Search for Low–Instability Strip Variables in the Young Open Cluster NGC 2516

In this paper we revise and complete the photometric survey of theinstability strip of the southern open cluster NGC 2516 published by Antonelloand Mantegazza (1986). No variable stars with amplitudes larger than $0^m.02$were found. However by means of an accurate analysis based on a new statisticalmethod two groups of small amplitude variables have been disentangled: one withperiods $< 0^d.25$ (probably $\delta$ Scuti stars) and one with periods$>0^d.025$. The position in the HR diagram and the apparent time-scale maysuggest that the stars of the second group belong to a recently discovered newclass of variables, named $\gamma$ Dor variables. They certainly deservefurther study. We also present a comparison between the results of thephotometric survey and the available pointed ROSAT observations of thiscluster.Comment: 7 pages, 2 ps figures. Accepted for P.A.S.