... environment

Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).

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... operation

We will refer hereafter to the summed spectra as simply the MOS spectra.

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... nebula

The E-W and N-S ellipses have large and small semi-axis of $3.3\hbox{$^\prime$ }\times 1.1\hbox{$^\prime$ }$and $1.7\hbox{$^\prime$ }\times 1.1\hbox{$^\prime$ }$, respectively.

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... acceptable

We regard a fit as statistically acceptable when the null hypothesis probability computed from the reduced $\chi ^2$ and number of degrees of freedom is greater then 5%.

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