1209.5747 (Koutarou Kyutoku et al.)

Ultra-Relativistic Counterparts to Binary Neutron Star Mergers in Every Direction, X-ray-to-Radio Bands and Second-to-Day Timescales    [PDF]

Koutarou Kyutoku, Kunihito Ioka, Masaru Shibata

We propose a possibility of ultra-relativistic electromagnetic counterparts to gravitational waves from binary neutron star mergers at any viewing angle. Mechanisms include the merger-shock propagation accelerating a smaller fraction of the neutron star surface to larger Lorentz factor, with the outer parts carrying less energy, ~10^{47} \Gamma^{-1} erg. This mechanism is difficult to resolve by current 3D numerical simulations, and depends on the neutron star equation of state. The outflows emit synchrotron flares for seconds to days by shocking the surrounding medium. Ultra-relativistic flares shine at early times and high energies, potentially detectable by current X-ray to radio instruments, such as Swift XRT and Pan-STARRS, and even in low ambient density ~10^{-2} cm^{-3} by EVLA. The flares probe the merger position and time, and the merger types as black hole-neutron star outflows would be non/mildly-relativistic.

View original: http://arxiv.org/abs/1209.5747