This is the command that actually extracts light curves (binned, or unbinned in a form suitable for XRONOS), spectra and images from the event lists. Additionally, you can output the filtered events lists, which will speed up later analysis. Any combination of the the possible outputs is allowed.
All the entered region, timing and pha selections are automatically applied. The GTI's created by the select hk and select mkf commands will also 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 or 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 XIMAGE.
The output of the extract curve command is the QDP format ascii light curve file, xsel_curve.xsl. It 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 lcevents command is an unbinned light curve, xsel_unbinned.xsl, and a binned light curve, xsel_curve.xsl. The former is suitable for reading into XRONOS, in which case the binned curve can act as the background file. If you save the unbinned light curve, using the command
xsel > save lcevents
the background file will be saved with the proper name so that Xronos will recognize it. The unbinned light curve can be a quite large file, so be prepared when you give this command.
The spectrum is 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 XSPECT 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. Writing this list can, particularly on heavily used networks, slow down the extract command quite a bit, so it should not be routinely used.
Xselect does not automatically use this filtered event list in future work. However, the command
xsel > save events
will both save your event list, and give you the option of reading it back in.
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.