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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: GOTO optical counterpart detection
  2. EP260507a: TRT optical counterpart detection
  3. EP260507a: Kinder optical counterpart candidate
  4. EP260507a: LCO optical counterpart
  5. EP260507a: Einstein Probe detection of an X-ray transient
  6. GRB 260504B: AstroSat CZTI detection
  7. GRB 260504B: SVOM/ECLAIRs refined analysis
  8. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  9. GRB 260506B: Fermi GBM Final Real-time Localization
  10. EP260502a is likely a flaring star
  11. Fermi GRB 260506A: Global MASTER-Net observations report
  12. GRB 260506A: Fermi GBM Final Real-time Localization
  13. GRB 260503A: GECAM-B observation of a burst
  14. IceCube Alert 260505A: Global MASTER-Net observations report
  15. GRB 260430B: Glowbug gamma-ray detection
  16. GRB 260504B: SVOM/VT optical upper limits
  17. GRB 260421B: radio observation with the VLA
  18. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  19. Konus-Wind detection of GRB 260504B (short/hard)
  20. GRB 260504B: GECAM-B detection
  21. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  22. GRB 260504C: SVOM/GRM observation of short GRB
  23. GRB 260504B: SVOM/GRM spectral analysis
  24. GRB 260430B: AstroSat CZTI detection of a long burst
  25. GRB 260504B: SVOM/MXT refined analysis and potential detection
  26. GRB 260504B: EP-FXT upper limit
  27. GRB 260502A: SVOM/GRM observation of a short GRB
  28. GRB 260503A: SVOM/GRM observation of a GRB
  29. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  30. Konus-Wind detection of GRB 260415C
  31. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  32. Konus-Wind detection of GRB 260411C
  33. GRB 260504B: REM optical/NIR observations
  34. IPN triangulation of GRB 260429A
  35. IPN triangulation of GRB 260428A
  36. GRB 260504B: AST3-2 i-band upper limit
  37. GRB 260504B: LCO z-band upper limit
  38. SVOM GRB 260504B: MASTER-OAFA optical observations
  39. GRB 260504B: SVOM detection of a short burst
  40. Fermi GRB 260504A: Global MASTER-Net observations report
  41. GRB 260504A: Fermi GBM Final Real-time Localization
  42. GRB 260503A: Fermi GBM Final Real-time Localization
  43. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  44. GRB 260502A: GECAM-B observation of a short burst
  45. IPN triangulation of a bright burst from SGR 1E1841-045
  46. GRB 260502A: Fermi GBM Final Localization
  47. The EP-WXT trigger 01709261576 is likely a flaring star
  48. GRB 260429B / EP260429a: EP-FXT follow-up observation
  49. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  50. GRB 260429B / EP260429a: AstroSat CZTI detection
  51. EP260502a: BOOTES-7: early optical upper limit
  52. EP260502a: Las Cumbres upper limit
  53. EP260502a: Einstein Probe detection of an X-ray transient
  54. GRB 260429A: SVOM/GRM observation of a short burst
  55. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  56. EP260429a: Global MASTER-Net observations report
  57. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  58. GRB 260424B: AstroSat CZTI detection
  59. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  60. EP260429a: LCO optical upper limits
  61. EP260430a: LCO optical upper limits
  62. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  63. GRB 260429A: Fermi GBM Detection
  64. Fermi GRB 260429A: Global MASTER-Net observations report
  65. EP260430a: Global MASTER-Net observations report
  66. EP260430a: Einstein Probe detection of an X-ray transient
  67. EP260429a: EP-WXT detection of a fast X-ray transient
  68. GRB 260429A: Fermi GBM Final Real-time Localization
  69. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  70. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  71. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  72. GRB 260428A: AstroSat CZTI detection
  73. Fermi GRB 260428A: Global MASTER-Net observations report
  74. EP260416a: Mondy and Terskol optical upper limits
  75. GRB 260424B: Glowbug gamma-ray detection of a short burst
  76. GRB 260424B: COLIBRÍ optical upper limit
  77. Konus-Wind detection of GRB 260424B
  78. GRB 260428A: Fermi GBM Final Real-time Localization
  79. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  80. GRB 260424C: Fermi GBM Final Localization
  81. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  82. IPN triangulation of GRB 260424B (short)
  83. GRB 260424B: SVOM/GRM detection of a short burst
  84. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  85. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  86. IceCube Alert 260425A: Global MASTER-Net observations report
  87. Fermi trigger No 798737427: Global MASTER-Net observations report
  88. GRB 260401A: cubesat Avion detection
  89. GRB 260424A: AstroSat CZTI detection of a long burst
  90. EP260321a: Upper limits from ATCA radio observations
  91. GRB 260421B: Kilonova-Catcher optical afterglow detection
  92. GRB 260421B: Insight-HXMT/HE detection
  93. The EP-WXT trigger 01709258652: Mondy optical observations
  94. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  95. EP260416a: Mondy optical observations
  96. GRB 260421B: SVOM/ECLAIRs refined analysis
  97. GRB 260421B: 3.6m DOT optical observation
  98. EP260416a: ZTSh R band observations
  99. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  100. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube

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