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

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