What is the real nature of HD 108?

Free access article

Issue		A&A Volume 372, Number 1, June II 2001


Page(s)		195 - 207
Section		Formation, structure and evolution of stars
DOI		http://dx.doi.org/10.1051/0004-6361:20010473

A&A 372, 195-207 (2001)
DOI: 10.1051/0004-6361:20010473

What is the real nature of HD 108?

Y. Nazé, J.-M. Vreux and G. Rauw

Institut d'Astrophysique et de Géophysique, Université de Liège, 5 avenue de Cointe, 4000 Liège, Belgium

(Received 2 February 2001 / Accepted 22 March 2001)

Abstract
Since the beginning of the past century, the nature of HD 108 has been a subject of intense debate. One after another, astronomers explored its variability and attributed it either to binarity, or to changes in the stellar wind of a single star. In this article, we analyse a 30 year campaign of spectroscopic observations of this star with special emphasis on the last 15 years during which photographic plates have been replaced by CCD detectors. Our investigation of the radial velocities of HD 108 yields no significant short- or long-term period and does not confirm the published periodicities either. Though the radial velocity of HD 108 appears clearly variable, the variations cannot be explained by the orbital motion in a spectroscopic binary. However, our data reveal spectacular changes in the H I Balmer lines and some He I profiles over the years. These lines continuously evolved from P Cygni profiles to "pure"absorption lines. A similar behaviour has already been observed in the past, suggesting that these changes are recurrent. HD 108 seems to share several characteristics of Oe stars and we discuss different hypotheses for the origin of the observed long-term variations. As we are now in a transition period, a continuous monitoring of HD 108 should be considered for the next few years.

Key words: stars: early-type -- stars: mass-loss -- stars: individual: HD 108

Offprint request: Y. Nazé, naze@astro.ulg.ac.be

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