Electromagnetic Afterglows Associated with Gamma-Ray Emission Coincident with Binary Black Hole Merger Event GW150914

Understand

The Fermi Gamma-ray Burst Monitor reported the possible detection of the gamma-ray counterpart of a binary black hole merger event, GW150914.

• We show that the gamma-ray emission is caused by a relativistic outflow with Lorentz factor larger than 10.
• Subsequently, debris outflow pushes the ambient gas to form a shock, which is responsible for the afterglow synchrotron emission.
• We find that the 1.4 GHz radio flux peaks at $\sim10^5$ sec after the burst trigger.