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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 260511A: LCO optical afterglow detection
  2. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  3. GRB 260511A: TRT optical counterpart detection
  4. GRB 260511A: SVOM detection of a bright burst
  5. GRB 260511A: BALROG localization (Fermi Trigger 800172815 / GRB 260511259)
  6. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  7. GRB 260511A: Fermi GBM Final Real-time Localization
  8. GRB 260510B: SVOM/VT optical upper limits
  9. GRB 260510C: SVOM/VT optical upper limits
  10. GRB 260510C: MAXI/GSC detection
  11. EP260509a: Global MASTER-Net observations report
  12. Fermi GBM Sub-Threshold Detection of GRB 260510B
  13. GRB 260510D: Fermi GBM Final Real-time Localization
  14. GRB 260510B: GOTO early upper limit
  15. GRB 260510C: SVOM detection of a burst
  16. GRB 260510C: Fermi GBM Final Real-time Localization
  17. GRB 260510A: GECAM-B observation
  18. GRB 260510B: LCO optical upper limits
  19. EP260509a: Einstein Probe detection of an X-ray transient
  20. GRB 260509A: Liverpool Telescope optical observations
  21. GRB 260510B: SVOM detection of a burst
  22. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  23. GRB 260509A: LCO optical observations
  24. SVOM GRB 260509A: MASTER-OAFA optical observation
  25. Fermi GRB 260510A: Global MASTER-Net observations report
  26. GRB 260509A: KAIT optical observations
  27. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  28. GRB 260510A: Fermi GBM Final Real-time Localization
  29. GRB 260509A: SVOM/VT optical candidate with VHF data
  30. GRB 260509A: LCO optical counterpart detection
  31. GRB 260509A: GOTO optical counterpart candidate
  32. GRB 260509A: SVOM detection of a burst
  33. GRB 260506B: AstroSat CZTI detection
  34. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  35. EP260507a: REM optical/NIR observations
  36. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  37. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  38. EP260507a: COLIBRÍ optical observations
  39. EP260507a: SVOM/VT optical observations
  40. EP260507a: NOT optical observations
  41. EP260507a: further Liverpool Telescope observations
  42. EP260507a: Liverpool Telescope optical upper limits
  43. GRB 260507A: Fermi GBM Final Real-time Localization
  44. EP260507a: GOTO optical counterpart detection
  45. EP260507a: TRT optical counterpart detection
  46. EP260507a: Kinder optical counterpart candidate
  47. EP260507a: LCO optical counterpart
  48. EP260507a: Einstein Probe detection of an X-ray transient
  49. GRB 260504B: AstroSat CZTI detection
  50. GRB 260504B: SVOM/ECLAIRs refined analysis
  51. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  52. GRB 260506B: Fermi GBM Final Real-time Localization
  53. EP260502a is likely a flaring star
  54. Fermi GRB 260506A: Global MASTER-Net observations report
  55. GRB 260506A: Fermi GBM Final Real-time Localization
  56. GRB 260503A: GECAM-B observation of a burst
  57. IceCube Alert 260505A: Global MASTER-Net observations report
  58. GRB 260430B: Glowbug gamma-ray detection
  59. GRB 260504B: SVOM/VT optical upper limits
  60. GRB 260421B: radio observation with the VLA
  61. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  62. Konus-Wind detection of GRB 260504B (short/hard)
  63. GRB 260504B: GECAM-B detection
  64. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  65. GRB 260504C: SVOM/GRM observation of short GRB
  66. GRB 260504B: SVOM/GRM spectral analysis
  67. GRB 260430B: AstroSat CZTI detection of a long burst
  68. GRB 260504B: SVOM/MXT refined analysis and potential detection
  69. GRB 260504B: EP-FXT upper limit
  70. GRB 260502A: SVOM/GRM observation of a short GRB
  71. GRB 260503A: SVOM/GRM observation of a GRB
  72. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  73. Konus-Wind detection of GRB 260415C
  74. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  75. Konus-Wind detection of GRB 260411C
  76. GRB 260504B: REM optical/NIR observations
  77. IPN triangulation of GRB 260429A
  78. IPN triangulation of GRB 260428A
  79. GRB 260504B: AST3-2 i-band upper limit
  80. GRB 260504B: LCO z-band upper limit
  81. SVOM GRB 260504B: MASTER-OAFA optical observations
  82. GRB 260504B: SVOM detection of a short burst
  83. Fermi GRB 260504A: Global MASTER-Net observations report
  84. GRB 260504A: Fermi GBM Final Real-time Localization
  85. GRB 260503A: Fermi GBM Final Real-time Localization
  86. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  87. GRB 260502A: GECAM-B observation of a short burst
  88. IPN triangulation of a bright burst from SGR 1E1841-045
  89. GRB 260502A: Fermi GBM Final Localization
  90. The EP-WXT trigger 01709261576 is likely a flaring star
  91. GRB 260429B / EP260429a: EP-FXT follow-up observation
  92. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  93. GRB 260429B / EP260429a: AstroSat CZTI detection
  94. EP260502a: BOOTES-7: early optical upper limit
  95. EP260502a: Las Cumbres upper limit
  96. EP260502a: Einstein Probe detection of an X-ray transient
  97. GRB 260429A: SVOM/GRM observation of a short burst
  98. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  99. EP260429a: Global MASTER-Net observations report
  100. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations

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