On the Energetics of a Possible Relativistic Jet Associated with the Binary Neutron Star Merger Candidate S190425z

Abstract

Abstract Advanced LIGO and Virgo (AdvLIGO/VIRGO) detectors reported the first binary neutron star merger candidate in the third observing run, S190425z , on 2019 April 25. A weak γ-ray excess was reported nearly coincidentally by the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) satellite, which accidentally covered the entire localization region of AdvLIGO/VIRGO. Electromagnetic follow-up in longer wavelengths has not lead to the detection of any associated counterparts. Here we combine the available information from gravitational wave measurements and upper limits of fluence from INTEGRAL to show that the observations are completely consistent with a relativistic Gaussian structured jet and a typical short duration gamma-ray burst (GRB) being produced in the merger. We obtain posterior bounds on the on-axis isotropic equivalent energy of the associated GRB under different prior distributions. This study demonstrates that even limited gravitational wave and electromagnetic information could be combined to produce valuable insights about outflows from mergers. Future follow-ups may help constrain the jet structure further, especially if there is an orphan afterglow detection associated with the candidate.