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

We report the discovery of the brightest nonsolar source of extreme ul traviolet 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 a ngstrom than the predicted emission from the hot white dwarf star HZ 4 3, previously believed to be the brightest EUV source. We have fitted a simple B star photospheric model to the observed broad-band EUV flux es 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 col umn 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 raref ied Local Bubble region which surrounds the Sun.