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WR 20a Is an Eclipsing Binary: Accurate Determination of Parameters for an Extremely Massive Wolf-Rayet System*

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Published 2004 July 8 © 2004. The American Astronomical Society. All rights reserved. Printed in U.S.A.
, , Citation A. Z. Bonanos et al 2004 ApJ 611 L33 DOI 10.1086/423671

1538-4357/611/1/L33

Abstract

We present a high-precision I-band light curve for the Wolf-Rayet binary WR 20a, obtained as a subproject of the Optical Gravitational Lensing Experiment. Rauw et al. have recently presented spectroscopy for this system, strongly suggesting extremely large minimum masses of 70.7 ± 4.0 and 68.8 ± 3.8 M for the component stars of the system, with the exact values depending strongly on the period of the system. We detect deep eclipses of about 0.4 mag in the light curve of WR 20a, confirming and refining the suspected period of P = 3.686 days and deriving an inclination angle of i = 74fdg5 ± 2fdg0. Using these photometric data and the radial velocity data of Rauw et al., we derive the masses for the two components of WR 20a to be 83.0 ± 5.0 and 82.0 ± 5.0 M. Therefore, WR 20a is confirmed to consist of two extremely massive stars and to be the most massive binary known with an accurate mass determination.

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Footnotes

  • Based on observations obtained with the 1.3 m Warsaw telescope at Las Campanas Observatory, which is operated by the Carnegie Institute of Washington.

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10.1086/423671