Stellar and circumstellar activity in the Be star EW Lacertae from the 1993 multi-site campaign

A multi-site, multi-technique campaign on the Be star EW Lac was held for a bout 9 days in August-September 1993. We present results of the analysis of visual, high S/N spectroscopic data (HeI 6678 Angstrom and Her). Search fo r shortterm 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) emiss ion peaks) and on Ha emission line (Line profiles, EW, V, R and V/R ratio). The presence of multi-periodicity is confirmed and we detected the frequen cies found in 1989 by Floquet et al. (1992) during a 8-day mono-site campai gn. Possible non-radial pulsation solutions for the main frequencies detect ed are l approximate to 2-3, \m\ approximate to 2-3. We found evidence on t he He I 6678 line of episodic matter outflows through the presence of relat ively broad, variable: absorption line-profile variations. At least one sha rp absorption feature was also observed slowly crossing the stellar disc. I t 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 polarizat ion level in the B-band and HeI 6678 A strength. Finally, we present a simp le model that reproduces rather well the additional "pseudo-photosphere" co ntribution in 1993 as opposed to 1989.