The symbiotic star CH Cygni. I. An analysis of the shocked nebulae at different epochs

TL;DR

This paper analyzes the spectra of the symbiotic star CH Cygni across different epochs, demonstrating that a colliding-wind model explains its observed features such as shocks, nebulae, and emissions.

Contribution

It provides a comprehensive spectral analysis confirming the colliding-wind model's validity for CH Cygni at various phases, integrating shock and photoionization effects.

Findings

Reverse shock causes broad lines during active phases.

Expanding shock explains data during transition phases.

Model accounts for radio, X-ray, and nebular features.

Abstract

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 photoionization 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.