Low metallicity indicates that the hypervelocity star he 0437-5439 was ejected from the large magellanic cloud

We measure the metallicity of the unusual hypervelocity star HE 0437-5439 from high-resolution spectroscopy to be half-solar. We determine a spectral type of B2 IV-III for the star and derive an effective temperature T-eff = 21,500 +/- 1000 K and a surface gravity log g = 3.7 +/- 0.2 (cgs). We also present BV time series photometry and find the star to be nonvariable at the 0.02 mag level. We refine the magnitude of the hypervelocity star to V = 16.36 +/- 0.04 mag, with a color B - V = -0.23 +/- 0.03 mag, confirming its early-type nature. Our metallicity result establishes the origin of HE 0437-5439 in the Large Magellanic Cloud and implies the existence of a massive black hole somewhere in this galaxy.