Документ взят из кэша поисковой машины. Адрес оригинального документа : http://xmm.vilspa.esa.es/sas/8.0.0/doc/ommag.ps.gz Дата изменения: Wed Jul 2 09:54:07 2008 Дата индексирования: Tue Oct 2 01:37:51 2012 Кодировка: Поисковые слова: mercury program

XMM-Newton Science Analysis System Page: 1
ommag
July 2, 2008
Abstract
Converts from count rates to magnitudes in the instrumental system.
1 Instruments/Modes
Instrument Mode
OM FAST
OM IMAGING
2 Use
pipeline processing yes
interactive analysis yes
3 Description
This task converts the 'list' of given counts to instrumental magnitudes in the appropriate instrumental
bandpasses. The 'list' can be a source-list from omdetect or a timeseries from evselect or trcon. The
output le will be a FITS le identical to the input source-list or time-series except that the count-rates
have been converted into instrumental magnitudes (in the specied lter bandpass - U , B, V , UV W 1,
UV M2, UV W 2, clear) and the new magnitudes written as an extra column in the source-list FITS le.
The program also calculates the limiting magnitude and writes the value in the source-list le. Presently
the computed magnitude error is the maximum of the two asymmetric ones.
Please note that no magnitude is computed for corrected count-rates greater than 1000- for such bright
sources the count rate is wrong because it is out of coincidence-loss correction. In these cases the
magnitude will be set to Null and the signicance to the negative of its signicance.
4 Parameters
This section documents the parameters recognized by this task (if any).
Parameter Mand Type Default Constraints
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set yes string none
OM OSW Source List lename
5 Errors
This section documents warnings and errors generated by this task (if any). Note that warnings and
errors can also be generated in the SAS infrastructure libraries, in which case they would not be docu-
mented here. Refer to the index of all errors and warnings available in the HTML version of the SAS
documentation.
Negative Count-Rate (warning)
There were instances of negative count-rate
corrective action:
Bad File Type (fatal)
Could not nd any compatibile blocks in set
GetFrameTime (fatal)
window%y0+window%dy > 256- can't continue
6 Input Files
1. OM OSW Source List le (taken from omdetect).
2. OM ODF Priority Window Data Auxiliary le
7 Output Files
1. Intermediate OM OSW source list (for input in to omatt).
8 Output Columns modied
1. CORR RATE - The count rate after the following corrections have been applied;
1) A further point-spread function correction may be applied, to extrapolate the counts from
12 to 35 pixels (presently only done for UV observations) 2) Correction for dead-time. 3)
Correction for the OM sensitivity-degradation. A key-word TDS CORR is added to the
table to record the correction value.
2. CORR RATE ERR - The error in the corrected count rates.
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9 Output Columns Added
1. PSF2 CORR - The point-spread function correction that may have been applied to extrap-
olate the corrected count rate from 12 to 35 unbinned pixels, dened by (corrected counts
at 35 pixels / corrected counts at 12 pixels) * 100. This correction is presently only done
for the UV lters, where the wings of the psf extend out a long way.
2. MAG The instrumental magnitude computed using the corrected count rate and using the
appropriate calibration constants for the lter.
3. MAG ERR The error in the computed instrumental magnitude.
10 New keywords added
1. CRMAG - The background limiting magnitude.
2. FRAMTIME - The CCD frame-time in milli-seconds.
3. DEADFRAC - The CCD dead-fraction.
11 Algorithm
subroutine ommag
Read in task parameters
Open OM OSW Source List file
Read in the detection-limit count rate.
Read in the source list table extension keywords from the primary header
Extract the background limiting counts from the SRLLIST binary-table
extension.
Convert this to a limiting magnitude.
Extract coordinates, photometry radii, count rate, count-error rate and
background counts, for each source, from the SRCLIST binary-table extension
Open OM ODF Priority Window Data Auxiliary file
Get the frame time from the OM ODF Priority Window Data Auxiliary file
Get the ccd mode
Loop over source list
For the ultraviolet filters, extraplolate the source count-rate to a
35-pixel aperture radius. Correct the count-rates for the CCD dead-time.
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Calculate the source magnitude using the corrected count-rate.
end loop
Write count rates and magnitudes to SRCLIST extension of OM OSW Source List file
Add the limiting magnitude and write it to the source-list file.
end subroutine ommag
12 Comments
 none
13 Future developments
 Asymmetric errors in the source list need to be implemented
References
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