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

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