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Astron. Astrophys. 318, 198-203 (1997)

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An H outburst in the B emission line star HD 76534

René D. Oudmaijer and Janet E. Drew

Imperial College of Science, Technology and Medicine, Blackett Laboratory, Prince Consort Road, London, SW7 2BZ, UK

Received 4 March 1996 / Accepted 10 June 1996

Abstract

We present the discovery of unusually rapid and strong variations in the H [FORMULA] emission line of the emission line star HD 76534. Within two days, a strong emission line changed to photospheric absorption, while the line was in emission only two hours later. The observed timescale is an order of magnitude shorter than has been observed before in Be-type stars.

Two different scenarios that may be able to explain the observed behaviour are explored. The deduced mass loss rates are in agreement with the mass ejection mechanism, that has been invoked to explain the H [FORMULA] outbursts of variable Be stars like [FORMULA] Eri and µ Cen. The fact however that the H [FORMULA] line profile appears to trace a steady-state circumstellar envelope is not in agreement with the expected variable emission from a disk-like structure which is being built up in a few days.

In this paper, a new hypothesis is brought forward to take into account the sudden increase of H [FORMULA] in HD 76534, a change in the ionizing continuum from the star which ionizes a different fraction of a steady state circumstellar envelope.

Key words: stars: activity – stars: circumstellar matter – stars: emission-line, Be – stars: individual: HD 76534 – stars: mass loss

Send offprint requests to: René D. Oudmaijer (e-mail: r.oudmaijer@ic.ac.uk)

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© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998
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