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HD 182917
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ATel 10142: A New Active Stage of the Symbiotic Star CH Cygni



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RE: CH Cygni
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ATel 6560: Reappearance of the optical flickering from the symbiotic star CH Cyg

 



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Google earth file: CH Cygni.kmz (2kb, kmz)



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The symbiotic variable star CH Cygni is in outburst.

Date: 24th February, 2012.
Magnitude range: 5.6 - 10.9 V
Period: 90-100, 155, 360, days (?)
Satellite period: - days
Type: -

Position(2000): RA=19 24 33.06773 | Dec=+50° 14' 29.1263"



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CH Cyg is a binary star system containing a white dwarf that feeds from the wind of a red giant star. The material from the wind forms a hot accretion disk around the white dwarf before crashing onto the star. CH Cyg is one of only a few hundred symbiotic systems known, and one of the closest to the Earth. Symbiotic systems are fascinating objects, where the components are codependent and influence each other's structure, daily life, and evolution. They are likely progenitors of bipolar planetary nebulas and they could make up some of the systems that later explode as Type Ia supernovas, spectacular explosions visible across cosmological distances.
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Researchers have reported that CH Cygni had an outburst from the 25th September, to the 21st October, 2009, with the star brightening from U = 10.9 to U = 9.7.
The star is currently at U = 11.1

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CH Cygni

Position(2000): RA  19 24 33.0681, Dec  +50 14 29.128

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Title: The symbiotic star CH Cygni. II. The broad Ly alpha emission line explained by shocks
Authors: M. Contini (1,2), R. Angeloni (1,2), P. Rafanelli (1) ((1) Dipartimento di Astronomia, University of Padova, Italy; (2) School of Physics and Astronomy, Tel-Aviv University, Israel)

Context. In 1985, at the end of the active phase 1977-1986, a broad (4000 km/s) Ly alpha 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 alpha line.
Methods. We suggest a new interpretation of the broad Ly alpha 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 alpha 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.

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Title: The symbiotic star CH Cygni. I. An analysis of the shocked nebulae at different epochs
Authors: M. Contini (1,2), R. Angeloni (1,2), P. Rafanelli (1) ((1) Dipartimento di Astronomia, University of Padova, Italy; (2) School of Physics and Astronomy, Tel-Aviv University, Israel)

Context. We analyse the line and continuum spectra of the symbiotic system CH Cygni.
Aims. To show that the colliding-wind model is valid to explain this symbiotic star at different phases.
Methods. Peculiar observed features such as flickering, radio variation, X-ray emission, as well as the distribution of the nebulae and shells throughout the system are investigated by modelling the spectra at different epochs. The models account consistently for shock and photoionisation and are constrained by absolute fluxes.
Results. We find that the reverse shock between the stars leads to the broad lines observed during the active phases, as well as to radio and hard X-ray emission, while the expanding shock is invoked to explain the data during the transition phases.

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