On the nature of the progenitors of three Type II-P supernovae: 2004et, 2006my and 2006ov

• Published in: Monthly notices of the Royal Astronomical Society 2011-02, Vol.410 (4), p.2767-2786
• Main Authors: Crockett, R. M., Smartt, S. J., Pastorello, A., Eldridge, J. J., Stephens, A. W., Maund, J. R., Mattila, S.
• Format: Article
• Language: English
• Subjects: Astronomical research; Astronomy; Earth, ocean, space; Exact sciences and technology; Space telescopes; stars: evolution; Supernovae; supernovae: general; supernovae: individual: SN 2004et; supernovae: individual: SN 2006my; supernovae: individual: SN 2006ov
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2010.17652.x

The pre-explosion observations of the Type II-P supernovae 2006my, 2006ov and 2004et are re-analysed. In the cases of supernovae 2006my and 2006ov we argue that the published candidate progenitors are not coincident with their respective supernova sites in pre-explosion Hubble Space Telescope observations. We therefore derive upper luminosity and mass limits for the unseen progenitors of both these supernovae, assuming they are red supergiants: 2006my (log L/L⊙= 4.51; m < 13 M⊙) and 2006ov (log L/L⊙= 4.29; m < 10 M⊙). In the case of supernova 2004et we show that the yellow supergiant progenitor candidate, originally identified in Canada-France-Hawaii Telescope images, is still visible ∼3 yr post-explosion in observations from the William Herschel Telescope. High-resolution Hubble Space Telescope and Gemini (North) adaptive optics late-time imagery reveal that this source is not a single yellow supergiant star, but rather is resolved into at least three distinct sources. We report the discovery of the unresolved progenitor as an excess of flux in pre-explosion Isaac Newton Telescope i′-band imaging. Accounting for the late-time contribution of the supernova using published optical spectra, we calculate the progenitor photometry as the difference between the pre- and post-explosion, ground-based observations. We find the progenitor was most likely a late K to late M-type supergiant of 8+5 −1 M⊙. In all cases we conclude that future, high-resolution observations of the supernova sites will be required to confirm these results.