The common envelope jets supernova (CEJSN) r-process scenario

TL;DR

This paper explores the potential of common envelope jets supernovae involving neutron stars to produce heavy r-process elements, suggesting they could be a significant source in the early Universe.

Contribution

It introduces a new scenario where neutron star jets during common envelope phases enable heavy r-process nucleosynthesis, supported by stellar evolution simulations.

Findings

Neutron star accretion rates inside giant star cores are sufficient for r-process.

Jets from accreting neutron stars can synthesize second and third r-process elements.

Approximately 10% of neutron star engulfment events may lead to r-process nucleosynthesis.

Abstract

We study r-process feasibility inside jets launched by a cold neutron star (NS) spiralling-in inside the core of a giant star, and find that such common envelope jets 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 metalicity 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 a 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 one in ten cases of a NS entering the envelope of a giant star ends as a CEJSN r-process event.