The size of ABDorA from VLTI/AMBER interferometry

Source: arXiv

ABSTRACT The pre-main sequence (PMS) star ABDorA is the main component of the
quadruple system ABDoradus. The precise determination of the mass and
photometry of the close companion to ABDorA, ABDorC, has provided an important
benchmark for calibration of theoretical evolutionary models of low-mass stars.
The limiting factor to the precision of this calibration is the age of the
system, as both the mass and luminosity of ABDorA and C are well monitored by
other ongoing programs. In this paper we present VLTI/AMBER observations of
ABDorA which provide a direct measurement of the size of this star, 0.96+/-0.06
Rsun. The latter estimate, combined with other fundamental parameters also
measured for this star, allows a precise test of PMS evolutionary models using
both H-R diagrams and mass-radius relationships. We have found that our radius
measurement is larger than that predicted by the models, which we interpret as
an evidence of the oversizing produced by the strong magnetic activity of
ABDorA. Considering, at least partially, this magnetic effect, theoretical
isochrones have been used to derive constraints to the age of ABDorA, favouring
an age about 40-50 Myr for this system. Older ages are not completely excluded
by our data.

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