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

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

Jul 1997

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997a%26a...323..429b&link_type=abstract

Astronomy and Astrophysics, v.323, p.429-441

Astronomy and Astrophysics

Astrophysics

6

Stars: Oscillations, Stars: Delta Sct, Sun: Oscillations, Stars: Individual: Delta Aql, Epsilon2 Ara

Scientific paper

During 3 consecutive nights, 13 southern F- and G-type dwarfs and giants outside the conventional δ Scuti instability strip were observed at high spectral (3km/s) and medium temporal (10-15min) resolution. The stars were selected for their reported broad spectral lines (vsini>=40km/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 ɛ2 Ara. In addition, ɛ2 Ara displayed line profile distortions at a larger scale as they would result from a mode with m~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, ɛ2 Ara would be the reddest candidate γ Dor star to date. For the remaining 8 stars, upper amplitude limits between 2 and 6km/s were derived for nonradial mode orders 6<=m<=16 and p-modes with periods ~20minutes. In 3 stars narrow absorption lines were detected which probably are due to a cool companion.

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