Abstract

" Strömgren differential uvby photometry of ? Eri and HR 2142 is analyzed. The data were taken during the time interval 1983-1994 in the framework of the Long-Term Photometry of Variables project at La Silla. ? Eri exhibited four photometric events (probably associated with line emission episodes) 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 fit a 486 d recurrence time. On the other hand, HR 2142 showed a relatively ""quiet"" long-term photometric behaviour, the orbital period being detected only marginally in the photometric data set. In contrast, a 344 d period optimally fits the data. We discuss the possibility of an internal ""clock"" regulating the outburst activity of ? Eri and show that the photometric variability of HR 2142 can hardly 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. "