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Swift data

Earlier this week I went to Leicester University to visit the UK Swift team and learn how to analyse data from the Swift satellite. It was fun and I learned a lot, but there was too much to take in in one day.

Swift has three instruments onboard which are co-aligned, they all point at the same patch of sky. The first of these is the Burst Alert Telescope (BAT), a gamma-ray detector which observes a large part of the sky at once (it has a field of view similar to your eye) looking for new burst events. Within seconds of detecting a burst, the instrument provides the position of the event to an accuracy of four arcminutes which is then passed to the X-Ray Telescope (XRT) which has a smaller field of view than the BAT but can provide positions to an accuracy of five arcseconds. The final instrument is the Ultra-Violet and Optical Telescope (UVOT) which has an even smaller field of view but can provide a position accuracy of less than an arcsecond.

The satellite generally operates in "survey mode". In this mode, astronomers can suggest targets for observation. For example, if you look down the list of recent targets on the quick look site you may see some targets that begin "SN", these are supernovae which have been observed by Swift. Looking on there today they have recently observed: SN2005df, Tempel 1, Mrk684, Abell2029 plus a whole bunch of GRBs. But when a GRB occurs in the field of view of the BAT it enters what is called "burst mode". If the burst was significant (had a high enough "merit") to trigger burst mode, the position provided by the BAT is passed to the satellite control software which automatically causes the Swift to slew to the position which enables the use of the more accurate XRT and UVOT instruments.

For each burst there is plenty of data to look at. There is gamma ray data from the BAT, X-ray data from the XRT, and UV and optical data from UVOT. Each instrument provides both images and spectra of each event which can be used to characterise the bursts. This all helps with GRB research: the more data we have on these energetic events the better we can constrain the models and work out just what is going on to produce such intense bursts of radiation.

Part of our training involved actually using the software to analyse archive data from each of the instruments. Unfortunately we didn't have time to get through all of the tutorials but when I have some spare time I will install the software, finish the tutorials and post some pictures. In the mean time, if you are interested in some more technical details try the following pages at Nasa's Goddard Space Flight Centre: BAT, XRT, UVOT.

Posted by Megan on Wednesday 21st Sep 2005 (23:56 UTC) | Add a comment | Permalink

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