THETA-TUCANAE - A BINARY WITH A DELTA-SCUTI PRIMARY

Using seven four-hour time series of high-resolution spectra, the bina ry nature and the oscillations of theta Tuc are investigated. The spec trum is double-lined, proving the binarity. theta Tuc is a binary with a circular orbit and with an anomalous mass ratio q=0.09. The for the first time determined orbital elements are P=7.1036 days, K-1=8.6 km/ s and K-2=95.6 km/s. The oscillations of the delta Scuti-type main com ponent are spectroscopically investigated. Line-profile variations are discovered, and radial-velocity variations reveal a main oscillation frequency of f(1)=20.27 c/d which corresponds to the main oscillation 20.2806 c/d in photometry. Another frequency, f(2)=18.82 c/d found in the spectroscopic data and not present in the photometric dataset, nee ds to be investigated more profoundly.