On the Progenitor of Supernova 2001du in NGC 1365

Hubble Space Telescope (HST) WFPC2 archival images obtained years prior to the explosion of the Type II-plateau supernova (SN) 2001du in NGC 1365 previously have been analyzed to isolate the progenitor star. The SN site was located using precise astrometry applied to the HST images, with significant uncertainty, leaving three possible progenitor candidates. Images of the fading SN have recently become publicly available in the HST archive, allowing us to pinpoint the SN's exact location on the preexplosion images. We show that the SN occurred in very close proximity to one of the blue candidate stars, but we argue that this star is not the actual progenitor. Instead, the progenitor was not detected on the pre-SN images, and we constrain the progenitor's mass to be less than 13⁺⁷_-4 M_solar. This is consistent with previous constraints on the progenitor masses of other Type II-plateau SNe, suggesting that such SNe arise from the iron core collapse of massive stars at the lower extreme of the possible mass range.

Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive of the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.