We report on our continuing efforts to compare the absolute effective areas of the current generation of CCD instruments onboard the active observatories, specifically: Chandra ACIS, XMM-Newton EPIC (MOS and pn), Suzaku XIS, and Swift XRT, using 1E 0102.2-7219, the brightest supernova remnant in the Small Magellanic Cloud. 1E 0102.2-7219 has strong lines of O, Ne, and Mg below 1.5 keV and little Fe emission to complicate the spectrum. The spectrum of 1E 0102.2-7219 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 that includes Gaussians for the identified lines, an absorption component in the Galaxy, another absorption component in 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 OVII triplet, OVIII Lyα line, the NeIX triplet, and the NeX Lyα) and an overall normalization are allowed to vary, while all other components are fixed. We adopted this approach to provide a straightforward comparison of the measured line fluxes at these four energies. We find that the measured fluxes of the OVII triplet, the OVIII Lyαline, the NeIX triplet, and the NeX Lyαline generally agree to within ±10% for all instruments, with the exception of the OVII triplet and the OVIII Lyαline normalizations for the Suzaku XIS1, XIS2, & XIS3, and the Swift XRT, which can be up to 20%lower compared to the reference model.
We study the gain variations in the HRC-I over the duration of the
Chandra mission. We analyze calibration observations of AR Lac obtained yearly at the nominal aimpoint and at 20 offset locations on the detector. We show that the gain is declining, and that the
time dependence of the gain can be modeled generally as a linear
decrease in PHAs. We describe the spatial and temporal characteristics
of the gain decline and discuss the creation of time-dependent gain
correction maps. These maps are used to convert PHAs to PI channels, thereby removing spatial and temporal dependence, and allowing source pulse-height distributions to be compared directly regardless of
observation date or location on the detector.