| Abstract | Radial velocities and CCD photometry suitable for a Baade-Wesselink analysis are now available for six short-period Cepheids (HV12198, HV12199, HV12202, HV12203, HV12204, and V4) in the LMC cluster NGC 1866. As a prerequisite for such an analysis, O-C diagrams have been constructed and examined for seven of the NGC 1866 Cepheids (HV12197, HV12198, HV12199, HV12200, HV12202, HV 12203, and HV 12204), yielding improved periods and estimates of the rate of period change in these coeval variables. One star, HV 12198, shows possible evidence for period change, but the phase mis- match due to that change is small enough to have negligible effect on its Baade-Wesselink radius. The computed radii are in good agreement with the Baade-Wesselink, theoretical and cluster/association period-radius relations of Fernie [ApJ, 282, 641(1984)] and the Galactic relation of Coulson & Caldwell [MNRAS, 240,285 (1989)]. The Flower [A&A, 54,31(1977)] color-effective temperature relation and the Becker et aL (1977) mass- luminosity relation lead to mean masses of 4.9+/-0.5M_sun_ and 4.6+/- 0.5M_sun_ for the respective metallicities of (Y,Z) = (0.0273,0.0016) and (0.026,0.02). Pulsation constants are also computed for these stars. |
