Eight Years of Swift and the Promise and Limitations of GRB High Energy Correlations

Abstract I review the use of tantalizing correlations between high energy observables (flux, duration, and hardness) to potentially probe the intrinsic physical properties of GRBs and their host environments. Evidence from 77 GRBs with measured redshifts detected by the Swift experiment (and also from prior missions) suggests that these relations may have more to do with detection properties than physics. However, in the Fermi era, there has been strong use and continued interest in the GRB high energy correlations. Here I update the Swift study using the three times larger current Swift sample. I discuss the extent to which these relations appear to be intrinsic and the promise and limitations for using the relations to study the GRB intrinsic physics and, in particular, whether a common G RB energetics can be assumed in order to use the relations for cosmography. Even if GRBs do imprint information in these relations, separating out sample trends (ie., tendencies of the overall population) to tease out information applicable to one particular GRB (for example to infer its intrinsic flux for use in a Hubble diagram) may be very challenging.