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XMM-Newton Science Analysis System


bkgfit (ebkgmap-1.2) [xmmsas_20070708_1801-7.1.0]

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Uncertainties in the coefficients:

It is known (see eg [1]) that the ML estimator $L$ as defined in equation 1 behaves approximately like $\chi^2$, but with an additive offset that varies with the nature of the fitting function. The variance matrix of the fitted model parameters can therefore be obtained (see [1] again, chapter 8) from twice the inverse of the Hessian or curvature matrix $\mathbf{C}$ which is defined in equation 3.