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Astron. Astrophys. 362, 673-682 (2000)

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6. Discussion

Due to a more reliable photometric analysis and a more realistic physical model (which considers, for instance, proximity effects in the computation of the radial velocity curves and the Kurucz stellar atmospheres) the discrepancy between a pure photometric mass ratio and the spectroscopic mass ratio of unity derived by Mammano et al. (1974) from their spectrographic orbit, has been alleviated considerably. The remaining difference is in magnitude and in the sense what we have to expect considering possible systematic error sources.

Despite the remaining uncertainties of the current simultaneous analysis of spectroscopic and photometric data, we adopt the following values for further discussion: [FORMULA] and [FORMULA] from which we derive [FORMULA], [FORMULA], and a mean [FORMULA] of [FORMULA] consistent with the value estimated from the Strömgren indices. Together with [FORMULA] and [FORMULA], this corresponds to a quite evolved stage on the main sequence. Further astrophysical parameters derived for the BF-Aur system are given in Table 10. The least squares solution clearly shows that the fits of the detached solutions are better than the fits of the semi-detached solutions.


Table 10. Astrophysical data for BF Aur. H is the orbital angular momentum in units of [FORMULA] g cm2s-1; h is the angular momentum per unit of reduced mass in units of [FORMULA] cm2 s-1; [FORMULA] is the specific angular momentum, and [FORMULA] is the mean stellar density in g cm-3. We define as primary the component eclipsed at primary minimum (phase 0:p0), which has, however, lower mass and luminosity, i.e., it is the spectroscopic secondary.

The period change detected by Demircan et al. (1997) may be interpreted as an indication for mass transfer. It seems that the phase of rapid mass transfer is about to start in BF Aur. This interpretation is consistent with the classification of BF Aur by Plavec (1968): the more massive component nearly fills its Roche lobe during its slow expansion (in phase I), or the systems actually is in the process of mass exchange.

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© European Southern Observatory (ESO) 2000

Online publication: October 24, 2000