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DIRECT MASSES FOR BXCIR AND PVTEL VARIABLES

The discovery of BXCir with properties very similar to V652Her and the subsequent analysis of its light and velocity curves gave Kilkenny et al. (1999) the opportunity to derive its radius using Baade's method. However, in conjunction with the Drilling et al. (1998) value for $\log g$, their results yielded a very low mass that was difficult to accept. A new study using AAT échelle spectroscopy and HST spectrophotometry has revised this value upwards to $M_{\rm D}=0.43\pm0.15\mbox{\,$\rm M_{\odot}$}$ (Woolf & Jeffery 2000).

Measuring $M_{\rm D}$ for the PVTel variables poses considerable difficulties. Since the pulsations are not strictly regular, comparing angular and radial variations requires that observations be obtained simultaneously. Moreover the radial-velocity amplitudes are small, the periods are long, and ultraviolet photometry is essential. In spite of these constraints, Jeffery et al. (2000) succeeded in obtaining nearly contiguous ultraviolet photometry and radial velocities ($v$) of three PVTel variables. Analysis of the UV photometry provided measures of $T, \theta$ and $\Pi$. Fitting $\theta$ and $v$ with sine curves provided estimates of their mean amplitudes, and hence their mean radii. The data for one are shown in Fig. 3. These data provided remarkably convincing estimates of $M_{\rm D}$ for two stars, albeit with significant errors. The final results from this project have been submitted for publication (Jeffery et al. 2000).