A Real-time Automated Triggering Framework for Solar Radio Burst Detection using Yamagawa Spectrograph for the Murchison Widefield Array

The observing time of the cutting-edge radio interferometers tends to be heavily oversubscribed. This, coupled with the fact that solar activity is inherently unpredictable leads to limited observing time being granted for solar observations. There are, of course, dedicated solar monitoring radio telescopes, but their data quality, and hence the resulting science, pales in comparison with what is possible with the best-in-class instruments. A robust and reliable automated near-real time observing trigger for cutting-edge radio interferometers derived from dedicated solar monitoring telescopes can improve this situation dramatically. By enabling one to use precious observing time only when some solar activity is known to have just taken place, such a system can vastly increase the efficiency of limited available observing time to capture instances of solar activity. With observatories like the Square Kilometre Array Observatory (SKAO) on the horizon, the need for such a system is even more imperative. We present such a system developed by us for the SKAO-low precursor, the Murchison Widefield Array (MWA) based on near-real time data from the Yamagawa spectrograph which observes the Sun daily from rise to set in the band from 70 MHz to 9 GHz and is located at similar longitude as the MWA.  Generating an observing trigger poses an interesting and challenging problem. Not only does one have to reliably detect and reject any radio frequency interference (RFI) which is inevitably present, to be successful, a trigger needs to be raised as early after the start of the event as feasible. We have devised, implemented and tested algorithms to identify and remove the RFI and do an effective ‘de-noising’ of the data to improve the contrast with which features of interest can be detected. We note that much of the event data lost due to the latency from Yamagawa can be recovered using the data buffer available at the MWA, which was designed exactly to meet such needs. These triggers have been tested and tuned using the archival Yamagawa data, end-to-end tests of triggered observations have successfully been carried out at the MWA. Very recently this real time triggering has been operationalized at the MWA, a very timely development in view of the approaching solar maxima.