On the nature and detectability of Type Ib/c supernova progenitors

Abstract

Context. The progenitors of many Type II supernovae have been observationally identified but the search for Type Ibc supernova (SN Ibc) progenitors has thus far been unsuccessful, despite the expectation that they are luminous Wolf-Rayet (WR) stars. Aims. We investigate how the evolution of massive helium stars affects their visual appearances, and discuss the implications for the detectability of SN Ibc progenitors.Methods. Evolutionary models of massive helium stars are analysed and their properties compared to Galactic WR stars. Results. Massive WR stars that rapidly lose their helium envelopes through stellar-wind mass-loss end their lives when their effective temperatures -related to their hydrostatic surfaces -exceed about 150 kK. At their pre-supernova stage, their surface properties resemble those of hot Galactic WR stars of WO sub-type. These are visually faint with narrow-band visual magnitudes M v = −1.5 · · · −2.5, despite their high bolometric luminosities (log L/L = 5.6 · · · 5.7), compared to the bulk of Galactic WR stars (M v < −4). In contrast, relatively low-mass helium stars that retain a thick helium envelope appear fairly bright in optical bands, depending on the final masses and the history of the envelope expansion during the late evolutionary stages. Conclusions. We conclude that SNe Ibc observations have so far not provided strong constraints on progenitor bolometric luminosities and masses, even with the deepest searches. We also argue that Ic progenitors are more challenging to identify than Ib progenitors in any optical images.

Helium stars: towards an understanding of Wolf–Rayet evolution

“…However, for models with mass loss, no such trend is apparent. With mass loss, the high-mass helium stars evolve to obtain higher stellar temperatures than lowmass helium stars, as first identified by Yoon et al (2012). Though the high-mass helium stars are more luminous, the majority of their flux is output in the UV bands due to their higher surface temperatures.…”

“…The prediction that the most luminous progenitors are, in fact, those of the lowest mass was first noted by Yoon et al (2012). It is, therefore, expected that helium giant Type Ib/c progenitors will be observable, while progenitors from WR stars will remain difficult to detect.…”

“…The non-detection of Type Ib/c supernovae progenitors are discussed by Yoon et al (2012) and Eldridge et al (2013). Included on the right ordinates of Figs.…”

Towards a better understanding of the evolution of Wolf–Rayet stars and Type Ib/Ic supernova progenitors

“…(i) Some WC stars are too bright (log L/L ⊙ > 5.5; Figs 3 and 6) to be explained by helium giants of which the luminosities would be lower than about log L/L ⊙ = 5.3 (Yoon et al 2012;McClelland & Eldridge 2016).…”

Fundamental properties of core-collapse supernova and GRB progenitors: predicting the look of massive stars before death

“…However, this scenario has yet to be observationally confirmed, specially because WR stars have not been directly detected as SN Ibc progenitors yet (Smartt 2009;Eldridge et al 2013). The non-detection could be due to the intrinsic faintness of WRs in the optical bands, which are the ones usually available for the SN explosion site (Yoon et al 2012), or because SN Ibc progenitors have lower masses and result from binary evolution (Podsiadlowski et al 1992;Smartt 2009;Eldridge et al 2013), or both. In addition, observations suggest that some massive stars can explode as SNe already during the LBV phase (e.g.…”