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F. P. Maloney, I. Ribas, E. L. Fitzpatrick, E. F. Guinan, L. E. DeWarf, J. E. Castora, J. F. Sepinsky (Villanova)
We have determined the distance to a third eclipsing binary (EB) system in the Large Magellanic Cloud, LMC-EROS 1044 (mV = 15.2; B2 IV-V + B2 IV-V; P = 2.728 d.). The measurements of the distance and properties of the system are based on optical photometry and spectroscopy, and HST UV/optical spectrophotometry. The analysis combines the classical EB study of light and radial velocity curves, which yield the stellar masses, radii and the temperature ratio of the stellar components, with a new analysis of the observed energy distribution. The UV/optical energy distribution of EROS 1044 is modeled using R.L. Kurucz's ATLAS9 model atmospheres to determine stellar effective temperature, reddening, and a "distance attenuation factor" (R/d)2. The data consist of HST/FOS (1150-4800 Å) and HST/STIS (3000-7500 Å) spectrophotometry, thus eliminating the need to include uncertain optical photometry in the analysis. The distance so determined is quite robust: resulting from a detailed study of well-understood objects (B stars) in a well- understood evolutionary phase (core H burning), and entirely consistent with stellar evolution calculations. There are no tuneable parameters and no zero-point uncertainties. The analysis is insensitive to stellar metallicity, although the metallicity is explicitly determined and incorporated. The reddening of the system is also determined explicitly and incorporated in the analysis. Moreover, the results do not depend on statistical averages, nor are they susceptible to sampling biases.
In this poster we describe the technique and present the results for EROS 1044. The results are consistent with those published earlier by us for the EB systems HV2274 and HV982 and offer a very strong argument in favor of the "short" LMC distance scale, corresponding to V0 - MV ~ 18.2 to 18.3.
This research is supported by NASA grants GO-06683 and GO-08691, which we gratefully acknowledge.
If you would like more information about this abstract, please follow the link to http://astro4.ast.villanova.edu/eros1044.pdf. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.