omlcbuild (omlcbuild-1.41) [xmmsas_20230412_1735-21.0.0]

Algorithm

subroutine omlcbuild read parameters if requested the use of the Imaging-window background: get handle on the Imaging-mode window file remove all the source from this image calculate the average value of the remaining pixels and use this value as the background estimate loop i=0, nSources get handle on source rates file get handle on source region file if (exposure IDs are different) issue warning get handle on background rates file get handle on background region file if (exposure IDs are different) issue warning if (exposure ID source != exposure ID background) call fatal get source extraction radius = s_radius get CAL coincidence loss correction radius = cal_radius get photometry radius = ph_radius calculate the instrumental limiting magnitude from the detection limit count rate compute area of source region = s_area compute area of background region = b_area tStart = max(tBack[0], tSource[0]) eEnd = min(tBack[nBack-1], tSource[nSource-1] tDel = (tEnd - tStart)/(nSource-1) determine the PSF fraction within the source extraction region determine the PSF fraction within the `background` extraction region loop i = 0, nTimeBins newTime = tStars + i * tDel linear interp to get background rate for each source bin compute source rate error compute background rate error if the use of the Imaging-mode background is requested, use the earlier calculated background value, otherwise: set up equations for counts recorded in each region. These allow for (point) source contamination of the `background` region: C(S+B) = PSF(S+B) *S + NPIX(S+B) * Bpix C(B) = PSF(B) *S + NPIX(B) * Bpix solve these for S, the source counts over the coincidence loss (CL) region (ie the CAL aperture) and for Bpix, the background counts per pixel. scale background to the CAL aperture area: bkgnd count rate = background count rate * cal_radius area / s_area recombine these bkgnd and source rates (now determined for the CAL aperture) apply CL correction to the source+bkgnd rate apply CL correction to the bkgnd rate CL corrected source rate = source+bkgnd rate - bkgnd rate correct result for dead time correct for PSF beyond the 12 pixel Cal aperture (mainly for UV) compute the source magnitude and insert it into the source list table perform the variability tests on rebinned net source counts ($\chi^2$ and Kolmogorov-Smirnov statistics) by calculating the mean count rate and variance; testing the null hypothesis (the source is not variable) by: - processing a $\chi^2$ fit between the count distribution and constant distribution whose value is equal to the observed mean count - processing the Kolmogorov-Smirnov test between the cumulative probability functions of the observed count distributions and theoretical Gaussian distribution whose mean and variance are both equal to the observed mean count. calculate the maximal deviation of the light curve from its mean value and express this value in the number of r.m.s. $\sigma_1$. introduce the variability tests data into the source list table end loop write time keywords to header write output rates file release handle and memory end loop end subroutine omlcbuild

XMM-Newton SOC -- 2023-04-16