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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[76.12] V684 Mon: An Eclipsing Duo of Very Young B stars in NGC 2264

D.H. Bradstreet, J.R. Hargis, J.S. Lake, J.M. Blair, D.C. Eagles, F.D. Jewett (Eastern College)

V684 Mon (HD 47755, W74, vM37, VSB52) is a young, hot (~B5V, ~B5V; V = +8.57) close eclipsing binary (P = 1.851 d) in the open cluster NGC 2264 (cluster age 3-4 Myr). Walker (1956) noted that this star exhibited double lines, but no published radial velocity curve exists. Koch et al. (1986) discovered that the system eclipsed, but the system was observed over a limited timescale, obtaining only one minimum with enough coverage to generate a reliable timing. The light curve analysis was tentative due to substantial noise in that first light curve. No other light curve has been published since that one. Because of the potential for investigating a very young pair of main sequence B-stars in a cluster of known age, this star was put on the observing program at the Bradstreet Observatory at Eastern College. In the 1999 winter observing season 7 eclipses in the V bandpass were obtained using a 40-cm telescope coupled with a SBIG ST8 CCD. The analysis of the nearly 3000 images using the IRAF point spread function task indicates that the binary now exhibits a small but definite eccentricity. This is also consistent with the slightly different eclipse widths noted in the 1981 data, although there was no evidence of eccentricity at that time relative to the position of the secondary eclipse. The non-circularity speaks favorably to the idea that this is indeed a young pair of B stars, since membership of V684 Mon in NGC 2264 has been questioned in the past. The observations, times of minimum light, period analysis, and preliminary light curve analysis using the Wilson-Devinney model will be presented.

If you would like more information about this abstract, please follow the link to http://www.eastern.edu/academic/undg/depts/physsci/v684.html. 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.

The author(s) of this abstract have provided an email address for comments about the abstract: dbradstr@eastern.edu

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