The interaction between short GRB jets and disk outflows from NSNS/BHNS mergers

Gerardo Urrutia, Agnieszka Janiuk, Fatemeh Hossein Nouri, Bestin James

Published 2024-01-18Version 1

Short Gamma-Ray Bursts (GRBs) are often associated with NSNS or BHNS mergers. The discovery of GW/GRB 170817A has enhanced our understanding, revealing that the interaction between relativistic jets and post-merger outflows influences the observed radiation. However, the nature of compact binary merger event suggests that the system can be more complex than the uniform jet interacting with a homologously expanding wind. We consider here an improved scenario by performing a set of two-dimensional, large scale numerical simulations, and we investigate the interaction between short GRB jets and post-merger disk wind outflows. We focus on two types of configurations, arising from NSNS and BHNS mergers. The simulations consider the effects of the r-process nucleosynthesis in the accretion disk wind on its pressure profile. The main properties of the jet, such as its energy distribution and collimation degree, are estimated from our simulations. We found that a) the impact of the r-process on initial wind pressure leads to significant changes in the jet collimation and cocoon expansion; b) the angular structure of thermal and kinetic energy components in the jets, cocoons, and winds differ with respect to simple homologous models, hence it would affect the predictions of GRB afterglow emission; c) the temporal evolution of the structure reveals conversion of thermal to kinetic energy being different for each component in the system (jet, cocoon, and wind); d) post-merger environments influence energy structure and material dispersion, altering the interaction between jets and disk winds. %Our study underscores the importance of post-merger disk wind in the jet propagation, emphasizing the need for careful parameter selection to avoid interpretation degeneracy in the electromagnetic counterparts.