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2 Observations

The observations of BH Vir were carried out on 9 nights in April-May 1991, with the 60 cm reflecting telescope at Yunnan observatory, the Sinica Academy of Sciences, in Johnson's B and V fitters. BD-1$^{\circ}$2897 (F5) was chosen as the comparison star and BD-1$^{\circ}$2868 (F8) as the check star. Both stars were constant inside the observational errors on all nights. The intrinsic errors of one magnitude difference (variable - comparison) are $\pm 0\hbox{$.\!\!^{\rm m}$ }020$ (B) and $\pm0\hbox{$.\!\!^{\rm m}$ }017$ (V). These observations and the reduction procedure are published separately (Xiang & Liu 1997).

Table 1 presents minimum times for BH Vir calculated with our observations. Our minimum times were obtained with the method of quadratic fitting. All the times of 23 primary minimum and 22 secondary minimum of Table 1 and archival sources (Scaltriti et al. 1985; Arévalo et al. 1987) were fitted with both linear and second order ephemeris. Considering the primary and secondary data both separately and combined, we can discard the second order terms, because their errors become larger than the coefficients. No significant difference was found from analyzing the primary and secondary minimum separately, either, indicating a constant period. The linear ephemeris found was:

$\displaystyle %
{\rm MIN~I} = 2438107.19082 + 0.81687060E$     (1)
$\displaystyle \quad \quad \pm 96 \quad \quad \pm 17$      
$\displaystyle {\rm MIN~II} = 2438107.1881 + 0.81687055E$      
$\displaystyle \quad \quad \pm 12 \quad \quad \pm 16.$     (2)

This is in agreement with the ephemeris calculated by Koch (1967), who quotes:

{\rm JD} = 2438107.19047 + 0.81687099E.
\end{displaymath} (3)

Noting that the period has stayed constant to the precision of 1 part in 107, which is marginally confirmed by Eq. (1), which gives the O-C quoted in Table 1. To the degree of precision of our determinations, the period of BH Vir shows no obvious changes in thirty years.


Table 1: Minimum times of BH Vir (Eqs. (1) and (2))
48360.1389 12551.5 II -0.0036
$\pm 01$      
48362.1816 12554.0 I -0.0025
$\pm 01$      
48389.1385 12587.0 I -0.0029
$\pm 01$      
48396.0866 12595.5 II +0.0019
$\pm 01$      

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