Subsections

• 7.10.1 Actions
• 7.10.2 Usage and Inputs

7.10 MODIFY ARF Stage

This stage is (optionally) run for each ObsId after EXTRACT_SPECTRA has been completed. It can be run one or more times to apply externally-computed correction curves to the ARFs. For example, prior to release of CALDB 2.26 this mechanism was used to apply a correction for ACIS blocking filter contamination.

7.10.1 Actions

The ARF is multiplied by the supplied correction curve.

7.10.2 Usage and Inputs

acis_extract, srclist_filename, obsname, ARF_CORRECTION_FILENAME=filepath

EXAMPLE:

acis_extract, 'all.srclist', '1875', ARF_CORRECTION_FILENAME='acisabs_1875.fits'

The AE ARF files contain additional columns (which are allowed by the OGIP standard) beyond the standard ENERG_LO, ENERG_HI, and SPECRESP. The column named BASE contains the specresp values produced by mkarf. The column named PSF_FRAC contains the PSF fraction corresponding to the source extraction region.

When the observer wishes to add another multiplicative ARF correction, the supplied ARF_CORRECTION table must have two columns, ENERGY and a second column with a meaningful name containing the desired correction. The energy sampling need not be the same as the ARF; the correction file is interpolated as required. The SPECRESP column is then recomputed by multiplying BASE by all the correction columns found.

When the observer wishes to revise an existing correction, the correction column name in the supplied file should match the existing correction column. For example, if an external calculation of a source's PSF fraction were performed (e.g. using a MARX simulation), then the PSF_FRAC column could be overwritten by running this stage on only that source.