On the impact of an intermediate duration X-ray burst on the accretion environment in IGR J17062-6143

TL;DR

This study analyzes the X-ray emission from IGR J17062-6143 after a Type I X-ray burst, revealing how the accretion environment and corona evolve, and detecting a potential gravitationally redshifted absorption line indicating surface burning ashes.

Contribution

First detailed spectroscopic monitoring of IGR J17062-6143 post-burst, identifying accretion disk recovery, corona evolution, and a candidate gravitationally redshifted line from surface ashes.

Findings

Inner accretion disk gradually recovers after burst

Transient corona evolution observed during flux dip

Detection of a 3.4 keV absorption line possibly from surface ashes

Abstract

We report on a spectroscopic analysis of the X-ray emission from IGR J17062-6143 in the aftermath of its June 2020 intermediate duration Type I X-ray burst. Using the Neutron Star Interior Composition Explorer, we started observing the source three hours after the burst was detected with MAXI/GSC, and monitored the source for the subsequent twelve days. We observed the tail end of the X-ray burst cooling phase, and find that the X-ray flux is severely depressed relative to its historic value for a three day period directly following the burst. We interpret this intensity dip as the inner accretion disk gradually restoring itself after being perturbed by the burst irradiation. Superimposed on this trend we observed a $1.5$ d interval during which the X-ray flux is sharply lower than the wider trend. This drop in flux could be isolated to the non-thermal components in the energy spectrum, suggesting that it may be caused by an evolving corona. Additionally, we detected a 3.4 keV absorption line at $6.3\sigma$ significance in a single $472$ s observation while the burst emission was still bright. We tentatively identify the line as a gravitationally redshifted absorption line from burning ashes on the stellar surface, possibly associated with ${}^{40}{\rm Ca}$ or ${}^{44}{\rm Ti}$.