Radial Velocities of the Four Stars of the Trapezium in Orion.

Abstract

Seventy-six spectrograms of the stars HD 37020, 37021, 37022, and 37023 have been obtained at the McDonald Observatory. The measures indicate that HD 37021 = BM Orionis has the following ele- ments: P = 6.50 days, ~` = +24.0 km/sec, K = 81 km/sec, e = 0.14, c~ = 194°, T = JD 2430787.86. The other three stars have relatively small ranges in velocity. The mean velocities of these four stars and of 02 Orionis = lID 37041 exceed the velocity of the Orion nebula by 15.0 km/sec. This may be due to a gravitational red shift or to a systematic motion of the four stars through the nebula