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

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