Results from a spectroscopic survey in the CoRoT fields. I. Search for chromospherically active stars

Abstract

Aims.In this paper we report the results of the spectroscopic survey we carried out to detect chromospheric activity of late-type stars in the fields of view of the CoRoT space mission. Methods.We give an accurate MK classification of all targets, which is valuable information on both the main CoRoT project and additional science programs, by means of cross-correlation with MK standard stars, by using artificial neural networks. The presence or absence of excess H$\alpha$ emission, determined using spectral subtraction technique, is used to characterize the chromospheric activity level. Results.In most cases our MK classification agrees with the spectral classification reported in the SIMBAD database; however, there are a few stars that are found to have very different MK classes. Our survey reveals that ~7% of late-type stars in our sample indeed possess a very active chromosphere. The measured H$\alpha$ excess and the presence of the 6708 Å Li line allow us to confirm the membership of 5 targets in the young open cluster NGC 2264.