2 Data scan

We use 1024 ms time resolution BATSE data (DISCLA) from the ftp archive of the Goddard Space Flight Center at ftp://cossc.gsfc.nasa.gov/compton/data/batse/daily/.

The procedure of data reduction contains the following steps:

Step 1. Conversion of the original BATSE records adding to them artificial test bursts prepared from real rescaled bursts taken from the BATSE database.

Test bursts were added to the data at a random time with an average time interval 25000 s (i.e., the number of test bursts exceeds the number of real bursts).

Step 2. Data scan

We performed automatic check for the trigger conditions. Each trigger was followed by a human decision whether the trigger is a GRB candidate. The person performing the scan was unaware whether it was a real or a test burst. All candidates were recorded as a fragments of daily records saving all original information.

Step 3. Event classification.

The candidate events were discarded or classified as non-GRBs if they do not satisfy a number of criteria.

Step 4. Separation of tests bursts using the protocols generated on step 1.