Interpreting GRB170817A as a giant flare from a jet-less double neutron star merger
Abstract
We show that the delay between GRB170817A and GW170817 is incompatible with de-beamed emission from an off-axis relativistic jet. The prompt emission and the subsequent radio and X-ray observations can instead be interpreted within a giant-flare-like scenario, being the result of a relativistic outflow driven by the ultra-strong magnetic field produced by magnetohydrodynamic amplification during the merger of the progenitor double neutron-star binary. Within such a picture, the data indicate that the outflow must be endowed with a steep velocity profile, with a relatively fast tail extending to Γ ∼ 8. Since the conditions for the launch of such an outflow are relatively general, and the presence of a velocity profile is a natural expectation of the acceleration process, most neutron star binary mergers should feature this quasi-isotropic, hard X-ray emission component, that could be a powerful guide to the discovery of additional kilonovae associated to relatively nearby gravitational wave events.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 2018
- DOI:
- 10.1051/0004-6361/201732259
- arXiv:
- arXiv:1711.03112
- Bibcode:
- 2018A&A...619A..18S
- Keywords:
-
- relativistic processes;
- gamma-ray burst: individual: GRB170817A;
- stars: neutron;
- gravitational waves;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 6 pages, 2 figures, accepted by Astronomy and Astrophysics