2012ApJ...755...55Z

A correlation between the peak luminosity and the peak energy has been found by Yonetoku et al. as L_p∝E ^2.0_p, i_ for 11 pre-Swift long gamma-ray bursts (GRBs). In this study, for a greatly expanded sample of 148 long GRBs in the Swift era, we find that the correlation still exists, but most likely with a slightly different power-law index, i.e., L_p∝ E ^1.7_p,i. In addition, we have collected 17 short GRBs with necessary data. We find that the correlation of L_p∝ E ^1.7_p,ialso exists for this sample of short events. It is argued that the radiation mechanism of both long and short GRBs should be similar, i.e., of quasi-thermal origin caused by the photosphere, with the dissipation occurring very near the central engine. Some key parameters of the process are constrained. Our results suggest that the radiation processes of both long and short bursts may be dominated by thermal emission, rather than by the single synchrotron radiation. This might put strong physical constraints on the theoretical models.