Absolute Flux Distributions of Solar Analogs from the UV to the Near-IR

The 0. 225-2. 695mu m absolute flux distributions of the solar analogs P041C, P177D, and P330E are presented. The ultraviolet and optical wavelength range from 0. 225mu m to 0. 825mu m is based on high signal-to-noise spectra obtained with the HST Faint Object Spectrograph (FOS). The spectra in the near-infrared longward of 0. 825mu m are scaled versions of the absolute flux calibrated reference spectrum of the Sun from Colina, Bohlin, & Castelli (1996). In the 0. 400mu m to 0. 825mu m range, the spectral energy distribution of P041C is slightly hotter than the Sun, 5900K vs. 5777K, and agrees with the shape of the solar spectrum to 5% in the optical. P177D shows evidence for interstellar absorption from the dust that corresponds to AV=0. 03 magnitudes in the visual. The spectral energy distribution of P330E is the same as the reference spectrum within 2%-3%. At wavelengths shortward of 0. 4mu m, the differences in the spectral energy distribution between the Sun and the solar analogs are larger, and not well understood. When normalized to the same V flux, P041C and P330E are brighter than the Sun by up to 50% below 0. 25mu m, whereas P177D is as much as 10% fainter. The synthesized visual magnitudes and B-V colors of the FOS absolute fluxes of P041C, P177D, and P330E agree with ground-based broad-band photometry to 0. 02 magnitudes. The flux distributions of our new solar analogs will help establish the absolute calibration of NICMOS, the HST near-infrared camera and multi-object spectrograph. The spectra are available via the WWW.