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 nonradial pulsations (NRPs) with an apparent period approximately equal to 0.047 days. This same period was derived from two data sets taken three months apart wherein the amplitude increased by 30 percent. Such high-degree NRP cannot explain the apparent reversals previously observed by Auvergne at al. (1979) for this star in the cores of the hydrogen Balmer lines and Ca-II K line. The present radial-velocity variations can be reconciled with their 0.25-day spectroscopic period if an amplitude of about 1 km/s is adopted, an order of magnitude less than previous measurements. The presence of line-profile variations from high-degree modes probably limits the accuracy of radial-velocity measurents and can appear as bumps in the radial-velocity curve.