A SPECTROSCOPIC SEARCH FOR HIGH AZIMUTHAL-ORDER PULSATION IN BROAD-LINED LATE F-STARS AND EARLY G-STARS

During 3 consecutive nights, 13 southern F- and G-type dwarfs and gian ts outside the conventional delta Scuti instability strip were observe d at high spectral (3 km/s) and medium temporal (10-15 min) resolution . The stars were selected for their reported broad spectral lines (nu sin i greater than or equal to 40 km/s) so that pulsation in higher az imuthal-order nonradial harmonics could, via the rotational Doppler ef fect, reveal itself by line profile variability. Two stars turned out to have very narrow lines, one was confirmed as a short-period double- lined binary. Line profile ondulations typical of pulsation with azimu thal order 8 less than or equal to m less than or equal to 14 were det ected in delta Aql and epsilon(2) Ara. In addition, epsilon(2) Ara dis played line profile distortions at a larger scale as they would result from a mode with m similar to 4. The observational sampling of all th ree variabilities constrains possible periods only poorly. However, if the variations are periodic, they may well be too slow for p-mode osc illations. This would suggest a relation to the new class of gamma Dor variables in which g-modes seem to be excited. If so, the two stars c ould be the first gamma Dor stars with detected higher nonradial-harmo nic pulsation. While uvby photometry places delta Aql still just withi n the delta Scuti strip, epsilon(2) Ara would be the reddest candidate gamma Dor star to date. For the remaining 8 stars, upper amplitude li mits between 2 and 6 km/s were derived for nonradial mode orders 6 les s than or equal to m less than or equal to 16 and p-modes with periods similar to 20 minutes. In 3 stars narrow absorption lines were detect ed which probably are due to a cool companion.