6.3.2 Count Rates for Power Law Sources

If one knows the spectral index (which is zero for a source with a flat continuum), V+AB can also be calculated as the monochromatic Oke system magnitude at the corrected mean wavelength of the filter:

where S is the flux in ergs cm^-2 s^-1 Hz^-1 as in Oke and Gunn, Ap. J., 266, 713 (1983) at the effective mean wavelength of the filter . It can be shown that

if the integrands are weighted by a source with spectral index in the definition of . See also Koornneef, J., et al. "Synthetic Photometry and the Calibration of the Hubble Space Telescope" in Highlights of Astronomy (7, 833, J.-P. Swings Ed (1983). Combining the above equations gives