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Astron. Astrophys. 326, 1167-1175


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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. Mennickent1 and C. Sterken2**, and N. Vogt3,4

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

Received 16 January 1997 / Accepted 5 June 1997

Abstract

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 V = R transits, the fainter state being followed by a V < R phase. V 1294 Aql, 48 Lib and MX Pup showed anticorrelated c1 and b-y colors during light cycles, the stars being redder in b-y when brightest. 48 Lib shows a complex color behaviour, exhibiting two minima during a V/R cycle and a pronounced b-y 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 - FORMULA Cas - 48 Lib - MX Pup - FORMULA Tau

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

Send offprint requests to: R.E. Mennickent


© European Southern Observatory (ESO) 1997

Online publication: October 1, 1997
Last change: April 8, 1998
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