Dynamics of jets during the common-envelope phase

Abstract

Common envelope (CE) is an important phase in the evolution of many binary systems. Giant star / compact object interaction in binaries plays an important role in highenergy phenomena as well as in the evolution of their environment. Material accreted onto the compact object may form a disk and power a jet. We study analytically and through numerical simulations the interaction between the jet and the CE. We determine the conditions under which accreting material quenches the jet or allows it to propagate successfully, in which case even the envelope may be ejected. Close to the stellar core of the companion the compact object accretes at a larger rate. A jet launched from this region needs a larger accretion-to-ejection efficiency to successfully propagate through the CE compared to a jet launched far from the stellar core, and is strongly deflected by the orbital motion. The energy deposited by the jet may be larger than the binding energy of the envelope. The jet can, thus, play a fundamental role in the CE evolution. We find that the energy dissipation of the jet into the CE may stop accretion onto the disk. We expect the jet to be intermittent, unless the energy deposited is large enough to lead to the unbinding of the outer layers of the CE. Given that the energy and duration of the jet are similar to those of ultra-long GRBs, we suggest this as a new channel to produce these events.

Simulating a binary system that experiences the grazing envelope evolution

“…As the secondary spirals in, the jets are deflected by the denser inner regions of the giant and bend towards the equatorial plane. The bending of jets inside a common envelope can be seen in earlier simulations (Soker et al 2013;Moreno Méndez et al 2017), as well as in the GEE (Shiber et al 2017). When the secondary spirals-in even deeper the jets are halt by the giant envelope, and escape only behind the companion in a trailing flow as discussed above.…”

Counteracting tidal circularization with the grazing envelope evolution

“…The envelope mass removal process operates in a negative feedback cycle (Soker 2016b). If the jets remove too much gas from their vicinity the accretion rate decreases and so does the power of the jets (e.g., simulations conducted by Moreno Méndez et al 2017). The removal of gas acts to increase the orbital separation, and this in turn can reduce accretion rate onto the secondary star, unless tidal forces overtake and cause the formation of a common enve-lope phase.…”

Common Envelope Evolution on a Moving Mesh

“…Finally, we note here that other processes may also aid the expulsion of the envelope. Much recent work have been focused on energy and momentum injection from jets produced by accretion onto the companion (Papish et al 2015;Moreno Méndez et al 2017;Shiber & Soker 2018;Chamandy et al 2018). In addition, the transition from laminar flow to accretion flows around the companion star can be complicated and also provide another mechanism by which orbital energy is dissipated (MacLeod & Ramirez-Ruiz 2015a,b;MacLeod et al 2017).…”