Spectral classification of selected ISOGAL sources using Himalayan Chandra Telescope

U. C. Joshi1*, S. Ganesh1, K. S. Baliyan1, M. Parthasarathy2,3, M. Schultheis4, A. Rajpurohit4, G. Simon5 and A. Omont6
1Physical Research Laboratory, Ahmedabad, India
2National Astronomical Observatory of Japan (NAOJ), 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan
3Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, India
4Observatoire de Besan¸con, Besancon, BP 1615, 25010, France
5Observatoire de Paris, 61, Av. de l'Observatoire, F-75014, Paris, France
6Institut d'Astrophysique de Paris, CNRS and UPMC, 98bis Bd Arago, F-75014 Paris, France

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Abstract

The ISOGAL survey (Omont et al. 1999) is devoted to the observation of selected regions of the Galactic plane in the mid-infrared with ISOCAM. More than 240 fields were observed at 7 and 15 micron wavebands with ISOCAM at an angular resolution of 6" which has provided a complete census, in the areas surveyed, of the stars in the late stages (RGB/AGB phases) of stellar evolution. Optical counterparts are detected for some of the ISOGAL sources in the directions where the extinction is relatively lower. We obtained optical spectra of ~100 such sources with the Himalayan Chandra Telescope (HCT), India and estimated their spectral classes. Optical spectroscopy together with mid-IR data is expected to allow us to obtain the spectral-type vs mass-loss relation which are important parameters to understand the late stages of stellar evolution. In this paper, we present a set of spectra taken in the field FC97 for which ISOGAL survey is complete.

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Keywords : Milky Way-extinction – ISOGAL survey stars – spectroscopy