2. Observations

Photoelectric observations in Johnson's B and V filters of BH Vir were made with the 60 cm reflecting telescope at Yunnan Observatory, Academy of Sciences, Sinica, on nine nights from April to May 1991. The extinction cofficients were low. The EMI6256B photomultiplier tube was cooled. was chosen as the comparison star and as the check star. Both stars were constant inside the observational errors in all observing nights. The intrinsic errors of one magnitude difference (variable-comparison) are and .

The light curves obtained in the two colours are shown in Figs. 1 (click here) and 2 (click here) and presented in Tables 1 and 2.

  
Figure 1: B observations of BH Vir

  
Figure 2: V observations of BH Vir

The phases used are based on the light elements given by Koch (1967):

The outside eclipse part of the first half of the light curve shows a very smooth curvature. Comparing with former light curves, the most striking aspects are:

1)

The depth of both minimua are similar to the observations of 1977 and 1986, but are different from data of 1963-1964.

2)

On the contrary of what observed from 1963-1964 to 1986, only a small decrease in the system brightness occurred around phase o.65 in 1991.

A photometric analysis of these and of previous data of BH Vir, including new times of minima, will be published separately (Xiang et al. 1996).