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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"

29 results found.

  1. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  2. GRB 250309B/AT2025dws: further ATCA observations
  3. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  4. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  5. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  6. GRB 250309B: 1.3m DFOT Optical observations
  7. GRB 250309B: PRIME near-infrared detection
  8. GRB 250309B: SVOM/VT optical observation
  9. GRB 250309B / AT2025dws: further SAO RAS optical observations
  10. IceCube-250309A: Upper limits from Fermi-GBM Observations
  11. Konus-Wind detection of GRB 250309B
  12. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  13. IPN triangulation of GRB 250309B
  14. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  15. GRB 250309B: Swift-XRT refined Analysis
  16. GRB 250309B / IceCube-250309A: GECAM-B observations
  17. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  18. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  19. GRB 250309B / AT2025dws: SAO RAS optical observations
  20. GRB 250309B / AT2025dws: Swift-UVOT detection
  21. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  22. GRB 250309B: Fermi GBM Observation
  23. Fermi GRB 250309B: Global MASTER-Net observations report
  24. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  25. Fermi-LAT gamma-ray observations of IceCube-250309A
  26. GRB 250309B: Fermi GBM Final Localization
  27. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  28. GRB 230509B: Tiled Swift observations
  29. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)

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Download all Circulars as a .tar.gz archive:
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