Possible binary star progenitor for SN1987A

Accurate optical astrometry gives a position (B 1950.0) for the Large Magellanic Cloud supernova, SN1987A, relative to the FK4 system as right ascension, RA = 05 h 35min 49.95 s± 0.039s (0.21″), declination δ −69° 17′ 57.9″ ±0.27″. Differential astrometry carried out on prime-focus plates taken with the Anglo-Australian telescope indicates that the component, star 1, of Sanduleak's star Sk–69202 is within 0.05±0.13arcs of the super-nova. Here we report that this precision astrometry, together with estimates of the probability of a chance association with a fore-ground or background star, lead us to conclude that the progenitor of SN1987A was star 1 or a fainter binary companion.