The Common Envelope Jet Supernova (CEJSN) r-process Scenario

We study r-process feasibility inside jets launched by a cold neutron star (NS) spiraling in inside the core of a giant star and find that such common envelope jet supernova events might be a significant source of heavy r-process elements in the early universe. We run the stellar evolution code MESA to follow the evolution of low-metallicity giant stars that swallow NSs during their late expansion phases and find that in some of the cases the NSs penetrate the core. The Bondi-Hoyle-Lyttleton (BHL) mass accretion rate onto an NS as it spirals in inside the core is sufficiently high to obtain a neutron-rich ejecta as required for the heavy r-process where the second and third r-process elements are synthesized. Due to the small radius of the NS, the accretion is through an accretion disk and the outflow is in jets (or bipolar disk winds). The r-process nucleosynthesis takes place inside the jets. To account for the r-process abundances in the Galaxy, we require that 1 in 10 cases of an NS entering the envelope of a giant star ends as a CEJSN r-process event.