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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 260506B: AstroSat CZTI detection
  2. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  3. EP260507a: REM optical/NIR observations
  4. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  5. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  6. EP260507a: COLIBRÍ optical observations
  7. EP260507a: SVOM/VT optical observations
  8. EP260507a: NOT optical observations
  9. EP260507a: further Liverpool Telescope observations
  10. EP260507a: Liverpool Telescope optical upper limits
  11. GRB 260507A: Fermi GBM Final Real-time Localization
  12. EP260507a: GOTO optical counterpart detection
  13. EP260507a: TRT optical counterpart detection
  14. EP260507a: Kinder optical counterpart candidate
  15. EP260507a: LCO optical counterpart
  16. EP260507a: Einstein Probe detection of an X-ray transient
  17. GRB 260504B: AstroSat CZTI detection
  18. GRB 260504B: SVOM/ECLAIRs refined analysis
  19. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  20. GRB 260506B: Fermi GBM Final Real-time Localization
  21. EP260502a is likely a flaring star
  22. Fermi GRB 260506A: Global MASTER-Net observations report
  23. GRB 260506A: Fermi GBM Final Real-time Localization
  24. GRB 260503A: GECAM-B observation of a burst
  25. IceCube Alert 260505A: Global MASTER-Net observations report
  26. GRB 260430B: Glowbug gamma-ray detection
  27. GRB 260504B: SVOM/VT optical upper limits
  28. GRB 260421B: radio observation with the VLA
  29. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  30. Konus-Wind detection of GRB 260504B (short/hard)
  31. GRB 260504B: GECAM-B detection
  32. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  33. GRB 260504C: SVOM/GRM observation of short GRB
  34. GRB 260504B: SVOM/GRM spectral analysis
  35. GRB 260430B: AstroSat CZTI detection of a long burst
  36. GRB 260504B: SVOM/MXT refined analysis and potential detection
  37. GRB 260504B: EP-FXT upper limit
  38. GRB 260502A: SVOM/GRM observation of a short GRB
  39. GRB 260503A: SVOM/GRM observation of a GRB
  40. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  41. Konus-Wind detection of GRB 260415C
  42. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  43. Konus-Wind detection of GRB 260411C
  44. GRB 260504B: REM optical/NIR observations
  45. IPN triangulation of GRB 260429A
  46. IPN triangulation of GRB 260428A
  47. GRB 260504B: AST3-2 i-band upper limit
  48. GRB 260504B: LCO z-band upper limit
  49. SVOM GRB 260504B: MASTER-OAFA optical observations
  50. GRB 260504B: SVOM detection of a short burst
  51. Fermi GRB 260504A: Global MASTER-Net observations report
  52. GRB 260504A: Fermi GBM Final Real-time Localization
  53. GRB 260503A: Fermi GBM Final Real-time Localization
  54. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  55. GRB 260502A: GECAM-B observation of a short burst
  56. IPN triangulation of a bright burst from SGR 1E1841-045
  57. GRB 260502A: Fermi GBM Final Localization
  58. The EP-WXT trigger 01709261576 is likely a flaring star
  59. GRB 260429B / EP260429a: EP-FXT follow-up observation
  60. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  61. GRB 260429B / EP260429a: AstroSat CZTI detection
  62. EP260502a: BOOTES-7: early optical upper limit
  63. EP260502a: Las Cumbres upper limit
  64. EP260502a: Einstein Probe detection of an X-ray transient
  65. GRB 260429A: SVOM/GRM observation of a short burst
  66. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  67. EP260429a: Global MASTER-Net observations report
  68. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  69. GRB 260424B: AstroSat CZTI detection
  70. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  71. EP260429a: LCO optical upper limits
  72. EP260430a: LCO optical upper limits
  73. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  74. GRB 260429A: Fermi GBM Detection
  75. Fermi GRB 260429A: Global MASTER-Net observations report
  76. EP260430a: Global MASTER-Net observations report
  77. EP260430a: Einstein Probe detection of an X-ray transient
  78. EP260429a: EP-WXT detection of a fast X-ray transient
  79. GRB 260429A: Fermi GBM Final Real-time Localization
  80. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  81. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  82. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  83. GRB 260428A: AstroSat CZTI detection
  84. Fermi GRB 260428A: Global MASTER-Net observations report
  85. EP260416a: Mondy and Terskol optical upper limits
  86. GRB 260424B: Glowbug gamma-ray detection of a short burst
  87. GRB 260424B: COLIBRÍ optical upper limit
  88. Konus-Wind detection of GRB 260424B
  89. GRB 260428A: Fermi GBM Final Real-time Localization
  90. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  91. GRB 260424C: Fermi GBM Final Localization
  92. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  93. IPN triangulation of GRB 260424B (short)
  94. GRB 260424B: SVOM/GRM detection of a short burst
  95. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  96. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  97. IceCube Alert 260425A: Global MASTER-Net observations report
  98. Fermi trigger No 798737427: Global MASTER-Net observations report
  99. GRB 260401A: cubesat Avion detection
  100. GRB 260424A: AstroSat CZTI detection of a long burst

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