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

TL;DR

This study re-analyzes pre-explosion data of three type II-P supernovae, refining progenitor properties and establishing upper mass limits, highlighting the importance of high-resolution imaging for accurate progenitor identification.

Contribution

It provides revised progenitor identifications and mass estimates for supernovae 2004et, 2006my, and 2006ov, correcting previous candidate identifications and demonstrating the need for high-resolution follow-up.

Findings

2006my and 2006ov progenitors are not coincident with supernova sites.

Upper mass limits for 2006my (<13Msun) and 2006ov (<10Msun) progenitors.

The 2004et progenitor was a late K to late M supergiant (~8Msun).

Abstract

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.