Cycle 25 Grating RMFs/ARFs
We have prepared sample grating RMFs and corresponding ARFs for proposal planning purposes. As in the CY24 release, all of the GRMF files below were built with mkgrmf, using the latest LSF parameter data for the HETG/ACIS-S, LETG/ACIS-S, and LETG/HRC-S configurations. In all cases, the grating pixel randomization, RAND_TG is set to 0 pixels (turned off).
The ACIS-related gARFs were built with the CIAO script fullgarf, using PHA2 files from specific archival observations and the appropriate GRMF energy grid as the seed energy grid. They therefore include dither, and do not have exactly the nominal aimpoints as their source positions. The configuration information, including SIM_Z position and ObsID numbers, are included in the GARF headers.
The ACIS-S configuration effective areas (*.garf or *.arf) were derived using CIAO 4.15, CALDB 4.10.2, including the ACIS contamination model file acisD1999-08-13contamN0015.fits, with the time delay value set at 832118469.184s, corresponding to the UTC date 2024-05-15T00:00:00, or half-way through the CY25 observation period. For the HRC-S configurations, all effective areas were derived from CIAO as well, using the latest QE and QE uniformity calibrations.
The HRC-S configuration GARFs were built with the HRC-S QE (N0016) and QEU (N0015) released with CalDB 4.9.6 on 2021-09-24. Relative to the CY24 GARFs, the CY25 GARFs are increased by a flat ~7.1% over the energy range 0.06-.630 keV. Above that range, the difference decreases exponentially from ~7.1% down to ~1.5%.
To download individual files, <Shift>-click on the
filename. The complete set of responses is available as
a gzipped tarfile located on the Chandra Archive server, under the directory:
Caveats and Notes
These gARFs and gRMFs are for proposal planning purposes only. They should not be used for analysis of any real Chandra data. The Grating Spectroscopy threads give instructions for building an observation-specific gRMF and gARF.
LETG/HRC-S proposal planners: the above gRMFs and gARFs for the LETG/HRC-S configuration must be used in gRMF/gARF pairs for appropriate response settings to be employed. The LETGS group also has convolved gRMFs and gARFs, known as "gRSP" files, available for download on the LETGS Effective Area webpage. That webpage explains the proper use and interpretation of these files.
A Note concerning the LETGS Encircled Energy Fraction: The LETG/HRC-S configuration requires that an encircled energy fraction, or EEARF, be considered in order to apply the appropriate response for these grating data. With the release of CalDB 4.6.9 in August 2015, an improved encircled energy fraction is included in the GRMF, and hence should not be included in the GARF. Therefore, the LETG/HRC-S GARFs (all orders) for LETG/HRC-S have been built so that the encircled energy fraction is not applied to the GARF. HOWEVER, in order for the users results to agree with the results of PIMMS for this configuration, one must either use the GRMF and GARF in tandem (in XSPEC, Sherpa, or similar fitting environment), or one must apply the encircled energy fraction to the GARF. The GARFs may be modified using the script factor_rsp, which is described in the documentation file factor_rsp.txt. The script may be [shift-click] downloaded for use in any shell with isis-script in one's path. ISIS is available from links at the ISIS Home Page, but is not included with CIAO 4.15.