A SEARCH FOR MULTIPERIODIC LINE-PROFILE VARIATIONS IN THE BE STAR 48-LIBRAE

High resolution, high signal-to-noise ratio CCD spectra of the Be-shel l star 48 Librae allowed the investigation of rapid variability in the photospheric He I 4471 and Mg II 4481 lines. Though our sample was li mited (51 spectra over four nights), 48 Lib has revealed itself to be a good candidate to display multiperiodic spectroscopic variations. Th ree frequencies, 1.86, 3.09 and 10.64 c/d, have been detected in the H e I line and seem to be present in Mg II 4481 though this latter, stro ngly blended in its core with a marked shell feature, is not appropria te for this kind of study. The higher frequency 10.64 c/d has been ded uced from a time series analysis with two methods and from a residual analysis. It has been associated with a l = \m\=8+/-2 sectorial g mode in the frame of non-radial oscillations. We did not succeed in findin g in our data the most probable photometric frequency 2.49 c/d, previo usly given by McDavid (1988) and Cuypers et al. (1989), and recently d etected in the UV flux by Peters (1994), however this photometric freq uency and the lower spectroscopic frequencies 1.86 and 3.09 c/d seem t o be mutually linked.