Self-regulating jets during the common-envelope phase

Abstract

Jets launched from a compact object (CO) during a common envelope (CE) may play a key role in the evolution of the system, and may also be an efficient removal channel for its material. In this work we study, through a large set of three-dimensional hydrodynamic simulations, the effects that jets launched from either a black hole (BH) or a neutron star (NS) have during a CE phase. The jet is self-consistently powered by a fraction (η) of the mass accretion rate that reaches the CO. For low mass accretion efficiencies (η < 0.1 per cent), the jet is not able to drill through the material accreting on to the CO and forms a bulge around it. For higher efficiencies, the jet is able to drill through the bulge and in intermediate efficiencies (η ∼ 1–5 per cent) may produce an oscillating mass accretion rate behaviour. We find that the jet may deposit enough energy to unbind the outer layers of the CE. The self-regulated jets present variability in size and orientation while their cocoons expand smoothly over the CE. The mass accretion rate initially decreases due to the ram pressure of the cocoon. If the launched jet is not able to drill through the bulge, the accretion is such that it may convert a NS into a BH within a decade or double the mass of a BH in a few years. If a jet is present, it deposits enough energy to unbind the outer layers of the CE and the system evolves into a grazing envelope, configuration.