Volume 517, July 2010
|Number of page(s)||22|
|Section||Stellar structure and evolution|
|Published online||06 August 2010|
ISDC Data Centre for Astrophysics & Geneva Observatory, University of Geneva,
chemin d'Ecogia 16, 1290 Versoix, Switzerland e-mail: Andres.Carmona@unige.ch
2 European Southern Observatory, Karl Schwarzschild Str 2, 85748 Garching bei München, Germany
3 Max-Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
4 ESA/ESTEC, Space Environments & Effects (TEC-EES), 2200 AG Noordwijk, The Netherlands
Accepted: 20 March 2010
We present FEROS high-resolution (R ~ 45 000) optical spectroscopy of 34 Herbig Ae/Be star candidates with previously unknown or poorly constrained spectral types. Within the sample, 16 sources are positionally coincident with nearby (d < 250 pc) star-forming regions (SFRs). All the candidates have reported infrared excess. We determine the spectral type and luminosity class of the sources, derive their radial and projected rotational velocities, and constrain their distances employing spectroscopic parallaxes and photometry from the literature. We confirm 13 sources as Herbig Ae/Be stars and find one classical T Tauri star. Three sources are emission line early-type giants (B, A, and F stars with luminosity class III) and may be Herbig Ae/Be stars. One source is a main-sequence A-type star. Fourteen sources are post-main-sequence giant and supergiant stars (7 with Hα emission and 7 without). Two sources are extreme emission-line stars and no accurate spectral classification was possible because of strong veiling. Most of the sources appear to be background stars at distances over 700 pc. We show that high-resolution optical spectroscopy is a crucial tool for distinguishing young stars (in particular Herbig Be stars) from post-main sequence stars in samples taken from emission-line star catalogs based on low-resolution spectroscopy. Within the sample, three young stars (CD-38 4380, Hen 3-1145, and HD 145718) and one early-type luminosity class III giant with emission lines (Hen 3-416) are at distances closer than 300 pc and are positionally coincident with a nearby SFR. These 4 sources are likely to be nearby young stars and are interesting for follow-up observations at high-angular resolution. Furthermore, seven confirmed Herbig Ae/Be stars at d>700 pc (Hen 2-80, Hen 3-1121 N&S, HD 313571, MWC 953, WRAY 15-1435, and Th 17-35) are inside or close (< 5') to regions with extended 8 μm continuum emission and in their 20' vicinity have astronomical sources characteristic of SFRs (e.g., HII regions, molecular clouds, dark nebulae, masers, young stellar-objects). These 7 sources are likely to be members of SFRs.
Key words: stars: pre-main sequence / stars: emission-line, Be / stars: fundamental parameters
Based on observations collected at the ESO-MPG 2.2 m telescope at la Silla Observatory, Chile (program IDs: 072.A-9006, 073.A-9008, 079.A-9014, 081.A-9003).
Appendix is only available in electronic form at http://www.aanda.org
© ESO, 2010
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