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Astron. Astrophys. 361, L49-L52 (2000)

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5. Results and conclusions

The photometric observations presented here have revealed that the low-mass PMS spectroscopic binary RXJ0529.4+0041 is an eclipsing system. We have derived orbital and stellar parameters for the system, in particular, absolute masses and radii for the two binary components, as well as an independent estimate of distance. The spatial location and kinematics strongly support the fact that RXJ 0529.3+0041 is a young star associated with the Ori OB-1a association. The derived lithium abundance, much higher than the ZAMS upper limit, provides further, independent evidence that this system is indeed very young. The comparison with different theoretical evolutionary tracks, although still preliminary, already provides new interesting constraints to the current evolutionary models for low-mass PMS stars. Although there are quite obvious differences from one model to the other for lower masses, the comparison indicates that the components of RXJ 0529.3+0041 are fairly coeval, within the uncertainties, with ages of nearly [FORMULA] years. The primary component lies already on the radiative part of the PMS track, while the secondary falls on the final part of the corresponding convective Hayashi track. Thus, at least the primary component can be considered as a `bona-fide' post-T Tauri star.

Our photometric data also contain indications of possible brightness variations, unrelated to the eclipses, in this system, presumably connected to rotational modulation induced by stellar spots and other phenomena driven by magnetic-activity. Such variability needs to be investigated in more detail as it may affect the determination of the out-of-eclipse light-level, which can be critical for the light-curve solution. Further study in different photometric bands (both optical and near-infrared) is thus planned in order to obtain a more precise determination of the effective temperatures for the components of this PMS eclipsing binary, as well as to investigate the out-of-eclipse variability.

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© European Southern Observatory (ESO) 2000

Online publication: October 10, 2000