X-ray flashes and X-ray rich Gamma Ray Bursts

TL;DR

X-ray flashes are soft, X-ray rich gamma-ray bursts undetected in gamma-ray monitors, with properties similar to GRB counterparts, and occur roughly 100 times annually, representing a significant subset of transient X-ray events.

Contribution

This paper demonstrates that X-ray flashes are essentially very soft, X-ray rich, untriggered gamma-ray bursts with peak energies up to 100 times lower than typical GRBs, expanding understanding of transient X-ray phenomena.

Findings

X-ray flashes are very soft, X-ray rich, untriggered gamma-ray bursts.

They have peak energies in X-rays up to 100 times higher than in gamma rays.

Approximately 100 such events occur annually.

Abstract

X-ray flashes are detected in the Wide Field Cameras on BeppoSAX in the energy range 2-25 keV as bright X-ray sources lasting of the order of minutes, but remaining undetected in the Gamma Ray Bursts Monitor on BeppoSAX. They have properties very similar to the x-ray counterparts of GRBs and account for some of the Fast X-ray Transient events seen in almost every x-ray satellite. We review their X-ray properties and show that x-ray flashes are in fact very soft, x-ray rich, untriggered gamma ray bursts, in which the peak energy in 2-10 keV x-rays could be up to a factor of 100 larger than the peak energy in the 50-300 keV gamma ray range. The frequency is ~100 per year.