Study of eclipsing binary and multiple systems in OB associations V: MQ Cen in Crux OB1

Abstract

The early-type massive binary MQ Cen (Porb=3.7 d) has been investigated by means of high-resolution (R∼48000) spectral analysis and multi-band (Johnson BVRI and Strömgren vby) light curve modeling. The physical parameters of the components have been found to be M1=4.26±0.10M⊙, R1=3.72±0.05R⊙, Teff1=16600±520 K, and M2=5.14±0.09M⊙, R2=7.32±0.03R⊙, Teff2=15000±500K for the primary and secondary, respectively. The orbital inclination is i=87.0±0.2 deg. The distance to MQ Cen has been derived to be d=2460±310 pc which locates it in the Crux OB1 association. However, the age of MQ Cen (∼70 Myr) is higher than the one reported for the Crux OB1 association (∼6 Myr). The derived masses are implying a spectral type of B5 for the primary and B4 for the secondary component. Nevertheless, the secondary component, which is more massive, appears to be cooler than the primary component: It has completed its lifetime on the main-sequence and it is now positioned at the turn-off point of the giant branch, meanwhile the less massive primary component is still staying on the main-sequence.