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The MWA uses a two-level triggering system for real-time events that can interrupt current observations and schedule new ones to catch a transient with low (~10-20 second) latency. The triggering system is described detail in Hancock et. al, 2019. The observations generated in response to a trigger can be of any duration, but anything longer than 30 minutes will need strong justification in your proposal. Both normal correlator and voltage-capture observations can be generated by a trigger. Your code can also request that a calibrator observation be scheduled immediately after the target observations, and the calibrator can be specified, or chosen automatically. If the trigger occurs during the day, your code can request that the primary beam direction be automatically offset slightly, to put the target location slightly off-center, but with the Sun in a primary beam null, to keep it out of the side-lobes. Your event handler code can also interrupt observations that it has generated for a previous event - for example, if a new VOEvent arrives with an updated source position, you can interrupt your first triggered observation/(s) and replace them with ones with the updated position.
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