XMM-Newton Science Analysis System


omphotom (omphotom-1.5.1) [xmmsas_20230412_1735-21.0.0]

Extended Sources

There are two methods available (phototype=-1 and -2) for recomputing the photometry of an extended source- For both cases, the total source-counts is the sum of the counts within the elliptical aperture specified by the parameters “aperturer, innera, outera, axialratio and pa”. Innera corresponds to the semi-major axis of the ellipse, axial-ratio to the ratio of the semi-major to semi-minor axes of the ellipse, and pa to the position-angle of the major-axis of the ellipse measured anti-clockwise from the +ve x-axis.

For phototype -1, the background at each pixel within the source is subtracted by interpolation using the background pixels within the background elliptical annulus. Each pixel is coincidence-loss corrected.

For phototype -2, the background at each pixel within the source is subtracted by using the given value for the background counts per pixel (parameter b̈ackground¨).