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|Title:||Dynamical masses of the low-mass stellar binary AB Doradus B||Authors:||Azulay, R.
Guirado, J. C.
Marcaide, J. M.
Jauncey, D. L.
Lestrade, J. -F.
Preston, R. A.
Reynolds, J. E.
|Issue Date:||2015||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||578||First Page:||A16||Abstract:||Context. AB Doradus is the main system of the AB Doradus moving group. It is a quadruple system formed by two widely separated binaries of pre-main-sequence (PMS) stars: AB Dor A/C and AB Dor Ba/Bb. The pair AB Dor A/C has been extensively studied and its dynamical masses have been determined with high precision, thus making AB Dor C a benchmark for calibrating PMS stellar models. If the orbit and dynamical masses of the pair AB Dor Ba/Bb could be determined, they could play a similar role to that of AB Dor C in calibrating PMS models, and would also help to better understand the dynamics of the whole AB Doradus system. <BR /> Aims: We aim to determine the individual masses of the pair AB Dor Ba/Bb using VLBI observations and archive infrared data as part of a larger program that monitors binary systems in the AB Doradus moving group. <BR /> Methods: We observed the system AB Dor B between 2007 and 2013 with the Australian Long Baseline Array (LBA) at a frequency of 8.4 GHz in phase-reference mode. <BR /> Results: We detected, for the first time, compact radio emission from both stars in the binary, AB Dor Ba and AB Dor Bb. This result allowed us to determine the orbital parameters of both the relative and absolute orbits and, consequently, their individual dynamical masses: 0.28 ± 0.05 M<SUB>☉</SUB> and 0.25 ± 0.05 M<SUB>☉</SUB>, respectively. <BR /> Conclusions: Comparisons of the dynamical masses with the prediction of PMS evolutionary models show that the models underpredict the dynamical masses of the binary components Ba and Bb by 10-30% and 10-40%, respectively, although they still agree at the 2σ level. Some of the stellar models considered favor an age between 50 and 100 Myr for this system, while others predict older ages. We also discuss the evolutionary status of AB Dor Ba/Bb in terms of an earlier double-double star scenario that might explain the strong radio emission detected in both components.||Acknowledgments:||This work has been partially supported by the Spanish MINECO projects AYA2009-13036-C02-02 and AYA2012-38491-C02-01 and by the Generalitat Valenciana projects PROMETEO/2009/104 and PROMETEOII/2014/057. The Long Baseline Array is part of the Australia Telescope National Facility which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. We thank J. Montalbán for providing the PMS models and for the guidance to use them appropriately. The data used in this study were acquired as part of NASA’s Earth Science Data Systems and archived and distributed by the Crustal Dynamics Data Information System (CDDIS). This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. R.A. acknowledges the Max-Planck-Institute für Radioastronomie for its hospitality and especially J. A. Zensus for support.||URI:||http://hdl.handle.net/20.500.12386/26493||URL:||https://www.aanda.org/articles/aa/abs/2015/06/aa25704-15/aa25704-15.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201525704||Bibcode ADS:||2015A&A...578A..16A||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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