Massive star evolution: luminous blue variables as unexpected supernova progenitors

Geneva Observatory, Geneva University, Chemin des Maillettes 51, 1290 Sauverny, Switzerland
e-mail: jose.groh@unige.ch

Received: 15 November 2012
Accepted: 17 December 2012

Abstract

Stars more massive than about 8 M_⊙ end their lives as a supernova (SN), an event of fundamental importance Universe-wide. Theoretically, these stars have been expected to be either at the red supergiant, blue supergiant, or Wolf-Rayet stage before the explosion. We performed coupled stellar evolution and atmospheric modeling of stars with initial masses between 20 M_⊙ and 120 M_⊙. We found that the 20 M_⊙ and 25 M_⊙ rotating models, before exploding as SN, have spectra that do not resemble any of the aforementioned classes of massive stars. Rather, they have remarkable similarities with rare, unstable massive stars known as luminous blue variables (LBV). While observations show that some SNe seem to have had LBVs as progenitors, no theoretical model had yet predicted that a star could explode at this stage. Our models provide theoretical support for relatively low-luminosity LBVs exploding as SN in the framework of single stellar evolution. This is a significant shift in paradigm, meaning that a fraction of LBVs could be the end stage of massive star evolution, rather than a transitory evolutionary phase. We suggest that type IIb SN could have LBV as progenitors, and a prime example could be SN 2008ax.