EDP Sciences
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Volume 408, Number 1, September II 2003
Page(s) 305 - 311
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20030965

A&A 408, 305-311 (2003)
DOI: 10.1051/0004-6361:20030965

Spectroscopy of the growing circumstellar disk in the $\delta$ Scorpii Be binary

A. S. Miroshnichenko1, 2, K. S. Bjorkman1, N. D. Morrison1, J. P. Wisniewski1, N. Manset3, H. Levato4, M. Grosso4, E. Pollmann5, C. Buil6 and D. C. Knauth7

1  Ritter Observatory, Dept. of Physics & Astronomy, The University of Toledo, Toledo, OH 43606-3390, USA
2  Pulkovo Observatory, Saint-Petersburg 196140, Russia
3  CFHT Corporation, 65-1238 Mamalahoa Hwy, Kamuela, HI 96743, USA
4  Complejo Astronómico El Leoncito (CASLEO), Casilla de Correo 467, 5400 San Juan, Argentina
5  Charlottenburgerstrasse 26c, 511377 Leverkusen, Germany
6  6 place Clémence Isaure, 31320 Castanet-Toloson, France
7  Dept. of Physics and Astronomy, John Hopkins University, 3400 N. Charles Str., Baltimore, MD 21218, USA

(Received 3 April 2003 / Accepted 20 June 2003)

We present the results of a spectroscopic monitoring program of the binary system $\delta$ Scorpii, whose primary became a Be star after the last periastron encounter in the Summer of 2000. The observations cover a period of 2 years (March 2001-June 2003) and are a continuation of our previous campaign reported in Miroshnichenko et al. (2001). We found that the emission-line spectrum was gradually strengthening over the whole monitoring period. Several short-term increases of the line emission, possibly due to outbursts of matter ejected from the stellar surface, were detected. The outbursts seem to be responsible for the brightness fadings, seen afterwards. We attempt to explain the overall observed line and continuum behaviour in terms of a circumstellar disk, growing in density and size. The disk is most likely Keplerian with an outer radius of ${\sim}10~ R_{\star}$ and a mean expansion speed of ~0.4 km s -1.

Key words: techniques: spectroscopic -- stars: circumstellar matter -- stars: individual: $\delta$ Scorpii -- stars: binaries: spectroscopic  -- stars: Be stars

Offprint request: A. S. Miroshnichenko, anatoly@physics.utoledo.edu

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