Spectral lags and counts of the RHESSI GRBs

The spectral lags and peak-count rates, which have been calculated for the first time in this paper, are studied, completing an earlier analysis of durations and hardness ratios. The analysis of the RHESSI database has already inferred the existence of a third group with intermediate duration, apart from the so-called short and long groups.

The first aim of this article is to discuss the properties of these intermediate-duration bursts in terms of peak-count rates and spectral lags. The second aim is to discuss the number of GRB groups using another statistical method and by also employing the peak-count rates and spectral lags. The standard parametric (model-based clustering) and non-parametric (K-means clustering) statistical tests together with the Kolmogorov-Smirnov and Anderson-Darling tests are used.