To model the particle-induced background spectrum for an arbitrary celestial observation with Chandra ACIS, we thoroughly analyzed all the available calibration data of the ACIS taken in 2002–2016 and have developed a tool to generate a model spectrum.
We found CCD position-to-position and temporal variations of their energy spectra. The spatial variations were mostly seen along CHIPY axis (as already found by Bartalucci et al. 2014). The temporal variations correspond to solar activity. Not only the fluxes but also the spectral-continuum shapes were found to vary.
The paper is under review but this tool is already available on the Github. https://github.com/hiromasasuzuki/mkacispback
The usage should be very simple. Basically just run
$ mkacispback <event file with expression>
$ mkacispback "evt2.fits[sky=region(source.reg)]"
For more details, please see README or type
$ mkacispback -h