On the evolutionary stage of the unclassified B[e] star CD-42o11721

Abstract

The star CD-42o11721 is a curious B[e] star sometimes pointed as an evolved B[e] supergiant and sometimes as a young HAeBe star, due to very uncertain or even unknown stellar parameters, especially the distance. In this paper, we present new data gained from high-resolution optical spectroscopy and a detailed description of IR data of this star. We present a qualitative study of the numerous emission lines in our optical spectra and the classification of their line profiles, which indicate a non-spherically symmetric circumstellar environment. The first real detection of numerous [Fe II] emission lines and of many other permitted and forbidden emission lines is reported. From our optical data, we derive an effective temperature of 14000 K, a radius of 17.3 +/- 0.6 Rsun, as well as a luminosity of 1.0 +/- 0.3 x 10^{4} Lsun. We advocate that CD-42o11721 might be a post-main sequence object, even though a pre-main sequence nature cannot be ruled out due to the uncertain distance. We further found that the SED in the optical and infrared can best be fitted with an outflowing disk-forming wind scenario rather than with a spherical symmetric envelope or with a flared disc, supporting our tentative classification as a B[e] supergiant.

The paper contains 20 pages, 13 figures and 9 tables. Accepted for publication in the MNRAS

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