Wolf-Rayet stars in M81 using GTC/OSIRIS: 7 new detections, analysis and
  classification of the full sample
  We report the detection of 7 new Wolf-Rayet (WR) star locations in M81 using
the Multi-Object Spectrograph of the OSIRIS instrument at Gran Telescopio
Canarias. These detections are the result of a follow-up of an earlier study
using the same instrumental set-up that resulted in the detection of 14 WR
locations. We analyse the entire sample of 21 spectra to classify them to one
of the known WR sub-types using template spectra of WR stars in the Large
Magellanic Cloud (LMC), with similar metallicity to M81. Taking into
consideration the dispersion in the strengths of the bumps for a given WR
sub-type, we found that 19 of the 21 locations correspond to individual stars,
including all the 7 new detections, of sub-types: WNL, WNE, WCE and the
transitional WN/C. None of the detections correspond to WCL or WO types. The
positions of these stars in the red bump vs blue bump luminosity diagram agrees
well with an evolutionary path according to the Conti scenario. Based on this,
we propose this diagram as a straightforward tool for spectral classification
of extragalactic WR sources. The detection of individual WR stars in M81, which
is at a distance of 3.6 Mpc, opens up a new environment for testing the massive
star evolutionary models.
