XMM-Newton Science Analysis System


omqualitymap (omqualitymap-1.5) [xmmsas_20230412_1735-21.0.0]

Setting of bit 2 (Smoke-rings)

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:

   $x (smoke ring) = a_1 + b_1 \times x + c_1 \times y + d_1 \times x +$ $e_1 \times y^{2} + f_1 \times x \times y + xCentre$

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

   and $a_1 = 9.6950, b_1 = 1.2052,$ $c_1 = 1.1027d-03, d_1 = 2.9117d-06$ $e_1 = 1.8790d-06, f_1 = 4.2347d-07$

   $y (smoke ring) = a_2 + b_2 \times x + c_2 \times y + d_2 \times x^{2} +$ $e_2 \times y ^{2} + f_2 \times x \times y + yCentre$

   and

   $a_2 = -4.8165, b_2 = 5.0884$ $c_2 = 1.2071, d_2 = -2.8810d-07,$ $e_2 = 1.549d-06, f_2 = -1.0783d-06$

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

Bit 2 of all the quality-image pixels within a circular region of radius 38 unbinned pixels, centred on the predicted coordinates of the smoke-ring, will be set.