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Astron. Astrophys. 331, 639-650 (1998)

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7. Conclusion

High-dispersion spectroscopy near the quadrature phases together with accurate photometry over a broad wavelength range have been used to identify TV Pic as one of the brightest near-contact binaries: the list of Shaw (1994 ) contains only 3 stars brighter than magnitude 7.5. All 130 stars in that list have larger light amplitudes than TV Pic. Presumably TV Pic, and the very similar, brighter ([FORMULA]) A-type star TU Hor = HR 1 081 = HD 21 981 (Waelkens, 1982 ), escaped attention because they do not show pronounced eclipses. Shaw's distance scale places TV Pic at 125 pc. These bright near-contact binaries are very interesting candidates for detailed high-dispersion spectroscopic studies.

Indeed, several properties of TV Pic described in this paper indicate that these binaries deserve further study:
(1) Both components are undermassive. This is characteristic of a small group of near-contact binaries (Yamasaki et al. 1990 ).
(2) To our knowledge, TV Pic is the first double-lined spectroscopic binary in this subgroup of near-contact binaries.
(3) The spectral types of primary and secondary (mid-A, early-F) are not too different.
(4) There is strong evidence that the F-type component rotates much faster than would be required for synchronous rotation. The stability of the light-curve indicates that no source of light variability co-rotates with this component. We suggest that checks for synchronous rotation should be made in similar systems, through the method applied here.
(5) TV Pic demonstrates that a strong O'Connell effect in the light-curves may occur when the system is seen at very moderate inclination.

Our analysis has led to the system parameters summarized in Table 9. Although the analysis of the light-curve is hampered by the very unequal brightness of its shoulders, several physical parameters have been determined to an informative degree of precision. Some improvements may be expected from more detailed light-curve solutions, but our analysis has indicated that ambiguities cannot at present be resolved. A more discriminatory data base, including spectroscopic observations in several other spectral windows, and over the whole orbital period, would provide a more direct foundation for a better physical model.


[TABLE]

Table 9. Predicted orbital and stellar parameters


Some improvements may be expected from more detailed light-curve solutions, but our analysis has indicated that ambiguities cannot at present be resolved. A more discriminatory data base, including spectroscopic observations in several spectral windows, would provide a more direct foundation for a better physical model.

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© European Southern Observatory (ESO) 1998

Online publication: February 16, 1998
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