The strange case of theta 1 Orionis

Abstract

We review the binary properties of the bright Orion Trapezium star theta^1 Ori A and include radial velocities from IUE in a new orbital solution; meanwhile, times of primary minimum are used to determine a new ephemeris. With these revised parameters, we strongly encourage further observations, especially a search for secondary minimum. Probably the system consists of a main sequence early B primary and a cooler pre-main-sequence companion.