The type IIb SN 2008ax: the nature of the progenitor
  A source coincident with the position of the type IIb supernova (SN) 2008ax is identified in pre-explosion Hubble Space Telescope (HST) Wide Field Planetary Camera 2 observations in three optical filters. We identify and constrain two possible progenitor systems: (i) a single massive star that lost most of its hydrogen envelope through radiatively driven mass loss processes, prior to exploding as a helium-rich Wolf-Rayet star with a residual hydrogen envelope, and (ii) an interacting binary in a low mass cluster producing a stripped progenitor. Late time, high resolution observations along with detailed modelling of the SN will be required to reveal the true nature of this progenitor star. 
R. M. Crockett, J. J. Eldridge, S. J. Smartt, A. Pastorello, A.   Gal-Yam, D. B. Fox, D. C. Leonard, M. M. Kasliwal, S. Matt...