| circulars | GCN Circular | GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. An archive of all GCN Circulars can be found at https://gcn.nasa.gov/circulars | - | - |