LETG/HRC-S Wavelength Coverage Adjustments

Wavelength Coverage Adjustments at HRC-S Plate Ends

B. Wargelin, May 2017

Issues

Prior to CALDB 4.7.4 (2017 May 4), the wavelengths covered by LETG/HRC-S GARFs and spectra did not match at some of the HRC-S plate ends (Figs. 1 and 2). This problem was traced to an incorrect specification in the HRC-S QE Uniformity files. The updated QEU files (hrcsDqeuN0008.fits) also include adjustments to QE and extend coverage through 2023.
Event density rises steeply (and is often nonuniform in the cross-disp direction) near 3 of the 6 edges of the HRC-S plates, creating anomalous spectral features. Pulse height spectra there are also anomalous, making gain/PI-filtering interactions unpredictable. The HRC-S BADPIX specifications were changed in CALDB 4.7.4 to exclude these regions, as described in detail here.

Figure 1: Spectra (from pha2 file of Mkn421 ObsID 4149) vs corresponding GARF effective areas, showing that wavelength boundaries only match at two of the six plate edges. (Note that the GARF is 1st order only and the data are not background-subtracted; GARF and spectrum are scaled to roughly match for illustration.) Spiky features near the plate gaps are from scrunched events on plate edges and are removed using the BADPIX file. Figure 2: Same as Fig. 1 but using new BADPIX and QEU files.

Last modified: 06/16/17

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Figure 1: Spectra (from pha2 file of Mkn421 ObsID 4149) vs corresponding GARF effective areas, showing that wavelength boundaries only match at two of the six plate edges. (Note that the GARF is 1st order only and the data are not background-subtracted; GARF and spectrum are scaled to roughly match for illustration.) Spiky features near the plate gaps are from scrunched events on plate edges and are removed using the BADPIX file.		Figure 2: Same as Fig. 1 but using new BADPIX and QEU files.