XMM-Newton Science Analysis System


bkgfit (ebkgmap-2.10.3) [22.0.0-9173c7d25-20250127]

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.