XMM-Newton Science Analysis System


arfgen (arfgen-1.104) [xmmsas_20230412_1735-21.0.0]

Using an image mask

A spectrum may be produced by filtering events using a 2-dimensional mask in either sky or detector coordinates. This is supported for the calculation of the ARF of an extended source. To maintain the resolution of the image mask it is important to use a finely binned detector map within arfgen (see section 5.3). Preferable is a detector pixel image which just encompasses the masked region, otherwise a flat detector map will be ok.

e.g.

arfgen spectrumset=spectrum.ds extendedsource=yes detxbins=400 detybins=400
detxoffset=10000 detyoffset=10000 withdetbounds=yes

The chip gap and bad pixel/column corrections will be correctly calculated if the detector map is fine enough. The backscale task will also produce the correct area calculation in this case.