STARBURSTS IN BARRED SPIRAL GALAXIES .1. MKN-712, A NEW WOLF-RAYET GALAXY

We report the discovery of emission from Wolf-Rayet stars in a giant H II region 4.5 arcsec South of the nucleus of the IRAS barred spiral ga laxy Mkn 712 (= UGC 5342). The ratio of WNL to OV stars, estimated fro m the luminosity of the He II lambda 4686 line, is 0.2. By comparison with starburst and stellar evolution models, we find that this high va lue is only compatible with a very young starburst episode (3 - 4 Myr) and a flat initial mass function (Gamma = -1). The presence of the [A rv] line reveals that the HII region is strongly ionized by the hot Wo lf-Rayet stars. The comparison with other barred Wolf-Rayet galaxies s uggests that the detection of Wolf-Rayet stars depends on the dust con tent and orientation of the galaxy.