Jets from main sequence and white dwarf companions during common envelope evolution

It has long been speculated that jet feedback from accretion on to the companion during a common envelope (CE) event could affect the orbital evolution and envelope unbinding process. We present global 3D hydrodynamical simulations of CE evolution (CEE) that include a jet subgrid model and compare them with an otherwise identical model without a jet. Our binary consists of a 2-M-circle dot red giant branch primary and a 1- or 0.5-M-circle dot main sequence (MS) or white dwarf (WD) secondary companion modelled as a point particle. We run the simulations for 10 orbits (40 d). Our jet model adds mass at a constant rate M(j )of the order of the Eddington rate, with maximum velocity v(j) of the order of the escape speed, to two spherical sectors with the jet axis perpendicular to the orbital plane. We explore the influence of the jet on orbital evolution, envelope morphology and envelope unbinding, and assess the dependence of the results on the jet mass-loss rate, launch speed, companion mass, opening angle, and accretion rate. In line with our theoretical estimates, jets are choked around the time of first periastron passage and remain choked thereafter. Subsequent to choking, but not before, jets efficiently transfer energy to bound envelope material. This leads to increases in unbound mass of up to similar to 10 per cent, as compared to the simulations without jets. We also estimate the cumulative effects of jets over a full CE phase, finding that jets launched by MS and WD companions are unlikely to dominate envelope unbinding.

Automated summary

This study investigates the effects of jet feedback on the orbital evolution and envelope unbinding process during a common envelope (CE) event. The results show that jets can efficiently transfer energy to bound envelope material, leading to an increase in unbound mass.