Statistical analysis of long GRBs' prompt emission and X-ray flares: multivariate clustering and correlations

TL;DR

This study analyzes long GRBs' prompt emission and X-ray flares using a large Swift dataset, revealing no strong correlations between prompt and flare properties but identifying two dominant flare classes based on variability and flux.

Contribution

It provides a comprehensive statistical analysis of prompt emission and X-ray flares, introducing a classification of flare types based on key parameters.

Findings

No evident correlation between prompt emission and flare parameters.

Positive correlation between flare variability timescale and duration.

Two dominant classes of X-ray flares driven by specific parameters.

Abstract

The extensive observations done by the X-ray telescope onboard Neil Gehrels Swift observatory has revealed the presence of late time flares concurrent with the decaying afterglow emission. However, the origin of these flares are elusive. In this work, we made use of the large database of Swift observations (2005 - 2020) of long GRBs to conduct a systematic statistical study between the prompt gamma ray emission and X-ray flares by characterising their temporal and spectral properties in terms of duration, quiescent period, peak flux, fluence, minimum variability timescale and spectral power-law index. The multi-dimensional database of parameters, thereby, generated was investigated by the principal component analysis which revealed there is no evident correlation between the different parameters of the prompt emission and X-ray flares. Furthermore, the correlation studies reveal that while there is a trend of positive correlation between the minimum variability timescale of flare and its duration, and a strong negative correlation with its peak flux, there are no such correlations observed in the prompt emission. Similarly, we find a positive correlation between the quiescent period and flare duration, and a negative correlation with the flare peak flux, while no such correlations are observed for the prompt emission of GRBs. Finally, among the X-ray flares, we find two dominant classes whose variations are driven by the minimum variability timescale, peak flux and fluences of the flares. A catalog of these different parameters characterising the prompt and flare emissions is presented.