CHINESE ACAD SCI,SHAANXI ASTRON OBSERV,XIAN 710600,PEOPLES R CHINA
; BEIJING NORMAL UNIV,DEPT ASTRON,BEIJING 100080,PEOPLES R CHINA
We present a test to investigate cosmological time dilation in long gamma-ray bursts (t(90) > 1.5 s) using V, the ratio of expected peak counts in 64 and in 1024 ms. The theoretical evolution of V with redshift shows that dimmer bursts have flatter peaks than brighter ones when we assume that (1) the bursters are at cosmological distances, (2) the bursts have standard exponential profiles, and (3) the burst peak duration follows a power law in narrowing with cosmological redshift energy. The calculated V-distribution of long bursts versus intensity in a Friedmann universe with Omega = 1 and Lambda = 0 is consistent with that found from previous results for long bursts. The estimated redshift is z similar to 2, and the time dilation factor with energy correction is similar to 1.8.