Fundamental Properties and Distances of LMC Eclipsing Binaries II. HV 982

Abstract

We have determined the distance to a second eclipsing binary system (EB) in the Large Magellanic Cloud, HV982 (~B1 IV-V + ~B1 IV-V). The measurement of the distance -- among other properties of the system -- is based on optical photometry and spectroscopy and space-based UV/optical spectrophotometry. The analysis combines the ``classical'' EB study of light and radial velocity curves, which yields the stellar masses and radii, with a new analysis of the observed energy distribution, which yields the effective temperature, metallicity, and reddening of the system plus the distance ``attenuation factor'', essentially (radius/distance)^2. Combining the results gives the distance to HV982, which is 50.2 +/- 1.2 kpc. This distance determination consists of a detailed study of well-understood objects (B stars) in a well-understood evolutionary phase (core H burning), and is free of the biases and uncertainties that plague various other techniques. After correcting for the location of HV982, we find an implied distance to the optical center of the LMC's bar of d(LMC) = 50.7 +/- 1.2 kpc. This result differs by nearly 5 kpc from our earlier result for the EB HV2274, which implies a bar distance of 45.9 kpc. These results may reflect either marginally compatible measures of a unique LMC distance or, alternatively, suggest a significant depth to the stellar distribution in the LMC. Some evidence for this latter hypothesis is discussed.