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5 Conclusion

From 1953 to 1990, a number of authors have made photometric observations of BH Vir and have given their solutions. However, the vast majority of observed light curves show large distortions, so there may be obvious deviations in their results. For instance, the photospheric temperature of the primary, T1, has been found different by many authors: about 6100 K (data from 1963-1964) and 5911 K (data from 1977, both results by Zhai et al. 1990), 6250 K (Wilson & Rafert 1980), and 6000 K (Zeilik et al. 1990). The light curve of BH Vir in 1991 shows a slight and reasonably smooth curvature excepting only a small decrease around phase 0.65. We have used two different models to fit it, and have obtained T1 = 5945 K. We think our solution is reliable.

The most significant result of the present work, in contrast with the results of former authors, is the evidence of the spot active regions not only on the primary star, but on the secondary component, also. In fact, the secondary is a solar-type star, and as such should satisfy the conditions of forming spot active regions. This is further evidence for BH Vir being a member of the short period RS CVn group.

We note that the average mass ratio (q = 0.967) and the radius ratio ( r2/r1 = 0.898) are less than unity and the visual luminosity of the secondary is about one-half that of the primary (see Table 2). This is in keeping with Zhai et al. photometric and spectroscopic solutions. The greater disparity of luminosities to masses suggests that the primary is approaching the end of its Main-Sequence lifetime, as pointed out by Zeilik et al. (1990).

Table 4 presents the relative size of spots on the primary star. From the changes of the relative areas we can suggest that BH Vir have active cycle as many authors have already found in other RS CVn systems (Hall 1972; Vogt 1983). However, we must be very cautious about believing these results. First, the observations of BH Vir are not continuous and systematic in epochs. These data can prove that the system is active, but are insufficient to confirm the existence of an activity cycle in BH Vir. Second, all of the former authors did not consider any activity on the secondary. The spot models used by them might be inappropriate, so there may be systematic deviations in their results. Third, the active cycle should be verified by spectroscopic observations. Hence, further observations and detailed study are important to confirm whether BH Vir have active cycle.


Table 4: BH Vir spot areas on the primary star
Data $S/S_{\rm d}$ Wavelength Source
1963-1964 0.152 U.B.V Zhai et al. (1990)
1963-1964 0.067 B.V This work
1977 0.048 U.B.V Zhai et al. (1990)
1984 0.06 V Scaltriti et al. (1985)
1991 0 B.V This work
1963-1964 0.020 B.V Zeilik et al. (1990)
1977 0.008 V Zeilik et al. (1990)
1984 0.019 U.B.V.R Zeilik et al. (1990)
1986 0.011 U.B.V.R.I Zeilik et al. (1990)

Notes: $S_{\rm d}$ = visible disc.

We would like to thank Dr. L.P.R. Vaz for his help in calculations and suggestions. The study was supported by Hunan Education Council.

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