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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. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  2. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  3. EP260507a: COLIBRÍ optical observations
  4. EP260507a: SVOM/VT optical observations
  5. EP260507a: NOT optical observations
  6. EP260507a: further Liverpool Telescope observations
  7. EP260507a: Liverpool Telescope optical upper limits
  8. GRB 260507A: Fermi GBM Final Real-time Localization
  9. EP260507a: GOTO optical counterpart detection
  10. EP260507a: TRT optical counterpart detection
  11. EP260507a: Kinder optical counterpart candidate
  12. EP260507a: LCO optical counterpart
  13. EP260507a: Einstein Probe detection of an X-ray transient
  14. GRB 260504B: AstroSat CZTI detection
  15. GRB 260504B: SVOM/ECLAIRs refined analysis
  16. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  17. GRB 260506B: Fermi GBM Final Real-time Localization
  18. EP260502a is likely a flaring star
  19. Fermi GRB 260506A: Global MASTER-Net observations report
  20. GRB 260506A: Fermi GBM Final Real-time Localization
  21. GRB 260503A: GECAM-B observation of a burst
  22. IceCube Alert 260505A: Global MASTER-Net observations report
  23. GRB 260430B: Glowbug gamma-ray detection
  24. GRB 260504B: SVOM/VT optical upper limits
  25. GRB 260421B: radio observation with the VLA
  26. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  27. Konus-Wind detection of GRB 260504B (short/hard)
  28. GRB 260504B: GECAM-B detection
  29. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  30. GRB 260504C: SVOM/GRM observation of short GRB
  31. GRB 260504B: SVOM/GRM spectral analysis
  32. GRB 260430B: AstroSat CZTI detection of a long burst
  33. GRB 260504B: SVOM/MXT refined analysis and potential detection
  34. GRB 260504B: EP-FXT upper limit
  35. GRB 260502A: SVOM/GRM observation of a short GRB
  36. GRB 260503A: SVOM/GRM observation of a GRB
  37. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  38. Konus-Wind detection of GRB 260415C
  39. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  40. Konus-Wind detection of GRB 260411C
  41. GRB 260504B: REM optical/NIR observations
  42. IPN triangulation of GRB 260429A
  43. IPN triangulation of GRB 260428A
  44. GRB 260504B: AST3-2 i-band upper limit
  45. GRB 260504B: LCO z-band upper limit
  46. SVOM GRB 260504B: MASTER-OAFA optical observations
  47. GRB 260504B: SVOM detection of a short burst
  48. Fermi GRB 260504A: Global MASTER-Net observations report
  49. GRB 260504A: Fermi GBM Final Real-time Localization
  50. GRB 260503A: Fermi GBM Final Real-time Localization
  51. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  52. GRB 260502A: GECAM-B observation of a short burst
  53. IPN triangulation of a bright burst from SGR 1E1841-045
  54. GRB 260502A: Fermi GBM Final Localization
  55. The EP-WXT trigger 01709261576 is likely a flaring star
  56. GRB 260429B / EP260429a: EP-FXT follow-up observation
  57. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  58. GRB 260429B / EP260429a: AstroSat CZTI detection
  59. EP260502a: BOOTES-7: early optical upper limit
  60. EP260502a: Las Cumbres upper limit
  61. EP260502a: Einstein Probe detection of an X-ray transient
  62. GRB 260429A: SVOM/GRM observation of a short burst
  63. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  64. EP260429a: Global MASTER-Net observations report
  65. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  66. GRB 260424B: AstroSat CZTI detection
  67. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  68. EP260429a: LCO optical upper limits
  69. EP260430a: LCO optical upper limits
  70. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  71. GRB 260429A: Fermi GBM Detection
  72. Fermi GRB 260429A: Global MASTER-Net observations report
  73. EP260430a: Global MASTER-Net observations report
  74. EP260430a: Einstein Probe detection of an X-ray transient
  75. EP260429a: EP-WXT detection of a fast X-ray transient
  76. GRB 260429A: Fermi GBM Final Real-time Localization
  77. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  78. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  79. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  80. GRB 260428A: AstroSat CZTI detection
  81. Fermi GRB 260428A: Global MASTER-Net observations report
  82. EP260416a: Mondy and Terskol optical upper limits
  83. GRB 260424B: Glowbug gamma-ray detection of a short burst
  84. GRB 260424B: COLIBRÍ optical upper limit
  85. Konus-Wind detection of GRB 260424B
  86. GRB 260428A: Fermi GBM Final Real-time Localization
  87. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  88. GRB 260424C: Fermi GBM Final Localization
  89. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  90. IPN triangulation of GRB 260424B (short)
  91. GRB 260424B: SVOM/GRM detection of a short burst
  92. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  93. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  94. IceCube Alert 260425A: Global MASTER-Net observations report
  95. Fermi trigger No 798737427: Global MASTER-Net observations report
  96. GRB 260401A: cubesat Avion detection
  97. GRB 260424A: AstroSat CZTI detection of a long burst
  98. EP260321a: Upper limits from ATCA radio observations
  99. GRB 260421B: Kilonova-Catcher optical afterglow detection
  100. GRB 260421B: Insight-HXMT/HE detection

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