Relationship between radial velocity and light variations in HR 7331 and other delta Scuti stars

Abstract

Simultaneous radial-velocity and photometric observations of the delta Scuti variable HR 7331 show a radial-velocity amplitude of 3 km/s and a visual light amplitude of 0.05 mag. Minimum radial velocity occurs 0.10 periods after maximum visual light. Radial-velocity and light variability data were collected from the literature for various delta Scuti stars. The phase shift appears to be constant, v.z, 0.09 periods. Maximum light occurs closer to minimum radius than in the cooler pulsators such as Cepheids and RR Lyrae stars. The ratio of radial velocity to visual light amplitudes ranges from 50 to 125 km/s/mag. The surface gravity dependence in this value is eliminated by computing the (ΔR/R)/ΔMbol ratio. This ratio is found to be 0.11 and equal to that of other types of pulsating variables. Implications of these results for the radial pulsation hypothesis are briefly discussed.