M. L. Litvak — Page 2

arXiv1999

Average Cosmological Invariant Parameters of Cosmic Gamma Ray Burst

Average cosmological invariant parameters (ACIPs) are calculated for six groups of BATSE cosmic gamma-ray bursts selected by their peak fluxes on the 1.024 s time scale. The ACIPs represent the average temporal and spectral properties of these events equally in the observer frame of reference and in the co-moving frames of outbursting emitters. The parameters are determined separately for rise fronts and for back slopes of bursts, defined as the time profiles before and after the main peaks, respectively. The ACIPs for the rise fronts are found to be different for different intensity groups, while the ACIPs for the back slopes show no significant dependence on intensity. We conclude that emitters of bursts manifest standard average properties only during the back slopes of bursts.

astro-ph↗

arXiv1997

The Direct Test of Cosmological Model for Cosmic Gamma-Ray Bursts Based on the Peak Alignment Averaging

The cosmological origin of cosmic gamma-ray bursts is tested using the method of peak alignment for the averaging of time profiles. The test is applied to the basic cosmological model with standard sources, which postulates that difference between bright and dim bursts results from different cosmological red-shifts of their sources. The average emissivity curve (ACEbright) of the group of bright BATSE bursts is approximated by a simple analytical function, which takes into account the effect of squeezing of the time pulses with increasing energy of photons. This function is used to build the model light curve for ACEdim of dim BATSE bursts, which takes into account both the cosmological time- stretching of bursts light curves and the red-shifting of photons energies. Direct comparison between the model light curve and the ACEdim of dim bursts is performed, which is based on the estimated probabilities of differences between ACEs of randomly selected groups of bursts. It shows no evidence for the predicted cosmological effects. The 3 sigma upper limit of the average red- shift Zdim of emitters of dim bursts is estimated to be as small, as 0.1-0.5, which is not consistent with values 1 predicted by the known cosmological models of gamma-ray bursts.

astro-ph↗