Spectral Cross-calibration of the Konus-Wind, the Suzaku/WAM, and the Swift/BAT Data using Gamma-Ray Bursts

TL;DR

This study uses simultaneous gamma-ray burst observations to perform spectral cross-calibration among Konus-Wind, Suzaku/WAM, and Swift/BAT instruments, revealing systematic differences and trends in their measurements.

Contribution

First use of simultaneous GRB observations for spectral calibration to identify systematic discrepancies among these instruments.

Findings

BAT constant factor is 10-20% smaller than Konus-Wind

Low-energy photon index becomes steeper with BAT data included

High-energy photon index agrees within 0.2 across instruments

Abstract

We report on the spectral cross-calibration results of the Konus-Wind, the Suzaku/WAM, and the Swift/BAT instruments using simultaneously observed gamma-ray bursts (GRBs). This is the first attempt to use simultaneously observed GRBs as a spectral calibration source to understand systematic problems among the instruments. Based on these joint spectral fits, we find that 1) although a constant factor (a normalization factor) agrees within 20% among the instruments, the BAT constant factor shows a systematically smaller value by 10-20% compared to that of Konus-Wind, 2) there is a systematic trend that the low-energy photon index becomes steeper by 0.1-0.2 and Epeak becomes systematically higher by 10-20% when including the BAT data in the joint fits, and 3) the high-energy photon index agrees within 0.2 among the instruments. Our results show that cross-calibration based on joint spectral analysis is an important step to understanding the instrumental effects which could be affecting the scientific results from the GRB prompt emission data.