 His most cited works include papers on the discovery of the origin of short gamma-ray bursts, the Swift satellite, Poisson statistics, observations of gamma-ray bursts at the edge of the visible universe, discovery of a relativistic tidal disruption event, and finding of two classes of active galactic nuclei (AGN) in the gamma-ray band.Gehrels was an astrophysicist with broad interests.He worked predominantly in the area of high energy astrophysics, studying explosive objects in the universe such as supernovae, gamma-ray bursts, gravitational wave transients and tidal disruption events (stars torn apart when they approach too close to a massive black hole).