The symbiotic star CH Cygni
The broad Ly emission line explained by shocksM. Contini1, 2, R. Angeloni1, 2, and P. Rafanelli1
1 Dipartimento di Astronomia, University of Padova, Vicolo dell'Osservatorio 2, 35122 Padova, Italy
2 School of Physics and Astronomy, Tel-Aviv University, 69978 Tel-Aviv, Israel
Received 19 December 2007 / Accepted 1 April 2008
Context. In 1985, at the end of the active phase 1977-1986, a broad (4000 ) Ly line appeared in the symbiotic system CH Cygni that had never been observed previously.
Aims. In this work we investigate the origin of this anomalous broad Ly line.
Methods. We suggest a new interpretation of the broad Ly based on the theory of charge transfer reactions between ambient hydrogen atoms and post-shock protons at a strong shock front.
Results. We have found that the broad Ly line originated from the blast wave created by the outburst, while the contemporary optical and UV lines arose from the nebula downstream of the expanding shock in the colliding-wind scenario.
Key words: stars: binaries: symbiotic -- stars: individual: CH Cyg
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