DETECTION OF HIGH-DEGREE NONRADIAL PULSATIONS IN GAMMA-BOOTIS

The line-profile variations of the rapidly rotating delta-Scuti star gamma-Bootis can be explained by high-degree (\m\ congruent-to 10) nonradial pulsations (NRPs) with an apparent period of DELTA-t congruent-to 0.047 days. This same period was derived from two data sets taken three months apart wherein the amplitude increased by 30%. Such high-degree NRP cannot explain the apparent reversals previously observed by Auvergne et al. for this star in the cores of the hydrogen Balmer lines and Ca II K line. Our radial-velocity variations can be reconciled with their 0.25 day spectroscopic period if an amplitude of approximately 1 km s-1 is adopted, an order of magnitude less than previous measurements. We demonstrate that the presence of line-profile variations from high-degree modes probably limits the accuracy of radial-velocity measurements and may appear as bumps in the radial-velocity curve.