The Red Supergiant Progenitor of Supernova 2012aw (PTF12bvh) in Messier
  95
  We report on the direct detection and characterization of the probable red
supergiant progenitor of the intermediate-luminosity Type II-Plateau (II-P)
supernova (SN) 2012aw in the nearby (10.0 Mpc) spiral galaxy Messier 95 (M95;
NGC 3351). We have identified the star in both Hubble Space Telescope images of
the host galaxy, obtained 17-18 yr prior to the explosion, and near-infrared
ground-based images, obtained 6-12 yr prior to the SN. The luminous supergiant
showed evidence for substantial circumstellar dust, manifested as excess
line-of-sight extinction. The effective total-to-selective ratio of extinction
to the star was R'_V \approx 4.35, which is significantly different from that
of diffuse interstellar dust (i.e., R_V=3.1), and the total extinction to the
star was therefore, on average, A_V \approx 3.1 mag. We find that the observed
spectral energy distribution for the progenitor star is consistent with an
effective temperature of 3600 K (spectral type M3), and that the star therefore
had a bolometric magnitude of -8.29. Through comparison with recent theoretical
massive-star evolutionary tracks we can infer that the red supergiant
progenitor had an initial mass 15 \lesssim M_{ini} (M_sun) < 20. Interpolating
by eye between the available tracks, we surmise that the star had initial mass
~17-18 M_sun. The circumstellar dust around the progenitor must have been
destroyed in the explosion, as the visual extinction to the SN is found to be
low (A_V=0.24 mag with R_V=3.1).
