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оригинального документа
: http://xmm.vilspa.esa.es/sas/8.0.0/doc/omlcbuild/node8.html
Дата изменения: Wed Jul 2 09:56:02 2008 Дата индексирования: Fri Sep 5 20:53:49 2008 Кодировка: |
subroutine omlcbuild read parameters 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 % calculate the ratio between counts inside and outside OSW: % PSF fraction = sum(PSF inside OSW)/ sum(complete PSF inside s_radius area) loop i = 0, ntimebins newTime = tStars + i * tDel % linear interp to get source rate linear interp to get background rate for each source bin % compute background subtracted rate error compute source rate error compute background rate error % scale background counts to the source area: % backround count rate = background count rate * source area / b_area % subtract background from the source: % background subracted rate = source rate - background count rate % correct source counts for the PSF fraction inside extraction area % (correction is to value expected within CAL (r=12 pixels) aperture): % source = source / PSF_fraction 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) end loop write time keywords to header write output rates file release handle end loop end subroutine omlcbuild