We present the first orbital elements for the massive close binary HD 101131 , one of the brightest objects in the young open cluster IC 2944 .
This system is a double-lined spectroscopic binary in an elliptical orbit with a period of 9.64659 \pm 0.00012 days .
It is a young system of unevolved stars ( approximately 2 million years old ) that are well within their critical Roche surfaces .
We use a Doppler tomography algorithm to reconstruct the individual component optical spectra , and we apply well known criteria to arrive at classifications of O6.5 V ( ( f ) ) and O8.5 V for the primary and secondary , respectively .
We compare the reconstructed spectra of the components to single-star spectrum standards to determine a flux ratio of f _ { 2 } / f _ { 1 } = 0.55 \pm 0.08 in the V -band .
Both components are rotating faster than synchronously .
We estimate the temperatures and luminosities of the components from the observed spectral classifications , composite V magnitude , and cluster distance modulus .
The lower limits on the masses derived from the orbital elements and the lack of eclipses are 25 M _ { \odot } and 14 M _ { \odot } for the primary and secondary , respectively .
These limits are consistent with the larger masses estimated from the positions of the stars in the Hertzsprung-Russell diagram and evolutionary tracks for single stars .