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We present observations of SN2009hd in the nearby galaxy M66. This SN is oneof the closest to us in recent years but heavily obscured by dust, rendering itunusually faint in the optical, given its proximity. We find that the observedproperties of SN2009hd support its classification as a possible Type II-L SN, arelatively rare subclass of CC-SNe. High-precision relative astrometry has beenemployed to attempt to identify a SN progenitor candidate, based on apixel-by-pixel comparison between HST F555W and F814W images of the SN siteprior to explosion and at late times. A progenitor candidate is identified inthe F814W images only; this object is undetected in F555W. Significantuncertainty exists in the astrometry, such that we cannot definitively identifythis object as the SN progenitor. Via insertion of artificial stars into thepre-SN HST images, we are able to constrain the progenitor's properties tothose of a possible supergiant, with M(F555W)0>-7.6 mag and (V-I) 0>0.99 mag.The magnitude and color limits are consistent with a luminous RSG; however,they also allow for the possibility that the star could have been more yellowthan red. From a comparison with theoretical massive-star evolutionary tracks,which include rotation and pulsationally enhanced mass loss, we can place aconservative upper limit on the initial mass for the progenitor of <20 M_sun.If the actual mass of the progenitor is near the upper range allowed by ourderived mass limit, then it would be consistent with that for the identifiedprogenitors of the SNII-L 2009kr and the high-luminosity SNII-P 2008cn. Theprogenitors of these three SNe may possibly bridge the gap between lower-massRSG that explode as SNeII-P and LBV, or more extreme RSG, from which the moreexotic SNeII-n may arise. Very late-time imaging of the SN2009hd site mayprovide us with more clues regarding the true nature of its progenitor.

The Massive Progenitor of the Possible Type II-Linear Supernova 2009hd in Messier 66