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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"

14832 results found.

  1. GRB 260510D: Glowbug gamma-ray detection of a likely short burst
  2. GRB 260511B: FRAM-ORM optical detection
  3. GRB 260511B: LCO optical counterpart detection
  4. GRB 260511B: GOTO optical counterpart detection
  5. GRB 260510A: AstroSat CZTI detection (Erroneous Submission)
  6. GRB 260511A: REM near-infrared detection
  7. GRB 260511B: AstroSat CZTI detection
  8. GRB 260506B: Glowbug gamma-ray detection
  9. GRB 260506A: Glowbug gamma-ray detection of a short burst
  10. GRB 260511B: NuSTAR detection of prompt emission
  11. GRB 260511A: NuSTAR detection of prompt emission
  12. GRB 260511B: Fermi GBM Detection
  13. GRB 260511C: Fermi GBM Final Real-time Localization
  14. GRB 260511B: TRT optical observation
  15. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  16. GRB 260511A: Fermi GBM Detection
  17. GRB 260511B SVOM/C-GFT optical counterpart detection
  18. EP260509a: LCO optical upper limits
  19. GRB 260510C: AstroSat CZTI detection
  20. GRB 260511B: SVOM detection of a burst
  21. GRB 260511B: Fermi GBM Final Real-time Localization
  22. EP260509a: EP-FXT non-detection and upper limit
  23. GRB 260511A: LCO optical afterglow detection
  24. GRB 260511A: TRT optical counterpart detection
  25. GRB 260511A: SVOM detection of a bright burst
  26. GRB 260511A: Fermi GBM Final Real-time Localization
  27. GRB 260510B: SVOM/VT optical upper limits
  28. GRB 260510C: MAXI/GSC detection
  29. Fermi GBM Sub-Threshold Detection of GRB 260510B
  30. GRB 260510D: Fermi GBM Final Real-time Localization
  31. GRB 260510B: GOTO early upper limit
  32. GRB 260510C: SVOM detection of a burst
  33. GRB 260510C: Fermi GBM Final Real-time Localization
  34. EP260509a: Einstein Probe detection of an X-ray transient
  35. GRB 260510B: SVOM detection of a burst
  36. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  37. GRB 260510A: Fermi GBM Final Real-time Localization
  38. GRB 260509A: LCO optical counterpart detection
  39. GRB 260509A: SVOM detection of a burst
  40. GRB 260506B: AstroSat CZTI detection
  41. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  42. EP260507a: NOT optical observations
  43. EP260507a: further Liverpool Telescope observations
  44. GRB 260507A: Fermi GBM Final Real-time Localization
  45. EP260507a: GOTO optical counterpart detection
  46. EP260507a: TRT optical counterpart detection
  47. EP260507a: Einstein Probe detection of an X-ray transient
  48. GRB 260504B: AstroSat CZTI detection
  49. GRB 260506B: Fermi GBM Final Real-time Localization
  50. GRB 260506A: Fermi GBM Final Real-time Localization
  51. GRB 260430B: Glowbug gamma-ray detection
  52. GRB 260421B: radio observation with the VLA
  53. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  54. Konus-Wind detection of GRB 260504B (short/hard)
  55. GRB 260504B: GECAM-B detection
  56. GRB 260430B: AstroSat CZTI detection of a long burst
  57. GRB 260504B: SVOM/MXT refined analysis and potential detection
  58. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  59. Konus-Wind detection of GRB 260415C
  60. Konus-Wind detection of GRB 260411C
  61. IPN triangulation of GRB 260429A
  62. IPN triangulation of GRB 260428A
  63. GRB 260504B: AST3-2 i-band upper limit
  64. GRB 260504B: SVOM detection of a short burst
  65. GRB 260504A: Fermi GBM Final Real-time Localization
  66. GRB 260503A: Fermi GBM Final Real-time Localization
  67. GRB 260502A: Fermi GBM Final Localization
  68. GRB 260429B / EP260429a: AstroSat CZTI detection
  69. EP260502a: BOOTES-7: early optical upper limit
  70. EP260502a: Einstein Probe detection of an X-ray transient
  71. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  72. GRB 260424B: AstroSat CZTI detection
  73. GRB 260429A: Fermi GBM Detection
  74. EP260430a: Einstein Probe detection of an X-ray transient
  75. EP260429a: EP-WXT detection of a fast X-ray transient
  76. GRB 260429A: Fermi GBM Final Real-time Localization
  77. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  78. GRB 260428A: AstroSat CZTI detection
  79. EP260416a: Mondy and Terskol optical upper limits
  80. GRB 260424B: Glowbug gamma-ray detection of a short burst
  81. Konus-Wind detection of GRB 260424B
  82. GRB 260428A: Fermi GBM Final Real-time Localization
  83. GRB 260424C: Fermi GBM Final Localization
  84. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  85. IPN triangulation of GRB 260424B (short)
  86. GRB 260424B: SVOM/GRM detection of a short burst
  87. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  88. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  89. GRB 260401A: cubesat Avion detection
  90. GRB 260424A: AstroSat CZTI detection of a long burst
  91. GRB 260421B: Kilonova-Catcher optical afterglow detection
  92. GRB 260421B: Insight-HXMT/HE detection
  93. EP260416a: Mondy optical observations
  94. GRB 260421B: 3.6m DOT optical observation
  95. EP260416a: ZTSh R band observations
  96. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  97. GRB 260419A: AstroSat CZTI detection
  98. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  99. GRB 260421B: EP-FXT follow-up observation
  100. GOTO26djh/AT2026jpw: ATCA radio detection

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