A supergiant progenitor for SN 2011dh

A set of hydrodynamical models based on stellar evolutionary progenitors is used to study the nature of SN 2011dh. Our modeling suggests that a large progenitor star - with R ~ 200 R _⊙- is needed to reproduce the early light curve (LC) of SN 2011dh. This is consistent with the suggestion that the progenitor is a yellow super-giant star detected at the location of the SN in deep pre-explosion images. From the main peak of the bolometric light curve (LC) and expansion velocities we constrain the mass of the ejecta to be ~2 M _⊙, the explosion energy to be E = 8 × 10⁵⁰ erg, and the ⁵⁶Ni mass to be 0.063 M _⊙. The progenitor star is composed of a helium core of ~4 M _⊙ and a thin hydrogen envelope, and it had a main-sequence mass of ~13 M _⊙. Our models rule out progenitors with helium-core masses larger than 8 M _⊙, which correspond to M _ZAMS >~ 25 M _⊙. This suggests that a single evolutionary scenario for SN 2011dh is highly unlikely.