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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"

28068 results found.

  1. GRB 260509A: SVOM/VT optical observations
  2. Konus-Wind detection of GRB 260511B
  3. EP260512a: Einstein Probe detection of an X-ray transient
  4. GRB 260511B: further J-band observations by the SYSU 80 cm infrared telescope
  5. GRB 260512A: NuSTAR detection of prompt emission
  6. GRB 260512A: Fermi GBM Final Real-time Localization
  7. GRB 260511A: Glowbug gamma-ray detection
  8. Konus-Wind detection of GRB 260511A
  9. MASS-Cube (GRID 2.0) detection of GRB 260511A
  10. MASS-Cube (GRID 2.0) detection of GRB 260507A
  11. GRB 260510D: Glowbug gamma-ray detection of a likely short burst
  12. GRB 260511B: FRAM-ORM optical detection
  13. GRB 260511B: LCO optical counterpart detection
  14. GRB 260511A: SVOM/VT optical observations
  15. GRB 260511B: GOTO optical counterpart detection
  16. GRB 260510A: AstroSat CZTI detection (Erroneous Submission)
  17. GRB 260511B: SVOM/VT optical observations
  18. GRB 260511B: OSIRIS+/GTC redshift z=2.006
  19. GRB 260511A: REM near-infrared detection
  20. GRB 260511B: AstroSat CZTI detection
  21. GRB 260506B: Glowbug gamma-ray detection
  22. GRB 260506A: Glowbug gamma-ray detection of a short burst
  23. GRB 260511B: NuSTAR detection of prompt emission
  24. GRB 260511A: NuSTAR detection of prompt emission
  25. GRB 260511B: Fermi GBM Detection
  26. GRB 260511C: Fermi GBM Final Real-time Localization
  27. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  28. GRB 260511A: Fermi GBM Detection
  29. GRB 260511B SVOM/C-GFT optical counterpart detection
  30. EP260509a: LCO optical upper limits
  31. GRB 260511A: UTGO H50 optical afterglow observation
  32. GRB 260510C: AstroSat CZTI detection
  33. GRB 260511B: SVOM detection of a burst
  34. GRB 260511B: Fermi GBM Final Real-time Localization
  35. EP260509a: EP-FXT non-detection and upper limit
  36. GRB 260511A: KAIT optical afterglow observations
  37. GRB 260511A: LCO optical afterglow detection
  38. GRB 260511A: TRT optical counterpart detection
  39. GRB 260511A: SVOM detection of a bright burst
  40. GRB 260511A: Fermi GBM Final Real-time Localization
  41. GRB 260510B: SVOM/VT optical upper limits
  42. GRB 260510C: MAXI/GSC detection
  43. Fermi GBM Sub-Threshold Detection of GRB 260510B
  44. GRB 260510D: Fermi GBM Final Real-time Localization
  45. GRB 260510B: GOTO early upper limit
  46. GRB 260510C: SVOM detection of a burst
  47. GRB 260510C: Fermi GBM Final Real-time Localization
  48. EP260509a: Einstein Probe detection of an X-ray transient
  49. GRB 260510B: SVOM detection of a burst
  50. GRB 260509A: KAIT optical observations
  51. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  52. GRB 260510A: Fermi GBM Final Real-time Localization
  53. GRB 260509A: LCO optical counterpart detection
  54. GRB 260509A: SVOM detection of a burst
  55. GRB 260506B: AstroSat CZTI detection
  56. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  57. EP260507a: NOT optical observations
  58. EP260507a: further Liverpool Telescope observations
  59. GRB 260507A: Fermi GBM Final Real-time Localization
  60. EP260507a: GOTO optical counterpart detection
  61. EP260507a: TRT optical counterpart detection
  62. EP260507a: Einstein Probe detection of an X-ray transient
  63. GRB 260504B: AstroSat CZTI detection
  64. GRB 260506B: Fermi GBM Final Real-time Localization
  65. GRB 260506A: Fermi GBM Final Real-time Localization
  66. GRB 260430B: Glowbug gamma-ray detection
  67. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  68. Konus-Wind detection of GRB 260504B (short/hard)
  69. GRB 260504B: GECAM-B detection
  70. GRB 260430B: AstroSat CZTI detection of a long burst
  71. GRB 260504B: SVOM/MXT refined analysis and potential detection
  72. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  73. Konus-Wind detection of GRB 260415C
  74. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  75. Konus-Wind detection of GRB 260411C
  76. IPN triangulation of GRB 260429A
  77. IPN triangulation of GRB 260428A
  78. GRB 260504B: AST3-2 i-band upper limit
  79. GRB 260504B: SVOM detection of a short burst
  80. GRB 260504A: Fermi GBM Final Real-time Localization
  81. GRB 260503A: Fermi GBM Final Real-time Localization
  82. GRB 260502A: Fermi GBM Final Localization
  83. GRB 260429B / EP260429a: EP-FXT follow-up observation
  84. GRB 260429B / EP260429a: AstroSat CZTI detection
  85. EP260502a: BOOTES-7: early optical upper limit
  86. EP260502a: Einstein Probe detection of an X-ray transient
  87. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  88. GRB 260424B: AstroSat CZTI detection
  89. GRB 260429A: Fermi GBM Detection
  90. EP260430a: Einstein Probe detection of an X-ray transient
  91. EP260429a: EP-WXT detection of a fast X-ray transient
  92. GRB 260429A: Fermi GBM Final Real-time Localization
  93. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  94. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  95. GRB 260428A: AstroSat CZTI detection
  96. GRB 260424B: Glowbug gamma-ray detection of a short burst
  97. Konus-Wind detection of GRB 260424B
  98. GRB 260428A: Fermi GBM Final Real-time Localization
  99. GRB 260424C: Fermi GBM Final Localization
  100. IPN triangulation of GRB 260424B (short)

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