The Swift gamma ray burst space telescope has measured a GRB according to the link below. But why the oscillations in the measured gamma rate? Why wasn't just an increase detected, but also as big decreases? The average rate doesn't look to have increased during the burst. If averaged out over a minute the line would've been flat. Is there a fundamental astronomical explanation or has it to do with the technicalities of the instrument? http://www.universetoday.com/112194/possible-gamma-ray-burst-detected-in-andromeda-would-be-closest-ever-observed/
It turned out to be not real GRB event, just a false alarm.
My understanding is that, since the source is actually a steady X-ray source, you have a high count rate level at the base:
I am not expert of GRBs, but this high-oscillation behavior seems a characteristics of GRBs: you can see few examples here. In fact, the BAT time resolution is very high ($\sim100\mu s$), then you can resolve very tiny details of the source's timing event.
About the source variability, this is something more theoretical (so I can not be of much help), and there is no accepted theory, but qualitatively, in some models the gamma rays are produced by clumpy clouds of relativistically ejected material, which could account for the high variability indeed.
Other source: Wikipedia classification .
The caption for the graph in the article linked says "Raw Data". And as far as I am acquainted with GRB measurements, the scale of oscillations would fit quite well within error margins.
Final Verdict: Could be anything, background noise, instrumental noise/error. It is raw data. Without the characteristics and calibration of instruments, the only relevant thing that can be said is "Look, a GRB!"