Radial density profile of the outer component of ξ Tau at the onset of RLOF (green drawn line). The dotted lines represent SPH models with varying core mass M_core (red, purple, blue and cyan dotted lines for M_core = 1, 2, 3 and 4 M_⊙, respectively). These core masses correspond to a fraction of 0.18, 0.36, 0.55 and 0.73 of the total mass of 5.5 M_⊙.