XMM-Newton Science Analysis System


evigweight (evigweight-1.8) [xmmsas_20201028_0905-19.0.0]

Pros and cons

Advantages: exact, easy to use (only one ARF), can deal with any complex spatial variation of the source.

Drawbacks: degradation of the statistical quality:

  $$\Delta O'(I)/O'(I) \; = \; \sqrt{\langle{w_{j}^{2}}\rangle}/\langle{w_{j}}\rangle \; \Delta O(I)/O(I)$$ (11)

from Eq.5 and 6. This is not a problem if the effective area is not varying much in the region considered ( $\sqrt{\langle{w_{j}^{2}}\rangle}/\langle{w_{j}}\rangle\sim 1$).