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XMMíNewton CCF Release Note
XMMíCCFíRELí12
RGS Effective Area
C. Erd
October 4, 2000
1 CCF components
Name of CCF VALDATE List of Blocks
changed
CAL VERSION XSCS flag
RGS1 QUANTUMEF 0006 1998í01í01T00:00:00 CCD DESC, SI1,
SI2, SI3, SI4,
SI5, SI6, SI7, SI8,
SI9, RGA EFF,
RGA INTERCEPT,
RGA OBSCURATE
--- NO
RGS2 QUANTUMEF 0006 1998í01í01T00:00:00 CCD DESC, SI1,
SI2, SI3, SI4,
SI5, SI6, SI7, SI8,
SI9, RGA EFF,
RGA INTERCEPT,
RGA OBSCURATE
--- NO
2 Changes
This is the initial version that is distributed to the public.
Description of contents:
CCD DESC The thicknesses of all passive materials Al, MgF 2 , Siíoxide and Alíoxide layers are stored.
The numbers are taken from the component data sheets that were provided by the supplier.
The oxide layers are set = 0 for the time being and will be updated later, one there is better
knowledge about the contamination levels.
1

XMMíNewton CCF Release XMMíCCFíRELí12 Page: 2
SI1íí9 contain the thicknesses of the CCD's and list the respective values of the at the center of
the CCD's. Additionally for CCD's 5--9 of both cameras, the thickness were also measured by
an interferometer and are stored as relative variation from the center thickness.
RGA EFF The reflectivity of the grating plates is stored based on electroímagnetic calculations of
the interactions on the surface. This table is known as new efficiency 7í8 35.table and
is corrected for effects of large angle scattering. Starting point for these data are measureí
ments taken at the BESSY synchrotron and at NEVIS labs. The instrumental setup at the
synchrotron had a detector of limited angular size, and thus the measured reflections from the
grating plates had to be corrected for scatter [1, 2, 3, 4].
RGA INTERCEPT The interception is based on rayítracing done by Columbia and is accurate to within
a few percent.
RGA OBSCURATE The obscuration was generated with SciSim 2.1a20000427, using the configuration
files telescopeí1.cfg & telescopeí2.cfg that are part of the standard SciSim distribution.
The obscuration is only effecting EPIC MOS. The function is energy dependent with a dip of
about 4% at 7 keV.
The table is estimated to be correct to a few percent. The data only contain the oníaxis obscuí
ration. This is used by the CAL function CAL getRGAObscure [5] which scales the obscuration
as a function of the dispersion axis component of the offíaxis angle. No scaling is performed
along the crossídispersion direction, and the obscuration by the RGA is assumed constant as
a function of crossídispersion offíaxis angle. The effect of this simplification is estimated to be
! 3% (see also [6]).
3 Scientific Impact of this Update
First release.
4 Estimated Scientific Quality
The thicknesses of the CCD material layers are accurate to about 10%. The thickness of the CCD's
was measured for CCD's 5,6,8,9 of both RGS to an accuracy of 140 nm (one interferometer fringe),
and varies acoress the surface of the CCD's by about 10%. For the remainder of the CCD's an
average thickness is implemented, which therefore is accurate to about 10%.
An open issue is the thicknesses of the oxide layers and users should be aware that these are not
provided at this point in time.
A broad absorption feature at oxygen has been seen in the data, which is not yet understood
(see Figure 1).
The differential changes of the quantum efficiency of the CCD's as a function of surface (XDET
/ YDET) could not yet be calibrated with Xírays, and therefore there is a residual uncertainty

XMMíNewton CCF Release XMMíCCFíRELí12 Page: 3
Columbia
Astrophysics
Laboratory
XMM-RGS
Doc.: RGS-COL-CAL-00006
Page: 4
Auth.: Jean Cottam
Date: March 7, 2000
Figure 2: An aluminum oxide absorption curve, derived from the HRC calibration, superimposed on the
observed oxygen edges in PKS 0558 (top left), LMC X-3 (top right) and HR1099 (bottom).
Figure 1: Evidence for Oxygen absorption edge in RGS [7]

XMMíNewton CCF Release XMMíCCFíRELí12 Page: 4
of the effective area as a function of dispersion element which is estimated to be about 1%. The
effect of this uncertainty, however, is small, as the counts in each bin of the dispersion spectrum are
averaged over several CCD elements in the crossídispersion direction.
There were some indications noted during the calibrations that the quantum efficiency of CCD2
of RGS2 is overestimated by the CCF's. This is currently under investigations.
The results from comparisons of the effective area with EPIC and with the Chandra spectromí
eters are not yet available. From comparisons with ground calibrations it is expected that the
effective area is accurate at about 10%. Larger uncertainties (estimated at about 20%) are expected
for wavelengths ! 7 Ú A.
4.1 Effects on the Effective Area of MOS1 & MOS2
The simplification of the azimuthal variation of the obscuration by the RGA may result in overestií
mates of the effective area of the MOS cameras at energies ? 10 keV. This overestimate is gradually
increasing with increasing energy up to 20%.
References
[1] Jean Cottam. Final Model of the RGS Grating Efficiency. RGSíCOLíCALí99005, Columbia
University, May 1999. http://xmm.astro.columbia.edu/cal files/cal99005.ps.
[2] Jean Cottam. New Model of the RGS Grating Efficiency. RGSíCOLíCALí98023, Columbia
University, 1998. http://xmm.astro.columbia.edu/cal files/cal98023.ps.
[3] Jean Cottam. How to Use the RAWíEFFICIENCY.TABLE file. RGSíCOLíCALí97003,
Columbia University, 1997. http://xmm.astro.columbia.edu/cal files/cal97003.ps.
[4] Jean Cottam. Preliminary Model of the RGS Grating Efficiency. RGSíCOLíCALí97001,
Columbia University, 1997. http://xmm.astro.columbia.edu/cal files/cal97001.ps.
[5] Christian Erd, Phillipe Gondoin, David Lumb, Rudi Much, Uwe Lammers, and Giuseppe Vaí
canti. Calibration Access and Data Handbook. XMMíPSíGMí20, issue 1.0, ESA/SSD, September
2000.
[6] Christian Erd. Transmission of the RGA --- A Simulaí
tion with SciSim. XMMíPSíTNí38, ESA/SSD, August 2000.
http://xmm.vilspa.esa.es/calibrations/docs/rgs/RGA transmission.ps.gz.
[7] Jean Cottam. An Instrumental Oxygen Edge on RGS. RGSíCOLíCALí00006, Columbia Unií
versity, March 2000. http://xmm.astro.columbia.edu/cal files/cal00006.ps.