by M. Borges Fernandes, M. Kraus, O. Chesneau, A. Domiciano de Souza, F.X. de Araujo, Ph. Stee, and A. Meilland 2009
A&A, 508, 309
The observed spectral variation of HD 50138 led different authors in the literature to classify it in a very large range of spectral types and luminosity classes (from B5 to A0 and III to Ia) and at different evolutionary stages, as either an HAeBe star or a classical Be.
Based on new high-resolution optical spectroscopic data from 1999 and 2007 associated to a photometric analysis, the aim of this work is to provide a deep spectroscopic description and a new set of parameters for this southern unclassified B[e] star and its interstellar extinction.
From our high-resolution optical spectroscopic data that are separated by 8 years, we perform a detailed spectral description, presenting the variations seen and discussing their possible origin. We derive the interstellar extinction to HD 50138 by taking into account the influences of the circumstellar matter in the form of dust and an ionized disk. Based on photometric data from the literature and the new Hipparcos distance, we obtain a revised set of parameters for HD 50138.
Due to the spectral changes, we tentatively suggest that a new shell phase could have taken place prior to our observations in 2007. We find a color excess value of E(B-V) = 0.08 mag and from the photometric analysis, we suggest that HD 50138 is a B6-7 III-V star. A discussion about the different evolutionary scenarios is also provided.
