Gamma-ray bursts are high energetic flashes of gamma-rays, who were first observed in the sixties. In 1997 it was discovered that they occured at several gpc distance. At the time of this research, possible causes were thought to be two colliding neutron stars, or a collapsing superheavy star of 30 solar masses or more. Since there are two kinds of grb's, it was thought that both theories were plausible: the colliding neutron stars could cause short bursts of two seconds or less, and the hypernova's could be the source for the longer grb's.
In this research we looked at several measurements made by the BATSE instrument on board the Compton Gamma Ray Observatory. We searched for a connection between the grb itself and the afterglow following the flash. First we divided the grb's into two groups: the ones with and the ones without an afterglow. BATSE measured their energy levels in four channels: 50KeV - 50 KeV; 50KeV - 100 KeV; 100 KeV - 300 KeV; > 300 KeV. When you divide one channel by the other, you get an hardness ratio. Since it's difficult to determine the starting and end point of a grb, we looked at two periods: at T50 50% of the grb is being studied, namely from 25% till 75%, and at T90 90% of the grb is studied, namely from 5% till 95%.
This study showed that there is no observable difference between T50 and T90, altough the latter one covers a larger period and is thus advised to be used. Furthermore we discovered a linear relationship between the main amount of grb's when looking at the hardness ratios of H3/2 and H3/21. This relationship is not visible at other hardness ratios. It also turned out that it was not possible to make a subdivision for grb's with an afterglow: every one of them is unique, as is the same case with the ones without an afterglow.
H-ratio's 3/21 plotted against T90.
H-ratio's of all known grb's plotted against T90.
On the left GRB 7343 is shown for all channels, while on the left all four separate channels are shown.
When we worked on the hardness ratios, dr. Chryssa Kouveliotou, listed by Time Magazine among the 25 Most Influential People in Space and an authority in the field of gamma-ray bursts, walked by. She recognized what we were working on, and immediately noticed some strange deviations in the graphs. This got her excited, and she was eager to find out what caused them. She was in a hurry tough, and was forced to leave. We then looked more closely at the graphs, and discovered that the strange deviations were caused by a stupid human error.