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

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