XMM-Newton Science Analysis System


eregionanalyse (especget-1.54) [xmmsas_20230412_1735-21.0.0]

Background subtracted source counts

The total counts emitted by the source, found from the counts in the source region minus the contribution from the background divided by the encircled energy fraction.

  $$counts = (S - B\times A_{S} / A_{B} ) / EEF$$ (1)

where $S$ is the counts within the source region, $B$ is the total background counts and $A_{S}$, $A_{B}$ are the area of the source and background regions respectively.

The background is simply scaled by the respective box areas; no vignetting correction of any sort is made. The error is calculated from photon statistics as:

  $$error = \sqrt{ S + B \times (A_{S} / B_{S})^{2} }$$ (2)

NB: This is only reliable for circular source regions, see section 3.2.9