Accurate flux calibration of GW170817: is the X-ray counterpart on the rise?

X-ray emission from the gravitational wave transient GW170817 is well described as non-thermal afterglow radiation produced by a structured relativistic jet viewed off-axis. We show that the X-ray counterpart continues to be detected at 3.3 years after the merger. Such long-lasting signal is not a prediction of the earlier jet models characterized by a narrow jet core and a viewing angle approximate to 20 deg, and is spurring a renewed interest in the origin of the X-ray emission. We present a comprehensive analysis of the X-ray dataset aimed at clarifying existing discrepancies in the literature, and in particular the presence of an X-ray rebrightening at late times. Our analysis does not find evidence for an increase in the X-ray flux, but confirms a growing tension between the observations and the jet model. Further observations at radio and X-ray wavelengths would be critical to break the degeneracy between models.

Automated summary

The X-ray emission from the GW170817 gravitational wave transient is described as non-thermal afterglow radiation produced by a structured relativistic jet viewed off-axis, and continues to be detected 3.3 years after the merger. While there is no evidence of an increase in X-ray flux, a growing tension between observations and the jet model is confirmed, prompting the need for further observations at radio and X-ray wavelengths to break the degeneracy between models.