Binary neutron star merger in common envelope jets supernovae

I explore a triple-star scenario where a tight neutron star (NS) - NS binary system enters the envelope of a red supergiant (RSG) star and spirals-in towards its core. The two NSs accrete mass through accretion disks and launch jets that power a very luminous and long transient event, a common envelope jets supernova (CEJSN) event. Dynamical friction brings the two NSs to merge either in the RSG envelope or core. The total energy of the event, radiation and kinetic, is >10^{52}erg. The light curve stays luminous for months to years and a signal of gravitational waves might be detected. The ejecta contains freshly synthesized r-process elements not only from the NS-NS merger as in kilonova events, but possibly also from the pre-merger jets that the NSs launch inside the core, as in the r-process CEJSN scenario. This scenario shortens the time to NS-NS merger compared with that of kilonovae, and might somewhat ease the problem of the NS-NS r-process scenario to account for r-process nucleosynthesis in the early Universe. I estimate the ratio of NS-NS merger in CEJSN events to core collapse supernova (CCSN) events to be
Accepted for publication in Monthly Notices of the Royal Astronomical Society