into account the regions without emission (horizontal black lines). Figure 2 is a HR diagram with evolutionary tracks from Schaller et al. (1992). Be stars from Tables 1 and 2 are reported on the diagram with blue circles. This corresponds to their position if no correction for fast rotation is applied. The red lines show the effect of fast rotation on the parameters and the importance of taking it into account. Note that some of the targets appear in the supergiants region (right from the green line), while Be stars are by definition a class of main sequence stars. Their apparent position in the HR diagram is due to the large error bars on the stellar parameters, to the presence of a companion or to the underestimation of the veiling effect. Figure 2 Work in progress The work presented in this poster corresponds to 30 Be stars. However, the total number of Be stars in the cones of COROT is around 70, including 13 Be stars which are close to primary targets of Corot. The data collected in Brazil are currently being analysed. The data that will be collected in France in January will be analysed early 2004. The correction for fast rotation will be applied to all the targets. Conclusions We determined the stellar parameters of Be stars in the cones of Corot and showed that the effects of fast rotation have to be taken into account. This study will allow us to select the most interesting targets for the Corot observations. Figure 1