Free Access
Volume 551, March 2013
Article Number A121
Number of page(s) 9
Section Stellar structure and evolution
Published online 06 March 2013

Online material

Appendix A: Interferometric observations

thumbnail Fig. A.1

Square visibilities (left), closure phases (middle) and corresponding reduced χ2 map (right) for the PIONIER observation of 2012-02-24. The corresponding best-fit binary model is shown in red.

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thumbnail Fig. A.2

Same as Fig. A.1 for the PIONIER observation of 2012-03-02.

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thumbnail Fig. A.3

Same as Fig. A.1 for the PIONIER observation of 2012-03-03.

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thumbnail Fig. A.4

Same as Fig. A.1 for the PIONIER observation of 2012-03-05.

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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 g2mR2), RT 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, m1 stands for the mass of the star we are considering, and m2 for the mass of the other star.

Appendix B.2: Dynamical tides

Zahn (1977) gave characteristic times.

The conventions are the same as above. E2 is a dimensionless constant characteristizing the strength of the dynamical tide. Zahn (1975) provided a table of E2 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

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