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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"

44409 results found.

  1. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  2. GRB 260511A: Fermi GBM Detection
  3. GRB 260511B SVOM/C-GFT optical counterpart detection
  4. EP260509a: LCO optical upper limits
  5. GRB 260511A: UTGO H50 optical afterglow observation
  6. GRB 260510C: AstroSat CZTI detection
  7. GRB 260511B: SVOM detection of a burst
  8. GRB 260511B: Fermi GBM Final Real-time Localization
  9. GRB 260510C: EP-FXT follow-up observation
  10. GRB 260510C: SVOM/VT optical counterpart confirmation
  11. EP260509a: EP-FXT non-detection and upper limit
  12. GRB 260511A: SVOM/VT optical observation with VHF data
  13. Fermi GRB 260511A: Global MASTER-Net observations report
  14. GRB 260511A: KAIT optical afterglow observations
  15. GRB 260511A: LCO optical afterglow detection
  16. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  17. GRB 260511A: TRT optical counterpart detection
  18. GRB 260511A: SVOM detection of a bright burst
  19. GRB 260511A: BALROG localization (Fermi Trigger 800172815 / GRB 260511259)
  20. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  21. GRB 260511A: Fermi GBM Final Real-time Localization
  22. GRB 260510B: SVOM/VT optical upper limits
  23. GRB 260510C: SVOM/VT optical upper limits
  24. GRB 260510C: MAXI/GSC detection
  25. EP260509a: Global MASTER-Net observations report
  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. GRB 260510A: GECAM-B observation
  32. GRB 260510B: LCO optical upper limits
  33. EP260509a: Einstein Probe detection of an X-ray transient
  34. GRB 260509A: Liverpool Telescope optical observations
  35. GRB 260510B: SVOM detection of a burst
  36. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  37. GRB 260509A: LCO optical observations
  38. SVOM GRB 260509A: MASTER-OAFA optical observation
  39. Fermi GRB 260510A: Global MASTER-Net observations report
  40. GRB 260509A: KAIT optical observations
  41. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  42. GRB 260510A: Fermi GBM Final Real-time Localization
  43. GRB 260509A: SVOM/VT optical candidate with VHF data
  44. GRB 260509A: LCO optical counterpart detection
  45. GRB 260509A: GOTO optical counterpart candidate
  46. GRB 260509A: SVOM detection of a burst
  47. GRB 260506B: AstroSat CZTI detection
  48. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  49. EP260507a: REM optical/NIR observations
  50. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  51. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  52. EP260507a: COLIBRÍ optical observations
  53. EP260507a: SVOM/VT optical observations
  54. EP260507a: NOT optical observations
  55. EP260507a: further Liverpool Telescope observations
  56. EP260507a: Liverpool Telescope optical upper limits
  57. GRB 260507A: Fermi GBM Final Real-time Localization
  58. EP260507a: GOTO optical counterpart detection
  59. EP260507a: TRT optical counterpart detection
  60. EP260507a: Kinder optical counterpart candidate
  61. EP260507a: LCO optical counterpart
  62. EP260507a: Einstein Probe detection of an X-ray transient
  63. GRB 260504B: AstroSat CZTI detection
  64. GRB 260504B: SVOM/ECLAIRs refined analysis
  65. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  66. GRB 260506B: Fermi GBM Final Real-time Localization
  67. EP260502a is likely a flaring star
  68. Fermi GRB 260506A: Global MASTER-Net observations report
  69. GRB 260506A: Fermi GBM Final Real-time Localization
  70. GRB 260503A: GECAM-B observation of a burst
  71. IceCube Alert 260505A: Global MASTER-Net observations report
  72. GRB 260430B: Glowbug gamma-ray detection
  73. GRB 260504B: SVOM/VT optical upper limits
  74. GRB 260421B: radio observation with the VLA
  75. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  76. Konus-Wind detection of GRB 260504B (short/hard)
  77. GRB 260504B: GECAM-B detection
  78. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  79. GRB 260504C: SVOM/GRM observation of short GRB
  80. GRB 260504B: SVOM/GRM spectral analysis
  81. GRB 260430B: AstroSat CZTI detection of a long burst
  82. GRB 260504B: SVOM/MXT refined analysis and potential detection
  83. GRB 260504B: EP-FXT upper limit
  84. GRB 260502A: SVOM/GRM observation of a short GRB
  85. GRB 260503A: SVOM/GRM observation of a GRB
  86. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  87. Konus-Wind detection of GRB 260415C
  88. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  89. Konus-Wind detection of GRB 260411C
  90. GRB 260504B: REM optical/NIR observations
  91. IPN triangulation of GRB 260429A
  92. IPN triangulation of GRB 260428A
  93. GRB 260504B: AST3-2 i-band upper limit
  94. GRB 260504B: LCO z-band upper limit
  95. SVOM GRB 260504B: MASTER-OAFA optical observations
  96. GRB 260504B: SVOM detection of a short burst
  97. Fermi GRB 260504A: Global MASTER-Net observations report
  98. GRB 260504A: Fermi GBM Final Real-time Localization
  99. GRB 260503A: Fermi GBM Final Real-time Localization
  100. SVOM/GRM observation of a bright burst from SGR 1E1841-045

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