The symbiotic star CH Cygni - I. Non-thermal bipolar jets

Abstract

Very Large Array surface brightness and spectral index maps of the evolving extended emission of the triple symbiotic star CH Cygni are presented. These are derived from observations at 4.8, 8.4 and 14 GHz between 1985 and 1999. The maps are dominated by thermal emission around the central bright peak of the nebula, but we also find unambiguous non‐thermal emission associated with the extended regions. Our observations confirm that this is a jet. The central region has been associated with the stellar components through Hubble Space Telescope imaging. If the jets are the result of ejection events at outburst, expansion velocities are consistent with those from other measurement methods. We propose that the non‐thermal emission is caused by material ejected in the bipolar jets interacting with the circumstellar wind envelope. The resulting shocks lead to local enhancements in the magnetic field from the compact component of the order of 3 mG.

Resolving the Dusty Circumstellar Structure of the Enigmatic Symbiotic Star CH Cygni with the MMT Adaptive Optics System

“…After subtracting out the symmetric component of the emission, the residual emission appears extended along a similar north-south axis to those of the radio jets reported by Crocker et al (2001). The residual structure peaks in flux ∼0.5 ′′ north of the star and is roughly coincident to the knotlike structure observed by Crocker et al (2001) at 0.7 ′′ north of the star in HST WFPC2 images (marked by the letter A in Fig.…”

“…CH Cyg is one of the most enigmatic symbiotic stars -previous to 1963, CH Cyg showed no variable behavior and was actually used as a M6III spectral type calibrator (see Kenyon 2001, for background details on CH Cyg's properties). Since 1963, CH Cyg has gone through multiple outbursting phases, producing bipolar radio jets in 1984 (Taylor et al 1986), 1992 (Karovska et al 1998(Crocker et al 2001, as well as X-ray jets (Galloway & Sokoloski 2004), and large ionized outflows (∼10 ′′ in size, see Eyres et al 2002;Corradi et al 2001). B band flickering studies also point to the existence of an unstable accretion disk around the hot white dwarf component (Sokoloski & Kenyon 2003a,b).…”

The Radio Light Curve of the Gamma-Ray Nova in V407 Cyg: Thermal Emission From the Ionized Symbiotic Envelope, Devoured From Within by the Nova Blast

“…In addition, no information on the spectral index exists for the 1993 detection of V407 Cyg, so the radio emission mechanism cannot be confirmed. In other symbiotic binaries, dramatic increases in radio flux have been associated with collimated mass ejection, which can produce both thermal and synchrotron radio emission (e.g., CH Cyg, R Aqr, and Mira; Taylor et al 1986;Crocker et al 2001;Nichols et al 2007;Meaburn et al 2009). While there is, to date, no evidence for fast collimated outflows in optical spectroscopic monitoring, V407 Cyg remains a promising candidate site for the production of synchrotron emission.…”

Recent photometry of symbiotic stars

“…Leahy & Taylor 1987;Mukai et al 2009a), producing collimated outflows in the radio (e.g. Taylor et al 1986;Crocker et al 2001;Karovska et al 2007Karovska et al , 2010, because of a high orbital inclination (e.g. Skopal et al 1996).…”