ACIS gains were computed with following steps (see C. Grant memo:ACIS Gain @ -120 C for more discussion ):

• All ACIS calibration event 1 files were extracted from Achieve, except squeegee files.
• Each data was compared with focal temperature, and only parts with focal temperature lower than -119.7 C before May 2006, and -119.0 C after May 2006, were extracted out. (See a list of data used:Input List).
• From these data, only ccdy <= 20 (first 20 raw of a CCD) and grade 0, 2, 3, 4, and 6 were extracted.
• A pulse height distribution was created from this data, and fit Lorentzian profiles to Al K-alpha (1486.7 eV), Ti K-alpha (4510.84 eV), and Mn K-alpha (5898.75 eV) to find peak postions in ADU.
• A straight line was fit between three peak position in ADU and eV, and a slope (Gain ADU/eV), and an intercept (Offset ADU) were found.

For a gain plot, an x axis is in unit of year, and a y axis is in ADU/eV, the range for the y axis is 0.01 for all the plots so that we can compare the general trend among the plots. Similarly for offset plots, a y axis is in ADU, and the range for the y axis is 18 for all the plots. The slopes are either ADU/eV per year, or ADU per year.

Data entries are: Date, Obsid, starting time in seconds from 1998 Jan 1, end time in seconds from 1998 Jan 1, Mn K-alpha position in ADU, Al K-alpha in ADU, Ti K-alpha in ADU, slopes (ADU/eV), errors for the slopes, intercepts (ADU), and errors for the intercepts.

Last Update: 8/24/2008