Spatial and temporal variations of the <i>Chandra</i> ACIS particle-induced background and development of a spectral-model generation tool

Context. In X-ray observations, estimating the particle-induced background is important, especially for faint and/or diffuse sources. Although software exists to generate total (sky and detector) data suitable a given Chandra ACIS observation, no public model separately. Aims. We aimed understand spatial temporal variations of C h n d r obtained in two modes, VFAINT FAINT. Methods. Observations performed with stowed position shielded from sky Deep Field South (CDF-S) sets were used. The spectra modeled combination instrumental lines Al, Si, Ni, Au continuum components. spectral shapes by dividing each CCD into 32 regions CHIPY direction. using all individual ACIS-stowed observations. Results. Similar found FAINT data, which are mainly due inappropriate correction charge transfer inefficiency events that convert frame-store regions. variation hardness ratio ∼10% maximum, seems be largely solar activity. this modifying hardnesses according count rate. Incorporating these properties, we developed tool, mkacispback, corresponding an arbitrary celestial observation. As example application, used spectrum produced mkacispback tool analysis unresolved cosmic CDF-S intensities 3.10 (2.98–3.21)×10 −12 erg s −1 cm −2 deg 2–8 keV band 8.35 (8.00–8.70)×10 1–2 band, consistent or lower than previous estimates. Conclusions. ACIS-I S1, S2, S3 CCDs,