UBV Photometry of the Massive Eclipsing Binary TT Aur

S. Oezdemir, H. Ak, M. Tanriver, H. Guelsecen, \\
S. Guelsecen,
A. T. Saygac, E. Budding, O. Demircan.
, PASA, 18 (2), in press.

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Discussion

Our light curve analysis differs from the older ones in two ways: firstly we used a revised mass ratio, taken from Popper and Hill (1991), who took account of distorting effects in the broad and overlapping line profiles in such OB type double-lined binaries. Secondly, our simultaneous solutions are based on new photometry of TT Aur. The solution presented in Table 3 shows a semi-detached configuration. As a result, the secondary component can be expected to be transferring material onto the primary. The long-term period increase of

$P = 1.6\times10^{-3}$ sec y-1, obtained from O - C analysis of the times of minimum, points to a semi-detached model with mass transfer from the secondary. Previous light curves, and ours, show an absorption effect in the shoulders of the primary minimum, in agreement with mass transfer in this semi-detached model. Also, the 12.2 y period sinusoidal variation of times of minima, superposed on the longer term period increase, may be caused by either a third body in the system or an episodic nature to the mass loss and transfer. The solution presented in Table 4 corresponds to a detached model. While the curve-fit allows feasibility to such a model, there are systematic irregularities in the light curves, which would be more in keeping with mass-transfer effects in a semi-detached scenario. While the detached model stars are both close to Main Sequence, it is also clear that these stars must be relatively very close, so we should naturally expect some interactive effects to have started with such proximity. TT Aur is a special example of a close eclipsing binary system consisting of a pair of young and massive stars. The evidence studied in this paper points to interesting interactive effects, but, by itself, does not convincingly resolve between physically somewhat different, alternative representations. We will continue to observe and analyse TT Aur and we appeal to others for further observations. For example, satellite-UV or IR data may help to get a clearer understanding of this interesting binary by establishing the amount of circumbinary matter.


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Title/Abstract Page: UBV Photometry of the
Previous Section: Absolute Parameters
Contents Page: Volume 18, Number 2

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