SEARCH FOR LOW-INSTABILITY STRIP VARIABLES IN THE YOUNG OPEN CLUSTER NGC-2516

In this paper we revise and complete the photometric survey of the ins tability strip of the southern open cluster NGC 2516 published by Anto nello & Mantegazza. No variable stars with amplitudes larger than 0.02 mag were found. However, by means of an accurate analysis based on a new statistical method. two groups of small-amplitude variables have b een disentangled: one with periods of less than 0.25 days (probably de lta Scuti stars) and one with periods of greater than 0.025 days. The position in the H-R diagram and the apparent timescale may suggest tha t the stars of the second group belong to a recently discovered new cl ass of variables, named gamma Dor variables. They certainly deserve fu rther study. We also present a comparison between the results of the p hotometric survey and the available pointed ROSAT observations of this cluster.