Stellar evolution theory predicts multiple pathways to the explosive deaths of stars as supernovae. Locating and characterizing the progenitors of well-studied supernovae is important to constrain the theory and to justify and design future surveys to improve on progenitor detections. Here we report the serendipitous preexplosion imaging, by the Hubble Space Telescope, of SN 2023ixf, one of the nearest extragalactic supernovae ever discovered, in the galaxy M101. The extremely red color and absolute magnitude M F 814 W = − 5.11 − 0.47 + 0.65 mag suggest that the progenitor was a red supergiant. Comparison with stellar evolutionary isochrones suggests it is within the relatively low initial mass range of ∼8–10 M ⊙ and that there is likely a lot of dust present at the supernova site.

This work presents measurements of the local H ii environment metallicities of core-collapse supernovae (SNe) within a luminosity distance of 30 Mpc. 76 targets were observed at the Isaac Newton Telescope and environment metallicities could be measured for 65 targets using the N2 and O3N2 strong emission line method. The cumulative distribution functions (CDFs) of the environment metallicities of Type Ib and Ic SNe tend to higher metallicity than Type IIP, however Type Ic are also present at lower metallicities whereas Type Ib are not. The Type Ib frequency distribution is narrower (standard deviation ∼0.06 dex) than the Ic and IIP distributions (∼0.15 dex) giving some evidence for a significant fraction of single massive progenitor stars; the low metallicity of Type Ic suggests a significant fraction of compact binary progenitors. However, both the Kolmogorov-Smirnov test and the Anderson-Darling test indicate no statistical significance for a difference in the local metallicities of the three SN types. Monte Carlo simulations reveal a strong sensitivity of these tests to the uncertainties of the derived metallicities. Given the uncertainties of the strong emission methods, the applicability of the tests seems limited. We extended our analysis with the data of the Type Ib/Ic/IIP SN sample from Galbany et al. (2018). The CDFs created with their sample confirm our CDFs very well. The statistical tests, combining our sample and the Galbany et al. (2018) sample, indicate a significant difference between Type Ib and Type IIP with <5 per cent probability that they are drawn from the same parent population.

Deep narrow-band HST imaging of the iconic spiral galaxy M101 has revealed over a thousand new Wolf Rayet (WR) candidates. We report spectrographic confirmation of 10 He iiemission line sources hosting 15 WR stars. We find WR stars present at both sub-and supersolar metalicities with WC stars favouring more metal-rich regions compared to WN stars. We investigate the association of WR stars with H ii regions using archival HST imaging and conclude that the majority of WR stars are in or associated with H ii regions. Of the 10 emission lines sources, only one appears to be unassociated with a star-forming region. Our spectroscopic survey provides confidence that our narrow-band photometric candidates are in fact bonafide WR stars, which will allow us to characterise the progenitors of any core-collapse supernovae that erupt in the future in M101.

To understand how complete our surveys of Wolf-Rayet (WR) stars can be with the current generation of telescopes, we study images of M33, a galaxy with a nearly complete WR catalogue, and degrade them to investigate the detectability of WRs out to 30Mpc. We lose almost half of our sample at 4.2Mpc, and at 30Mpc we detect only those WRs in bright regions.

We analyse the impact that spatial resolution has on the inferred numbers and types of Wolf-Rayet (WR) and other massive stars in external galaxies. Continuum and line images of the nearby galaxy M33 are increasingly blurred to mimic effects of different distances from 8.4 Mpc to 30 Mpc, for a constant level of seeing. We use differences in magnitudes between continuum and Helium II line images, plus visual inspection of images, to identify WR candidates via their ionized helium excess. The result is a surprisingly large decrease in the numbers of WR detections, with only 15% of the known WR stars predicted to be detected at 30Mpc. The mixture of WR subtypes is also shown to vary significantly with increasing distance (poorer resolution), with cooler WN stars more easily detectable than other subtypes. We discuss how spatial clustering of different subtypes and line dilution could cause these differences and the implications for their ages, this will be useful for calibrating numbers of massive stars detected in current surveys. We investigate the ability of ELT/HARMONI to undertake WR surveys and show that by using adaptive optics at visible wavelengths even the faintest (MV = –3 mag) WR stars will be detectable out to 30 Mpc.