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I. B. Rook, R. G. Samec (Bob Jones University), D. R. Faulkner (USC Lancaster), N. C. Hawkins (University of Oklahoma), W. Van Hamme (FIU)
We present new observations of XZ CMi taken at the National Undergraduate Research Observatory (NURO). Our CCD observations were taken 08-12 March 2005 by DRF and NCH with the Lowell Observatory 31-inch reflector and a LN cooled CCD camera with a metachrome coated TEK 512 X 512 chip. Standard UBVRI filters were used. A preliminary light curve analysis and an updated periodicity study is presented.
XZ CMi [\alpha(2000)=07h 54m 07.056s,\delta(2000)=+03 39 20.32] is a near-contact binary discovered by C. Hoffmeister (AN 253, 1934). Our light curves show eclipse amplitudes of magnitudes 0.722 and 0.104 in B and 0.651 and 0.18 in V, for the primary and secondary eclipses, respectively. The curves are fairly symmetrical, but show some irregularities, possibly due to solar-type activity. We took 87 images in B, 78 images in each of VRI, and 27 in U and determined three eclipse timings. They are HJD Min I=2453440.6116 ± 0.0003, 2453441.7676 ± 0.0001 and HJD Min II=2453442.6428 ± 0.0019.
Our periodicity study of the last 25,000 orbital cycles reveals a rather noisy (R = 0.7) sinusoidal ephemeris: HJD Hel Min I =2453441.77548±0.0032d + 0.5788087±0.0000002*E + (0.0068±0.0005) Sin[(1.07810 ±0.0001)*E+5.8±0.1]. A light time effect indicates an a(sin i) = 1.17±0.08 AU. Indeed, a third body is seen in images of XZ CMi in fair to good seeing. On the other hand, this effect may be due to the solar cycle of XZ CMi or possibly the period of nodal regression of the orbit. The period of the oscillation is 25.7 ±0.7 years.
We wish to thank the NURO for their allocation of observing time, as well as NASA and the American Astronomical Society for their support in paying for travel and publication expenses.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.