Wolf-Rayet Stars in M31

Extract

We have completed a survey of the closest giant spiral galaxy beyond our own for Wolf-Rayet stars, using narrow band imaging techniques (cf. Moffat and Shara 1983, Ap. J., 273, 544). About 90% of the main body of M31 has been thoroughly searched to B ≅ 21.5 (M_B ≅ −3.5) to a level of emission line equivalent width W_e(HeII 4686 A) ≳ 60 A. We do not expect interstellar extinction to be a limiting factor in the detection of WR stars, except possibly in the localized neighborhoods of massive HII regions. The mean extinction for stars in the disk is estimated to be A_B ≲ 0.9 mag. Although some weak-line WN stars will have escaped detection, the survey should be complete for WC stars.