Fundamental Properties and Distances of the Large Magellanic Cloud from Eclipsing Binaries. II. HV 982^*

We have determined the distance to a second eclipsing binary (EB) system in the Large Magellanic Cloud, HV 982 (~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 HV 982, 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). The results are entirely consistent with—but do not depend on—stellar evolution calculations. There are no "zero-point" uncertainties as, for example, with the use of Cepheid variables. Neither is the result subject to sampling biases, as may affect techniques that utilize whole stellar populations, such as red giant branch stars. Moreover, the analysis is insensitive to stellar metallicity (although the metallicity of the stars is explicitly determined), and the effects of interstellar extinction are determined for each object studied. After correcting for the location of HV 982, 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 HV 2274, which implies a bar distance of 45.9 kpc. These results may either reflect 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.