Constraining cosmological parameters through gamma-ray bursts

Several independent gamma-ray burst luminosity indicators currently exist, two of which were used in this study. One relates the variability, V, or spikiness of a burst’s light curve to its luminosity, LV; while the other relates the time lag, τlag, between peaks of hard and soft photons to the luminosity, Llag. Both relations have been calibrated. If the redshift, z, photon flux, P, and mean photon energy, ε  , are known, then the burst’s luminosity LΩ=4πεPdL2, where dL is the luminosity distance for an assumed cosmological model. By carrying out a minimization procedure one can investigate the parameter space for certain cosmological parameters (for instance, ΩM), that bring LΩ in agreement with LV and Llag. The above procedure was carried out for a small sample of bursts for which z, V, τlag, and P are currently available. Given the paucity of current data, this procedure should be considered more as a proof of method. Our analysis indicates that at this stage it is very difficult to distinguish among the different cosmological models. However, as data becomes available from the Swift satellite, this procedure could prove a useful tool in probing and investigating cosmological models.