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').

12 results found.

  1. GRB 231017A: Mondy optical observations. A possible candidate for an afterglow or host galaxy.
  2. GRB 231017A: 1.3m DFOT Optical upper limit
  3. GRB 231017A: Swift/UVOT Upper Limit
  4. GRB 231017A: GOTO optical upper limits
  5. GRB 231017A: JinShan optical upper limit
  6. GRB 231017A: Las Cumbres optical upper limit
  7. GRB 231017A: LCOGT Optical Upper Limits
  8. GRB231017A: GROWTH-India upper limits on the optical afterglow
  9. GRB 231017A: Fermi GBM Detection
  10. GRB 231017A: Swift-XRT observations
  11. GRB 231017A: Swift ToO observations
  12. GRB 231017A: Swift/BAT-GUANO candidate arcminute localization of a burst


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