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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: SVOM detection of a bright burst
  2. GRB 260511A: BALROG localization (Fermi Trigger 800172815 / GRB 260511259)
  3. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  4. GRB 260511A: Fermi GBM Final Real-time Localization
  5. GRB 260510B: SVOM/VT optical upper limits
  6. GRB 260510C: SVOM/VT optical upper limits
  7. GRB 260510C: MAXI/GSC detection
  8. EP260509a: Global MASTER-Net observations report
  9. Fermi GBM Sub-Threshold Detection of GRB 260510B
  10. GRB 260510D: Fermi GBM Final Real-time Localization
  11. GRB 260510B: GOTO early upper limit
  12. GRB 260510C: SVOM detection of a burst
  13. GRB 260510C: Fermi GBM Final Real-time Localization
  14. GRB 260510A: GECAM-B observation
  15. GRB 260510B: LCO optical upper limits
  16. EP260509a: Einstein Probe detection of an X-ray transient
  17. GRB 260509A: Liverpool Telescope optical observations
  18. GRB 260510B: SVOM detection of a burst
  19. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  20. GRB 260509A: LCO optical observations
  21. SVOM GRB 260509A: MASTER-OAFA optical observation
  22. Fermi GRB 260510A: Global MASTER-Net observations report
  23. GRB 260509A: KAIT optical observations
  24. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  25. GRB 260510A: Fermi GBM Final Real-time Localization
  26. GRB 260509A: SVOM/VT optical candidate with VHF data
  27. GRB 260509A: LCO optical counterpart detection
  28. GRB 260509A: GOTO optical counterpart candidate
  29. GRB 260509A: SVOM detection of a burst
  30. GRB 260506B: AstroSat CZTI detection
  31. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  32. EP260507a: REM optical/NIR observations
  33. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  34. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  35. EP260507a: COLIBRÍ optical observations
  36. EP260507a: SVOM/VT optical observations
  37. EP260507a: NOT optical observations
  38. EP260507a: further Liverpool Telescope observations
  39. EP260507a: Liverpool Telescope optical upper limits
  40. GRB 260507A: Fermi GBM Final Real-time Localization
  41. EP260507a: GOTO optical counterpart detection
  42. EP260507a: TRT optical counterpart detection
  43. EP260507a: Kinder optical counterpart candidate
  44. EP260507a: LCO optical counterpart
  45. EP260507a: Einstein Probe detection of an X-ray transient
  46. GRB 260504B: AstroSat CZTI detection
  47. GRB 260504B: SVOM/ECLAIRs refined analysis
  48. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  49. GRB 260506B: Fermi GBM Final Real-time Localization
  50. EP260502a is likely a flaring star
  51. Fermi GRB 260506A: Global MASTER-Net observations report
  52. GRB 260506A: Fermi GBM Final Real-time Localization
  53. GRB 260503A: GECAM-B observation of a burst
  54. IceCube Alert 260505A: Global MASTER-Net observations report
  55. GRB 260430B: Glowbug gamma-ray detection
  56. GRB 260504B: SVOM/VT optical upper limits
  57. GRB 260421B: radio observation with the VLA
  58. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  59. Konus-Wind detection of GRB 260504B (short/hard)
  60. GRB 260504B: GECAM-B detection
  61. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  62. GRB 260504C: SVOM/GRM observation of short GRB
  63. GRB 260504B: SVOM/GRM spectral analysis
  64. GRB 260430B: AstroSat CZTI detection of a long burst
  65. GRB 260504B: SVOM/MXT refined analysis and potential detection
  66. GRB 260504B: EP-FXT upper limit
  67. GRB 260502A: SVOM/GRM observation of a short GRB
  68. GRB 260503A: SVOM/GRM observation of a GRB
  69. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  70. Konus-Wind detection of GRB 260415C
  71. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  72. Konus-Wind detection of GRB 260411C
  73. GRB 260504B: REM optical/NIR observations
  74. IPN triangulation of GRB 260429A
  75. IPN triangulation of GRB 260428A
  76. GRB 260504B: AST3-2 i-band upper limit
  77. GRB 260504B: LCO z-band upper limit
  78. SVOM GRB 260504B: MASTER-OAFA optical observations
  79. GRB 260504B: SVOM detection of a short burst
  80. Fermi GRB 260504A: Global MASTER-Net observations report
  81. GRB 260504A: Fermi GBM Final Real-time Localization
  82. GRB 260503A: Fermi GBM Final Real-time Localization
  83. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  84. GRB 260502A: GECAM-B observation of a short burst
  85. IPN triangulation of a bright burst from SGR 1E1841-045
  86. GRB 260502A: Fermi GBM Final Localization
  87. The EP-WXT trigger 01709261576 is likely a flaring star
  88. GRB 260429B / EP260429a: EP-FXT follow-up observation
  89. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  90. GRB 260429B / EP260429a: AstroSat CZTI detection
  91. EP260502a: BOOTES-7: early optical upper limit
  92. EP260502a: Las Cumbres upper limit
  93. EP260502a: Einstein Probe detection of an X-ray transient
  94. GRB 260429A: SVOM/GRM observation of a short burst
  95. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  96. EP260429a: Global MASTER-Net observations report
  97. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  98. GRB 260424B: AstroSat CZTI detection
  99. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  100. EP260429a: LCO optical upper limits

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