The Physical Properties of the Red Supergiant Woh G64: the Largest Star Known?

WOH G64 is an unusual red supergiant (RSG) in the Large Magellanic Cloud (LMC), with a number of properties that set it apart from the rest of the LMC RSG population, including a thick circumstellar dust torus, an unusually late spectral type, maser activity, and nebular emission lines. Its reported physical properties are also extreme, including the largest radius for any star known and an effective temperature that is much cooler than other RSGs in the LMC, both of which are at variance with stellar evolutionary theory. We fit moderate-resolution optical spectrophotometry of WOH G64 with the MARCS stellar atmosphere This paper is based on data gathered with the 6.5 m Magellan telescopes located at Las Campanas, Chile. Predoctoral Fellow, Smithsonian Astrophysical Observatory, 60 Garden St., Cambridge, MA 02138