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Дата изменения: Tue Aug 16 06:51:56 2005
Дата индексирования: Sat Dec 22 13:23:50 2007
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Поисковые слова: hst

XMM-Newton Science Analysis System


esensitivity (esensitivity-1.5) [xmmsas_20050815_1803-6.5.0]

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Source spectrum

eboxdetect in its present form makes no assumptions about the source spectrum, but I have not thought of a way to calculate any sort of generic sensitivity: it seems to me impossible to disassociate the detection sensitivity from the source spectrum. In other words, though the detection procedure may be generic, I would naturally expect it to function with different efficiency on source populations with differing spectra. Hence the spectrum of the source of interest must be supplied as a list of weights $\mu_i$ to the parameter weights. The interpretation of the $i$th weight $\mu_i$ is the total number of detected counts within energy band $i$ during a given exposure time, on the optic axis, assuming no chip gaps or bad pixels under the PSF. The weight values don't have to be normalized to 1 (esensitivity will do this itself), but it is not permitted to have them all = 0. A good way to get a generic set of weight values is to average normalized sets of SCTS values from an ensemble of sources detected in the same set of energy bands. Note that by `spectrum' is meant the detected spectrum of the x-ray source, that is the x-ray spectrum after multiplication by the instrument response function. Note also that this unfortunately introduces an approximation to the esensitivity algorithm, because due to the energy dependence of the mirror vignetting function the same source will have a slightly different detected spectrum at the edge of the field of view than at the centre.