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Astron. Astrophys. 336, 251-262 (1998)

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Large-scale perturbations in the circumstellar envelopes of Be/X-ray binaries

I. Negueruela 1, 2, P. Reig 2, M.J. Coe 2 and J. Fabregat 3

1 Astrophysics Research Institute, Liverpool John Moores University, Byrom St., Liverpool, L3 3AF, UK
2 Physics and Astronomy Department, Southampton University, Southampton, SO17 1BJ, UK
3 Departamento de Astronomía y Astrofísica, Universidad de Valencia, E-46100 Burjassot, Valencia, Spain

Received 8 July 1997 / Accepted 18 April 1998

Abstract

We investigate the spectroscopic characteristics of the optical components of Be/X-ray binary systems, using data collected during our seven-year monitoring campaign. We find examples of major changes in the emission line profiles associated with Type II X-ray outbursts, later developing into V/R variability cycles. We show that the time-scales for V/R variability in Be/X-ray transients extend from a few weeks to years and interpret all these changes as due to the presence of global disruptions of the axisymmetric density distribution in the extended envelopes of the Be stars in these systems. The association between X-ray outbursts and V/R variability, the occurrence of very fast changes and the very short quasi-periods of variability displayed by Be/X-ray binaries lead us to conclude that the presence of the neutron star is an important factor affecting the dynamics of the disc-like envelopes. The interaction between the compact companion and the disc would explain the correlation between H[FORMULA] strength and orbital period recently found. The characteristics of the V/R cycles are, however, mainly independent of the binary parameters.

Key words: stars: circumstellar matter – stars: emission line, Be – binaries: close – stars: neutron – X-rays: stars

Send offprint requests to: I. Negueruela (Liverpool address)

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© European Southern Observatory (ESO) 1998

Online publication: July 7, 1998
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