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Symposium 241

Abstract details

The Cepheid variable star population in the Local Group dwarf galaxy Pegasus
I. Meschin, C. Gallart, S. Cassisi, A. Aparicio, A. Rosenberg

We present the results of a search for Cepheid variable stars in the Local Group dwarf galaxy Pegasus. The search was made from a collection of images compiled throughout several years (1993-2004). The photometry was carried out with the DAOPHOT/ ALLSTAR/ALLFRAME suite of programs (Stetson 1987, 1994). And a first selection of variable star candidates was performed based on the variability index "var", as calculated by DAOMASTER from the individual magnitudes of the 55 V and 24 I images. The light variations of all the candidate pulsating variables were searched for periodicities. We used the phase-dispersion minimization (PDM) algorithm by Stellingwerf (1978). We visually inspected the light curves that each of the most likely periods would produce for each variable, and 46 Cepheid candidates were retained. After a second selection using the position in the colour-magnitude diagram and period- luminosity (PL) relation, we retain 25 of them. Finally we have compared the number of found Cepheids and their periods, with theoretical predictions assuming 2 different star formation histories (SFH) of the Pegasus dIr galaxy: constant SFH and SFH with one event of enhanced star formation activity in the last 0.1 Gyr. (Aparicio et al. 1997)

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