AAS 205th Meeting, 9-13 January 2005
Session 9 NURO Asteroids and Stars
Poster, Monday, January 10, 2005, 9:20am-6:30pm, Exhibit Hall

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[9.05] A New Very Early Contact Binary in Cyg OB2

L. Y. Rios, K. DeGioia-Eastwood (NAU)

As part of a long-term program to improve the calibration of the mass-luminosity relation for the most massive stars, we have initiated a search for eclipsing O binaries by monitoring a sample of O stars photometrically. Out of the first 18 stars, we have already found an unusual contact binary (W UMa type) consisting of a late O and an early B star. The star was first cataloged by Massey and Thompson (1991, AJ 101, p. 1408) as number 696 in the association Cyg OB2. The original spectral type assigned to the star was O9.5 V. The period of the binary is only 1.46 days, and a spectrum taken at the MMT confirms that the star is indeed a double-lined spectroscopic binary. We will present the light curve and available spectra.

This research was performed at the Lowell Observatory 31-inch telescope which, under an agreement with Northern Arizona University, is shared with the National Undergraduate Research Observatory. LYR and KDE both acknowledge the support of the NSF REU program at Northern Arizona University under AST-9988007.

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