A Geometric Determination of the Distance to SN 1987A and the LMC

Using the definitive reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved our original analysis (Panagia et al. 1991) to derive a better determination of the distance to the supernova. In this way we have obtained an absolute size of the ring R(abs) = (6.23 +/- 0.08)e17 cm and an angular size R'' = 808 +/- 17 mas, which give a distance to the supernova d(SN1987A) = 51.4 +/- 1.2 kpc and a distance modulus (m-M)_SN1987A}} = 18.55 +/- 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to be d(LMC)=51.7 +/- 1.3 kpc, which corresponds to a distance modulus of (m-M)_LMC = 18.56 +/- 0.05.