We present visual-wavelength photometry and spectroscopy of supernova ( SN ) 2008S .
Based on the low peak luminosity for a SN of M _ { R } = -13.9 mag , photometric and spectral evolution unlike that of low-luminosity SNe , a late-time decline rate slower than ^ { 56 } Co decay , and slow outflow speeds of 600–1000 km s ^ { -1 } , we conclude that SN 2008S is not a true core-collapse SN and is probably not an electron-capture SN .
Instead , we show that SN 2008S more closely resembles a “ SN impostor ” event like SN 1997bs , analogous to the giant eruptions of luminous blue variables ( LBVs ) .
Its total radiated energy was \sim 10 ^ { 47.8 } ergs , and it may have ejected 0.05–0.2 M _ { \odot } in the event .
We discover an uncanny similarity between the spectrum of SN 2008S and that of the Galactic hypergiant IRC+10420 , which is dominated by narrow H \alpha , [ Ca ii ] , and Ca ii emission lines formed in an opaque wind .
We propose a scenario where the vastly super-Eddington ( \Gamma \approx 40 ) wind of SN 2008S partly fails because of reduced opacity due to recombination , as suggested for IRC+10420 .
The range of initial masses susceptible to eruptive LBV-like mass loss was known to extend down to 20–25 M _ { \odot } , but estimates for the progenitor of SN 2008S ( and the similar NGC 300 transient ) may extend this range to \lesssim 15 M _ { \odot } .
As such , SN 2008S may have implications for the progenitor of SN 1987A .