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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. SVOM GRB 260509A: MASTER-OAFA optical observation
  2. Fermi GRB 260510A: Global MASTER-Net observations report
  3. GRB 260509A: KAIT optical observations
  4. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  5. GRB 260510A: Fermi GBM Final Real-time Localization
  6. GRB 260509A: SVOM/VT optical candidate with VHF data
  7. GRB 260509A: LCO optical counterpart detection
  8. GRB 260509A: GOTO optical counterpart candidate
  9. GRB 260509A: SVOM detection of a burst
  10. GRB 260506B: AstroSat CZTI detection
  11. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  12. EP260507a: REM optical/NIR observations
  13. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  14. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  15. EP260507a: COLIBRÍ optical observations
  16. EP260507a: SVOM/VT optical observations
  17. EP260507a: NOT optical observations
  18. EP260507a: further Liverpool Telescope observations
  19. EP260507a: Liverpool Telescope optical upper limits
  20. GRB 260507A: Fermi GBM Final Real-time Localization
  21. EP260507a: GOTO optical counterpart detection
  22. EP260507a: TRT optical counterpart detection
  23. EP260507a: Kinder optical counterpart candidate
  24. EP260507a: LCO optical counterpart
  25. EP260507a: Einstein Probe detection of an X-ray transient
  26. GRB 260504B: AstroSat CZTI detection
  27. GRB 260504B: SVOM/ECLAIRs refined analysis
  28. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  29. GRB 260506B: Fermi GBM Final Real-time Localization
  30. EP260502a is likely a flaring star
  31. Fermi GRB 260506A: Global MASTER-Net observations report
  32. GRB 260506A: Fermi GBM Final Real-time Localization
  33. GRB 260503A: GECAM-B observation of a burst
  34. IceCube Alert 260505A: Global MASTER-Net observations report
  35. GRB 260430B: Glowbug gamma-ray detection
  36. GRB 260504B: SVOM/VT optical upper limits
  37. GRB 260421B: radio observation with the VLA
  38. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  39. Konus-Wind detection of GRB 260504B (short/hard)
  40. GRB 260504B: GECAM-B detection
  41. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  42. GRB 260504C: SVOM/GRM observation of short GRB
  43. GRB 260504B: SVOM/GRM spectral analysis
  44. GRB 260430B: AstroSat CZTI detection of a long burst
  45. GRB 260504B: SVOM/MXT refined analysis and potential detection
  46. GRB 260504B: EP-FXT upper limit
  47. GRB 260502A: SVOM/GRM observation of a short GRB
  48. GRB 260503A: SVOM/GRM observation of a GRB
  49. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  50. Konus-Wind detection of GRB 260415C
  51. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  52. Konus-Wind detection of GRB 260411C
  53. GRB 260504B: REM optical/NIR observations
  54. IPN triangulation of GRB 260429A
  55. IPN triangulation of GRB 260428A
  56. GRB 260504B: AST3-2 i-band upper limit
  57. GRB 260504B: LCO z-band upper limit
  58. SVOM GRB 260504B: MASTER-OAFA optical observations
  59. GRB 260504B: SVOM detection of a short burst
  60. Fermi GRB 260504A: Global MASTER-Net observations report
  61. GRB 260504A: Fermi GBM Final Real-time Localization
  62. GRB 260503A: Fermi GBM Final Real-time Localization
  63. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  64. GRB 260502A: GECAM-B observation of a short burst
  65. IPN triangulation of a bright burst from SGR 1E1841-045
  66. GRB 260502A: Fermi GBM Final Localization
  67. The EP-WXT trigger 01709261576 is likely a flaring star
  68. GRB 260429B / EP260429a: EP-FXT follow-up observation
  69. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  70. GRB 260429B / EP260429a: AstroSat CZTI detection
  71. EP260502a: BOOTES-7: early optical upper limit
  72. EP260502a: Las Cumbres upper limit
  73. EP260502a: Einstein Probe detection of an X-ray transient
  74. GRB 260429A: SVOM/GRM observation of a short burst
  75. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  76. EP260429a: Global MASTER-Net observations report
  77. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  78. GRB 260424B: AstroSat CZTI detection
  79. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  80. EP260429a: LCO optical upper limits
  81. EP260430a: LCO optical upper limits
  82. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  83. GRB 260429A: Fermi GBM Detection
  84. Fermi GRB 260429A: Global MASTER-Net observations report
  85. EP260430a: Global MASTER-Net observations report
  86. EP260430a: Einstein Probe detection of an X-ray transient
  87. EP260429a: EP-WXT detection of a fast X-ray transient
  88. GRB 260429A: Fermi GBM Final Real-time Localization
  89. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  90. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  91. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  92. GRB 260428A: AstroSat CZTI detection
  93. Fermi GRB 260428A: Global MASTER-Net observations report
  94. EP260416a: Mondy and Terskol optical upper limits
  95. GRB 260424B: Glowbug gamma-ray detection of a short burst
  96. GRB 260424B: COLIBRÍ optical upper limit
  97. Konus-Wind detection of GRB 260424B
  98. GRB 260428A: Fermi GBM Final Real-time Localization
  99. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  100. GRB 260424C: Fermi GBM Final Localization

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