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cplinear: a non-physical piecewise-linear model for low count background spectra.

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

 

 

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