This study investigates the antineutrinos production by β-decay of r-process nuclei in two astrophysical sites that are capable of producing gamma-ray bursts (GRBs): binary neutron star mergers (BNSMs) and collapsars, which are promising sites for heavy element nucleosynthesis. We employ a simplified method to compute the β-decay νˉe energy spectrum and consider a number of different representative thermodynamic trajectories for r-process simulations, each with four sets of Ye distribution. The time evolution of the νˉe spectrum is derived for both the dynamical ejecta and the disk wind for BNSMs and collapsar outflow, based on approximated mass outflow rates. Our results show that the νˉe has an average energy of approximately 3 to 9~MeV, with a high energy tail of up to 20 MeV. The νˉe flux evolution is primarily determined by the outflow duration, and can thus remain large for O(10)~s and O(100)~s for BNSMs and collapsars, respectively. For a single merger or collapsar at 40~Mpc, the νˉe flux is O(10−100)~cm−2~s−1, indicating a possible detection horizon up to 0.1−1~Mpc for Hyper-Kamiokande. We also estimate their contributions to the diffuse νˉe background, and find that both sources should only contribute subdominantly to the diffuse background when compared to that expected from core-collapse supernovae.
@article{arxiv.2306.07659,
title = {R-process beta-decay neutrino flux from binary neutron star mergers and collapsars},
author = {Yu An and Meng-Ru Wu and Gang Guo and Yue-Lin Sming Tsai and Shih-Jie Huang and Yi-Zhong Fan},
journal= {arXiv preprint arXiv:2306.07659},
year = {2023}
}