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XMM-Newton CCF Release Note
XMM-CCF-REL-136
OM Flux conversion factors
Bing Chen
December 10, 2002
1 CCF components
Name of CCF VALDATE List of Blocks
changed
CAL VERSION XSCS ag
OM COLORTRANS 0008 2000-01-01T00:00:00 COLORMAG No
2 Changes
Flux conversion factors for U, B, V, UVW1, UVM2 and UVW2 lters are added in the keyword in
the colormag extension. These ux conversion factors help users to get a rough estimation of ux
(expressed in erg=cm 2 =s=A) from countrates directly. The zeropoints and color-transformations in
this CCF are not changed.
3 Scientic Impact of this update
No SAS task uses these ux conversion factors. Therefore, the scientic outputs from SAS are not
changed. The users need to derive the ux using these factors external to SAS.
4 Estimated Scientic Quality
We have derived the ux conversion factors from three white dwarfs (LBB227, BPM16274 and
GD153). For each lter, if you multiply the countrates (counts/s) from SAS by the following
numbers, you will get the ux (erg=cm 2 =s=A).
1

XMM-Newton CCF Release XMM-CCF-REL-136 Page: 2
V B U UVW1 UVM2 UVW2
Flux conversion factors 2.178E-16 1.041E-16 1.776E-16 4.169E-16 1.754E-15 5.242E-15
We should point out, these ux conversion numbers provide an approximate measurement of the
ux without a priori knowledge of the spectral type. For an accurate determination of the ux, the
users are invited to check our SAS watchout page to nd ux conversion factors for a given spectral
type.
5 Test procedures
This new CCF has been tested using SAS public version 5.3.3. The OM calibration observation
in the eld of GD153 in the Rev. 472 has been run through SAS "omichain" task. Everything is
nominal.
6 Summary of the test results
In the led of GD153, I randomly took a star with countrates (counts/s) 119.55, 143.79, 73.114,
10.543, 0.210, 0.092 for V, B, U, UVW1, UVM2, UVM2, respectively. Then I multiplied these
countrates by the conversion factors shown in section 3 to get the ux. Figure 1 show the ux
against eective wavelengths for this star (lower plot) and GD153 (upper plot). From the spectral
shape, we can say that this unknown star has spectral type similar to a K star.
7 Expected updates
A update is expected before March, 2003 when the analysis of new white dwarf observations is
nished.
8 Acknowledgements
Thanks to OM team members, especially Alice, Elizabeth, Antonio, Simon for their contributions.

XMM-Newton CCF Release XMM-CCF-REL-136 Page: 3
Figure 1: The ux as a function of wavelength for white dwarf GD153 (upper plot) and a randomly
chosen star (lower plot) in the eld of GD153.