  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 spirals-in
inside an RSG envelope and because of mass accretion and dynamical friction the
two NS merge. We deposit merger-explosion energies of 3e50 and 1e51 erg at
distances of 25Ro and 50Ro 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 per cent of the RSG envelope mass inner to the merger site stays bound to
the RSG. NSs that experience a 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 in-spiral and by mass accretion by the merger
product. Massive RSG envelopes can force the merger product to spiral-in into
the core of the RSG, leading to an even more energetic CEJSN.
