The Large‐Scale Ionized Outflow of CH Cygni

HST and ground-based [OII} and [NII] images obtained from 1996 to 1999 revealthe existence of a ionised optical nebula around the symbiotic binary CH Cygextending out to 5000 A.U. from the central stars. The observed velocity rangeof the nebula, derived from long-slit echelle spectra, is of 130 km/s. In spiteof its complex appearence, the velocity data show that the basic morphology ofthe inner regions of the optical nebula is that of a bipolar (or conical)outflow extending nearly along the plane of the sky out to some 2000 A.U. fromthe centre. Even if the extension of this bipolar outflow and its positionangle are consistent with those of the radio jet produced in 1984 (extrapolatedto the time of our optical imagery), no obvious counterpart is visible of theoriginal, dense radio bullets ejected by the system. We speculate that theoptical bipolar outflow might be the remannt of the interaction of the bulletswith a relatively dense circumstellar medium.Comment: 8 text pages + 3 figures (jpeg). ApJ in press. For a full PostScript version with figures inline see ftp://ftp.ll.iac.es/pub/research/preprints/PP252001.ps.g