Astronomy and Astrophysics, volume 477, 193-202 (2008/1-1)
Extended shells around B[e] stars. Implications for B[e] star evolution.
MARSTON A.P. and McCOLLUM B.
Abstract (from CDS):
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.We performed an Hα 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 MWC137 has been previously observed extensively. 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 MWC314. The possible links between B[e] stars and other evolved stars, implied by our observations, are investigated.
stars: emission-line, Be - stars: circumstellar material - stars: evolution