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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').
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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"

55 results found.

  1. GRB 251222A: radio detection with the VLA
  2. GRB 251222A: Mondy Optical Observations
  3. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  4. GRB 251222A: NUTTelA-TAO Early Measurements
  5. GRB 251222A/EP251222b: Optical detection with Kinder observations
  6. GRB 251222A/EP251222b: FTW optical and NIR observations
  7. GRB 251222A: AbAO optical observations
  8. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  9. GRB 251222A: ZTSH BVRI optical observations
  10. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  11. GRB 251222A: Continued 1.3m DFOT optical observation
  12. GRB 251222A: Fermi GBM Observation
  13. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  14. GRB 251222A / EP251222b: GOTO optical counterpart detection
  15. GRB 251222A: 1.3m DFOT optical detection
  16. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  17. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  18. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  19. GRB 251013C: further SAO RAS optical observations
  20. GRB 251013C: ISON-Castelgrande observatory optical observations
  21. GRB 251013C: OHP/T193 third epoch optical observations and detected rebrightening
  22. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  23. GRB 251013C: MAO/AZT-22 optical observations
  24. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) further multi-band optical observations
  25. GRB 251013C: OHP/T193 further optical observations and possible color evolution
  26. GRB 251013C: Calapai Observatory, Massa S. Giorgio (Messina), optical observation
  27. GRB 251002A: LAST optical observations
  28. GRB 251002A: Mondy/AZT-33IK optical observations
  29. GRB 251002A: NIR observations with WINTER
  30. GRB 251002A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  31. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  32. GRB 250702F: radio detection with the VLA
  33. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  34. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  35. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  36. GRB 250615A/EP250615a: FTW optical and NIR observations
  37. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  38. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  39. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  40. GRB 250419A: Mondy Optical Observations
  41. GRB 250419A: Liverpool Telescope optical upper limit
  42. GRB250419A: VLA radio detection
  43. GRB 250419A: Mephisto Multi-band Optical Detection
  44. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  45. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  46. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  47. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  48. GRB 250205A: Leavitt Observatory optical upper limit
  49. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  50. GRB 250129A: Continued AbAO and Mondy optical observations
  51. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  52. GRB 240129A: further SAO RAS optical observations
  53. GRB 250129A: Skynet Continued Optical Observations
  54. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  55. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.

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