The triple system θ1 orionis A in the heart of the orion trapezium cluster

Abstract

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) θ1 Orionis A2 is a binary and radio flaring originates from interactions between the magnetic structures of both stars. © 2008 Springer-Verlag Berlin Heidelberg.