The ‘amplitude’ parameter of gamma-ray bursts and its implications for GRB classification

Traditionally, gamma-ray bursts (GRBs) are classified in the T 90–hardness ratio two-dimensional plane into long/soft and short/hard GRBs. In this paper, we suggest to add the ‘amplitude’ of GRB prompt emission as the third dimension as a complementary criterion to classify GRBs, especially those of short durations. We define three new parameters f, f eff and f eff, z as ratios between the measured/simulated peak flux of a GRB/pseudo-GRB and the flux background, and discuss the applications of these parameters to GRB classification. We systematically derive these parameters to find that most short GRBs are likely not ‘tip-of-iceberg’ of long GRBs. However, one needs to be cautious if a short GRB has a relatively small f (e.g. f