Skip to main content
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circulars

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. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').

10 results found.

  1. GRB 230506B: Chandra localization of the X-ray afterglow
  2. GRB 230506B: Fermi GBM detection
  3. GRB 230506B: Swift/UVOT further analysis
  4. GRB 230506B: Swift-BAT refined analysis
  5. GRB 230506B: LCOGT Optical Upper Limits
  6. GRB 230506B: Swift-XRT refined Analysis
  7. GRB 230506B: Swift/UVOT Detection
  8. GRB 230506B: Swift detection of a burst
  9. GRB 230506B: MASTER optical observations
  10. GRB 230506B: Swift detection of a burst


Download all Circulars as a .tar.gz archive:
Looking for U.S. government information and services? Visit