High-excitation nebulae around Magellanic Wolf-Rayet stars
  The SMC harbours a class of hot nitrogen-sequence Wolf-Rayet stars (WNE) that
display only relatively weak broad emission lines. This indicates low mass-loss
rates and makes them also hard to detect. However, such stars are possible
emitters of strong He+ Lyman continua that in turn could ionize observable
HeIII regions, i.e. highly excited HII regions emitting nebular HeII4686
emission. We here report the discovery of a rare HeIII region in the SMC which
is located in the OB association NGC249 around the weak-lined WN star SMC WR10.
WR10 is particularly interesting since it is a single star showing the presence
of atmospheric hydrogen. While analysing the spectrum in the framework of two
popular WR atmosphere models, we found for the same input parameters strongly
discrepant predictions (by 1 dex) for the He+ Lyman continuum. A second aspect
of the work reported here concerns the beautiful MCELS images which clearly
reveal a class of strongly [OIII]5007 emitting (blue-coded) nebulae. Not
unexpectedly, most of the 'blue' nebulae are known Wolf-Rayet bubbles, but new
bubbles around a few WRs are also detected. Moreover, we report the existence
of blue nebulae without associated known WRs and discuss the possibility that
they reveal weak-wind WR stars with very faint stellar HeII4686 emission.
Alternatively, such nebulae might hint at the hitherto missing population of
relatively low-mass, hot He stars predicted by massive binary evolution
calculations. Such a binary system is probably responsible for the ionization
of the unique HeII4686-emitting nebula N44C.
