So far, there are no corrections for the particle background component that may be different in the source and background regions. This is due to an insufficient knowledge of what the spatial distribution of the particle background will be. Therefore it is likely that the task will evolve after the launch of XMM, once the first in-flight calibrations are performed. These calibrations, which are critically required, should tell us about the most reliable way to estimate the particle component in a given region. Once this is known with sufficient accuracy, it will be fairly easy to modify backcorr.
The most straightforward way will be to decompose the background input spectrum as the sum of a “sky” component and a particle component computed in the background region. The correction will be done in such a way:
Bsrc(E) = (Asrc(E)/Abkg(E)) x (Bbkg(E) - Cbkg(E)) + Csrc(E) where we define: Bsrc(E) is the estimated background spectrum in the source region (output) Bbkg(E) is the background spectrum in the background region (input) Asrc(E) is the effective area integrated over the source region Abkg(E) is the effective area integrated over the background region Csrc(E) is the particle background in the source region Cbkg(E) is the particle background in the background region E is the energy.
The present version assumes that Cbkg and Csrc are equal to zero at all energies.
