Investigating the Lag‐Luminosity Relation in the Swift Era with the Burst Alert Telescope (BAT)

We report on an investigation that confronts the lag‐luminosity relation (LLR), i.e. a surrogate redshift parameterization based upon an empirically determined anti‐correlation between the observed isotropic luminosity and the temporal lag between the arrivals of photon pulses in low (25–50 keV) and high (100–300 keV) energy bands, with observations of gamma‐ray bursts (GRBs) with Swift's Burst Alert Telescope (BAT). Our initial methodology is based upon a cross‐correlation function (CCF) analysis of 64 ms BAT light curves (temporal spectra), for a small subset of GRBs with observed spectroscopic redshift (zobs). Our preliminary results span 4 temporal decades and indicate an agreement with LLR, within the margins of error (excluding GRBs 980425 and 060218).