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

¹ Department of Physics and AstronomyVanderbilt University, Nashville, TN 37235, USA
e-mail: leslie.hebb@vanderbilt.edu
² Summer REU Program, Vanderbilt University, Nashville, Tennessee 37235, USA
³ Astrophysics Research Centre, School of Mathematics & Physics, Queen’s University, University Road, Belfast, BT7 1NN, UK
⁴ Physics Department, Fisk University, Nashville, Tennessee 37208, USA
⁵ Department of Physics & Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden

Received: 1 December 2010
Accepted: 16 May 2011

Abstract

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, v_γ = +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 v_γ between 2006 and 2009 providing further evidence for the presence of a the third body in a wide (several year) orbit.