What Causes GRB Time Dilation?

That groups of apparently faint GRBs are detected as having longer durations than groups of apparently bright GRBs is well known, and is sometimes referred to as “time dilation.” Reasons for GRB time‐dilation remain ambiguous, and likely convolve intrinsic effects, cosmological effects, and even detector threshold effects. With redshifts of a significant number of GRBs now in hand, attempts at an accurate deconvolution are now possible, and carry interesting cosmological implications. Toward this goal, we use redshift estimates of a large subset of BATSE GRBs obtained by Band et al. (2004) from the lag‐luminosity relation of Norris et al. (2000). Inspection of different sets of GRBs separated in estimated redshift appear to qualitatively show the expected time‐dilation effect, indicating that cosmological information was and is convolved in GRB BATSE data.