2006AJ....132.1763H

θ¹ Ori E (θ¹E), the fifth brightest member of the Orion Nebula Trapezium, has been discovered to be a double-line spectroscopic binary. This paper describes the 1998-2006 Keck HIRES observations, the resulting spectroscopic orbit, and what can be inferred from the limited photometric information now available. The period is 9.89 days, and the components are essentially identical mid-G-type giants; their location in the H-R diagram and their possession of strong Li I λ6707 lines indicate that they are pre-main-sequence members of the Orion Nebula Cluster (ONC), with masses of about 3-4 M_☉. θ¹E is among the brightest X-ray sources in the ONC. It is variable in X-rays and is also a variable nonthermal radio source, but it is uncertain whether the object is also optically variable.