We present the results of a 10.5‐yr, volume‐limited (28‐Mpc) search for supernova (SN) progenitor stars. In doing so we compile all SNe discovered within this volume (132, of which 27 per cent are Type Ia) and determine the relative rates of each subtype from literature studies. The core‐collapse SNe break down into 59 per cent II‐P and 29 per cent Ib/c, with the remainder being IIb (5 per cent), IIn (4 per cent) and II‐L (3 per cent). There have been 20 II‐P SNe with high‐quality optical or near‐infrared pre‐explosion images that allow a meaningful search for the progenitor stars. In five cases they are clearly red supergiants, one case is unconstrained, two fall on compact coeval star clusters and the other twelve have no progenitor detected. We review and update all the available data for the host galaxies and SN environments (distance, metallicity and extinction) and determine masses and upper mass estimates for these 20 progenitor stars using the stars stellar evolutionary code and a single consistent homogeneous method. A maximum likelihood calculation suggests that the minimum stellar mass for a Type II‐P to form is mmin= 8.5+1−1.5 M⊙ and the maximum mass for II‐P progenitors is mmax= 16.5 ± 1.5 M⊙, assuming a Salpeter initial mass function holds for the progenitor population (in the range Γ=−1.35+0.3−0.7). The minimum mass is consistent with current estimates for the upper limit to white dwarf progenitor masses, but the maximum mass does not appear consistent with massive star populations in Local Group galaxies. Red supergiants in the Local Group have masses up to 25 M⊙ and the minimum mass to produce a Wolf–Rayet star in single star evolution (between solar and LMC metallicity) is similarly 25–30 M⊙. The reason we have not detected any high‐mass red supergiant progenitors above 17 M⊙ is unclear, but we estimate that it is statistically significant at 2.4σ confidence. Two simple reasons for this could be that we have systematically underestimated the progenitor masses due to dust extinction or that stars between 17–25 M⊙ produce other kinds of SNe which are not II‐P. We discuss these possibilities and find that neither provides a satisfactory solution. We term this discrepancy the ‘red supergiant problem’ and speculate that these stars could have core masses high enough to form black holes and SNe which are too faint to have been detected. We compare the 56Ni masses ejected in the SNe to the progenitor mass estimates and find that low‐luminosity SNe with low 56Ni production are most likely to arise from explosions of low‐mass progenitors near the mass threshold that can produce a core‐collapse.

The progenitors of many type II core-collapse supernovae have now been identified directly on pre-discovery imaging. Here we present an extensive search for the progenitors of type Ibc supernovae in all available pre-discovery imaging since 1998. There are 12 type Ibc supernovae with no detections of progenitors in either deep ground-based or Hubble Space Telescope archival imaging. The deepest absolute BV R magnitude limits are between −4 m and −5 m . We compare these limits with the observed Wolf-Rayet population in the Large Magellanic Cloud and estimate a 16 per cent probability we have failed to detect such a progenitor by chance. Alternatively the progenitors evolve significantly before core-collapse or we have underestimated the extinction towards the progenitors.Reviewing the relative rates and ejecta mass estimates from lightcurve modelling of Ibc SNe, we find both incompatible with Wolf-Rayet stars with initial masses > 25M ⊙ being the only progenitors. We present binary evolution models that fit these observational constraints. Stars in binaries with initial masses 20M ⊙ lose their hydrogen envelopes in binary interactions to become low mass helium stars. They retain a low mass hydrogen envelope until ≈ 10 4 years before core-collapse; hence it is not surprising that galactic analogues have been difficult to identify.

We present comprehensive photometric and spectroscopic observations of the faint transient SN 2008S discovered in the nearby galaxy NGC 6946. SN 2008S exhibited slow photometric evolution and almost no spectral variability during the first nine months, implying a long photon diffusion time and a high-density circumstellar medium. Its bolometric luminosity ( 10 41 erg s −1 at peak) is low with respect to most core-collapse supernovae but is comparable to the faintest Type II-P events. Our quasi-bolometric light curve extends to 300 d and shows a tail phase decay rate consistent with that of 56 Co. We propose that this is evidence for an explosion and formation of 56 Ni (0.0014 ± 0.0003 M ). Spectra of SN 2008S show intense emission lines of Hα, [Ca II] doublet and Ca II near-infrared (NIR) triplet, all without obvious P-Cygni absorption troughs. The large mid-infrared (MIR) flux detected shortly after explosion can be explained by a light echo from pre-existing dust. The late NIR flux excess is plausibly due to a combination of warm newly formed ejecta dust together with shock-heated dust in the circumstellar environment. We reassess the progenitor object detected previously in Spitzer archive images, supplementing this discussion with a model of the MIR spectral energy distribution. This supports the idea of a dusty, optically thick shell around SN 2008S with an inner radius of nearly 90 AU and outer radius of 450 AU, and an inferred heating source

We present spectroscopy and photometry of the He‐rich supernova (SN) 2008ax. The early‐time spectra show prominent P‐Cygni H lines, which decrease with time and disappear completely about 2 months after the explosion. In the same period He i lines become the most prominent spectral features. SN 2008ax displays the ordinary spectral evolution of a Type IIb supernova. A stringent pre‐discovery limit constrains the time of the shock breakout of SN 2008ax to within only a few hours. Its light curve, which peaks in the B band about 20 d after the explosion, strongly resembles that of other He‐rich core‐collapse supernovae. The observed evolution of SN 2008ax is consistent with the explosion of a young Wolf–Rayet (of WNL type) star, which had retained a thin, low‐mass shell of its original H envelope. The overall characteristics of SN 2008ax are reminiscent of those of SN 1993J, except for a likely smaller H mass. This may account for the findings that the progenitor of SN 2008ax was a WNL star and not a K supergiant as in the case of SN 1993J, that a prominent early‐time peak is missing in the light curve of SN 2008ax, and that Hα is observed at higher velocities in SN 2008ax than in SN 1993J.

We present photometric and spectroscopic data of the peculiar SN 2005la, an object which shows an optical light curve with some luminosity fluctuations and spectra with comparably strong narrow hydrogen and helium lines, probably of circumstellar nature. The increasing full width at half‐maximum velocity of these lines is indicative of an acceleration of the circumstellar material. SN 2005la exhibits hybrid properties, sharing some similarities with both Type IIn supernovae and 2006jc‐like (Type Ibn) events. We propose that the progenitor of SN 2005la was a very young Wolf–Rayet (WN‐type) star which experienced mass ejection episodes shortly before core collapse.