Observation of an H-alpha outburst in the Be star HR 4123

Abstract

During routine monitoring of the Be star HR 4123 during the year 1987-1988, a burst of H-alpha emission was observed on May 11, 1987. The increase was observed on May 9 and lasted until June 7, peaking to an equivalent width of 31.6 A on May 11. This short-term burst is interpreted as due to the presence of a compact object in binary motion around the Be star, which accretes the matter ejected by the Be star to give out X-rays, which in turn produce ionization in the gas to give out the H-alpha emission. The broad line at 6577.5 A observed to accompany H-alpha emission during the burst is suggested to be emission from dielectronic recombination from C III ions in a C II region around the H II region formed by the X radiation.