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 ^ { \prime } _ { 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 } _ { \odot } ) < 20 .
Interpolating by eye between the available tracks , we surmise that the star had initial mass \sim 17 – 18 { M } _ { \odot } .
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 ) .