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Astron. Astrophys. 330, 631-640 (1998)

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Long-term photometry of Be stars

III. Evidence for periodic outbursts of [FORMULA] Eri and photometric activity in HR 2142 * **

R.E. Mennickent 1, C. Sterken** 2 and N. Vogt 3, 4

1 Departamento de Fsica, Facultad de Ciencias Fsicas y Matemáticas, Universidad de Concepción, Casilla 4009, Concepción, Chile (rmennick@phys.cfm.udec.cl)
2 University of Brussels (VUB), Pleinlaan 2, B-1050 Brussels, Belgium (csterken@vub.ac.be)
3 Grupo de Astrofsica, Universidad Católica de Chile, Casilla 314, Santiago, Chile
4 Sternwarte Sonneberg, Sternwartenstr. 32, D-96515 Sonneberg, Germany (nikolaus.vogt@stw.tu-ilmenau.de)

Received 1 July 1997 / Accepted 15 September 1997

Abstract

Strömgren differential uvby photometry of [FORMULA] 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. [FORMULA]  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 ([FORMULA] 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 [FORMULA] 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 [FORMULA] and [FORMULA] in a sample of 11 Be stars.

Key words: stars: emission-line, Be - stars: individual:  Eri – HR 2142

* Based on observations obtained at ESO, Chile

** Belgium Fund for Scientific Research (FWO)

Send offprint requests to: R.E. Mennickent

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© European Southern Observatory (ESO) 1998

Online publication: January 16, 1998
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