LONG-TERM PHOTOMETRY OF BE STARS. III. EVIDENCE FOR PERIODIC OUTBURSTS OF LAMBDA ERI AND PHOTOMETRIC ACTIVITY IN HR 2142

Str¨ omgrendifferentialuvby photometryofEriand HR2142 is analyzed. The data were taken during the time inter- val 1983{1994 in the framework of the Long-Term Photometry of Variables project at La Silla. Eri exhibited four photomet- ricevents(probablyassociatedwithlineemissionepisodes)that last several months and which were characterized by a common pattern of change in all passbands (10 3 mag/day) along with an apparent decrease of the amplitude of the short-term variability and an increase of the stellar temperature. A search for periodicities reveals that these events t a 486d recurrence time. On the other hand, HR2142 showed a relatively \quiet" long-term photometric behaviour, the orbital period being de- tected only marginally in the photometric data set. In contrast, a 344d period optimally ts the data. We discuss the possibility of an internal \clock" regulating the outburst activity of Eri andshowthatthephotometricvariabilityofHR2142canhardly be explained by its interacting binary nature. We also discuss an empirical relationship found between @c 1 @u and v sini in a sample of 11 Be stars.