On the nature of the progenitors of three type II-P supernovae: 2004et,
  2006my and 2006ov
  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/Lsun = 4.51; mass < 13Msun) and 2006ov (log L/Lsun = 4.29; mass <
10Msun). 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 years 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 Msun.
In all cases we conclude that future, high-resolution observations of the
supernova sites will be required to confirm these results.
