epic flux comparison from 2xmm sources
DESCRIPTION
EPIC flux comparison from 2XMM sources. S. Mateos, R. Saxton, S. Sembay & A. Read. Sources Used. Point-like sources from 2XMM detected in 2+ cameras > 200 counts in each camera Off-axis angle 0-12 arcmins F 2-10 > 6E-12 have been excluded to avoid pile-up effects. - PowerPoint PPT PresentationTRANSCRIPT
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EPIC flux comparisonfrom 2XMM sources
S. Mateos, R. Saxton, S. Sembay & A. Read
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Sources Used• Point-like sources from 2XMM detected in 2+ cameras
• > 200 counts in each camera
• Off-axis angle 0-12 arcmins
• F2-10 > 6E-12 have been excluded to avoid pile-up effects
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Count rate – flux conversion
Count rates converted to fluxes using energy conversion factors (ECF) which are based on a spectral model of an absorbed power-law with
NH=3E20, slope=1.7
ECFs calculated using the detector matrices:
MOS: On-axis RMF for revolution 375 + on-axis ARF
PN: Latest, canned, on-axis, full-frame RMF for single andsingle+double events + on-axis ARF
Count rates found with - MOS: pattern=0-12, PN: 0.2-0.5 keV, pattern=0; 0.5-12 keV, pattern=0-4
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PN v MOS-1: Band 3 (1-2 keV)
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PN v MOS-1: Band 1 (0.2-0.5)
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PN v MOS-1: Band 2 (0.5-1)
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PN v MOS-1: Band 4 (2-4.5)
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PN v MOS-1: Band 5 (4.5-12)
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PN v MOS-1: Flux comparison
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PN v MOS-2: Flux comparison
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MOS-1 v MOS-2: Flux comparison
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Flux Ratios (%)
Energy (keV) (m1-pn)/m1 (m2-pn)/m2 (m2-m1)/m1
0.2 - 0.5 2.7±0.6 0.9±0.4 -1.3±0.4
0.5 - 1.0 8.4±0.1 8.4±0.2 0.8±0.2
1.0 - 2.0 8.8±0.2 9.4±0.2 0.3±0.2
2.0 - 4.5 7.3±0.2 6.7±0.2 -0.8±0.2
4.5 - 12.0 12.5±0.4 9.0±0.4 -3.7±0.3The Kirsch relation: mos = k * pn where k is an energy independent constant, ~1.05 – 1.08
CAL-TN-0052-5 (Stuhlinger et al. 2008)
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First Results‡ MOS cameras agree to better than 4% at all energies.
‡ PN has a ~constant offset from MOS cameras of 7-9% from 0.5-4.5 keV
‡ PN / MOS agreement much better (<3%) in 0.2-0.5 keV band
‡ PN / MOS agreement worse at high energies at least for MOS-1 (12.5%)
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Low-Energy difference
Why so good ??
Is the use of a single RMF ok ?
Reminder:
MOS flux conversion uses RMF for on-axis (i.e. on patch) at Rev 0375.
PN: Uses on-axis (Y=9) RMF
These approximations will mainly effect low energies.
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PN v MOS-1: Change with time
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PN v MOS-2: Change with time
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MOS-1 v MOS-2: Change with time
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PN v MOS-1: Off-axis angle
Iufh
Yth
Tj
Tyj
e
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PN v MOS-2: Off-axis angle
F
F
F
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Low-Energy summary
• Ignoring sources which fall on the MOS patches, i.e. using Θ = 2 – 12 arcmins we get:
(m1-pn)/m1 = 10 - 12%
(m2-pn)/m2 = 2 - 7%
Time variability makes these numbers unreliable but m2/pn looks to be less than ~8%
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PN v MOS-1: Flux comparison
?
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High-Energy difference
(m1-pn) / m1=12.5% Why so high ??
Is the Kirsch relation wrong ??
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PN v MOS-1: Off-axis angle
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PN v MOS-2: Off-axis angle
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MOS-1 v MOS-2: Off-axis angle
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What depends on off-axis angle?
• Vignetting (all cameras)
• RGS obscuration (MOS)
• PSF (all cameras)
Azimuthal-angle dependent
Azimuthal-angle dependent (MOS)
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MOS PSF
A measure of the XMM PSFs, lighter colour means a sharper PSF.
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MOS CCDs
A measure of the XMM PSFs, lighter colour means a sharper PSF.
1
2
3
4 1
2
3
4
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PN v MOS-1: Azimuthal angle
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PN v MOS-2: Azimuthal angle
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Conclusions for MOS / PN
• MOS = PN * 1.08 from 0.5 – 4.5 keV
• With this analysis we can’t say what the relation is in the 0.2-0.5 keV band.
• At high energies there is an extra off-axis angle, azimuthal-angle dependent effect which increases the MOS excess. This aligns with the RGS dispersion direction and probably means that the RGS absorption needs recalibrating.