Upper Limit to the Distance to the Large Magellanic Cloud

Research paper by Andrew Gould, Osamu Uza

Indexed on: 19 May '97Published on: 19 May '97Published in: Astrophysics

Abstract

We remeasure the light echo'' times to the near and far side of the ring around SN 1987A using the method of Gould (1995) and the new reductions of the original UV spectra by Sonneborn et al. (1996). Under the assumption that the ring is circular, we obtain an upper limit to the distance to the Large Magellanic Cloud \mu_lmc < 18.37 +/- 0.04. This result is very close to Gould's original value, and contradicts claims that the new spectra measurements lead to a significant increase in the distance estimate and a substantial increase in the statistical errors. We present new evidence (partly provided by A.P.S. Crotts) that the ring is intrinsically elliptical, with axis ratio b/a ~ 0.95. For an elliptical ring, \mu_lmc < 18.44 +/- 0.05. We elaborate on Gould's original argument that the upper limit is robust, i.e., that it is only weakly sensitive to unmodeled aspects of the ring such as its hydrodynamic properties and ionization history.