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Дата изменения: Wed Oct 22 17:31:27 2008
Дата индексирования: Tue Aug 18 14:54:20 2009
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XMM-Newton Science Analysis System


omdetect (omdetect-5.14.2) [???]

Meta Index / Home Page / Source Flagging Algorithms

SMOKE RINGS - bit 2

Any object with either a raw count-rate > 60 or flagged as having a mod-8 pattern is considered to have produced a smoke-ring - any other source within or near to the smoke-ring is flagged.

The predicted position of a smoke-ring is obtained from the following:

1. Compute the radial distance of the star (xstar, ystar) from the centre of the OM field of view (xCentre=1024.5, yCentre=1024.5)

2. Compute the position of the smoke-ring using:

   x (smoke ring) = real(a1 + b1 $\times$ x + c1 $\times$ y + d1 $\times$ x $\times$ x + e1 $\times$ y $\times$ y + f1 $\times$ x $\times$ y) + xCentre

   where x = xStar - xCentre, y = yStar - yCentre

   and a1 = 9.6950, b1 = 1.2052, c1 = 1.1027d-03, d1 = 2.9117d-06 e1 = 1.8790d-06, f1 = 4.2347d-07

   y (smoke ring) = real(a2 + b2 $\times$ x + c2 $\times$ y + d2 $\times$ x $\times$ x + e2 $\times$ y $\times$ y + f2 $\times$ x $\times$ y) + yCentre

   and

   a2 = -4.8165, b2 = 5.0884 c2 = 1.2071, d2 = -2.8810d-07, e2 = 1.549d-06, f2 = -1.0783d-06

   These coefficients were obtained by Simon Rosen from a least-squares fit to about 100 measured positions of stars and their associated smoke-ring.

Any source within a radius of 38 pixels is then flagged (the 38 was derived from an average radius of 26 + 12 photometry radius).