Chandra images of the NGC 4993, the host galaxy of the counterpart to GW170817.
We present Chandra X-ray observations of the optical counterpart to GW170817, providing the first detection of X-ray emission from a gravitational wave source. Our observations revealed a brightening in the X-ray emission with time. We interpret this brightening as the signature of a relativistic jet launched at the time of the merger and originally pointing away from our line of sight. The observable emission increases with time as the jet slows down and spreads out causing more and more radiation to intercept our line of sight. We further rule out a central-engine origin of the X-ray emission, based on the inferred kilonova parameters. These observations provide the first observational evidence for the launching of a relativistic jet from a binary neutron star merger.