1 Comparison of Xmm-newton Epic, Chandra Acis-s3, Asca Sis and Gis, and Rosat Pspc Results for G21.5-0.9, 1e0102.2-7219, and Ms1054.4-0321

This paper presents a " man on the street " view of the current status of the spectral cross calibration between the XMM-Newton EPIC, Chandra ACIS-S3, ASCA SIS and GIS, and ROSAT PSPC instruments. Using publicly released software for the extraction of spectra and the production of spectral redistribution response matrices and effective areas, the spectral fits of data from three astronomical objects are compared. The three sources are G21.5-0.9 (a heavily absorbed Galactic SNR with a power law spectrum), 1E0102.2-7219 (a SNR in the SMC with a line-dominated spectrum), and MS1054.4-0321 (a high redshift cluster with a thermal spectrum). The agreement between the measured fluxes of the various instruments is within the ±10% range, and is better when just XMM-Newton and Chandra are compared. Fitted spectral parameters are also in relatively good agreement although the results are more limited.