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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. GRB 260511B: NuSTAR detection of prompt emission
  2. GRB 260511A: NuSTAR detection of prompt emission
  3. GRB 260511B: Fermi GBM Detection
  4. GRB 260511C: Fermi GBM Final Real-time Localization
  5. GRB 260511B: SVOM/VT optical observation with VHF data
  6. GRB 260511B: TRT optical observation
  7. GRB 260510B: SVOM/ECLAIRs refined analysis
  8. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  9. GRB 260511A: Fermi GBM Detection
  10. GRB 260511B SVOM/C-GFT optical counterpart detection
  11. EP260509a: LCO optical upper limits
  12. GRB 260511A: UTGO H50 optical afterglow observation
  13. GRB 260510C: AstroSat CZTI detection
  14. GRB 260511B: SVOM detection of a burst
  15. GRB 260511B: Fermi GBM Final Real-time Localization
  16. GRB 260510C: EP-FXT follow-up observation
  17. GRB 260510C: SVOM/VT optical counterpart confirmation
  18. EP260509a: EP-FXT non-detection and upper limit
  19. GRB 260511A: SVOM/VT optical observation with VHF data
  20. Fermi GRB 260511A: Global MASTER-Net observations report
  21. GRB 260511A: KAIT optical afterglow observations
  22. GRB 260511A: LCO optical afterglow detection
  23. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  24. GRB 260511A: TRT optical counterpart detection
  25. GRB 260511A: SVOM detection of a bright burst
  26. GRB 260511A: BALROG localization (Fermi Trigger 800172815 / GRB 260511259)
  27. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  28. GRB 260511A: Fermi GBM Final Real-time Localization
  29. GRB 260510B: SVOM/VT optical upper limits
  30. GRB 260510C: SVOM/VT optical upper limits
  31. GRB 260510C: MAXI/GSC detection
  32. EP260509a: Global MASTER-Net observations report
  33. Fermi GBM Sub-Threshold Detection of GRB 260510B
  34. GRB 260510D: Fermi GBM Final Real-time Localization
  35. GRB 260510B: GOTO early upper limit
  36. GRB 260510C: SVOM detection of a burst
  37. GRB 260510C: Fermi GBM Final Real-time Localization
  38. GRB 260510A: GECAM-B observation
  39. GRB 260510B: LCO optical upper limits
  40. EP260509a: Einstein Probe detection of an X-ray transient
  41. GRB 260509A: Liverpool Telescope optical observations
  42. GRB 260510B: SVOM detection of a burst
  43. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  44. GRB 260509A: LCO optical observations
  45. SVOM GRB 260509A: MASTER-OAFA optical observation
  46. Fermi GRB 260510A: Global MASTER-Net observations report
  47. GRB 260509A: KAIT optical observations
  48. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  49. GRB 260510A: Fermi GBM Final Real-time Localization
  50. GRB 260509A: SVOM/VT optical candidate with VHF data
  51. GRB 260509A: LCO optical counterpart detection
  52. GRB 260509A: GOTO optical counterpart candidate
  53. GRB 260509A: SVOM detection of a burst
  54. GRB 260506B: AstroSat CZTI detection
  55. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  56. EP260507a: REM optical/NIR observations
  57. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  58. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  59. EP260507a: COLIBRÍ optical observations
  60. EP260507a: SVOM/VT optical observations
  61. EP260507a: NOT optical observations
  62. EP260507a: further Liverpool Telescope observations
  63. EP260507a: Liverpool Telescope optical upper limits
  64. GRB 260507A: Fermi GBM Final Real-time Localization
  65. EP260507a: GOTO optical counterpart detection
  66. EP260507a: TRT optical counterpart detection
  67. EP260507a: Kinder optical counterpart candidate
  68. EP260507a: LCO optical counterpart
  69. EP260507a: Einstein Probe detection of an X-ray transient
  70. GRB 260504B: AstroSat CZTI detection
  71. GRB 260504B: SVOM/ECLAIRs refined analysis
  72. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  73. GRB 260506B: Fermi GBM Final Real-time Localization
  74. EP260502a is likely a flaring star
  75. Fermi GRB 260506A: Global MASTER-Net observations report
  76. GRB 260506A: Fermi GBM Final Real-time Localization
  77. GRB 260503A: GECAM-B observation of a burst
  78. IceCube Alert 260505A: Global MASTER-Net observations report
  79. GRB 260430B: Glowbug gamma-ray detection
  80. GRB 260504B: SVOM/VT optical upper limits
  81. GRB 260421B: radio observation with the VLA
  82. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  83. Konus-Wind detection of GRB 260504B (short/hard)
  84. GRB 260504B: GECAM-B detection
  85. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  86. GRB 260504C: SVOM/GRM observation of short GRB
  87. GRB 260504B: SVOM/GRM spectral analysis
  88. GRB 260430B: AstroSat CZTI detection of a long burst
  89. GRB 260504B: SVOM/MXT refined analysis and potential detection
  90. GRB 260504B: EP-FXT upper limit
  91. GRB 260502A: SVOM/GRM observation of a short GRB
  92. GRB 260503A: SVOM/GRM observation of a GRB
  93. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  94. Konus-Wind detection of GRB 260415C
  95. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  96. Konus-Wind detection of GRB 260411C
  97. GRB 260504B: REM optical/NIR observations
  98. IPN triangulation of GRB 260429A
  99. IPN triangulation of GRB 260428A
  100. GRB 260504B: AST3-2 i-band upper limit

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