Variable stars in the field and in the clusters of the Fornax dwarf spheroidal galaxy

We present the first results of a variable star search in the field and in the globular clusters of the Fornax dwarf spheroidal galaxy. Variable stars were identified using the Image Subtraction Technique (Alard 2000) on time-series data obtained with the ESO 2.2 m and the Magellan 6.5 m tele- scopes. The variable star sample includes RR Lyrae stars, Dwarf Cepheids and Anomalous Cepheids. The pulsation properties (namely: periods, light curves, period-amplitude relations and classification in Oosterhoff types) of Fornax vari- ables from the present study are discussed in some detail. 1. Why to study the variable stars in an external galaxy? Pulsating variable stars such as RR Lyrae stars, Dwarf Cepheids and Anomalous Cepheids are very interesting astronomical objects that can be used to derive important information on the stellar system they belong to. They can be eas- ily identified, even in high crowding conditions, thanks to their light variation, and their periods are independent from reddening and distance. Variable stars are good tracers of the different stellar generations in a galaxy; in particular