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

Abstract

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.