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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"

36138 results found.

  1. GRB 260610B: DDOTI optical observations
  2. GRB 260610B: GOTO optical counterpart candidate
  3. GRB 260610B: Fermi GBM Final Localization
  4. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  5. GRB 260515A: SOAR optical observations
  6. Konus-Wind detection of GRB 260601A
  7. IPN triangulation of GRB 260601A (short/hard)
  8. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  9. GRB 260610A: Fermi GBM Final Real-time Localization
  10. GRB 260609A: Fermi GBM Final Localization
  11. Konus-Wind detection of GRB 260604C
  12. GRB 260608A: Fermi GRB Observation
  13. GRB 260604C: AstroSat CZTI detection
  14. IPN triangulation of GRB 260601B / EP260601a
  15. GRB 260604C: SVOM/ECLAIRs refined analysis
  16. GRB 260608A: SVOM/ECLAIRs refined analysis
  17. Konus-Wind detection of GRB 260607B
  18. GRB 260607B: GECAM-B observation
  19. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  20. GRB 260608C: Fermi GBM Final Real-time Localization
  21. GRB 260604C: further SAO RAS optical observations
  22. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  23. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  24. GRB 260608B: Fermi GBM Final Localization
  25. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  26. GRB 260604C: SVOM/C-GFT upper limit
  27. GRB 260607B: AstroSat CZTI detection
  28. GRB 260608A: SVOM detection of a burst
  29. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  30. GRB 260608A: Fermi GBM Final Real-time Localization
  31. GRB 260607A: TRT optical observations
  32. GRB 260604C: GRANDMA further observations
  33. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  34. GRB 260604A: SVOM/GRM detection
  35. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  36. GRB 260607B: Fermi GBM Observation
  37. GRB 260607B: Fermi-LAT detection
  38. GRB 260607B: Fermi GBM Final Localization Correction
  39. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  40. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  41. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  42. GRB 260607A: Fermi GBM Final Real-time Localization
  43. GRB 260604C: GECAM-B observation
  44. GRB 260604C: 6 GHz VLA observations
  45. GRB 260604C: SAO RAS optical observations
  46. GRB 260604C: GRANDMA observations
  47. GRB 260604B: SVOM/GRM detection
  48. GRB 260605A: Insight-HXMT/HE detection
  49. GRB260603A: SVOM/ECLAIRs refined analysis
  50. GRB 260604A: Glowbug gamma-ray detection
  51. GRB 260604C: LCO optical upper limit
  52. GRB 260604C: Liverpool Telescope optical detection
  53. GRB 260601B / EP260601a: AstroSat CZTI detection
  54. GRB 260527A/EP260527a: 6 GHz VLA observations
  55. GRB 260604C: GOTO detections of the optical afterglow
  56. GRB 260604C: Correction to GCN 44828
  57. GRB 260604C: Kilonova-Catcher optical afterglow detection
  58. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  59. GRB 260604C: Jinshan optical observations
  60. GRB 260604C: Fermi GBM Observation
  61. GRB 260604C: LAST detection of optical counterpart candidate
  62. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  63. Fermi GRB 260604C: Global MASTER-Net observations report
  64. Fermi GRB 260604C: Global MASTER-Net observations report
  65. GRB 260604C: SVOM detection of a long burst
  66. GRB 260604C: Fermi GBM Final Real-time Localization
  67. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  68. GRB 260603A: NOT optical observations
  69. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  70. GRB 260604B: Fermi GBM Final Real-time Localization
  71. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  72. GRB 260604A: Fermi GBM Final Real-time Localization
  73. GRB 260603B: Fermi GBM Final Localization
  74. Konus-Wind detection of GRB 260601B/EP260601a
  75. GRB 260603A: EP-FXT follow-up observation
  76. EP260601a/GRB 260601B: EP-FXT follow-up observation
  77. GRB 260601B / EP260601a: Mondy optical upper limit
  78. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  79. GRB 260603A: Kilonova-Catcher optical upper limit
  80. GRB 260603A: SVOM/VT optical observations
  81. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  82. GRB 260601A: SVOM/GRM observation of a short burst
  83. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  84. GRB 260603A: SVOM detection of a burst
  85. GRB 260601B/EP260601a: Insight-HXMT detection
  86. Fermi GRB 260602B: Global MASTER-Net observations report
  87. Fermi GRB 260602B: Global MASTER-Net observations report
  88. GRB 260602B: Fermi GBM Final Localization
  89. GRB 260601A: GECAM-B observation of a short burst
  90. GRB 260601B/EP260601a: J-band upper limit with WINTER
  91. EP260530a/AT 2026nwl: KAIT optical observations
  92. GRB 260602A: Fermi GBM Final Real-time Localization
  93. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  94. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  95. GRB 260601B/EP260601a: SVOM/VT optical observations
  96. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  97. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  98. GRB 260601A: Glowbug gamma-ray detection of a short burst
  99. GRB 260531B: Glowbug gamma-ray detection
  100. GRB 260516D: VLA radio detection

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