A luminous blue kilonova and an off-axis jet from a compact binary merger at z=0.1341

Understand

The recent discovery of a faint gamma-ray burst (GRB) coincident with the gravitational wave (GW) event GW 170817 revealed the existence of a population of low-luminosity short duration gamma-ray transients produced by neutron star mergers in the nearby Universe.

• These events could be routinely detected by existing gamma-ray monitors, yet previous observations failed to identify them without the aid of GW triggers.
• Here we show that GRB150101B was an analogue of GRB170817A located at a cosmological distance.
• GRB 150101B was a faint short duration GRB characterized by a bright optical counterpart and a long-lived X-ray afterglow.