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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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Absolute Parameters

Absolute parameters of the system were computed from the data given in Tables 3 and 4, using the revised radial velocities of the system from Popper & Hill (1991).

**Table 5:** Absolute parameters for TT Aur*
Parameter	Primary	Secondary

M( $\odot$ )	7.2 $\pm$ 0.1	4.80 $\pm$ 0.03
	6.9, 8.9	4.6, 5.2
R( $\odot$ )	4.16 $\pm$ 0.03	4.21 $\pm$ 0.03
	4.47, 4.29	3.22, 3.20
T K (adopted)	23400 (B2.5V)	18000 $\pm$ 180 (B5IV)
	21500	15500
L $\odot$	$(4.6\pm0.02)\times10^3$	$(1.6\pm0.2)\times10^3$
	5.4, 3.5	0.97, 0.53
a ( $\odot$ )	$6.98 \pm 0.14$	$4.66 \pm 0.03$
	6.90	4.60
$<\rho>$ (g cm^-3)	$0.14\pm0.02$	$0.091 \pm0.003$
	0.11	0.19
log g (cgs)	$4.05\pm0.02$	$3.87 \pm 0.02$
	3.98	4.08
M_V	-2.13 (mag)	-1.47 (mag)
	-2.29, -2.5	-1.10, -1.2
d(kpc) (adopted)	1.1	1.1

*SD solutions given on first line; D solutions on second; MS comparisons follow in italics.

E_{(B - V)} = 0.29, adopted from Wachmann et al. (1986), and

R = A_V/E_(B-V) = 3.2 assumed.

The detached model conforms to typical Main Sequence values for early type stars, as may be seen in the comparisons of Popper (1980). Although the derived masses are somewhat lower than typical for early Main Sequence stars of types comparable to those adopted, the mass ratio (0.67) is in keeping with a near-MS configuration. Low masses might reflect the difficulties of deriving accurate radial velocities for such rapidly rotating stars. It is similar with the adopted temperatures and correspondingly derived luminosities. Thus, while the temperature ratio (0.77) concurs with a near-MS configuration, the adopted values (cf. Figueiredo et al., 1994) are higher than typical. The radii, on the other hand, being relatively insensitive to the masses, are close to normal MS stars of similar types. The separately derived absolute magnitude values are also close to MS values.

Next Section: Discussion
Title/Abstract Page: UBV Photometry of the
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Contents Page: Volume 18, Number 2

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