2000A&A...362.1020F

A multi-site, multi-technique campaign on the Be star EWLac was held for about 9 days in August-September 1993. We present results of the analysis of visual, high S/N spectroscopic data (HeI 6678Å and Hα). Search for short-term variability was carried out on HeI 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. (1992A&A...264..177F) 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 HeI 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 HeI 6678Å strength. Finally, we present a simple model that reproduces rather well the additional ``pseudo-photosphere" contribution in 1993 as opposed to 1989.