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A Note on HRC Spectra

CIAO 4.15 Science Threads

A question about the High Resolution Camera

There are several threads that deal with imaging spectroscopy of ACIS observations, for both point and extended sources. Why are there no equivalent threads for HRC observations?

The energy resolution of the High Resolution Camera (HRC) is extremely limited. Only when coupled with the Low Energy Transmission Grating (LETG) is it possible to get meaningful energy and order-sorting information. This also allows some discrimination between X-ray and background events.

For LETG spectra, background reduction of more than 50% can be achieved with negligible X-ray event loss; see the LETG/HRC-S Grating Spectra thread for more information. Background filtering in the HRC-S is based on PI values, which, like ACIS PI values, are derived from PHA values using a gain map to correct for gain variations across the detector.

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. The calibration team has constructed response matrices for the HRC-I and HRC-S. For details, refer to the HRC RMFs why topic.

Details on calibration and analysis of the HRC are available from the HRC Spectral Response calibration page.