Companion-launched jets at varying companion masses

Abstract

ABSTRACT We conduct three-dimensional hydrodynamic simulations, and show that when a secondary star launches jets while interacting with a primary $0.88~\mathrm{ M}_{\rm \odot }$ giant star in a close orbit, the system can avoid entering the common envelope evolution (CEE). Instead of a fast in-spiral, the companion slowly enters the envelope as the jets facilitate the unbinding of the giant star envelope outside the companion orbit, in what is termed the grazing envelope evolution (GEE). The assumptions are that the secondary main-sequence star accretes mass via an accretion disc, and that the accretion disc launches the jets. We perform two sets of simulations with and without jets for different companion masses at the range of 0.1–0.9 M$_{\odot }$, maintaining a constant jet power in the former case of $1.5\times 10^{38}~{\rm ergs~s^{-1}}$. We examine which of the simulated systems undergo a GEE rather than a CEE and how efficiently the jets unbind the envelope. The results indicate that systems with companion masses at the range of 0.1–0.3 M$_{\odot }$ are more likely to result in a phase of GEE lasting 1–3 yr. With the smallest companion, a 0.1 solar mass star, the jets unbind 65 per cent of the envelope mass, while almost none of the envelope is unbound if jets are not present. The results of the simulations show that the GEE can serve as an alternative to the CEE, in forming short-period binaries that have compact objects and an ejected envelope.