Broadband Photometric Research Articles

Absolute UV Calibration of Rocket Photometers Used to Up-Date the OAO Calibration

Accurate rocket observations are needed to estimate the post-launch sensitivity of the Wisconsin OAO instruments and to set the absolute scale of the OAO broad-band photometry and spectrophotometry. Seven broad-band photometers, equipping a pointable Aerobee rocket, are calibrated against a source of synchrotron radiation in an attempt to determine, as accurately as possible, the absolute energy distribution of OAO reference stars. The first flight (July 1st, 1970) failed for technical reasons but the experiment will be repeated in 1971.

Concerning the interpretation of the ultraviolet radiation from B stars

Measurements of the shape of the ultraviolet spectrum from B stars are compared with the theoretical spectra predicted from a homogeneous series of eight model atmospheres which are known to be close to a state of radiative equilibrium and to give a good representation of the ordinarily observed spectral region. The broad-band photometer measurements of Byram, Chubb, and Friedman in the region λ 1314 indicate that the stars become brighter in the ultraviolet as their temperature increases. The theoretical spectra reproduce this trend. However, the theoretical spectra are about three times as bright at λ 1314 relative to their brightness at λ 5560 as is observed.