A Deep Chandra X-ray Study of Neutron Star Coalescence GW170817

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We report Chandra observations of GW170817, the first neutron star-neutron star merger discovered by the joint LIGO-Virgo Collaboration, and the first direct detection of gravitational radiation associated with an electromagnetic counterpart, Fermi short gamma-ray burst GRB 170817A.

• The event occurred on 2017 August 17 and subsequent observations identified an optical counterpart, SSS17a, coincident with NGC 4993 (~10 arcsec separation).
• Early Chandra (\Delta t ~ 2 days) and Swift (\Delta t ~ 1-3 days) observations yielded non-detections at the optical position, but ~9 days post-trigger Chandra monitoring revealed an X-ray point source coincident with SSS17a.
• We present two deep Chandra observations totaling ~95 ks, collected on 2017 September 01-02 (\Delta t ~ 15-16 days).