AAS 203rd Meeting, January 2004
Session 12 Eclipsing Binary Stars
Poster, Monday, January 5, 2004, 9:20am-6:30pm, Grand Hall

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[12.21] Analysis of the Solar Type Near Contact Eclipsing Binary, HM Monocerotis

C. Duddles, M. Hussey, T. S. Loflin, R. G. Samec, J. Miller (Bob Jones University)

Here we present an initial analysis of the solar type near contact binary, HM Monocerotis [GSC 162 265, \alpha(2000) = 7h 3m 2.89s, \delta(2000) = 00\arcdeg 13' 49.1"]. The observations were taken at CTIO, 23, 27 and 28 December 2002, by RGS with the 0.9-m reflector and the CFIM T2K CCD camera in quad mode. Standard UBVRcIc filters were used. Nearly 275 observations were taken in each pass band. The comparison and check star were GSC 162 1551 (\alpha (2000) = 7h02m59.60s, \delta(2000) = 00\arcdeg14'32.8") and GSC 162 1709 (\alpha (2000) = 7h03m12.16s, \delta(2000) = 00\arcdeg14'31.1"), respectively. Mean epochs of minimum light for two primary eclipses, HJD = 2452632.7926 (4) and 2452637.6842 (5) as well as one secondary eclipse 2452636.6638 (8)were calculated. These were averaged from parabola fits in each of the 5 bands of the eclipse curves. Some 89 minima spaning some 27 years were collected. The period shows at least two major constant period eras or may reflect a higher order period behavior than a quadratic. We calculated the following ephemerides:

J.D. Hel Min I = 2430110.1954 (40) + 0.40765733 (48) d*E, (1)


J.D. Hel Min I = 2452632.7895 (42) + 0.40765554 (38) d*E. (2)

Equation (1) represents a fit to all early times of minimum light (era I) and equation (2) is from later times (era II) of minimum light including our timings. The light curve amplitude of HM Mon is 0.82 mags for the primary eclipse and 0.21 for the secondary. The curves are somewhat asymmetrical. A Binary Maker fit and a Wilson program solution is presented. This work was done by our undergrade students this fall. 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.

The author(s) of this abstract have provided an email address for comments about the abstract: ronsamec@msn.com

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