Shaping the nebula around the symbiotic system R Aquarii

Abstract

ABSTRACT We present an analysis of high-dispersion spectroscopic observations of the symbiotic system R Aquarii (R Aqr) obtained with the Manchester Echelle Spectrograph at the 2.1-m telescope of the San Pedro Mártir Observatory (Mexico) in conjunction with available narrow-band images. The data are interpreted by means of the shape software to disclose the morpho-kinematics of the nebulosities associated with R Aqr. The model that best reproduces narrow-band images and position–velocity diagrams consists of three structures: an outer (large) hourglass structure surrounding an inner bipolar with a spiral-like filament entwined around the latter. The expansion velocity pattern of each structure is defined by different homologous expansion laws, which correspond to kinematic ages of $\tau _1$ = 450 $\pm$ 25 yr (outer hourglass), $\tau _2$ = 270 $\pm$ 20 yr (inner bipolar), and $\tau _3$ = 285$\pm$ 20 yr (spiral-like filament). We suggest that the spiral-like filament is tracing the regions of the interaction of a precessing jet with the circumstellar material, which simultaneously carves the inner bipolar structure. If a similar process created the large hourglass structure, it means that the action of the jet ceased for about 170 yr. We discuss the implications for other unresolved symbiotic systems detected in X-rays.