Ultra-violet Continuum Brightnesses of Stars Measured by a Rocket-borne Photoelectric Spectrophotometer

Photoelectric spectrophotometric measures of 40 early-type stars in the range 1800–2800 Å and with 200 Å resolution have been obtained by precessing scans of an objective dispersion monochromator. Normal, and three β Canis Majoris, stars show brightness well correlated with spectral type but three Ap stars have anomalous fluxes corresponding to late B-types. The interstellar extinction curves peak at 4.75 μ^–1 with an observed f.w.h.m. of 0.45 μ^–1 . The total interstellar flux density near 2400 Å and in the neighbourhood of the Sun is estimated at $$3.5\,\times\,{10}^{-17}\,\text{erg}\,\text{cm}^{-3}$$ Å ^–1 , with only a small contribution from resolved stars.