The Luminosity Function, Intrinsic Redshift Distribution, and Emission Timescale Distribution of Fermi-GBM GRBs From Collapsars

Despite decades of gamma-ray burst (GRB) observations, the luminosity function and intrinsic redshift distribution of GRBs are still not well understood. This is in part due to the dearth of redshift measurements for GRBs. A further complication however is the separation of these distributions into those describing long (>2s) GRBs and those describing short (<2s) GRBs. Observationally, long GRBs have been linked to a special class of Type Ib/c supernovae (i.e., collapsars) and short GRBs have been connected to binary neutron star mergers. However due to cosmological, relativistic, and observational effects, there is known cross-contamination between long and short GRB populations, making the strict classification of GRBs based on duration inadequate for correctly inferring the luminosity functions and intrinsic redshift distributions of GRBs. We propose using progenitor properties to classify GRBs rather than observed duration. In particular, we introduce a forward-folding method to fit Fermi Gamma-ray Burst (GBM) data for the luminosity functions, intrinsic redshift distributions, and emission timescale distributions of GRBs from collapsars and binary neutron star mergers. Here, we demonstrate the feasibility of our method and present preliminary results.