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arXiv · 1511.07971

The Araucaria Project: High-precision orbital parallax and masses of the eclipsing binary TZ~Fornacis

A. Gallenne·G. Pietrzyński·D. Graczyk·P. Konorski·P. Kervella·A. Mérand·W. Gieren·R. I. Anderson·S. Villanova
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Abstract

Context: Independent distance estimates are particularly useful to check the precision of other distance indicators, while accurate and precise masses are necessary to constrain evolution models. Aim: The goal is to measure the masses and distance of the detached eclipsing-binary TZ~For with a precision level lower than 1\,\% using a fully geometrical and empirical method. Method: We obtained the first interferometric observations of TZ~For with the VLTI/PIONIER combiner, which we combined with new and precise radial velocity measurements to derive its three-dimensional orbit, masses, and distance. Results: The system is well resolved by PIONIER at each observing epoch, which allowed a combined fit with eleven astrometric positions. Our derived values are in a good agreement with previous work, but with an improved precision. We measured the mass of both components to be $M_1 = 2.057 \pm 0.001\,M_\odot$ and $M_2 = 1.958 \pm 0.001\,M_\odot$. The comparison with stellar evolution models gives an age of the system of $1.20 \pm 0.10$\,Gyr. We also derived the distance to the system with a precision level of 1.1\,\%: $d = 185.9 \pm 1.9$\,pc. Such precise and accurate geometrical distances to eclipsing binaries provide a unique opportunity to test the absolute calibration of the surface brightness-colour relation for late-type stars, and will also provide the best opportunity to check on the future Gaia measurements for possible systematic errors.

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A. Gallenne, G. Pietrzyński, D. Graczyk, P. Konorski, P. Kervella, A. Mérand, W. Gieren, R. I. Anderson, S. Villanova. 2015-11-25. The Araucaria Project: High-precision orbital parallax and masses of the eclipsing binary TZ~Fornacis. https://doi.org/10.1051/0004-6361%2F201526764

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