3‐10 keV and 0.1 to 2 MeV observations of four gamma‐ray bursts

Four catalogued γ‐ray bursts that occurred between 79/3/7 and 79/7/31 have been observed over the 3‐10 keV range by a joint NRL/Los Alamos experiment on the Air Force P78‐1 satellite. The bursts were also well observed by members of the interplanetary network. In this paper we present hardness ratios, X‐ray/γ‐ray luminosity ratios, and time histories. The most significant results presented herein can be summarized as follows: (1) Gamma‐ray bursters can emit fairly strongly at X‐ray energies near the time of the γ burst with Lx/Lγ∼.02 (Lx∼103− ergs s−1, 3‐10 keV, assuming a distance of 1 kpc). (2) The centroid of the X‐ray emission generally lags the γ‐ray centroid, but there is also evidence for one or more types of X‐ray precursor activity. (3) The γ‐ray hardness ratios were not highly variable for these particular events. However, there is some evidence that the γ‐ray spectra softened near the ends of the bursts when the X‐ray/γ‐ray ratios were high. (4) The X‐ray/γ‐ray power law number index during tim...