12 Boötis: A test-bed for extra-mixing processes in stars

Abstract

12 Boötis is a spectroscopic binary whose visual orbit has been resolved by interferometry. Though the physical parameters of the system have been determined with an excellent precision, the theoretical modelling of the components is still uncertain. We study the capability of solar-like oscillations to distinguish between calibrated models of the system obtained by including in the stellar modelling different mixing processes. We consider different scenarios for the chemical transport processes: classical overshooting, microscopic diffusion and turbulent mixing. For each of them we calibrate the stellar models of 12 Boo A and B by fitting the available observational constraints by means of a Levenberg-Marquardt minimization algorithm and, finally, we analyse the asteroseismic properties of different calibrated models. Several solutions with 12 Boo A in (or close to) post-main-sequence (post-MS) and 12 Boo B on MS are found by assuming a thickness of the overshooting layer between 0.06 and 0.23 the pressure scaleheight. Solutions with both components on the MS can be found only by assuming an overshoot larger in the primary than in the secondary, or a more efficient central mixing for 12 Boo A than for 12 Boo B. We show that the detection of solar-like oscillations expected in these stars would allow us to distinguish between different scenarios and provide therefore an estimation of the overshooting parameters and of the properties of extra-mixing processes. © 2007 RAS.