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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"

36144 results found.

  1. EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
  2. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  3. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  4. GRB 260610B / AT2026owq: Early ATLAS observations
  5. GRB 260610B: TRT optical observation
  6. GRB 260611A: Fermi GBM Final Real-time Localization
  7. GRB 260610B: DDOTI optical observations
  8. GRB 260610B: GOTO optical counterpart candidate
  9. GRB 260610B: Fermi GBM Final Localization
  10. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  11. GRB 260515A: SOAR optical observations
  12. Konus-Wind detection of GRB 260601A
  13. IPN triangulation of GRB 260601A (short/hard)
  14. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  15. GRB 260610A: Fermi GBM Final Real-time Localization
  16. GRB 260609A: Fermi GBM Final Localization
  17. Konus-Wind detection of GRB 260604C
  18. GRB 260608A: Fermi GRB Observation
  19. GRB 260604C: AstroSat CZTI detection
  20. IPN triangulation of GRB 260601B / EP260601a
  21. GRB 260604C: SVOM/ECLAIRs refined analysis
  22. GRB 260608A: SVOM/ECLAIRs refined analysis
  23. Konus-Wind detection of GRB 260607B
  24. GRB 260607B: GECAM-B observation
  25. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  26. GRB 260608C: Fermi GBM Final Real-time Localization
  27. GRB 260604C: further SAO RAS optical observations
  28. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  29. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  30. GRB 260608B: Fermi GBM Final Localization
  31. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  32. GRB 260604C: SVOM/C-GFT upper limit
  33. GRB 260607B: AstroSat CZTI detection
  34. GRB 260608A: SVOM detection of a burst
  35. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  36. GRB 260608A: Fermi GBM Final Real-time Localization
  37. GRB 260607A: TRT optical observations
  38. GRB 260604C: GRANDMA further observations
  39. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  40. GRB 260604A: SVOM/GRM detection
  41. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  42. GRB 260607B: Fermi GBM Observation
  43. GRB 260607B: Fermi-LAT detection
  44. GRB 260607B: Fermi GBM Final Localization Correction
  45. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  46. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  47. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  48. GRB 260607A: Fermi GBM Final Real-time Localization
  49. GRB 260604C: GECAM-B observation
  50. GRB 260604C: 6 GHz VLA observations
  51. GRB 260604C: SAO RAS optical observations
  52. GRB 260604C: GRANDMA observations
  53. GRB 260604B: SVOM/GRM detection
  54. GRB 260605A: Insight-HXMT/HE detection
  55. GRB260603A: SVOM/ECLAIRs refined analysis
  56. GRB 260604A: Glowbug gamma-ray detection
  57. GRB 260604C: LCO optical upper limit
  58. GRB 260604C: Liverpool Telescope optical detection
  59. GRB 260601B / EP260601a: AstroSat CZTI detection
  60. GRB 260527A/EP260527a: 6 GHz VLA observations
  61. GRB 260604C: GOTO detections of the optical afterglow
  62. GRB 260604C: Correction to GCN 44828
  63. GRB 260604C: Kilonova-Catcher optical afterglow detection
  64. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  65. GRB 260604C: Jinshan optical observations
  66. GRB 260604C: Fermi GBM Observation
  67. GRB 260604C: LAST detection of optical counterpart candidate
  68. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  69. Fermi GRB 260604C: Global MASTER-Net observations report
  70. Fermi GRB 260604C: Global MASTER-Net observations report
  71. GRB 260604C: SVOM detection of a long burst
  72. GRB 260604C: Fermi GBM Final Real-time Localization
  73. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  74. GRB 260603A: NOT optical observations
  75. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  76. GRB 260604B: Fermi GBM Final Real-time Localization
  77. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  78. GRB 260604A: Fermi GBM Final Real-time Localization
  79. GRB 260603B: Fermi GBM Final Localization
  80. Konus-Wind detection of GRB 260601B/EP260601a
  81. GRB 260603A: EP-FXT follow-up observation
  82. EP260601a/GRB 260601B: EP-FXT follow-up observation
  83. GRB 260601B / EP260601a: Mondy optical upper limit
  84. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  85. GRB 260603A: Kilonova-Catcher optical upper limit
  86. GRB 260603A: SVOM/VT optical observations
  87. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  88. GRB 260601A: SVOM/GRM observation of a short burst
  89. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  90. GRB 260603A: SVOM detection of a burst
  91. GRB 260601B/EP260601a: Insight-HXMT detection
  92. Fermi GRB 260602B: Global MASTER-Net observations report
  93. Fermi GRB 260602B: Global MASTER-Net observations report
  94. GRB 260602B: Fermi GBM Final Localization
  95. GRB 260601A: GECAM-B observation of a short burst
  96. GRB 260601B/EP260601a: J-band upper limit with WINTER
  97. EP260530a/AT 2026nwl: KAIT optical observations
  98. GRB 260602A: Fermi GBM Final Real-time Localization
  99. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  100. GRB 260601B / EP260601a: NuSTAR detection of prompt emission

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