Blue supergiants as a progenitor of intermediate-luminosity red transients

Abstract The current perspective about the explosions of massive hydrogen-rich blue supergiants is that they resemble SN 1987A. These so-called peculiar Type II supernovae, however, are one of the rarest types of supernovae and may not hence be the fate of all blue supergiants. In this work, we explore other explosion scenarios for blue supergiants. We create synthetic light curves from the explosions of blue supergiant models born from binary mergers, over a range of explosion energies and $^{56}\mathrm{Ni}$ masses. We find that blue supergiant explosions may also lead to intermediate-luminosity red transients. We thus identify two categories of supernovae possible from blue supergiant explosions: those with high $^{56}\mathrm{Ni}$ masses ($\gtrsim$0.01 ${M}_\odot$) result in slow-rising, dome-shaped light curves like SN 1987A. Lower $^{56}\mathrm{Ni}$ masses result in low-luminosity, short-plateau light curves resembling some intermediate-luminosity red transients and Type II supernovae like SN 2008bp, which are possible from the explosions of compact blue supergiants and not from the far more extended red supergiants. Our results indicate that blue supergiant explosions are more diverse than SN 1987A-like events and may be hidden among different kinds of transients, explaining the possible discrepancies between the expected fraction of blue supergiants born from binary mergers and the observed fraction of SN 1987A-like supernovae.