  We present observations of SN2009hd in the nearby galaxy M66. This SN is one
of the closest to us in recent years but heavily obscured by dust, rendering it
unusually faint in the optical, given its proximity. We find that the observed
properties of SN2009hd support its classification as a possible Type II-L SN, a
relatively rare subclass of CC-SNe. High-precision relative astrometry has been
employed to attempt to identify a SN progenitor candidate, based on a
pixel-by-pixel comparison between HST F555W and F814W images of the SN site
prior to explosion and at late times. A progenitor candidate is identified in
the F814W images only; this object is undetected in F555W. Significant
uncertainty exists in the astrometry, such that we cannot definitively identify
this object as the SN progenitor. Via insertion of artificial stars into the
pre-SN HST images, we are able to constrain the progenitor's properties to
those 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 yellow
than red. From a comparison with theoretical massive-star evolutionary tracks,
which include rotation and pulsationally enhanced mass loss, we can place a
conservative 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 our
derived mass limit, then it would be consistent with that for the identified
progenitors of the SNII-L 2009kr and the high-luminosity SNII-P 2008cn. The
progenitors of these three SNe may possibly bridge the gap between lower-mass
RSG that explode as SNeII-P and LBV, or more extreme RSG, from which the more
exotic SNeII-n may arise. Very late-time imaging of the SN2009hd site may
provide us with more clues regarding the true nature of its progenitor.

Solar and Stellar Astrophysics