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

Using the definitive reductions of the IUE light curves by [14] and an extensive set of HST images of SN 1987A we have repeated and improved our original analysis [8] to derive a better determination of the distance to the supernova. In this way we have obtained an absolute size of the ring Rabs = (6.23 ± 0.08) × 10 17 cm and an angular size R′′ = 808 ± 17mas, 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.