AAS 202nd Meeting, May 2003
Session 8 Binary Stars
Poster, Monday, May 26, 2003, 9:20am-6:30pm, West Exhibit Hall

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[8.09] A Photometric Study of the Neglected, Dwarf Contact Binary V524 Monocerotis

R. G. Samec, T. S. Loflin (Bob Jones University)

Recent observations of the neglected shallow contact binary, V524 Monocerotis [HBV 463, GSC 153 1410, \alpha(2000) = 6h 59m 1.2s , \delta(2000) = +02\circ 12' 51"] were taken at Cerro Tololo InterAmerican Observatory in Chili. Our present observations were taken with the 0.9-m reflector and the CFIM T2K CCD camera with standard UBVRcIc filters in quad mode on 31 December 2002 and 1 January 2003, by RGS. Around 100 observations were taken in each pass band. An unnamed comparison star (\alpha(2000) = 06h59m3.8s, \delta(2000) = +02\circ1452) and the check star (GSC 153 1435, \alpha(2000) = 6h58m54.8s, \delta(2000) = +02\circ1537) were used in the IRAF reductions. Two mean epochs of minimum light were determined from a primary and secondary eclipse, 2452640.74555 (28) and 2452640.74555 (28). A linear ephemeris was calculated using the most recent timings from the last 29,000 orbits.

J.D. Hel Min I = 2452641.73735(213) d + 0.283616062 (126) E. (1)

A quadratic ephemeris was used to fit some 50 minima, spanning 82,500 orbital cycles or 64 years.

J.D. Hel Min I = 2452641.73797(113) d + 0.2836160386 (9) E -1.1(1) x 10-11 x E2 . (2)

This quadratic result indicates that the system is losing angular momentum via magnetic breaking, i.e., it is slowly coalescing. An unspotted synthetic light curve solution was calculated using the Wilson Code. The final parameters include the mass ratio, m2/m1 = 1.83(2), Roche lobe fill-out 9 T1-T2 = 348(6). The curves are of W-type, with the larger star having the cooler surface. This indicates heavy, saturated magnetic activity on the primary component (star 1). Further results of this study will be presented. We wish to thank Cerro Tololo InterAmerican Observatory for their allocation of observing time, and the grant from NASA administered by the American Astronomical Society which supported this run.

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