Illuminating Gravitational Waves: A Concordant Picture of Photons from a
  Neutron Star Merger
  Merging neutron stars offer an exquisite laboratory for simultaneously
studying strong-field gravity and matter in extreme environments. We establish
the physical association of an electromagnetic counterpart EM170817 to
gravitational waves (GW170817) detected from merging neutron stars. By
synthesizing a panchromatic dataset, we demonstrate that merging neutron stars
are a long-sought production site forging heavy elements by r-process
nucleosynthesis. The weak gamma-rays seen in EM170817 are dissimilar to
classical short gamma-ray bursts with ultra-relativistic jets. Instead, we
suggest that breakout of a wide-angle, mildly-relativistic cocoon engulfing the
jet elegantly explains the low-luminosity gamma-rays, the high-luminosity
ultraviolet-optical-infrared and the delayed radio/X-ray emission. We posit
that all merging neutron stars may lead to a wide-angle cocoon breakout;
sometimes accompanied by a successful jet and sometimes a choked jet.
