Brightening X-ray Emission from GW170817/GRB170817A: Further Evidence for an Outflow

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The origin of the X-ray emission from neutron star coalescence GW170817/GRB170817A is a key diagnostic of the unsettled post-merger narrative, and different scenarios predict distinct evolution in its X-ray light curve.

• Due to its sky proximity to the Sun, sensitive X-ray monitoring of GW170817/GRB170817A has not been possible since a previous detection at 16 days post-burst.
• We present new, deep Chandra observations of GW170817/GRB170817A at 109 days post-burst, immediately after Sun constraints were lifted.
• The X-ray emission has brightened from a 0.3-8.0 keV flux of 3.6 x 10^-15 erg/s/cm^2 at 16 days to 15.8 x 10^-15 erg/s/cm^2 at 109 days, at a rate similar to the radio observations.