XMM-Newton Science Analysis System

omsrclistcomb (omsrclistcomb-2.23) [xmmsas_20211130_0941-20.0.0]

# Algorithm

```subroutine omsrclistcomb

Read in all OSW source lists

Collate all sources into a main list

For each source in the list, i

if this source has not been identified with other sources
list-of-same-sources(1) = i
no-of-same-sources = 1
endif

Loop over all other sources in the main list, j

if ( i /= j) then

If the position of source i is the same as position of source j
(to within  tolerance nsigma and systematic error) then

no-of-same-sources++
list-of-same-source(no-of-same-sources) = j

Endif
End loop

Loop over same sources list, m

Loop over rest of same source list, n

if source m and n are in the same OSW

flag as being in the same OSW

endif
end loop
end loop

Loop over sources in same OSW

use nearest source and delete others from list_of_same_sources

end loop

now we have a list of sources that are the same

end for

create an index array giving the order of the sources in increasing
Right-Ascension.

create a matrix of magnitudes containing n independent sources and m filters

set matrix to NaN

Loop over all independent sources

find weighted mean of source position

For each filter

if source has been observed in filter more than once
find mean position and magnitude.
endif

end for

end loop

Loop over matrix

compute colours in standard system from CAL colour transformation
matrices

end loop

define possible colours (mag1-mag2) e.g. (B-V) and (U-B) etc

for each colour combination

if ANY(matrix(mag1) /= NaN) and ANY(matrix(mag2) /= NaN) then
compute colour and error
endif

endfor

for each independent source

Convert any undetermined (eg standard magnitude, colour) parameter value
to NULL and then insert the source information at its correct Right-Ascension
position in table.

Endfor

add a SRC-ID column to each OSW source list
for each OSW source
write the appopriate source number from the observation source list
endfor

end subroutine omsrclistcomb
```

XMM-Newton SOC -- 2021-11-30