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Multimessenger Observations in GW Era May Solve the Long-standing Problems of GRBs and Making Better Constraint on the Equation of State of Neutron stars

The research on gamma-ray bursts (GRBs) has been carried out for over fifty years, but we are still unable to reveal all of their mysteries, such as the central engine, the properties of the relativistic outflow and the radiation mechanisms of prompt emission. The era of gravitational wave astronomy offers us a great chance to make breakthroughs on the relevant fields.


Fig. 1 Rescaled PDFs of constrained from the outflow energy of GW170817 based on the BZ mechanism. Left: in the case of Gaussian structure; right: in the case of jet+cocoon structure. The vertical dashed lines are the symmetric 90% credible intervals. (Image by WANG Yuanzhu)


Recently, a research team from Purple Mountain Observatory studied on GRB 170817A which followed the only known BNS coalescence to date. They used the information from the GW measurement to constrain the accretion disk mass of the central remnant, and found that under the general assumptions, the magnetic process is favored rather than the neutrino process to explain the energy extraction on the central engine of the GRB's relativistic outflow. They proposed a new way to use GRB observations to constrain the combined tidal parameter of the progenitor neutron stars, and the tidal parameter are constrained within 309-954 for this event. A stronger constraint can be made by combining their result with the GW measured tidal parameter distribution. 


The research has built a bridge connecting the GW signals and the afterwards EM emissions, making similar analyses on future events are critical to understand the unified picture of NS mergers. The work is published in the Astrophysical Journal.