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

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