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7 HD 33363 = CL Cam

7.1 Brief history

HD 33363 was added to the second edition of the CABS catalog on the basis of its strong CaII H and K emission (Bidelman 1991; Strassmeier 1994) and its variable velocity. Henry et al. (1995) classified the star as K0 III, noted a preliminary orbital period of 20.9 days, and found a period of 41.5 days for its photometric variability. Such disparate periods are unusual but not unknown among active binaries. In fact, the orbital and rotational periods found for HD 33363 are similar to those of the well-known asynchronous rotator $\lambda$ And.

7.2 Orbital elements

Between 1991 and 1998 two radial-velocity data sets were obtained at the KPNO for HD 33363; a more extensive set of 28 velocities by FCF and 10 velocities in January 1996 by the Vienna group. A preliminary set of orbital elements was determined for the FCF velocities with BISP. After one velocity was given zero weight, those elements were refined with SB1. The Vienna group's velocities were compared with this orbit. As a result, no zero-point correction was applied to the January 1996 velocities, and those individual velocities were given a weight of 0.05 in the final orbital solution, whose elements are listed in Table 5. The individual velocities and residuals to the computed fit are given in Table A6 in the Appendix. Shown in Fig. 5 is the computed velocity curve compared with our velocities.

 
\begin{figure}
\includegraphics [angle=-90,width=8.7cm]{hd33363.eps}
\end{figure} Figure 5: Radial-velocity curve of HD 33363. All data were obtained at KPNO  

We note that for the final solution the standard error of an observation of unit weight is 0.15 kms-1, the best so far achieved with the coudé feed telescope for an orbit of a chromospherically active star. Since the orbit has a small but definite eccentricity of $0.071\pm 0.003$, HD 33363 is still in the process of both circularization and synchronization. A time of conjunction with the primary behind the secondary is HJD $2\,449\,311.371$.


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