SN 2006tf is the third most luminous supernova ( SN ) discovered so far , after SN 2005ap and SN 2006gy .
SN 2006tf is valuable because it provides a link between two regimes : ( 1 ) luminous type IIn supernovae powered by emission directly from interaction with circumstellar material ( CSM ) , and ( 2 ) the most extremely luminous SNe where the CSM interaction is so optically thick that energy must diffuse out from an opaque shocked shell .
As SN 2006tf evolves , it slowly transitions from the second to the first regime as the clumpy shell becomes more porous .
This link suggests that the range in properties of the most luminous SNe is largely determined by the density and speed of hydrogen-rich material ejected shortly before they explode .
The total energy radiated by SN 2006tf was at least 7 \times 10 ^ { 50 } ergs .
If the bulk of this luminosity came from the thermalization of shock kinetic energy , then the star needs to have ejected \sim 18 M _ { \odot } in the 4–8 yr before core collapse , and another 2–6 M _ { \odot } in the decades before that .
A Type Ia explosion is therefore excluded .
From the H \alpha emission-line profile , we derive a blast-wave speed of 2,000 km s ^ { -1 } that does not decelerate , and from the narrow P Cygni absorption from pre-shock gas we deduce that the progenitor ’ s wind speed was \sim 190 km s ^ { -1 } .
This is reminiscent of the wind speeds of luminous blue variables ( LBVs ) , but not of red supergiants or Wolf-Rayet stars .
We propose that like SN 2006gy , SN 2006tf marked the death of a very massive star that retained a hydrogen envelope until the end of its life , and suffered extreme LBV-like mass loss in the decades before it exploded .