Jet parameters for a diverse sample of jet-launching post-AGB binaries

Abstract

ABSTRACT Jets are a commonly observed phenomenon in post-asymptotic giant branch (post-AGB) binaries. Due to the orbital motion of the binary, the jet causes variable absorption in the Balmer profiles. In previous work, we have developed spatio-kinematic and radiative transfer models to reproduce the observed Balmer line variability and derive the spatio-kinematic structure of the jet and its mass-loss rate. Here, we apply our jet model to five post-AGB binaries with distinct H α line variability and diverse orbital properties. Our models fit the H α line variations very well. We estimate jet mass-loss rates between $10^{-8}\,$M$_\odot \, \text{yr}^{-1}$ and $10^{-4}\,$ M$_\odot \, \text{yr}^{-1}$, from which we deduce accretion rates on to the companion between $10^{-7}\,$ M$_\odot \, \text{yr}^{-1}$ and $10^{-3}\,$ M$_\odot \, \text{yr}^{-1}$. These accretion rates are somewhat higher than can be comfortably explained with reasonable sources of accretion, but we argue that the circumbinary disc in these systems is most likely the source feeding the accretion, although accretion from the post-AGB star cannot be ruled out. The diversity of the variability in the five objects is due to their wide ejection cones combined with a range of viewing angles, rather than inherent differences between the objects. The nature of the observations does not let us easily distinguish which jet launching model (stellar jet, disc wind, or X-wind) should be favoured. In conclusion, we show that our jet model includes the physical parameters to successfully reproduce the H α line variations and retrieve the structure and mass-loss rates of the jet for all five objects that are representative of the diverse sample of Galactic post-AGB binaries.