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| Artikel: Extended shells around B[e] stars https://forum.vdsastro.de/viewtopic.php?t=2215 |
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| Autor: | Wolfgang Renz [ 16. Dezember 2007, 12:18:12 PM ] |
| Betreff des Beitrags: | Artikel: Extended shells around B[e] stars |
Hallo Hier ein neuer A&A Artikel, der mit einem kostenlosen A&A EDPS- Account noch bis ~ Dienstag frei heruntergeladen werden kann. 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 |
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