A Principal Component Analysis of the 3B Gamma‐Ray Burst Data

We have carried out a principal component analysis for 625 gamma-ray burstsin the BATSE 3B catalog for which non-zero values exist for the nine measuredvariables. This shows that only two out of the three basic quantities ofduration, peak flux and fluence are independent, even if this relation isstrongly affected by instrumental effects, and these two account for 91.6% ofthe total information content. The next most important variable is the fluencein the fourth energy channel (at energies above 320 keV). This has a largervariance and is less correlated with the fluences in the remaining threechannels than the latter correlate among themselves. Thus a separateconsideration of the fourth channel, and increased attention on the relatedhardness ratio $H43$ appears useful for future studies. The analysis gives theweights for the individual measurements needed to define a single duration,peak flux and fluence. It also shows that, in logarithmic variables, thehardness ratio $H32$ is significantly correlated with peak flux, while $H43$ issignificantly anticorrelated with peak flux. The principal component analysisprovides a potentially useful tool for estimating the improvement ininformation content to be achieved by considering alternative variables orperforming various corrections on available measurementsComment: Ap.J., accepted 12/9/97; revised version contains a new appendix, somewhat expanded discussion; latex, aaspp4, 15 page