  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 high-energy 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.
