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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: SVOM/VT optical observations
  2. EP260507a: NOT optical observations
  3. EP260507a: further Liverpool Telescope observations
  4. EP260507a: Liverpool Telescope optical upper limits
  5. GRB 260507A: Fermi GBM Final Real-time Localization
  6. EP260507a: GOTO optical counterpart detection
  7. EP260507a: TRT optical counterpart detection
  8. EP260507a: Kinder optical counterpart candidate
  9. EP260507a: LCO optical counterpart
  10. EP260507a: Einstein Probe detection of an X-ray transient
  11. GRB 260504B: AstroSat CZTI detection
  12. GRB 260504B: SVOM/ECLAIRs refined analysis
  13. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  14. GRB 260506B: Fermi GBM Final Real-time Localization
  15. EP260502a is likely a flaring star
  16. Fermi GRB 260506A: Global MASTER-Net observations report
  17. GRB 260506A: Fermi GBM Final Real-time Localization
  18. GRB 260503A: GECAM-B observation of a burst
  19. IceCube Alert 260505A: Global MASTER-Net observations report
  20. GRB 260430B: Glowbug gamma-ray detection
  21. GRB 260504B: SVOM/VT optical upper limits
  22. GRB 260421B: radio observation with the VLA
  23. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  24. Konus-Wind detection of GRB 260504B (short/hard)
  25. GRB 260504B: GECAM-B detection
  26. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  27. GRB 260504C: SVOM/GRM observation of short GRB
  28. GRB 260504B: SVOM/GRM spectral analysis
  29. GRB 260430B: AstroSat CZTI detection of a long burst
  30. GRB 260504B: SVOM/MXT refined analysis and potential detection
  31. GRB 260504B: EP-FXT upper limit
  32. GRB 260502A: SVOM/GRM observation of a short GRB
  33. GRB 260503A: SVOM/GRM observation of a GRB
  34. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  35. Konus-Wind detection of GRB 260415C
  36. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  37. Konus-Wind detection of GRB 260411C
  38. GRB 260504B: REM optical/NIR observations
  39. IPN triangulation of GRB 260429A
  40. IPN triangulation of GRB 260428A
  41. GRB 260504B: AST3-2 i-band upper limit
  42. GRB 260504B: LCO z-band upper limit
  43. SVOM GRB 260504B: MASTER-OAFA optical observations
  44. GRB 260504B: SVOM detection of a short burst
  45. Fermi GRB 260504A: Global MASTER-Net observations report
  46. GRB 260504A: Fermi GBM Final Real-time Localization
  47. GRB 260503A: Fermi GBM Final Real-time Localization
  48. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  49. GRB 260502A: GECAM-B observation of a short burst
  50. IPN triangulation of a bright burst from SGR 1E1841-045
  51. GRB 260502A: Fermi GBM Final Localization
  52. The EP-WXT trigger 01709261576 is likely a flaring star
  53. GRB 260429B / EP260429a: EP-FXT follow-up observation
  54. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  55. GRB 260429B / EP260429a: AstroSat CZTI detection
  56. EP260502a: BOOTES-7: early optical upper limit
  57. EP260502a: Las Cumbres upper limit
  58. EP260502a: Einstein Probe detection of an X-ray transient
  59. GRB 260429A: SVOM/GRM observation of a short burst
  60. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  61. EP260429a: Global MASTER-Net observations report
  62. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  63. GRB 260424B: AstroSat CZTI detection
  64. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  65. EP260429a: LCO optical upper limits
  66. EP260430a: LCO optical upper limits
  67. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  68. GRB 260429A: Fermi GBM Detection
  69. Fermi GRB 260429A: Global MASTER-Net observations report
  70. EP260430a: Global MASTER-Net observations report
  71. EP260430a: Einstein Probe detection of an X-ray transient
  72. EP260429a: EP-WXT detection of a fast X-ray transient
  73. GRB 260429A: Fermi GBM Final Real-time Localization
  74. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  75. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  76. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  77. GRB 260428A: AstroSat CZTI detection
  78. Fermi GRB 260428A: Global MASTER-Net observations report
  79. EP260416a: Mondy and Terskol optical upper limits
  80. GRB 260424B: Glowbug gamma-ray detection of a short burst
  81. GRB 260424B: COLIBRÍ optical upper limit
  82. Konus-Wind detection of GRB 260424B
  83. GRB 260428A: Fermi GBM Final Real-time Localization
  84. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  85. GRB 260424C: Fermi GBM Final Localization
  86. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  87. IPN triangulation of GRB 260424B (short)
  88. GRB 260424B: SVOM/GRM detection of a short burst
  89. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  90. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  91. IceCube Alert 260425A: Global MASTER-Net observations report
  92. Fermi trigger No 798737427: Global MASTER-Net observations report
  93. GRB 260401A: cubesat Avion detection
  94. GRB 260424A: AstroSat CZTI detection of a long burst
  95. EP260321a: Upper limits from ATCA radio observations
  96. GRB 260421B: Kilonova-Catcher optical afterglow detection
  97. GRB 260421B: Insight-HXMT/HE detection
  98. The EP-WXT trigger 01709258652: Mondy optical observations
  99. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  100. EP260416a: Mondy optical observations

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