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XMM­Newton CCF Release Note
XMM­CCF­REL­101
OM Photometry
Bing Chen
January 4, 2002
1 CCF components
Name of CCF VALDATE List of Blocks
changed
CAL VERSION XSCS flag
OM COLORTRANS 0006 2000­01­01T00:00:00 COLORMAG No
2 Changes
The zero­points are updated using new routine calibration observations of spectrophotometric stan­
dards LLB 227 and GD153. New color­transformation is set by folding the Bruzual Persson Gunn Stryker
spactra with the in­flight response curves of the OM.
The actual values of the colour transformation are determined from the new algorithm described
in the current CAL handbook. Therefore the ALGOID keyword is set to 1 now.
3 Scientific Impact of this Update
This update should improve the accuracy of the OM photometry. This has been confirmed from
published photometry in M67 field and the ground­based calibration programme. However, since
OM photometric calibration is still on­going, a new update will be released soon once we have got
enough ground­based and OM in­flight observations.
1

XMM­Newton CCF Release XMM­CCF­REL­101 Page: 2
4 Estimated Scientific Quality
The colour transformation of model spectra was found to be good at the 0.05 mag level or even
better.
The accuracy of U,B,V calibration is generally better than 0.1 mag. The UV calibration is more
uncertain (especially for UVW2) than the visible calibration mainly due to variable contamination
in the ultraviolet wavelength.
5 Acknowledgements
Thanks to OM team members, especially Igor Antokhin for his contributions.