AAS 195th Meeting, January 2000
Session 76. Geometrically Variable Stars
Display, Friday, January 14, 2000, 9:20am-6:30pm, Grand Hall

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[76.01] The LMC Eclipsing Binary EROS 1044: Fundamental Properties and Evolutionary States

F. P. Maloney, E. L. Fitzpatrick, E. F. Guinan (Villanova U.), Y. W. Kang (Sejong U.), I. Ribas (U. Barcelona), L. E. DeWarf (Villanova U.), D. H. Bradstreet (Eastern C.), J. F. Sepinsky (Villanova U.)

We report on the progress in our study of selected eclipsing binaries in the Magellanic Clouds, begun with IUE and continued with HST. The chief aims are the determination of accurate temperatures, reddenings, and chemical abundances for the component stars. Twelve systems were observed with IUE during 1993-1995, mainly with the SWPLO camera (115- 200nm). During 1996/97, HST/FOS observations (in the 115-480 nm range) were secured from ten of these systems. These UV results are being combined with radii and masses of the stars obtained from ground-based photometry and spectroscopy. This yields the first directly determined Mass-Luminosity relation for stars outside our Galaxy. Moreover, these eclipsing binaries can serve as "standard candles", providing direct, independent and accurate distances to the LMC and SMC. We present preliminary results for the LMC eclipsing binary EROS 1044 (B2 V + B3 V; V max = +15.2 mag; P = 2.727 d). EROS 1044 was discovered as part of the photometric microlensing project using stars in the bar of the LMC. We have determined the orbital inclination (i = 79 deg.), and stellar physical properties (mass ratio, and fractional radii, temperatures, luminosities, and chemical abundances) from the Wilson-Devinney analysis of the light curve and from Kurucz (Atlas 9) model atmosphere fits to the HST/FOS spectra. Both components have similar properties: r1 = .23, r2 = .32, T = 21 300 K, log g = 3.73, [Fe/H] = -0.20, and E(B-V) = 0.16.

The work is supported by grants from NASA (NAG5-7113), HST (GO-06683), and NSF (RUI AST-9315365).

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