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

Long-term photometry of Be stars

III. Evidence for periodic outbursts of Eri and photometric activity in HR 2142 ^* **

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

1</sup> 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 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 ( 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 and 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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Contents

• 1. Introduction
• 2. Observations
• 3. Results
  • 3.1. Eri = HD 33328 = HR 1679
    • 3.1.1. A search for periodicities
    • 3.1.2. "Fading-rising" and "flare-like" events
    • 3.1.3. General properties of rising-fading events
    • 3.1.4. Color changes
  • 3.2. Temperature changes
  • 3.3. HD 41335 = HR 2142
    • 3.3.1. Color changes
• 4. Discussion
  • 4.1. Periodic outbursts of Eri
  • 4.2. HR 2142: photometric variations probably not due to mass transfer
  • 4.3. The relationship in Be stars
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: January 16, 1998
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