Extracting products and applying filters

Extract is the command that actually extracts light curves, spectra and images from the event lists. Additionally, you can output the filtered events lists, which will speed up later analysis (this is not currently supported for ASCA GIS MPC data). Any combination of the possible outputs is allowed.

All the entered intensity, region, detector, grade, timing, pha and phase filters are automatically applied. The GTI's created by the SELECT MKF commands will be used. Also the binsize for light curves, and the rebinning factors for the spectra and the image, which have been entered with the SET command, are applied. If any product files have been made, for example the output files from the select event commands, they will be used in place of the original files.

The output of the extract image command is an image in the primary extension of the FITS file xsel_image.xsl. It has all the keywords necessary for input into SAOimage, SAOtng, or XIMAGE.

The output of the extract curve command is both an ascii QDP format, and a FITS format light curve file, xsel_curve.xsl. The former also contains, as comments, the accumulated spatial, timing and pha selections. This is primarily intended for a quick look, and to aid in further timing selection.

The output of the extract spec command is a spectrum, contained in the first extension of the FITS file xsel_hist.xsl, which also contains a weighted map image in the primary extension of the file. All the keywords necessary for XSPEC are written into the spectrum file.

The output of the extract events command is a FITS event list. The resultant GTI's are contained in the second extension of the file. This events list is suitable for input to the new, FITS-reading Xronos. However, if the input data to Xselect is not time ordered, this events list will not be either, so you will need to process it through the FMEMSORT ftool before passing it to Xronos. By default only the events and GTI extensions are written. If the copyall=yes option is set then the extra extensions from the (first) input events file are appended to the output file.

As mentioned above, Xselect will continue to use this filtered event list in future work. If you want to save it, the command

xsel >  save events

The extractor also outputs an ascii and a Xronos window format file containing the resultant timing selections. The former can be viewed with the command

xsel >  show goodtime

These resultant timing selections, in ASCII and Xronos format, as well as the event list, the spectrum, light curve and image, can be saved with the save command.

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Last modified: Tuesday, 10-Jan-2023 11:03:00 EST

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