Astronomy and Astrophysics, volume 453, 1041-1050 (2006/7-3)
Non-radial pulsations in the γ Doradus star HD 195068.
JANKOV S., MATHIAS P., CHAPELLIER E., LE CONTEL J.-M. and SAREYAN J.-P.
Abstract (from CDS):
We present high resolution spectroscopic observations of the γ Doradus star HD195068
. About 230 spectra were collected over 2 years. Time series analysis performed on radial velocity data shows a main peak at 1.61d–1
, a frequency not yet detected in photometry. The Hipparcos photometric 1.25d–1
frequency is easily recovered as is 1.30d–1
while the third photometric frequency, 0.97d–1
, is only marginally present. The good quality of our data, which includes 196 spectra collected over seven consecutive nights, shows that both the 1.61d–1
and intermediate 1.27d–1
(mixture of 1.25 and 1.30d–1
) frequencies are present in the line profile variations. Using the Fourier-Doppler Imaging (FDI) method, the variability associated with 1.61d–1
can be successfully modeled by a non-radial pulsation mode l=5±1, |m|=4±1. For the intermediate frequency 1.27d–1
we deduce l=4±1, |m|=3±1. Evidence that the star is not pulsating in the radial mode (l=0) rules out a previous classification as an RR Lyrae type star. We investigate the time variability of FDI power spectra concluding that the observed temporal variability of modes can be explained by a beating phenomenon between closely spaced frequencies of two non-radial modes. The distribution of the oscillation power within the line profile indicates that there is a significant tangential velocity component of oscillations characteristic of high radial order gravity modes which are predicted to be observed in γ Doradus type stars.
line: profiles - stars: variables: general - stars: oscillations
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