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Astron. Astrophys. 356, 603-611 (2000)

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5. Conclusions

The new results presented in this paper can be summarized as follows.

1. We reported the first uvby photometric and medium resolution spectroscopic observations of the short-period variable star HV Ursae Majoris. Contrary to the RRc classification given by ESA (1997), the star turned out to be a new contact binary with early-type components.

2. An improved ephemeris was determined using our and Hipparcos epoch photometric data: [FORMULA] = 2451346.743+0.7107523(3)[FORMULA]E. There is no indication of changing period over almost 10 years.

3. A radial velocity curve was measured directly from the H[FORMULA] profiles by two-component Gaussian fitting of the line core regions in spectra recorded around the quadratures. We calculated a spectroscopic mass ratio of 0.19[FORMULA]0.03.

4. The effective temperature and the surface gravity were determined using the mean Strömgren indices, synthetic colours of Kurucz (1993) and theoretical (ATLAS9) line profiles giving [FORMULA] K and log [FORMULA]. The light curve modelling resulted in a complete set of physical parameters.

5. The physical parameters of HV UMa together with the parallax measurement indicate that this binary is situated far from the galactic plane, and the primary component is an evolved object, probably a subgiant or giant star. The large temperature excess of the secondary may be indicative of a poor thermal contact between the components due to a relatively recent formation of this contact system via case B mass transfer.

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© European Southern Observatory (ESO) 2000

Online publication: April 10, 2000