Jul 5 – 10, 2021
Europe/Rome timezone

A new source of X-rays in GW170817 3.4 years after the merger

Jul 5, 2021, 6:35 PM
Invited talk in the parallel session GRB 170817A and Binary Models GRB 170817A and Binary Models


Aprajita Hajela (Northwestern University)


GW170817 was detected 3.4 years ago as the first object to have both a gravitational wave and an EM counterpart. It provided the first confirmation of the connection between short gamma-ray bursts and binary neutron star mergers. For almost 3 years, the broadband EM observations of GW170817 from radio to X-rays showed a very well-behaved simple power-law spectrum, with no spectral evolution. The non-thermal emission across multiple wavelengths was best explained by a model with a structured jet viewed off-axis. However, observations after 3.4 years narrate a story different from expectations. We have observed a statistically significant excess in X-rays compared to the predictions from a structured jet model at the current epoch, which was not accompanied by an excess in radio. We investigate several theoretical models that could lead to such an excess in X-rays only, including a plausible emergence of a kilonova afterglow, which if true, would make it the first-ever to be observed. We finally discuss the implications of these observations on the nature of the merger remnant.

Primary author

Aprajita Hajela (Northwestern University)

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