Identification of 13 Cepheids and 333 other variables in M31

Abstract

We present Cousins R and I band photometry of variable stars in a ∼13` × 13` region in the disk of M31 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 24.49 ± 0.11 mag for M31 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.