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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"

27783 results found.

  1. GRB 260510C: MAXI/GSC detection
  2. Fermi GBM Sub-Threshold Detection of GRB 260510B
  3. GRB 260510D: Fermi GBM Final Real-time Localization
  4. GRB 260510B: GOTO early upper limit
  5. GRB 260510C: SVOM detection of a burst
  6. GRB 260510C: Fermi GBM Final Real-time Localization
  7. EP260509a: Einstein Probe detection of an X-ray transient
  8. GRB 260510B: SVOM detection of a burst
  9. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  10. GRB 260510A: Fermi GBM Final Real-time Localization
  11. GRB 260509A: LCO optical counterpart detection
  12. GRB 260509A: SVOM detection of a burst
  13. GRB 260506B: AstroSat CZTI detection
  14. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  15. EP260507a: further Liverpool Telescope observations
  16. GRB 260507A: Fermi GBM Final Real-time Localization
  17. EP260507a: GOTO optical counterpart detection
  18. EP260507a: TRT optical counterpart detection
  19. EP260507a: Einstein Probe detection of an X-ray transient
  20. GRB 260504B: AstroSat CZTI detection
  21. GRB 260506B: Fermi GBM Final Real-time Localization
  22. GRB 260506A: Fermi GBM Final Real-time Localization
  23. GRB 260430B: Glowbug gamma-ray detection
  24. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  25. Konus-Wind detection of GRB 260504B (short/hard)
  26. GRB 260504B: GECAM-B detection
  27. GRB 260430B: AstroSat CZTI detection of a long burst
  28. GRB 260504B: SVOM/MXT refined analysis and potential detection
  29. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  30. Konus-Wind detection of GRB 260415C
  31. Konus-Wind detection of GRB 260411C
  32. IPN triangulation of GRB 260429A
  33. IPN triangulation of GRB 260428A
  34. GRB 260504B: AST3-2 i-band upper limit
  35. GRB 260504B: SVOM detection of a short burst
  36. GRB 260504A: Fermi GBM Final Real-time Localization
  37. GRB 260503A: Fermi GBM Final Real-time Localization
  38. GRB 260502A: Fermi GBM Final Localization
  39. GRB 260429B / EP260429a: AstroSat CZTI detection
  40. EP260502a: BOOTES-7: early optical upper limit
  41. EP260502a: Einstein Probe detection of an X-ray transient
  42. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  43. GRB 260424B: AstroSat CZTI detection
  44. GRB 260429A: Fermi GBM Detection
  45. EP260430a: Einstein Probe detection of an X-ray transient
  46. EP260429a: EP-WXT detection of a fast X-ray transient
  47. GRB 260429A: Fermi GBM Final Real-time Localization
  48. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  49. GRB 260428A: AstroSat CZTI detection
  50. GRB 260424B: Glowbug gamma-ray detection of a short burst
  51. Konus-Wind detection of GRB 260424B
  52. GRB 260428A: Fermi GBM Final Real-time Localization
  53. GRB 260424C: Fermi GBM Final Localization
  54. IPN triangulation of GRB 260424B (short)
  55. GRB 260424B: SVOM/GRM detection of a short burst
  56. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  57. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  58. GRB 260401A: cubesat Avion detection
  59. GRB 260424A: AstroSat CZTI detection of a long burst
  60. GRB 260421B: Kilonova-Catcher optical afterglow detection
  61. GRB 260421B: Insight-HXMT/HE detection
  62. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  63. GRB 260419A: AstroSat CZTI detection
  64. GOTO26djh/AT2026jpw: ATCA radio detection
  65. GRB 260421B: LCO optical counterpart detection
  66. GRB 260421A: AstroSat CZTI detection
  67. GOTO26djh/AT2026jpw: radio detection at 15GHz
  68. GRB 260310A: Late-time Chandra X-ray Detection
  69. GRB 260418A: Insight-HXMT/HE detection
  70. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  71. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  72. GRB 260421C: Fermi GBM Final Real-time Localization
  73. GRB 260421B: BOOTES-7 early optical afterglow detection
  74. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  75. GRB 260421B: TRT optical counterpart detection
  76. GRB 260421B: SVOM detection of a long burst
  77. GRB 260421B: Fermi GBM Final Real-time Localization
  78. GRB 260421A: Fermi GBM Final Real-time Localization
  79. EP260416a: Optical follow-up observations with Kinder
  80. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  81. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  82. GRB 260419B: Fermi GBM Final Real-time Localization
  83. GRB 260419A: Fermi GBM Final Real-time Localization
  84. EP260416a: Ondrejov D50 optical detection
  85. GRB 260418B: Fermi GBM Final Real-time Localization
  86. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  87. GRB 260418A: Fermi GBM Final Real-time Localization
  88. Konus-Wind detection of GRB 260411B
  89. GRB 260417B: Fermi GBM Final Real-time Localization
  90. GRB 260417A: AstroSat CZTI detection
  91. IPN triangulation of GRB 260411B
  92. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  93. EP260417a: TRT optical counterpart detection
  94. EP260417a: Einstein Probe detection of an X-ray transient
  95. EP260417b: Einstein Probe detection of a fast X-ray transient
  96. GRB 260414A: Insight-HXMT/HE detection
  97. EP260416a: WFST optical observations and rebrightening
  98. GRB 260417A: Fermi GBM Final Real-time Localization
  99. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  100. GRB 260415B: Glowbug gamma-ray detection

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