Spectral Irradiance Calibration in the Infrared. XVI. Improved Accuracy in the Infrared Spectra of the Secondary and Tertiary Standard Calibration Stars

We have increased the spectral resolution and accuracy of the absolute infrared spectral flux for a subset of stellar standards created by Cohen and his collaborators in previous papers in this series. We combined the moderate-resolution (l/ lambda ~ 400) spectroscopy obtained on infrared standard stars by the Short Wavelength Spectrometer on the Infrared Space Observatory with high-quality photometry that is tied to our recent absolute calibration from the Midcourse Space Experiment. New spectra were created for 33 stars, 9 of which are Cohen et al. secondary standards and another 20 of which are tertiary standards for which Cohen adopted spectral templates. The effective temperatures and angular diameters for the stars are derived from the absolute spectra and compare favorably with independent measures of these quantities in the literature. The present spectra display systematic differences with those of Cohen and colleagues in that they have 4%-7% lower fluxes in the 1-4 mm spectral region. Our spectra remove the A-K star calibration bias recently noted in the calibration of the Spitzer Space Telescope camera.