2 The data

The EXPLORER data cover certain period during the year 1991, '95, '97, because maintenance and upgrades in the experimental apparatus, for a total of about 700 non continuous days. The signals coming from the antenna are sampled with a frequency of nearly 3 Hz and filtered with a Wiener-Kolmogoroff filter, matched to delta-like 1 ms signals for maximizing the signal to noise ratio (SNR). Due to different antenna behaviour, different event selection criteria were adopted. During the 1991 we have used a fixed lower threshold in energy, while during the subsequent years this threshold was chosen in an adaptive mode: we have considered an event when the SNR was $\ge 6$.For the whole period we selected only those events with an energy of $\le 10$ K, in order to not consider measurements presumably due to noise.

The data from BATSE detector are available in the 4B and Current Catalogs (Paciesas et al. 1998; Meegan et al. 1999). For our analysis we have considered the trigger times, peak fluxes and position informations.