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Questions about Swift? Try our guide to Swift or the guide to data processing and analysis. If these don't solve your problem, please feel free to e-mail us at swifthelp@le.ac.uk.

List of acronyms and abbreviations

We are located in the Department of Physics & Astronomy , at the University of Leicester (directions).

Extracting an image using XSELECT

Here we demonstrate how to extract an image over various energy bands. The PC data from the first observation of GRB 091029 are used as an example. 

>xselect
              **  XSELECT V2.2a  ** 
> Enter session name >[xsel]
xsel:ASCA >read event
> Enter the Event file dir >[./]
> Enter Event file list >[ ] sw00374210000xpcw3po_cl.evt

Got new mission: SWIFT
> Reset the mission ? >[yes]

 Notes: XSELECT set up for      SWIFT
 Time keyword is TIME       in units of s
 Default timing binsize =   5.0000

Setting...
 Image  keywords   = X          Y           with binning =    1
 WMAP   keywords   = X          Y           with binning =    1
 Energy keywords   = PI                     with binning =    1

Getting Min and Max for Energy Column...
Got min and max for PI:     0   1023

Got the minimum time resolution of the read data:   2.5073
MJDREF =  5.1910000742870E+04 with TIMESYS = TT
 Number of files read in:            1

******************** Observation Catalogue ********************

Data Directory is: /home/work/kpa/2009/grb091029/00374210000-xrt/
HK Directory is: /home/work/kpa/2009/grb091029/00374210000-xrt/

        OBJECT      OBS_ID      DATE-OBS    DATAMODE

      1 GRB091029 ( 00374210991 2009-10-29T PHOTON

> extract image

extractor v5.11    11 May 2009
 Getting FITS WCS Keywords
 Doing file: /home/work/kpa/2009/grb091029/00374210000-xrt/sw00374210000xpcw3po_cl.evt
100% completed

          Total      Good    Bad: Time     Phase     Grade       Cut
           5858      5858            0         0         0         0
===============================================================================
    Grand Total      Good    Bad: Time     Phase     Grade       Cut
           5858      5858            0         0         0         0
   in  15790.     seconds
 Image            has     5858 counts for 0.3710     counts/sec


> plot image
PC image
XSELECT output

The image above was extracted for the full energy range of the XRT: about 0.2-10 keV. However, the data can be filtered to produce images over any energy band within this range, using the command filter pha_cutoff, where the range must be given in terms of channels. For the XRT, 1 channel = 10 eV. 

> filter pha_cutoff 30 100
> extract image
> save image 0.3-1keV.im
> clear pha_cutoff
> filter pha_cutoff 100 1000
> extract image
> save im 1-10keV.im

The commands above extract and save images over soft (0.3-1 keV) and hard (1-10 keV) bands for the full field of view. Filtering on regions and time can also be performed, as explained in the Introduction to XSELECT thread.

Index