Evaluation of the EPIC flux cross-calibration from 2XMM sources R. Saxton, S. Mateos, A. Read, S. Sembay Mateos et al., 2009, A&A, arXiv

2XMM sources

pn vs MOS1 energy dependence MOS1 vs MOS2 energy dependence Distributions of flux ratios fitted with Gaussian profiles:

pn vs MOS1:energy dependence pn / MOS agreement worse above ~4.5 keV (12.5%) ~constant offset from MOS cameras of 7-9% from keV pn / MOS agreement better than 3% in keV band 1: keV 2:0.5-1 keV 3:1-2 keV 4:2-4.5 keV 5: keV

MOS1 vs MOS2:energy dependence MOS cameras agree to better than 4% at all energies 1: keV 2:0.5-1 keV 3:1-2 keV 4:2-4.5 keV 5: keV

pn vs MOS1:time dependence MOS to pn flux cross-calibration ~constant >0.5 keV strong dependence on time <0.5 keV: evolution of the MOS RMF with time

MOS1 vs MOS2: time dependence MOS flux cross-calibration ~constant at all energies

pn vs MOS1:offaxis dependence 1: keV 2:0.5-1 keV 3:1-2 keV 4:2-4.5 keV 5: keV Variations of MOS vs pn relative flux calibration vs offaxis ARF effect:  QE: spatial variation in QE offaxis (MOS and pn)  Vignetting: General vignetting function  PSF: Uncertainties in offaxis PSF

MOS1 vs MOS2:offaxis dependence Variations of MOS relative flux calibration vs offaxis ARF effect:  QE: spatial variation in QE offaxis (MOS and pn)  Vignetting: General vignetting function  PSF: Uncertainties in offaxis PSF 1: keV 2:0.5-1 keV 3:1-2 keV 4:2-4.5 keV 5: keV

Azimuthal dependence - PN v MOS-2 1: keV 2:0.5-1 keV 3:1-2 keV 4:2-4.5 keV 5: keV Strong azimuthal-angle dependence at high energies

RGA obscuration: Azimuthal dependence Excluded sources at offaxis<2 arcmin 1: keV 2:0.5-1 keV 3:1-2 keV 4:2-4.5 keV 5: keV Sources divided in 4 azimuthal angle bins based on DETX/DETY coordinates Strong azimuthal angle dependence at high energies Sources lying along the RGA dispersion axis show a large gradient in relative flux Calibration of RGA blocking factor incorrect at high energies? B-4 B-5

RGA obscuration: Azimuthal depencence Strong azimuthal angle dependence at high energies Sources lying along the RGA dispersion axis show a large gradient in relative flux Calibration of RGA blocking factor incorrect at high energies? Excluded sources at offaxis <2 arcmin 1: keV 2:0.5-1 keV 3:1-2 keV 4:2-4.5 keV 5: keV Sources divided in 4 azimuthal angle bins based on DETX/DETY coordinates B-5 B-4 B-5B-4 B-5

Current azimuthal vignetting factor for MOS amin offax 9 9 amin offax

Low-energy azimuthal dependence: MOS-1 Strong azimuthal angle dependence at low energies Sources lying on CCDs from different batches show a large gradient in relative flux Excluded sources at offaxis< 2arcmin 1: keV 2:0.5-1 keV 3:1-2 keV 4:2-4.5 keV 5: keV Sources divided in 4 azimuthal angle bins based on DETX/DETY coordinates B-5 B-4 B-5B-4 B-5

Excluded sources at offaxis<2 arcmin 1: keV 2:0.5-1 keV 3:1-2 keV 4:2-4.5 keV 5: keV Sources divided in 4 azimuthal angle bins based on DETX/DETY coordinates Smallish azimuthal angle dependence at low energies. Batch effect not so strong here ? B-4 B-5 Low-energy azimuthal dependence: MOS-2

Consistent improvements in the MOS2/pn flux ratio, with some evidence for similar improvements for MOS1/pn Large scatter, low stats at very lowest energy so far

Conclusions Excellent agreement of the two MOS cameras (<4%) at all energies MOS cameras register 7-9% higher flux than pn below 4.5 keV 10-13% flux excess at the highest energies No evolution of flux ratios with time except in the keV band Gradual degrading of the MOS redistribution function MOS to pn excess increases with offaxis: ARF effect Strong dependency of MOS to pn excess keV flux on azimuthal-angle

TO DO Fudge RGA obscuration to give larger azimuthal effect for MOS’s at high energies ? Use SCISIM to justify physical parameters ? Put in a batch-specific, low-energy QE contribution for MOS- CCDs ? 2XMM could benefit from: - MOS RMFs made spatially, temporally dependent. - EBG PSF ? - Spectral dependence in flux calculation Strong dependency of MOS to pn excess keV flux on azimuthal-angle Calibration of RGA blocking factor (RGA absorption) incorrect at high energies?