Description
Star formation is associated with high-energy processes and Young Stellar Objects (YSOs) are known to be energetic radio sources. Radio observations enable studies of the impact of high-energy processes such as powerful magnetic reconnection flares which are thought to impact disk and even planet formation. The Orion Nebula Cluster (ONC) is a relatively close region of active star formation, and the recent upgrade to a software correlator, allows the study of many sources simultaneously. In the context of YSOs emission is either thermal free-free or non-thermal gyrosynchrotron. VLBI observations are only sensitive to non-thermal emission resulting in 'filtering out' of thermal emission. This allows a census of the non-thermal source population and associated variability. Phase referenced VLBI observations allow high precision astrometry and thus measurements of absolute proper motions. The high resolution of the VLBA is one milliarcsecond corresponding to 0.4 AU at the distance of the ONC. We present multi-epoch results of VLBA data in the C-band (4-8 GHz) covering several years. This is focused on the non-thermal source population, associated radio variability and proper motions. There are currently limited examples of flares on shorter timescales e.g. hours or even minutes. We find variability occurring on different timescales with the highest occurring across two years associated with a class I YSO. The high resolution combined with astrometry allow for the search for multiple systems in otherwise inaccessible parameter space.
