Method of separation of celestial gamma‐ray bursts from solar flares

We recently discovered 217 ‘‘new’’ celestial gamma‐ray burst candidates from the ‘‘new’’ burst search of the PVO real time data base.¹ The burst search covered the time period from September 1978 to July 1988. Sixty were confirmed by at lest on other spacecraft, e.g., ISEE‐3, V‐11, V‐12, etc. None triggered the PVO high time resolution memory. In this paper we describe a new algorithm based ont eh relationship between time width T_w and hardness ratio HR, to distinguish cosmic gamma‐ray bursts from solar flares without knowing the directions of the events. The criteria for identification as a gamma‐ray burst candidate are: If T_ww≤a then HR≥bT_w, or T_w≳a then HR≳c. Otherwise, the event is a solar flare candidate. Here, a, b, and c are parameter which differ for different gamma‐ray burst detectors. For PVO, a=18.8 s, b=(1.38/18.8) s⁻¹, and c=1.38. This algorithm was tested with 83 triggered and 60 nontriggered confirmed gamma‐ray burst and 30 confirmed solar flares from PVO.