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http://www.aanda.org/articles/aa/abs/20 ... 86-06.html

A&A 477, 193-202 (2008)
DOI: 10.1051/0004-6361:20066086
Extended shells around B[e] stars
Implications for B[e] star evolution
A. P. Marston1 and B. McCollum2

1  ESA/ESAC, Villafranca del Castillo, 28080 Madrid, Spain
    e-mail: tmarston(==>)sciops.esa.int
2  Spitzer Science Center, IPAC, Caltech, Pasadena, CA 91125, USA
    e-mail: mccollum(==>)ipac.caltech.edu

(Received 21 July 2006 / Accepted 15 October 2007)
Abstract 
Aims.The position of B[e] stars in the upper left part of the Hertzsprung-Russell diagram creates a quandary. Are these stars young stars evolving onto the main sequence or old stars that are evolving off of it? Spectral characteristics suggest that B[e] stars can be placed into five subclasses and are not a homogeneous set. Such sub-classification is believed to coincide with varying origins and different evolutions. However, the evolutionary connection of B[e] stars - and notably sgB[e] - to other stars is unclear, particularly to evolved massive stars. We attempt to provide insight into the evolutionary past of B[e] stars.
Methods.We performed an H alpha narrow-band CCD imaging survey of B[e] stars, in the northern hemisphere. Prior to the current work, no emission-line survey of B[e] stars had yet been made, while only two B[e] stars appeared to have a shell nebula as seen in the Digital Sky Survey. Of nebulae around B[e] stars, only the ring nebula around MWC 137 has been previously observed extensively. 
Results.In this presentation we report the findings from our narrow-band optical imaging survey of the environments of 25 B[e] stars. Of the objects surveyed, 7 show bipolar or uni- polar structures up to 15' across; 5 show faint, large, or filamentary shells; and 2 are compact planetary nebula-type systems. The most spectacular system observed is a large bipolar structure associated with MWC 314.
Conclusions.The possible links between B[e] stars and other evolved stars, implied by our observations, are investigated.

Key words: stars: emission-line, Be -- stars: circumstellar material -- stars: evolution

© ESO 2007


Die untersuchten Be Sterne sind im Bereich von 6.58 (MWC 158) -14.7
(Hen 2-461) mag V.

Clear skies
Wolfgang

--
Wolfgang Renz, Karlsruhe, Germany
Rz.BAV = WRe.vsnet = RWG.AAVSO