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Last modified: 14 July 2010

URL: http://cxc-newtest.cfa.harvard.edu/ciao4.2/why/hrc_rmf.html

HRC-I RMF


The intrinsic energy resolution of the HRC is poor compared with the ACIS, but it does have some ability to discriminate between hard and soft spectra. Using observations of HR1099 carried out with the HRC-I/LETG at various locations on the detector, the calibration team has constructed a response matrix for the HRC-I. This HRC-I RMF was first released in CALDB 3.2.1 (15 December 2005).

A new HRC-I RMF file, hrciD1999-07-22samprmfN0001.fits, was released in CALDB 4.2.0 (15 December 2009). It is required for use with event data that have PI values derived from the new HRC-I gain maps, also released in CALDB 4.2.0.

For details on the file, refer to the HRC-I RMF calibration page.

The files are distributed in the CALDB:

$CALDB/data/chandra/hrc/rmf/hrciD1999-07-22rmfN0001.fits
$CALDB/data/chandra/hrc/rmf/hrciD1999-07-22rmfN0002.fits
$CALDB/data/chandra/hrc/rmf/hrciD1999-07-22samprmfN0001.fits

The RMF can be used to calibrate hardness ratios or quantile color-color diagrams (QCCDs) to distinguish between gross differences in the spectra. We recommend the QCCD, as it is relatively less dependent on temporal variations in the gain that are known to exist, and are not yet accounted for, in the HRC gain maps. The calibration page contains several example QCCDs.

We do not advocate using this RMF in spectral fits; the spectral response is not sufficiently constraining to achieve a good fit with reasonable errors. If unavoidable, work in channel space, not energy space. To set the analysis to channel space in Sherpa:

sherpa> set_analysis("channel")

Because the correspondence between PI bins and energy values is not well-defined and is not monotonic, the energy grid in the EBOUNDS extension of the RMF has been deliberately set to be meaningless, which matters only when spectra are plotted or data are filtered in energy space.


Last modified: 14 July 2010