A spectroscopic search for high azimuthal-order pulsation in broad-lined late F- and early G-stars

During 3 consecutive nights, 13 southern Fand Gtype dwarfs and giants outside the conventional δ Scuti instability strip were observed at high spectral (3 km/s) and medium temporal (10-15 min) resolution. The stars were selected for their reported broad spectral lines (v sin i≥ 40 km/s) so that pulsation in higher azimuthal-order nonradial harmonics could, via the rotational Doppler effect, 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 azimuthal order 8≤m≤ 14 were detected in δ Aql and 2 Ara. In addition, 2 Ara displayed line profile distortions at a larger scale as they would result from amodewithm∼ 4. The observational sampling of all three variabilities constrains possible periods only poorly. However, if the variations are periodic, they may well be too slow for p-mode oscillations. This would suggest a relation to the new class of γ Dor variables in which g-modes seem to be excited. If so, the two stars could be the first γ Dor stars with detected higher nonradial-harmonic pulsation. While uvby photometry places δ Aql still just within the δ Scuti strip, 2 Ara would be the reddest candidate γ Dor star to date. For the remaining 8 stars, upper amplitude limits between 2 and 6 km/s were derived for nonradial mode orders 6≤m≤ 16 and p-modes with periods ∼20 minutes. In 3 stars narrow absorption lines were detected which probably are due to a cool companion.