Cross-calibration Of The X-ray Instruments Onboard The Chandra, Suzaku, Swift, And XMM-Newton Observatories Using 1E 0102.2-7219

The flight calibration of the spectral response of CCD instruments below 1.5 keV is difficult in general because of the lack of strong lines in the on-board calibration sources. This calibration is also a function of time due to the effects of radiation damage on the CCDs and/or the accumulation of a contamination layer on the filters or CCDs. We desire a simple comparison of the absolute effective areas of the current generation of CCD instruments in the 0.5-1.0 keV range, specifically: Chandra ACIS, XMM-Newton EPIC (MOS and pn), Suzaku XIS, and Swift XRT. We have been using 1E 0102.2-7219 (hereafter E0102) since it has strong lines of O, Ne, and Mg below 1.5 keV and little or no Fe emission. The spectrum of E0102 has been well-characterized using the RGS grating instrument on XMM-Newton and the HETG grating instrument on Chandra. We have developed an empirical model for E0102 that includes Gaussians for the identified lines, two absorption components (one for the Galaxy and one for the SMC), and two continuum components with different temperatures. In our fits, the model is highly constrained in that only the normalizations of the four brightest line complexes (the O VII triplet, the O VIII Ly-α line, the Ne IX triplet, and the Ne X Ly-α line) and an overall normalization are allowed to vary. In our previous study in 2008, we found that most of the fitted line normalizations agreed to within +/- 10% (28 of 32 line normalizations). We have now expanded this study to include more recent data from these missions using the latest calibration updates and we will report on the current level of agreement amongst these instruments.

This work is based on the activities of the International Astronomical

Consortium for High Energy Calibration (IACHEC).