SAS Watchout - EPIC spectra from narrow regions - XMM-Newton
Caution when analysing EPIC Timing Mode spectra extracted from very narrow regions
An issue has been identified with running the backscale task for PN Timing Mode spectral analysis.
In cases where the spectral extraction region is narrow (comprised of 6 or fewer RAWX columns), the calculated BACKSCAL value may be wrong by up to 4%.
This issue has been traced to an insufficient spatial resolution when calculating the BACKSCAL value, and will be fixed in the upcoming SAS release.
In the meantime, it is recommended to follow the below workaround, which affects step 8. in the respective analysis thread.
Instead of running:
backscale spectrumset=PNsource_spectrum.fits badpixlocation=PNclean.fits
backscale spectrumset=PNbackground_spectrum.fits badpixlocation=PNclean.fits
the user should run:
arfgen spectrumset=PNsource_spectrum.fits badpixlocation=PNclean.fits setbackscale=yes badpixelresolution=0.25
arfgen spectrumset=PNbackground_spectrum.fits badpixlocation=PNclean.fits setbackscale=yes badpixelresolution=0.25
and then proceed with the thread at step 9..