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Almost two decades ago, strong non-thermal variable radio-emission had been detected from θ1 Orionis A, the third most luminous OB star in the Orion Trapezium Cluster. The source of the emission, has been a puzzling issue since then. Now, it is established that θ1 Orionis A is a close triple stellar system and that the radio emission originates from the visual companion θ1 Orionis A2. In this contribution we re-analyse available radio data combined with near-infrared observations in order to constrain the nature of θ1 Orionis A2. Stringent constraints on the size of the non-thermal radio emission imply the presence of very large magnetic structures. Conceivable scenarii are a) θ1 Orionis A2 is a single young intermediate-mass star with strong magnetic interactions between the star and its circumstellar disk, b) θ^1 Orionis A2 is a binary and radio flaring originates from interactions between the magnetic structures of both stars. [ABSTRACT FROM AUTHOR]

We report on the results of a binary survey in the outer parts of the Orion Nebula Cluster, 0.7 to 2 pc from the cluster center. The results should help to decide if the binary formation rate was lower in Orion than in Taurus-Auriga, or if many binaries formed initially, but were destroyed in close stellar encounters. We find that the binary frequency of low-mass stars does not depend on the distance to the cluster center. The companion star frequency of intermediate- to high-mass stars shows a trend to decrease with cluster radius, but the statistical significance of this trend is rather weak. [ABSTRACT FROM AUTHOR]