<title>Limits on GRB early optical emission from Pi-of-the-Sky system</title>

Abstract

There is currently no experiment running that can perform non-accidental observations of Gamma Ray Bursts (GRB) optical counterparts from their very beginning, not mentioning seconds before the GRB. The main reason is the time that even small telescopes need for moving to the burst coordinates after receiving a trigger from a satellite and the time of the trigger propagation itself. "&#960; of the Sky" project overcomes this obstacle by introducing an array of CCD cameras aimed at simultaneous observations of large sky area - and thus the location of the GRB source during and even before the burst itself. The price for this solutions is, however, a lower magnitudo range, reaching only about 14^<i>m</i> - 15^<i>m</i>. In this paper we present a preliminary analysis, based on most of the currently available optical lightcurve measurements, indicating that a significant fraction of GRB optical counterparts should lie in this range.