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Astron. Astrophys. 326, 1167-1175 (1997)

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Coupled long-term photometric and V/R variations in Be stars: evidence for prograde global one-armed disk oscillations *

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

1 Dpto. de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Casilla 4009, Concepción, Chile
2 University of Brussels (VUB), Pleinlaan 2, B-1050 Brussels, Belgium (csterken@vub.ac.be)
3 Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 104, Santiago 22, Chile
4 Sternwarte Sonneberg, Sternwartenstr. 32, D-96515 Sonneberg, Germany (nikolaus.vogt@stw.tu-ilmenau.de)

Received 16 January 1997 / Accepted 5 June 1997


We review theoretical work on global oscillations of Be star disks and summarize possible observational tests. In addition, we analyze existing records on photometric data and V/R ratio for a sample of 6 V/R variable Be stars. Five stars showed coupled long-term photometric-V/R variations. In all cases the photometric extrema coincided with times of [FORMULA] transits, the fainter state being followed by a [FORMULA] phase. V 1294 Aql, 48 Lib and MX Pup showed anticorrelated [FORMULA] and [FORMULA] colors during light cycles, the stars being redder in [FORMULA] when brightest. 48 Lib shows a complex color behaviour, exhibiting two minima during a V/R cycle and a pronounced [FORMULA] drop just at maximum light. In addition, this star shows enigmatic, non-periodic, eclipse-like features in its light curve. In general, the V/R-photometric observations can be grouped in three main groups, depending on the degree of correlation exhibited by the V/R ratio and the photometric fluxes and the rate of change of the u flux. These groups are compatible with prograde global disk oscillations observed under different system inclinations.

Key words: stars: emission-line, Be - stars: individual: V 923 Aql – V 1294 Aql – fl Cas – 48 Lib – MX Pup – i Tau

* Based, in part, on observations obtained at the European Southern Observatory at La Silla, Chile
** Belgian Fund for Scientific Research (NFWO)

Send offprint requests to: R.E. Mennickent

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© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998