Precise orbit solution of MML?53, a low-mass, pre-main sequence eclipsing binary in Upper Centaurus Lupus

摘要

Aims. We present a double-lined orbit solution for MML?53, the recently discovered low-mass pre-main sequence eclipsing binary. Methods. Using high-resolution spectra from the SMARTS?1.5?m echelle spectrograph, we measure precise radial velocities and derive the orbital parameters of the system. Results. The 2.1?d orbit of the eclipsing pair is circular, and we find the minimum masses of the eclipsing components to be M1sin3i?=?0.97???M⊙ and M2sin3i?=?0.84???M⊙, 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 ?~15?Myr). The systemic radial velocity from our orbit solution, vγ?= +1.4?±?0.3?±?0.8?km?s-1 (statistical and systematic), is also consistent with kinematic membership in this association. In addition, we detect a change in vγ between 2006 and 2009 providing further evidence for the presence of a the third body in a wide (several year) orbit.