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W. Priedhorsky (Los Alamos National Laboratory), V. Arefiev, K. Borozdin (Space Research Institute Moscow)
Essentially all missions sensitive to cosmic X-rays have detected intense flashes of X-ray emissions, with typical timescales from seconds to hours. However, the net harvest from 25 years of observation is not much more than 100 flashes, plus another ~200 X-ray counterparts of gamma-ray bursts (GRBs). The existing sample is consistent with an isotropic sky distribution of sources. Our best estimate of the log N/log S distribution suggests that the slope of the distribution is significantly flatter than 3/2, ruling out an homogeneous source population. Only a few percent of x-ray flashes can be ascribed to the counterparts of classical gamma-ray bursts. Other candidate sources include magnetic energy release in nearby stars, transient accretion on nearby compact objects, and matter-choked versions of gamma ray bursts. Because the sample is so restricted, our understanding of X-ray flashes is reminiscent of gamma-ray bursts before BATSE. However, a dedicated experiment and modern, real-time follow-up could revolutionize our understanding. A simple non-focusing experiment could detect hundreds of events per year, and a wide-field focusing system based on lobster-eye x-ray optics could catalog thousands.
The author(s) of this abstract have provided an email address for comments about the abstract: wpriedhorsky@lanl.gov