1996A&A...310..849F

High resolution, high signal-to-noise ratio CCD spectra of the Be-shell star 48 Librae allowed the investigation of rapid variability in the photospheric He I 4471 and Mg II 4481 lines. Though our sample was limited (51 spectra over four nights), 48 Lib has revealed itself to be a good candidate to display multiperiodic spectroscopic variations. Three frequencies, 1.86, 3.09 and 10.64c/d, have been detected in the He I line and seem to be present in Mg II 4481 though this latter, strongly blended in its core with a marked shell feature, is not appropriate for this kind of study. The higher frequency 10.64c/d has been deduced 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 finding in our data the most probable photometric frequency 2.49c/d, previously given by McDavid (1988) and Cuypers et al. (1989), and recently detected in the UV flux by Peters (1994), however this photometric frequency and the lower spectroscopic frequencies 1.86 and 3.09 c/d seem to be mutually linked.