Skip to main content
New! Browse Circulars by Event, Advanced Search, Sample Codes, Schema Release. 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').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

22 results found.

  1. GRB 250221A: ATCA Detections and Upper Limits
  2. GRB 250221A: EP-FXT detection of the X-ray afterglow
  3. GRB 250221A: Swift-BAT refined analysis
  4. GRB 250221A: TNOT detection of the optical counterpart
  5. GRB 250221A: VLA radio detection
  6. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  7. GRB 250221A: continued Mondy optical observations, brightening afterglow
  8. GRB 250221A: Optical counterpart detection by LCO.
  9. GRB 250221A: Mondy optical observations
  10. Konus-Wind detection of GRB 250221A
  11. GRB 250221A: Assy optical observations
  12. GRB 250221A: VLT/X-shooter redshift z = 0.768
  13. GRB 250221A: GRANDMA/TAROT Detection
  14. GRB 250221A: Swift-XRT refined Analysis
  15. GRB 250221A: NOT optical observations
  16. GRB 250221A: 1.6m Mephisto optical detection
  17. GRB 250221A: AKO Optical Upper Limit
  18. GRB 250221A: Swift/UVOT Detection
  19. GRB 250221A: REM optical/NIR afterglow detection
  20. GRB 250221A: Enhanced Swift-XRT position
  21. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  22. GRB 250221A: Swift detection of a burst with an optical counterpart

Advanced

Download all Circulars as a .tar.gz archive:
Questions or comments?
Contact GCN directly.
Have you found a bug in GCN?
Open an issue.
Want to contribute code to GCN?
Get involved on GitHub.

gcn.nasa.gov

A service of the Astrophysics Science Division at NASA Goddard Space Flight Center

Looking for U.S. government information and services? Visit USA.gov