Results from a spectroscopic survey in the CoRoT fields^*,**

I. Search for chromospherically active stars

¹ Department of Physics, Gauhati University, Assam 781014, India e-mail: bimanjm@yahoo.com
² Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263129, India
³ INAF - Catania Astrophysical Observatory, via S. Sofia 78, 95123 Catania, Italy e-mail: [sme;ipa]@oact.inaf.it
⁴ Indian Institute of Astrophysics, CREST, Block II, Koramangala, Bangalore 560034, India e-mail: psp@iiap.res.in
⁵ Indian Institute of Astrophysics, VBO, Bangalore, India e-mail: muneer_melathil@yahoo.com

Received: 8 September 2005
Accepted: 12 April 2007

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 Hα 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 Hα 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.