1 Introduction

A key feature of gamma-ray burst (GRB) phenomena is their bimodal duration distribution, which separates GRBs into two classes of events: those with durations shorter and longer than 2 s. The GRB durations are found to be anti-correlated with their spectral hardness ratios, the shorter GRBs being predominantly harder than the longer ones. Events in both classes, however, have the same peak intensity range and the same isotropic and inhomogeneous spatial distribution (Kouveliotou et al. 1993). The 4B BATSE catalogue shows that the number of events shorter than 1 s comprises $\sim$ 20% of all GRBs, although the numerical consistency of the sample varies slightly in different catalogues, depending on the instrumental trigger bin size. The bimodality suggests different geometries of emission sites or even different physical models for the central engine of the burst, but despite recent results from BeppoSAX and BATSE, the origin of the duration distribution is yet to be explained coherently.

A counterpart identification of a sub-second GRB would therefore be a crucial addition to the understanding of the underlying processes in GRB phenomena, but as yet no successful identification has been possible. As has been shown in the case of longer duration GRBs, and as may be realistically expected for the short GRBs, the rapid detection of an X-ray afterglow is, at least currently, a crucial step in allowing a swift search for optical and radio counterparts.

The BeppoSAX satellite is a natural candidate for the real-time monitoring of the high energy sky. The on-line scientific operations at the BeppoSAX Scientific Operation Centre (SOC) (Coletta et al. 1998) have the potential to be modified in order to perform a quick-look study of the short bursts category with as main scientific objective the detection and rapid position determination of sub-second GRBs.

We present an in-progress procedure for sub-second GRB detection to be implemented at the BeppoSAX SOC. This new program is complementary to the current proven procedure for GRB and afterglow detection and will extend the quick-look capabilities to the high-time resolution data domain. Extended and systematic analysis of GRB monitor (GRBM) triggers (Feroci et al. 1997) and Wide Field Camera (WFC) (Jager et al. 1997) light curves will be performed in order to select and study the short burst category.