S18B0101abst

S18B0101

We propose the first systematic search for Wolf-Rayet stars (WRs) and Ultra-luminous X-ray sources (ULXs) in the M81 galaxy through deep HeII λ4686Å imaging observations. First, we propose a census of WRs (ZAMS> 20M_⊙). This census will constrain stellar evolutionary theory: via the detection and classification of WRs; by the detection of WR X-ray binaries, likely progenitors of gravitational-wave sources; and by tabulating WRs that may be progenitors of Type Ib/c and Type IIb supernovae. Second, most ULXs are neutron stars or stellar-mass black holes accreting in unusual super-Eddington states, apparently so luminous mainly because their X-ray emission is beamed toward us. Strong winds, jets, and radiation emanate from their accretion disks to inflate and ionize large (≥ 150 pc diameter) bubbles in the ISM, which are isotropic He II emitters. Newly discovered bubbles will reveal the hidden population of sources beamed away from us and constrain the beaming angle of their disks.

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