INTENSE EXTREME-ULTRAVIOLET EMISSION FROM THE B-STAR EPSILON-CANIS MAJORIS

We report the discovery of the brightest nonsolar source of extreme ultraviolet emission: the B2 II star epsilon Canis Majoris. This source has been detected by the: Extreme Ultraviolet Explorer satellite's all-sky photometric survey. It is approximately 30 times brighter at 60 angstrom than the predicted emission from the hot white dwarf star HZ 43, previously believed to be the brightest EUV source. We have fitted a simple B star photospheric model to the observed broad-band EUV fluxes to explain this emission. Assuming a stellar temperature of 25,000 K and a gravity (log g) of 3.3, we derive an interstellar hydrogen column density N(H) of 1.05 +/- 0.05 x 10(18) cm-2 over the 187 pc to the star. This corresponds to a line-of-sight number density of hydrogen, nBAR, of 0.002 cm-3, which is comparable to values found in the rarefied Local Bubble region which surrounds the Sun.