Astronomy and Astrophysics – Astrophysics
Scientific paper
Oct 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000a%26a...362.1020f&link_type=abstract
Astronomy and Astrophysics, v.362, p.1020-1040 (2000)
Astronomy and Astrophysics
Astrophysics
16
Stars: Circumstellar Matter, Stars: Emission-Line, Be, Stars: Oscillations, Stars: Individual: Ew Lac, Stars: Variables: General
Scientific paper
A multi-site, multi-technique campaign on the Be star EW Lac was held for about 9 days in August-September 1993. We present results of the analysis of visual, high S/N spectroscopic data (He I 6678 Å and Hα ). Search for short-term variability was carried out on He I 6678 (line profiles, radial velocity (RV), equivalent width (EW), full width at half-maximum (FWHM) on the absorption part of the line profile and on violet (V) and red (R) emission peaks) and on Hα emission line (line profiles, EW, V, R and V/R ratio). The presence of multi-periodicity is confirmed and we detected the frequencies found in 1989 by Floquet et al. (1992) during a 8-day mono-site campaign. Possible non-radial pulsation solutions for the main frequencies detected are l ~ 2-3, | m | ~ 2-3. We found evidence on the He I 6678 line of episodic matter outflows through the presence of relatively broad, variable absorption line-profile variations. At least one sharp absorption feature was also observed slowly crossing the stellar disc. It is attributed to a blob of matter temporarily orbiting the star. A brief account is given of broad-band polarimetric observations, performed over 6 nights. A correlation is found between the variation in intrinsic polarization level in the B-band and He I 6678 Å strength. Finally, we present a simple model that reproduces rather well the additional ``pseudo-photosphere" contribution in 1993 as opposed to 1989.
Floquet Michele
Gies Doug
Hahula M.
Hirata Ryuko
Hubert Anne-Marie
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