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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: Fermi GBM Final Real-time Localization
  2. GRB 260510A: GECAM-B observation
  3. GRB 260510B: LCO optical upper limits
  4. EP260509a: Einstein Probe detection of an X-ray transient
  5. GRB 260509A: Liverpool Telescope optical observations
  6. GRB 260510B: SVOM detection of a burst
  7. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  8. GRB 260509A: LCO optical observations
  9. SVOM GRB 260509A: MASTER-OAFA optical observation
  10. Fermi GRB 260510A: Global MASTER-Net observations report
  11. GRB 260509A: KAIT optical observations
  12. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  13. GRB 260510A: Fermi GBM Final Real-time Localization
  14. GRB 260509A: SVOM/VT optical candidate with VHF data
  15. GRB 260509A: LCO optical counterpart detection
  16. GRB 260509A: GOTO optical counterpart candidate
  17. GRB 260509A: SVOM detection of a burst
  18. GRB 260506B: AstroSat CZTI detection
  19. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  20. EP260507a: REM optical/NIR observations
  21. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  22. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  23. EP260507a: COLIBRÍ optical observations
  24. EP260507a: SVOM/VT optical observations
  25. EP260507a: NOT optical observations
  26. EP260507a: further Liverpool Telescope observations
  27. EP260507a: Liverpool Telescope optical upper limits
  28. GRB 260507A: Fermi GBM Final Real-time Localization
  29. EP260507a: GOTO optical counterpart detection
  30. EP260507a: TRT optical counterpart detection
  31. EP260507a: Kinder optical counterpart candidate
  32. EP260507a: LCO optical counterpart
  33. EP260507a: Einstein Probe detection of an X-ray transient
  34. GRB 260504B: AstroSat CZTI detection
  35. GRB 260504B: SVOM/ECLAIRs refined analysis
  36. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  37. GRB 260506B: Fermi GBM Final Real-time Localization
  38. EP260502a is likely a flaring star
  39. Fermi GRB 260506A: Global MASTER-Net observations report
  40. GRB 260506A: Fermi GBM Final Real-time Localization
  41. GRB 260503A: GECAM-B observation of a burst
  42. IceCube Alert 260505A: Global MASTER-Net observations report
  43. GRB 260430B: Glowbug gamma-ray detection
  44. GRB 260504B: SVOM/VT optical upper limits
  45. GRB 260421B: radio observation with the VLA
  46. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  47. Konus-Wind detection of GRB 260504B (short/hard)
  48. GRB 260504B: GECAM-B detection
  49. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  50. GRB 260504C: SVOM/GRM observation of short GRB
  51. GRB 260504B: SVOM/GRM spectral analysis
  52. GRB 260430B: AstroSat CZTI detection of a long burst
  53. GRB 260504B: SVOM/MXT refined analysis and potential detection
  54. GRB 260504B: EP-FXT upper limit
  55. GRB 260502A: SVOM/GRM observation of a short GRB
  56. GRB 260503A: SVOM/GRM observation of a GRB
  57. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  58. Konus-Wind detection of GRB 260415C
  59. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  60. Konus-Wind detection of GRB 260411C
  61. GRB 260504B: REM optical/NIR observations
  62. IPN triangulation of GRB 260429A
  63. IPN triangulation of GRB 260428A
  64. GRB 260504B: AST3-2 i-band upper limit
  65. GRB 260504B: LCO z-band upper limit
  66. SVOM GRB 260504B: MASTER-OAFA optical observations
  67. GRB 260504B: SVOM detection of a short burst
  68. Fermi GRB 260504A: Global MASTER-Net observations report
  69. GRB 260504A: Fermi GBM Final Real-time Localization
  70. GRB 260503A: Fermi GBM Final Real-time Localization
  71. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  72. GRB 260502A: GECAM-B observation of a short burst
  73. IPN triangulation of a bright burst from SGR 1E1841-045
  74. GRB 260502A: Fermi GBM Final Localization
  75. The EP-WXT trigger 01709261576 is likely a flaring star
  76. GRB 260429B / EP260429a: EP-FXT follow-up observation
  77. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  78. GRB 260429B / EP260429a: AstroSat CZTI detection
  79. EP260502a: BOOTES-7: early optical upper limit
  80. EP260502a: Las Cumbres upper limit
  81. EP260502a: Einstein Probe detection of an X-ray transient
  82. GRB 260429A: SVOM/GRM observation of a short burst
  83. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  84. EP260429a: Global MASTER-Net observations report
  85. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  86. GRB 260424B: AstroSat CZTI detection
  87. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  88. EP260429a: LCO optical upper limits
  89. EP260430a: LCO optical upper limits
  90. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  91. GRB 260429A: Fermi GBM Detection
  92. Fermi GRB 260429A: Global MASTER-Net observations report
  93. EP260430a: Global MASTER-Net observations report
  94. EP260430a: Einstein Probe detection of an X-ray transient
  95. EP260429a: EP-WXT detection of a fast X-ray transient
  96. GRB 260429A: Fermi GBM Final Real-time Localization
  97. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  98. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  99. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  100. GRB 260428A: AstroSat CZTI detection

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