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This is a simple non-physical model for low-count background spectra, used by fitting scripts in the ACIS Extract (AE) package. Using this model outside the context of the AE package should be done with extreme caution since it requires a choice on vertex energies and number of segments. AE places the first and last vertices at the lowest and highest energy of the background counts. Intermediate vertices are placed at energies where a background count exists such that each segment covers a similar number of background counts. Any results using this model should cite Broos et al. (2010).
Note that if all the rate parameters in use are thawed then the norm parameter is degenerate and must be frozen. Freezing one of the rate parameters will not work because if that vertex is driven to zero in the fit then the norm will be zero and the other rate parameters infinite.
| par1 | energy00 (keV) |
| par2 | energy01 (keV) |
| par3 | energy02 (keV) |
| par4 | energy03 (keV) |
| par5 | energy04 (keV) |
| par6 | energy05 (keV) |
| par7 | energy06 (keV) |
| par8 | energy07 (keV) |
| par9 | energy08 (keV) |
| par10 | energy09 (keV) |
| par11 | log_rate00 |
| par12 | log_rate01 |
| par13 | log_rate02 |
| par14 | log_rate03 |
| par15 | log_rate04 |
| par16 | log_rate05 |
| par17 | log_rate06 |
| par18 | log_rate07 |
| par19 | log_rate08 |
| par10 | log_rate09 |
| norm |