Statistical Study of the Swift X-ray Flash and X-ray Rich Gamma-Ray Bursts

TL;DR

This study statistically analyzes the properties of X-ray flashes, X-ray riches, and classical gamma-ray bursts from the Swift BAT3 catalog, revealing their similarities, differences, and associations with supernovae.

Contribution

It provides a comprehensive statistical comparison of XRFs, XRRs, and C-GRBs, including their properties, correlations, and host galaxy characteristics, based on the latest Swift data.

Findings

XRFs and XRRs are mostly long, low-luminosity GRBs.

All three types follow similar energy correlations.

XRFs are more often associated with supernovae.

Abstract

We build a comprehensive sample to statistically describe the properties of X-ray flashes (XRFs) and X-ray riches (XRRs) from the latest third Swift Burst Alert Telescope (BAT3) catalog of Gamma-ray bursts (GRBs). We obtain 81 XRFs, 540 XRRs, and 394 classical GRBs (C-GRBs). We statistically explore the different properties of the $\gamma$-ray prompt emission, the X-ray emission, the X-ray lightcurve type, the association with supernovae (SNe), and the host galaxy properties for these sources. We confirm that most XRFs/XRRs are long GRBs with low values of peak energy $E^{obs}_{peak}$ and they are low-luminosity GRBs. XRFs, XRRs, and C-GRBs follow the same $E_{X,iso}$-$E_{\gamma,iso}$-$E_{peak,z}$ correlations. Compared to the classical GRBs, XRFs are favorable to have the association with SN explosions. We do not find any significant differences of redshift distribution and host galaxy properties among XRFs, XRRs, and C-GRBs. We also discuss some observational biases and selection effects that may affect on our statistical results. The GRB detectors with wide energy range and low energy threshold are expected for the XRF/XRR research in the future.