Identification of the pulsation modes of the evolved hot delta Scuti star SAO 4710.

The analysis of a set of 1020 new observations in B-light made at Merate Observatory has led to the determination of a second period in the light variation of SAO 4710. The period ratio (0^d.05839/0^d.09874 = 0.5913) rules out the existence of two radial modes. The determination of indices allowed us to derive the following physical parameters:T _eff = 8300 K, log g = 3.8 and M_ν = +0.9. The corresponding Q values suggest that the first period is due to the third radial overtone, while the second period was identified as a p₁ non-radial mode of order l=1. The periods and the physical parameters are in excellent agreement with those proposed by theoretical models of δScuti variables located near the hot border of the instability strip. The Strömgren colour indices of SAO 4710 are very similar to those of HD 153747, another δScuti variable with a prevailing third radial overtone.