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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. EP260509a: Einstein Probe detection of an X-ray transient
  2. GRB 260509A: Liverpool Telescope optical observations
  3. GRB 260510B: SVOM detection of a burst
  4. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  5. GRB 260509A: LCO optical observations
  6. SVOM GRB 260509A: MASTER-OAFA optical observation
  7. Fermi GRB 260510A: Global MASTER-Net observations report
  8. GRB 260509A: KAIT optical observations
  9. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  10. GRB 260510A: Fermi GBM Final Real-time Localization
  11. GRB 260509A: SVOM/VT optical candidate with VHF data
  12. GRB 260509A: LCO optical counterpart detection
  13. GRB 260509A: GOTO optical counterpart candidate
  14. GRB 260509A: SVOM detection of a burst
  15. GRB 260506B: AstroSat CZTI detection
  16. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  17. EP260507a: REM optical/NIR observations
  18. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  19. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  20. EP260507a: COLIBRÍ optical observations
  21. EP260507a: SVOM/VT optical observations
  22. EP260507a: NOT optical observations
  23. EP260507a: further Liverpool Telescope observations
  24. EP260507a: Liverpool Telescope optical upper limits
  25. GRB 260507A: Fermi GBM Final Real-time Localization
  26. EP260507a: GOTO optical counterpart detection
  27. EP260507a: TRT optical counterpart detection
  28. EP260507a: Kinder optical counterpart candidate
  29. EP260507a: LCO optical counterpart
  30. EP260507a: Einstein Probe detection of an X-ray transient
  31. GRB 260504B: AstroSat CZTI detection
  32. GRB 260504B: SVOM/ECLAIRs refined analysis
  33. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  34. GRB 260506B: Fermi GBM Final Real-time Localization
  35. EP260502a is likely a flaring star
  36. Fermi GRB 260506A: Global MASTER-Net observations report
  37. GRB 260506A: Fermi GBM Final Real-time Localization
  38. GRB 260503A: GECAM-B observation of a burst
  39. IceCube Alert 260505A: Global MASTER-Net observations report
  40. GRB 260430B: Glowbug gamma-ray detection
  41. GRB 260504B: SVOM/VT optical upper limits
  42. GRB 260421B: radio observation with the VLA
  43. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  44. Konus-Wind detection of GRB 260504B (short/hard)
  45. GRB 260504B: GECAM-B detection
  46. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  47. GRB 260504C: SVOM/GRM observation of short GRB
  48. GRB 260504B: SVOM/GRM spectral analysis
  49. GRB 260430B: AstroSat CZTI detection of a long burst
  50. GRB 260504B: SVOM/MXT refined analysis and potential detection
  51. GRB 260504B: EP-FXT upper limit
  52. GRB 260502A: SVOM/GRM observation of a short GRB
  53. GRB 260503A: SVOM/GRM observation of a GRB
  54. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  55. Konus-Wind detection of GRB 260415C
  56. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  57. Konus-Wind detection of GRB 260411C
  58. GRB 260504B: REM optical/NIR observations
  59. IPN triangulation of GRB 260429A
  60. IPN triangulation of GRB 260428A
  61. GRB 260504B: AST3-2 i-band upper limit
  62. GRB 260504B: LCO z-band upper limit
  63. SVOM GRB 260504B: MASTER-OAFA optical observations
  64. GRB 260504B: SVOM detection of a short burst
  65. Fermi GRB 260504A: Global MASTER-Net observations report
  66. GRB 260504A: Fermi GBM Final Real-time Localization
  67. GRB 260503A: Fermi GBM Final Real-time Localization
  68. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  69. GRB 260502A: GECAM-B observation of a short burst
  70. IPN triangulation of a bright burst from SGR 1E1841-045
  71. GRB 260502A: Fermi GBM Final Localization
  72. The EP-WXT trigger 01709261576 is likely a flaring star
  73. GRB 260429B / EP260429a: EP-FXT follow-up observation
  74. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  75. GRB 260429B / EP260429a: AstroSat CZTI detection
  76. EP260502a: BOOTES-7: early optical upper limit
  77. EP260502a: Las Cumbres upper limit
  78. EP260502a: Einstein Probe detection of an X-ray transient
  79. GRB 260429A: SVOM/GRM observation of a short burst
  80. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  81. EP260429a: Global MASTER-Net observations report
  82. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  83. GRB 260424B: AstroSat CZTI detection
  84. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  85. EP260429a: LCO optical upper limits
  86. EP260430a: LCO optical upper limits
  87. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  88. GRB 260429A: Fermi GBM Detection
  89. Fermi GRB 260429A: Global MASTER-Net observations report
  90. EP260430a: Global MASTER-Net observations report
  91. EP260430a: Einstein Probe detection of an X-ray transient
  92. EP260429a: EP-WXT detection of a fast X-ray transient
  93. GRB 260429A: Fermi GBM Final Real-time Localization
  94. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  95. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  96. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  97. GRB 260428A: AstroSat CZTI detection
  98. Fermi GRB 260428A: Global MASTER-Net observations report
  99. EP260416a: Mondy and Terskol optical upper limits
  100. GRB 260424B: Glowbug gamma-ray detection of a short burst

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