THE 0.12-2.5 MU-M ABSOLUTE FLUX DISTRIBUTION OF THE SUN FOR COMPARISON WITH SOLAR ANALOG STARS

An absolute flux calibrated reference spectrum of the Sun covering the 0.12-2.5 mu m wavelength range is presented. The ultraviolet and opti cal spectrum is based on absolute flux measurements from satellites an d from the ground. The near-infrared spectrum is based on measurements using the NASA CV-990 aircraft and on a model spectrum. The synthetic optical and near-infrared magnitudes of the absolute calibrated solar reference spectrum agree with published values to 0.01-0.03 mag, i.e. , within the uncertainties of the measurements. The absolute flux of t he reference spectrum over the optical and near-infrared 0.4-2.5 mu m range is known with an uncertainty of 5%, or better. In the blue and u ltraviolet, especially for wavelengths in the 0.12-0.2 mu m interval, the uncertainty increases up to about 20% due to the variability of th e solar energy output at these wavelengths. The absolute flux spectrum of the Sun presented here will help to establish the absolute calibra tion of NICMOS, the HST near-infrared camera and multi-object spectrog raph. (C) 1996 American Astronomical Society.