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

TL;DR

This paper analyzes long-term X-ray observations of GW170817, revealing that the X-ray emission persists beyond previous predictions and challenges existing jet models, emphasizing the need for further multi-wavelength observations.

Contribution

It provides a comprehensive analysis of late-time X-ray data, clarifies discrepancies, and questions the adequacy of current jet models for GW170817's afterglow.

Findings

X-ray emission detected 3.3 years post-merger

No evidence for X-ray rebrightening at late times

Tension between observations and narrow jet models

Abstract

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 of about 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.