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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"
  1. GRB 260510C: SVOM/VT optical upper limits
  2. GRB 260510C: MAXI/GSC detection
  3. EP260509a: Global MASTER-Net observations report
  4. Fermi GBM Sub-Threshold Detection of GRB 260510B
  5. GRB 260510D: Fermi GBM Final Real-time Localization
  6. GRB 260510B: GOTO early upper limit
  7. GRB 260510C: SVOM detection of a burst
  8. GRB 260510C: Fermi GBM Final Real-time Localization
  9. GRB 260510A: GECAM-B observation
  10. GRB 260510B: LCO optical upper limits
  11. EP260509a: Einstein Probe detection of an X-ray transient
  12. GRB 260509A: Liverpool Telescope optical observations
  13. GRB 260510B: SVOM detection of a burst
  14. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  15. GRB 260509A: LCO optical observations
  16. SVOM GRB 260509A: MASTER-OAFA optical observation
  17. Fermi GRB 260510A: Global MASTER-Net observations report
  18. GRB 260509A: KAIT optical observations
  19. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  20. GRB 260510A: Fermi GBM Final Real-time Localization
  21. GRB 260509A: SVOM/VT optical candidate with VHF data
  22. GRB 260509A: LCO optical counterpart detection
  23. GRB 260509A: GOTO optical counterpart candidate
  24. GRB 260509A: SVOM detection of a burst
  25. GRB 260506B: AstroSat CZTI detection
  26. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  27. EP260507a: REM optical/NIR observations
  28. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  29. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  30. EP260507a: COLIBRÍ optical observations
  31. EP260507a: SVOM/VT optical observations
  32. EP260507a: NOT optical observations
  33. EP260507a: further Liverpool Telescope observations
  34. EP260507a: Liverpool Telescope optical upper limits
  35. GRB 260507A: Fermi GBM Final Real-time Localization
  36. EP260507a: GOTO optical counterpart detection
  37. EP260507a: TRT optical counterpart detection
  38. EP260507a: Kinder optical counterpart candidate
  39. EP260507a: LCO optical counterpart
  40. EP260507a: Einstein Probe detection of an X-ray transient
  41. GRB 260504B: AstroSat CZTI detection
  42. GRB 260504B: SVOM/ECLAIRs refined analysis
  43. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  44. GRB 260506B: Fermi GBM Final Real-time Localization
  45. EP260502a is likely a flaring star
  46. Fermi GRB 260506A: Global MASTER-Net observations report
  47. GRB 260506A: Fermi GBM Final Real-time Localization
  48. GRB 260503A: GECAM-B observation of a burst
  49. IceCube Alert 260505A: Global MASTER-Net observations report
  50. GRB 260430B: Glowbug gamma-ray detection
  51. GRB 260504B: SVOM/VT optical upper limits
  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. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  57. GRB 260504C: SVOM/GRM observation of short GRB
  58. GRB 260504B: SVOM/GRM spectral analysis
  59. GRB 260430B: AstroSat CZTI detection of a long burst
  60. GRB 260504B: SVOM/MXT refined analysis and potential detection
  61. GRB 260504B: EP-FXT upper limit
  62. GRB 260502A: SVOM/GRM observation of a short GRB
  63. GRB 260503A: SVOM/GRM observation of a GRB
  64. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  65. Konus-Wind detection of GRB 260415C
  66. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  67. Konus-Wind detection of GRB 260411C
  68. GRB 260504B: REM optical/NIR observations
  69. IPN triangulation of GRB 260429A
  70. IPN triangulation of GRB 260428A
  71. GRB 260504B: AST3-2 i-band upper limit
  72. GRB 260504B: LCO z-band upper limit
  73. SVOM GRB 260504B: MASTER-OAFA optical observations
  74. GRB 260504B: SVOM detection of a short burst
  75. Fermi GRB 260504A: Global MASTER-Net observations report
  76. GRB 260504A: Fermi GBM Final Real-time Localization
  77. GRB 260503A: Fermi GBM Final Real-time Localization
  78. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  79. GRB 260502A: GECAM-B observation of a short burst
  80. IPN triangulation of a bright burst from SGR 1E1841-045
  81. GRB 260502A: Fermi GBM Final Localization
  82. The EP-WXT trigger 01709261576 is likely a flaring star
  83. GRB 260429B / EP260429a: EP-FXT follow-up observation
  84. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  85. GRB 260429B / EP260429a: AstroSat CZTI detection
  86. EP260502a: BOOTES-7: early optical upper limit
  87. EP260502a: Las Cumbres upper limit
  88. EP260502a: Einstein Probe detection of an X-ray transient
  89. GRB 260429A: SVOM/GRM observation of a short burst
  90. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  91. EP260429a: Global MASTER-Net observations report
  92. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  93. GRB 260424B: AstroSat CZTI detection
  94. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  95. EP260429a: LCO optical upper limits
  96. EP260430a: LCO optical upper limits
  97. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  98. GRB 260429A: Fermi GBM Detection
  99. Fermi GRB 260429A: Global MASTER-Net observations report
  100. EP260430a: Global MASTER-Net observations report

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