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B. E. Schaefer (Louisiana S. U.)
Four luminosity indicators are now known for Gamma Ray Bursts; the spectral lag, the ‘variability’, the number of peaks, and the minimum rise time. These indicators allow for the burst luminosity to be determined from the gamma ray light curves alone, and then for the burster’s luminosity distance to be determined. This suddenly allows for all BATSE and SWIFT bursts to have known distances and hence to be useful for demographics. In addition, SWIFT bursts can have their red shifts calculated in near real time, for example so that the very highest red shift bursts (z > 10) can be immediately recognized and followed up. A temporary difficulty is that SWIFT will be observing bursts with different energy bands than with BATSE (on which the luminosity indicators were calibrated), while the various indicators all change with energy even within a burst. This paper will report on the calibration of luminosity indicators as a function of the energy band for the light curves. The characterization of the changes with energy band has been made by measuring the indicators over a wide range of energy bands within a single burst for many bursts (including those with known optical red shifts). In addition, a theoretical model will be presented which explains these observed dependencies. And finally, the observed energy for the spectral peak will be shown as the observable parameter that can be used to substantially improve the accuracy of the four luminosity indicators.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.