Gamma-Ray Bursts - About Once a Day
9. "About Once a Day"
Scientists will tell you that the BATSE experiment aboard the Compton Gamma-Ray Observatory detects "about one GRB per day". What exactly does that mean? Once you detect a burst, do you not have to look for another 24 hours in order to see the next one? That would certainly be easier and cheaper! Or does "about one burst per day" mean no such thing? Below is given small part of the BATSE GRB catalog which scientists use to analyze the frequency of GRBs. We selected 20 bursts detected during August 1996 from the catalog of over 7500 bursts.A note about GRB names. Each burst is given a unique name. They contain a 6 digit number "yymmdd" for the two-digit year, two-digit month, and two-digit day of month of the burst occurrence. When more than one GRB is detected on the same calendar day, the suffixes A, B, C, etc are added after the yymmdd, usually depending on how bright each burst was relative to the other bursts of that day. So for example, 920503B refers to the second brightest burst detected on May 3, 1992.
Catalog Entry #
5561
5562
5563
5564
5565
5566
5567
5568
5569
5570
5571
5572
5573
5574
5575
5576
5580
5581
5585
5586
• From these data, determine the mean, median, and mode of the data set which represents the time intervals between GRB detections.
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• What do these measures of central tendency tell us about the data?
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• What is the maximum time interval between successive bursts?
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• What is the minimum interval between successive bursts?
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• What do all of these values tell you about how you must organize your observing program in order not to miss a burst?
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Extension:
Get on the World Wide Web and download other sections of the BATSE GRB catalog (the 4th version of the catalog, which is the most current through July 1999) is available online at http://www.batse.msfc.nasa.gov/batse/grb/catalog/4b/4br_basic.html). Do you obtain the same results, no matter which section of the catalog list you take? Caution: be careful about using the most recent data...before verification, it can contain many false triggers, i.e. listings for bursts that never really happened!
