Simulating the Outcome of a Binary Neutron Star Merger in a Common Envelope Jets Supernova

Abstract

Abstract We simulate the influence of the energy that the merger process of two neutron stars (NSs) releases inside a red supergiant (RSG) star on the RSG envelope inner to the merger location. In the triple-star common envelope evolution (CEE) that we consider, a tight binary system of two NSs spiraling in inside an RSG envelope and because of mass accretion and dynamical friction, the two NSs merge. We deposit merger-explosion energies of 3 × 1050 and 1051 erg at distances of 25 and 50 R ⊙ from the center of the RSG, and with the three-dimensional hydrodynamical code FLASH we follow the evolution of the RSG envelope in inner regions. For the parameters we explore, we find that more than 90% of the RSG envelope mass inward of the merger site stays bound to the RSG. NSs that experience CEE are likely to accrete RSG envelope mass through an accretion disk that launches jets. These jets power a luminous transient event, a common envelope jets supernova (CEJSN). The merger process adds to the CEJSN energy. Our finding implies that the interaction of the merger product, a massive NS or a BH, with the envelope can continue to release more energy, both by further inspiraling and by mass accretion by the merger product. Massive RSG envelopes can force the merger product to spiral into the core of the RSG, leading to an even more energetic CEJSN.