2011A&A...531A..61H

We present a double-lined orbit solution for MML 53, the recently discovered low-mass pre-main sequence eclipsing binary. Using high-resolution spectra from the SMARTS 1.5m echelle spectrograph, we measure precise radial velocities and derive the orbital parameters of the system. The 2.1 d orbit of the eclipsing pair is circular, and we find the minimum masses of the eclipsing components to be M₁sin³i=0.97M_☉ and M₂ sin³i=0.84M_☉, with formal uncertainties of 2.0% and an additional systematic uncertainty of ≃2.5% most likely caused by large star spots on the primary star. MML 53 has been previously identified as a member of the Upper Centaurus Lupus (UCL) star forming region (age ∼15Myr). The systemic radial velocity from our orbit solution, v_γ=+1.4±0.3±0.8km/s (statistical and systematic), is also consistent with kinematic membership in this association. In addition, we detect a change in v_γ between 2006 and 2009 providing further evidence for the presence of a the third body in a wide (several year) orbit.