HXD: Absolute effective area

Calibration status and caveats

• HXD-PIN
  Reproducibility of the PIN spectra was examined by fitting the Crab spectra measured at two nominal positions, "XIS nominal" and "HXD nominal", using relevant response files over an energy range of 12-70 keV (Figure 1). The single power-law model was assumed. Systematic errors of the spectral parameters, the photon index and the normalization, are summarized in Table1, based on a comparison to the results from Toor & Seward (1974). Thus the reproducibility is as good as **% in the 12-70 keV band, while the deviation becomes larger up to 10% below 10 keV. See this page for relative normalization of PIN and XIS.
  
  
  Figure 1: Background-subtracted PIN spectra (64 summed) of the Crab Nebula, at the XIS nominal (left) and HXD nominal (right) positions. The best-fit power-law model obtained from the fit to the 12-70 keV spectrum is shown with the red curve in each panel.
  
  

  Table 1: Best-fit parameters and 90% errors for the PIN spectra of the Crab Nebula

  Target position	Photon index	Photon index uncertainty(*)	Normalization	Normalization uncertainty(*)
  XIS nominal	2.11+-0.01	0.5%	11.7+-0.14	**%
  HXD nominal	2.10+-0.01	0%	11.2+-0.09	**%

  (*) Evaluated from the comparison with the spectral parameters presented in Toor & Seward (1974). The statistical errors are not included.
  
  
• HXD-GSO
  Figure 2 shows the GSO spectra, summed over the 16 units, of the Crab Nebula, after subtracting blank-sky background. The power-law model fitting was performed in the 100-300 keV band, resulting successful reproduction of the data within +-10%. Outside the energy range, the uncertainty is larger. See this page for relative normalization of GSO and PIN.
  
  Figure 2: Background-subtracted GSO spectra (summed over the 16 units), obtained at the XIS nominal and HXD nominal positions.
  
  

  Table 2: Best-fit parameters and 90% errors for the GSO spectra of the Crab Nebula

  Target position	Photon index	Photon index uncertainty	Normalization	Normalization uncertainty
  XIS nominal	2.12+-0.03	**%	10.6+-1.4	**%
  HXD nominal	2.15+-0.03	**%	11.7+-1.4	**%