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Appendix A: Interferometric observations
Fig. A.1
Square visibilities (left), closure phases (middle) and corresponding reduced χ^{2} map (right) for the PIONIER observation of 20120224. The corresponding bestfit binary model is shown in red. 

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Fig. A.2
Same as Fig. A.1 for the PIONIER observation of 20120302. 

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Fig. A.3
Same as Fig. A.1 for the PIONIER observation of 20120303. 

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Fig. A.4
Same as Fig. A.1 for the PIONIER observation of 20120305. 

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Appendix B: Computation of characteristic times for circularization and synchronization
Appendix B.1: Equilibrium tide
Press et al. (1975) provide explicit formulas. For each component of the binary, we have Here N is the angular rotation velocity of the star, g is its gyration radius (the moment of inertia is defined as g^{2}mR^{2}), R_{T} is an effective Reynolds number that can be taken ~20, and K and δ are numerical parameters. According to Press et al. (1975), we can typically assume K = 0.025 and δ = 0.1. The other symbols have their meaning introduced above. These formulas are valid for either component of the binary. In each case, m_{1} stands for the mass of the star we are considering, and m_{2} for the mass of the other star.
Appendix B.2: Dynamical tides
Zahn (1977) gave characteristic times.
The conventions are the same as above. E_{2} is a dimensionless constant characteristizing the strength of the dynamical tide. Zahn (1975) provided a table of E_{2} and gyration radius at ZAMS for various masses. We interpolated these values for the actual masses and computed the characteristic times, assuming n = N and e = 0.
Appendix B.3: Tidally driven meridional currents
According to Tassoul & Tassoul (1992), the characteristic times in years are (B.5)and (B.6)L is the stellar luminosity and N is a charateristic exponent that can be taken as 10 for stars with a convective envelope, and 0 for stars with a radiative envelope, which is the case here.
© ESO, 2013