Identification of 13 Cepheids and 333 other variables in M 31 ^*

¹ State Observatory, Manora peak, Naini Tal – 263129, Uttaranchal, India
² Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai – 400 005, India
³ Laboratoire de Physique Corpusculaire, Collège de France, Laboratoire associé au CNRS-IN2P3 (URA 6411), 11 place Marcelin Berthelot, 75231 Paris Cedex 05, France

Corresponding author: Y. C. Joshi, yogesh@upso.ernet.in

Received: 17 October 2002
Accepted: 24 January 2003

Abstract

We present Cousins R and I band photometry of variable stars in a region in the disk of M 31 galaxy, obtained during 141 nights. Of the 26 Cepheid variables present in the region, two are newly discovered, 11 are classified as Cepheids for the first time and 13 are confirmed as Cepheids. The extensive photometry of these Cepheids enabled us to determine precise phase and amplitude of pulsation which ranges from 0.11 to 0.48 mag in R band. The period of variability ranges from ~7.5 to 56 days. The period-luminosity diagram is used to derive a distance modulus of  mag for M 31 galaxy. We also report variability in 333 other stars, of them, 115 stars appear to be long period variables, 2 suspected eclipsing binaries and remaining 216 are irregular variables.