Jets in Common Envelopes: a low mass main sequence star in a red giant

We present small-scale three-dimensional hydrodynamical simulations of the evolution of a 0.3Msun main sequence star which launches two perpendicular jets within the envelope of a 0.88Msun red giant. Based on previous large-scale simulations, we study the dynamics of the jets either when the secondary star is grazing, when it has plunged-in, or when it is well-within the envelope of the red giant (in each stage for ~11 days). The dynamics of the jets through the common envelope (CE) depend on the conditions of the environment as well as on their powering. In the grazing stage and the commencement of the plunge self-regulated jets need higher efficiencies to break out of the envelope of the RG. Deep inside the CE, on the timescales simulated, jets are choked independently of whether they are self-regulated or constantly powered. Jets able to break out of the envelope of the RG in large-scale simulations, are choked in our small-scale simulations. The accreted angular momentum onto the secondary star is not large enough to form a disk. The mass accretion onto the MS star is 1-10% of the Bondi-Hoyle-Littleton rate (~1e-3 - 1e-1 Msun yr/s). High luminosity emission, from X-rays to UV and optical, is expected if the jets break out of the CE. Our simulations illustrate the need for inclusion of more realistic accretion and jet models in the dynamical evolution of the CEs.
Comment: 13 pages, 7 figures, 1 table, published in MNRAS