(postscript version)
(IDL to make this is here.)
I have made a new ACIS mean QE ARD (acisD1997-04-17qeN0004.fits) incorporating Herman's modification of the ACIS-S filter transmission at low energies (near the carbon edge). This has only been approved for use with ACIS-S/LETG with SIM_Z offset to put the spectrum near the readout. Herman suspects that it applies to the whole array, but the jury is still out, and calibration observations are planned. Hence, to use it, you have to explicitly change the ardlib parameters before running mkgarf (or mkarf if you are doing imaging on S3). (Footnote)
I used ObsID 1198 (3C273, LETG/ACIS-S) as a test case. I made ARFs for +/- 1st orders. I used them to fit an absorbed powerlaw w/ ISIS.
Here is a comparison of the new vs old effective areas:
(postscript version)
(IDL to make this is here.)
Spectral fits:
Postscript versions:
Obs_1198_m1_newqe.ps --- New, -1st order
Obs_1198_m1_oldqe.ps --- Old, -1st order
Obs_1198_p1_newqe.ps --- New, +1st order
Obs_1198_p1_oldqe.ps --- Old, +1st order
Fit parameters are here.
Test gARFs are:
acisf01198_001N001LEG_-1_garf.fits
acisf01198_001N001LEG_1_garf.fits
acisf01198_002N001LEG_-1_garf.fits
acisf01198_002N001LEG_1_garf.fits
("_002" are new; "_001" are old).
ISIS commands are here.
2001.05.16 d.p.huenemoerder dph@space.mit.edu