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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"
  1. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  2. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  3. GRB 260610B / AT2026owq: Early ATLAS observations
  4. GRB 260610B: TRT optical observation
  5. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  6. GRB 260611A: Fermi GBM Final Real-time Localization
  7. EP260610b: COLIBRÍ optical observations
  8. GRB 260610B: DDOTI optical observations
  9. EP260610b: MAO/AZT-22 optical observations
  10. GRB 260610B: GOTO optical counterpart candidate
  11. EP260610b: NOT optical observation
  12. GRB 260610B: Fermi GBM Final Localization
  13. EP260610b: SVOM/VT optical confirmation with blue color
  14. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  15. GRB 260515A: SOAR optical observations
  16. EP260610b: Gemini North optical counterpart candidate
  17. EP260610a: SVOM/VT optical upper limits
  18. EP260610b: Einstein Probe detection of an X-ray transient
  19. Konus-Wind detection of GRB 260601A
  20. IPN triangulation of GRB 260601A (short/hard)
  21. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  22. GRB 260610A: Fermi GBM Final Real-time Localization
  23. EP260610a: COLIBRÍ optical upper limits
  24. EP260610a: Einstein Probe detection of a fast X-ray transient
  25. GRB 260609A: Fermi GBM Final Localization
  26. Konus-Wind detection of GRB 260604C
  27. GRB 260608A: Fermi GRB Observation
  28. GRB 260604C: AstroSat CZTI detection
  29. IPN triangulation of GRB 260601B / EP260601a
  30. GRB 260604C: SVOM/ECLAIRs refined analysis
  31. GRB 260608A: SVOM/ECLAIRs refined analysis
  32. Konus-Wind detection of GRB 260607B
  33. GRB 260607B: GECAM-B observation
  34. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  35. GRB 260608C: Fermi GBM Final Real-time Localization
  36. GRB 260604C: further SAO RAS optical observations
  37. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  38. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  39. GRB 260608B: Fermi GBM Final Localization
  40. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  41. GRB 260604C: SVOM/C-GFT upper limit
  42. GRB 260607B: AstroSat CZTI detection
  43. GRB 260608A: SVOM detection of a burst
  44. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  45. GRB 260608A: Fermi GBM Final Real-time Localization
  46. EP260605a: EP-FXT follow-up observation
  47. GRB 260607A: TRT optical observations
  48. GRB 260604C: GRANDMA further observations
  49. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  50. GRB 260604A: SVOM/GRM detection
  51. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  52. GRB 260607B: Fermi GBM Observation
  53. GRB 260607B: Fermi-LAT detection
  54. GRB 260607B: Fermi GBM Final Localization Correction
  55. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  56. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  57. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  58. GRB 260607A: Fermi GBM Final Real-time Localization
  59. GRB 260604C: GECAM-B observation
  60. GRB 260604C: 6 GHz VLA observations
  61. GRB 260604C: SAO RAS optical observations
  62. GRB 260604C: GRANDMA observations
  63. GRB 260604B: SVOM/GRM detection
  64. GRB 260605A: Insight-HXMT/HE detection
  65. GRB260603A: SVOM/ECLAIRs refined analysis
  66. EP260605a: Einstein Probe detection of a fast X-ray transient
  67. EP260603a: COLIBRÍ optical upper limit
  68. GRB 260604A: Glowbug gamma-ray detection
  69. GRB 260604C: LCO optical upper limit
  70. GRB 260604C: Liverpool Telescope optical detection
  71. The EP-WXT trigger 01709267001 is likely a flaring star
  72. EP260602d: EP-FXT follow-up observation
  73. EP260602c: EP-FXT follow-up observation
  74. GRB 260601B / EP260601a: AstroSat CZTI detection
  75. GRB 260527A/EP260527a: 6 GHz VLA observations
  76. GRB 260604C: GOTO detections of the optical afterglow
  77. GRB 260604C: Correction to GCN 44828
  78. GRB 260604C: Kilonova-Catcher optical afterglow detection
  79. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  80. The EP-WXT trigger 01709266798 is likely a flaring star
  81. GRB 260604C: Jinshan optical observations
  82. GRB 260604C: Fermi GBM Observation
  83. EP260602d: J-band upper limit with WINTER
  84. EP260602b: J-band upper limit with WINTER
  85. GRB 260604C: LAST detection of optical counterpart candidate
  86. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  87. Fermi GRB 260604C: Global MASTER-Net observations report
  88. Fermi GRB 260604C: Global MASTER-Net observations report
  89. SVOM GRB260604.85: Global MASTER-Net observations report
  90. GRB 260604C: SVOM detection of a long burst
  91. GRB 260604C: Fermi GBM Final Real-time Localization
  92. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  93. GRB 260603A: NOT optical observations
  94. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  95. GRB 260604B: Fermi GBM Final Real-time Localization
  96. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  97. EP260602a: EP-FXT follow-up observation
  98. EP260603a: Global MASTER-Net observations report
  99. EP260603a: Einstein Probe detection of a fast X-ray transient
  100. EP260602d: Optical Upper limits with kinder observations

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