Chandra observations and data reduction

The 3C 401 system was observed by Chandra on the 20-Sept-2002 (22.7ks exposure; obs-id 3083) and the 21-Sept-2002 (24.9ks exposure; obs-id 4370). The core of 3C 401 was centered 1arcmin from the aim point on the S3 back-illuminated ACIS chip (7) such that the core of its cluster could be imaged entirely by the S3 chip. These observations were taken in imaging-mode, i.e., the diffraction gratings are not placed in the X-ray path. The two level-2 events files for these two observations were merged using the merge_all script, and then filtered so as to include only events with ASCA grades 0,2,3,4, and 6. Exposure corrected images and spectra were created following the standard process outlined in the Chandra Interactive Analysis of Observations (CIAO) analysis threads . All ACIS data reduction was performed using the CIAO version 3.0, and spectral analysis was performed using version 11.3 of the XSPEC fitting package.