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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"

14829 results found.

  1. GRB 260511B: GOTO optical counterpart detection
  2. GRB 260510A: AstroSat CZTI detection (Erroneous Submission)
  3. GRB 260511A: REM near-infrared detection
  4. GRB 260511B: AstroSat CZTI detection
  5. GRB 260506B: Glowbug gamma-ray detection
  6. GRB 260506A: Glowbug gamma-ray detection of a short burst
  7. GRB 260511B: NuSTAR detection of prompt emission
  8. GRB 260511A: NuSTAR detection of prompt emission
  9. GRB 260511B: Fermi GBM Detection
  10. GRB 260511C: Fermi GBM Final Real-time Localization
  11. GRB 260511B: TRT optical observation
  12. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  13. GRB 260511A: Fermi GBM Detection
  14. GRB 260511B SVOM/C-GFT optical counterpart detection
  15. EP260509a: LCO optical upper limits
  16. GRB 260510C: AstroSat CZTI detection
  17. GRB 260511B: SVOM detection of a burst
  18. GRB 260511B: Fermi GBM Final Real-time Localization
  19. EP260509a: EP-FXT non-detection and upper limit
  20. GRB 260511A: LCO optical afterglow detection
  21. GRB 260511A: TRT optical counterpart detection
  22. GRB 260511A: SVOM detection of a bright burst
  23. GRB 260511A: Fermi GBM Final Real-time Localization
  24. GRB 260510B: SVOM/VT optical upper limits
  25. GRB 260510C: MAXI/GSC detection
  26. Fermi GBM Sub-Threshold Detection of GRB 260510B
  27. GRB 260510D: Fermi GBM Final Real-time Localization
  28. GRB 260510B: GOTO early upper limit
  29. GRB 260510C: SVOM detection of a burst
  30. GRB 260510C: Fermi GBM Final Real-time Localization
  31. EP260509a: Einstein Probe detection of an X-ray transient
  32. GRB 260510B: SVOM detection of a burst
  33. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  34. GRB 260510A: Fermi GBM Final Real-time Localization
  35. GRB 260509A: LCO optical counterpart detection
  36. GRB 260509A: SVOM detection of a burst
  37. GRB 260506B: AstroSat CZTI detection
  38. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  39. EP260507a: NOT optical observations
  40. EP260507a: further Liverpool Telescope observations
  41. GRB 260507A: Fermi GBM Final Real-time Localization
  42. EP260507a: GOTO optical counterpart detection
  43. EP260507a: TRT optical counterpart detection
  44. EP260507a: Einstein Probe detection of an X-ray transient
  45. GRB 260504B: AstroSat CZTI detection
  46. GRB 260506B: Fermi GBM Final Real-time Localization
  47. GRB 260506A: Fermi GBM Final Real-time Localization
  48. GRB 260430B: Glowbug gamma-ray detection
  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. GRB 260430B: AstroSat CZTI detection of a long burst
  54. GRB 260504B: SVOM/MXT refined analysis and potential detection
  55. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  56. Konus-Wind detection of GRB 260415C
  57. Konus-Wind detection of GRB 260411C
  58. IPN triangulation of GRB 260429A
  59. IPN triangulation of GRB 260428A
  60. GRB 260504B: AST3-2 i-band upper limit
  61. GRB 260504B: SVOM detection of a short burst
  62. GRB 260504A: Fermi GBM Final Real-time Localization
  63. GRB 260503A: Fermi GBM Final Real-time Localization
  64. GRB 260502A: Fermi GBM Final Localization
  65. GRB 260429B / EP260429a: AstroSat CZTI detection
  66. EP260502a: BOOTES-7: early optical upper limit
  67. EP260502a: Einstein Probe detection of an X-ray transient
  68. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  69. GRB 260424B: AstroSat CZTI detection
  70. GRB 260429A: Fermi GBM Detection
  71. EP260430a: Einstein Probe detection of an X-ray transient
  72. EP260429a: EP-WXT detection of a fast X-ray transient
  73. GRB 260429A: Fermi GBM Final Real-time Localization
  74. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  75. GRB 260428A: AstroSat CZTI detection
  76. EP260416a: Mondy and Terskol optical upper limits
  77. GRB 260424B: Glowbug gamma-ray detection of a short burst
  78. Konus-Wind detection of GRB 260424B
  79. GRB 260428A: Fermi GBM Final Real-time Localization
  80. GRB 260424C: Fermi GBM Final Localization
  81. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  82. IPN triangulation of GRB 260424B (short)
  83. GRB 260424B: SVOM/GRM detection of a short burst
  84. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  85. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  86. GRB 260401A: cubesat Avion detection
  87. GRB 260424A: AstroSat CZTI detection of a long burst
  88. GRB 260421B: Kilonova-Catcher optical afterglow detection
  89. GRB 260421B: Insight-HXMT/HE detection
  90. EP260416a: Mondy optical observations
  91. GRB 260421B: 3.6m DOT optical observation
  92. EP260416a: ZTSh R band observations
  93. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  94. GRB 260419A: AstroSat CZTI detection
  95. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  96. GRB 260421B: EP-FXT follow-up observation
  97. GOTO26djh/AT2026jpw: ATCA radio detection
  98. GRB 260421B: J-band upper limit with WINTER
  99. GRB 260421B: LCO optical counterpart detection
  100. GRB 260421A: AstroSat CZTI detection

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