SPECTRAL EVOLUTION OF SHORT GRBS ON SUB-MILLISECOND TIME SCALE

There has been growing consensus that short and long GRBs are associated with two different populations of astrophysical sources: mergers and SN explosions, respectively. While temporal properties of short and long GRBs could be considered with similar depth and accuracy, patterns of spectral variability of the 2 classes of GRBs are much harder to compare. This is due to the fact, that short GRBs exhibit variability on time scales shorter than 1 ms and count rate, measured at such short time scales, is not sufficient for reliable spectroscopy even for the brightest events. In this situation, any new possibility to look at spectral evolution of short GRBs on sub-millisecond time scales in terms of spectral parameters, may provide more solid background for theoretical analysis. In this paper we present analysis of spectral evolution of short GRBs in terms of Band spectral function parameters, using the earlier developed Global Fit approach (GFA).