Maloney, student L. M. Barge, I. Ribas (U. de Barcelona), DeWarf,
Fitzpatrick, and Guinan are investigating the LMC eclipsing binary HV 2241
as part of a larger project directed toward the determination of the
physical properties of LMC stars and the distance to the LMC. HV 2241 is a
semi-detached system, consisting of an 
III primary component and an
B0 III secondary (filling its Roche equipotential surface) in a 4.34 d
orbit. The datasets being analyzed consist of previously published CCD
photometry (Strömgren u, Cousins Ic, and V), HST/FOS 110-480 nm
spectrophotometry, and newly acquired 400-530 nm echelle spectroscopy using
the Blanco 4-meter telescope at CTIO. Preliminary values for the temperature
ratios of the components, the stellar radii and masses, and the inclination
of the stars' orbits are used to model the system with the Wilson-Devinney
eclipsing binary code. Analyzes of the spectrophotometry yield surface
temperatures of the stars and the amount of interstellar reddening. The
resulting stellar properties for the primary star (radius, temperature, and
mass) are compared with stellar evolution models for consistency. The
distance to HV 2241 is computed from a knowledge of the stars' radii and
temperatures as well as the amount of reddening.
Fitzpatrick, I. Ribas (U. of Barcelona), Guinan, Maloney, and A. Claret (Instituto de Astrofisica de Andalucia) published a paper in the April 20, 2003 issue of the Astrophysical Journal describing a detailed analysis of the eclipsing binary system HV5936 in the Large Magellanic Cloud As in the previous studies of LMC eclipsing binaries, this analysis combines ''classical'' EB light curve and radial velocity curve analyzes with modeling of the UV-through-optical spectral energy distribution of HV5936, to produce a detailed characterization of the system. This study also includes an analysis of the high-resolution optical absorption line spectra of the binary components. The optical spectra of the primary and secondary were extracted separately from spectra of the system via a Fourier ''disentangling'' algorithm. HV 5936 was found to be an Algol-class system, in which the masses of the primary and secondary stars have evolved via mass transfer to their current values of 11.6 M¤ and 4.7 M¤, respectively. The initial masses of the two stars were approximately 7.5 M¤ and 13 M¤, respectively. The properties of the primary star (i.e., temperature, mass, luminosity, and radius) are indistinguishable from those of a ''normal'' single star of the same current mass. The secondary is found to be overluminous for its current mass and exhibits a factor-of-2 enhancement in its surface He abundance. These results are compatible with ``Case A'' mass exchange occurring during the core hydrogen burning phase of the current secondary
Financial support from the NASA - Delaware Valley Space Grant Consortium, and from the National Science Foundation through HST grant GO-06683 is gratefully acknowledged. We are grateful for the skilled assistance of the CTIO staff during our January 2000 observing run.