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Дата изменения: Fri Jan 25 15:37:51 2002 Дата индексирования: Tue Oct 2 09:36:06 2012 Кодировка: Поисковые слова: voyager |
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 , 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
(Woolf & Jeffery 2000).
Measuring
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 (
) of three
PVTel variables. Analysis of the UV photometry provided measures of
and
. Fitting
and
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
for two stars,
albeit with significant errors. The final results from this project
have been submitted for publication (Jeffery et al. 2000).