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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 260510C: SVOM/VT optical counterpart confirmation
  2. EP260509a: EP-FXT non-detection and upper limit
  3. GRB 260511A: SVOM/VT optical observation with VHF data
  4. Fermi GRB 260511A: Global MASTER-Net observations report
  5. GRB 260511A: KAIT optical afterglow observations
  6. GRB 260511A: LCO optical afterglow detection
  7. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  8. GRB 260511A: TRT optical counterpart detection
  9. GRB 260511A: SVOM detection of a bright burst
  10. GRB 260511A: BALROG localization (Fermi Trigger 800172815 / GRB 260511259)
  11. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  12. GRB 260511A: Fermi GBM Final Real-time Localization
  13. GRB 260510B: SVOM/VT optical upper limits
  14. GRB 260510C: SVOM/VT optical upper limits
  15. GRB 260510C: MAXI/GSC detection
  16. EP260509a: Global MASTER-Net observations report
  17. Fermi GBM Sub-Threshold Detection of GRB 260510B
  18. GRB 260510D: Fermi GBM Final Real-time Localization
  19. GRB 260510B: GOTO early upper limit
  20. GRB 260510C: SVOM detection of a burst
  21. GRB 260510C: Fermi GBM Final Real-time Localization
  22. GRB 260510A: GECAM-B observation
  23. GRB 260510B: LCO optical upper limits
  24. EP260509a: Einstein Probe detection of an X-ray transient
  25. GRB 260509A: Liverpool Telescope optical observations
  26. GRB 260510B: SVOM detection of a burst
  27. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  28. GRB 260509A: LCO optical observations
  29. SVOM GRB 260509A: MASTER-OAFA optical observation
  30. Fermi GRB 260510A: Global MASTER-Net observations report
  31. GRB 260509A: KAIT optical observations
  32. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  33. GRB 260510A: Fermi GBM Final Real-time Localization
  34. GRB 260509A: SVOM/VT optical candidate with VHF data
  35. GRB 260509A: LCO optical counterpart detection
  36. GRB 260509A: GOTO optical counterpart candidate
  37. GRB 260509A: SVOM detection of a burst
  38. GRB 260506B: AstroSat CZTI detection
  39. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  40. EP260507a: REM optical/NIR observations
  41. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  42. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  43. EP260507a: COLIBRÍ optical observations
  44. EP260507a: SVOM/VT optical observations
  45. EP260507a: NOT optical observations
  46. EP260507a: further Liverpool Telescope observations
  47. EP260507a: Liverpool Telescope optical upper limits
  48. GRB 260507A: Fermi GBM Final Real-time Localization
  49. EP260507a: GOTO optical counterpart detection
  50. EP260507a: TRT optical counterpart detection
  51. EP260507a: Kinder optical counterpart candidate
  52. EP260507a: LCO optical counterpart
  53. EP260507a: Einstein Probe detection of an X-ray transient
  54. GRB 260504B: AstroSat CZTI detection
  55. GRB 260504B: SVOM/ECLAIRs refined analysis
  56. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  57. GRB 260506B: Fermi GBM Final Real-time Localization
  58. EP260502a is likely a flaring star
  59. Fermi GRB 260506A: Global MASTER-Net observations report
  60. GRB 260506A: Fermi GBM Final Real-time Localization
  61. GRB 260503A: GECAM-B observation of a burst
  62. IceCube Alert 260505A: Global MASTER-Net observations report
  63. GRB 260430B: Glowbug gamma-ray detection
  64. GRB 260504B: SVOM/VT optical upper limits
  65. GRB 260421B: radio observation with the VLA
  66. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  67. Konus-Wind detection of GRB 260504B (short/hard)
  68. GRB 260504B: GECAM-B detection
  69. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  70. GRB 260504C: SVOM/GRM observation of short GRB
  71. GRB 260504B: SVOM/GRM spectral analysis
  72. GRB 260430B: AstroSat CZTI detection of a long burst
  73. GRB 260504B: SVOM/MXT refined analysis and potential detection
  74. GRB 260504B: EP-FXT upper limit
  75. GRB 260502A: SVOM/GRM observation of a short GRB
  76. GRB 260503A: SVOM/GRM observation of a GRB
  77. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  78. Konus-Wind detection of GRB 260415C
  79. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  80. Konus-Wind detection of GRB 260411C
  81. GRB 260504B: REM optical/NIR observations
  82. IPN triangulation of GRB 260429A
  83. IPN triangulation of GRB 260428A
  84. GRB 260504B: AST3-2 i-band upper limit
  85. GRB 260504B: LCO z-band upper limit
  86. SVOM GRB 260504B: MASTER-OAFA optical observations
  87. GRB 260504B: SVOM detection of a short burst
  88. Fermi GRB 260504A: Global MASTER-Net observations report
  89. GRB 260504A: Fermi GBM Final Real-time Localization
  90. GRB 260503A: Fermi GBM Final Real-time Localization
  91. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  92. GRB 260502A: GECAM-B observation of a short burst
  93. IPN triangulation of a bright burst from SGR 1E1841-045
  94. GRB 260502A: Fermi GBM Final Localization
  95. The EP-WXT trigger 01709261576 is likely a flaring star
  96. GRB 260429B / EP260429a: EP-FXT follow-up observation
  97. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  98. GRB 260429B / EP260429a: AstroSat CZTI detection
  99. EP260502a: BOOTES-7: early optical upper limit
  100. EP260502a: Las Cumbres upper limit

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