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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. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  2. Konus-Wind detection of GRB 260504B (short/hard)
  3. GRB 260504B: GECAM-B detection
  4. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  5. GRB 260504C: SVOM/GRM observation of short GRB
  6. GRB 260504B: SVOM/GRM spectral analysis
  7. GRB 260430B: AstroSat CZTI detection of a long burst
  8. GRB 260504B: SVOM/MXT refined analysis and potential detection
  9. GRB 260504B: EP-FXT upper limit
  10. GRB 260502A: SVOM/GRM observation of a short GRB
  11. GRB 260503A: SVOM/GRM observation of a GRB
  12. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  13. Konus-Wind detection of GRB 260415C
  14. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  15. Konus-Wind detection of GRB 260411C
  16. GRB 260504B: REM optical/NIR observations
  17. IPN triangulation of GRB 260429A
  18. IPN triangulation of GRB 260428A
  19. GRB 260504B: AST3-2 i-band upper limit
  20. GRB 260504B: LCO z-band upper limit
  21. SVOM GRB 260504B: MASTER-OAFA optical observations
  22. GRB 260504B: SVOM detection of a short burst
  23. Fermi GRB 260504A: Global MASTER-Net observations report
  24. GRB 260504A: Fermi GBM Final Real-time Localization
  25. GRB 260503A: Fermi GBM Final Real-time Localization
  26. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  27. GRB 260502A: GECAM-B observation of a short burst
  28. IPN triangulation of a bright burst from SGR 1E1841-045
  29. GRB 260502A: Fermi GBM Final Localization
  30. The EP-WXT trigger 01709261576 is likely a flaring star
  31. GRB 260429B / EP260429a: EP-FXT follow-up observation
  32. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  33. GRB 260429B / EP260429a: AstroSat CZTI detection
  34. EP260502a: BOOTES-7: early optical upper limit
  35. EP260502a: Las Cumbres upper limit
  36. EP260502a: Einstein Probe detection of an X-ray transient
  37. GRB 260429A: SVOM/GRM observation of a short burst
  38. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  39. EP260429a: Global MASTER-Net observations report
  40. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  41. GRB 260424B: AstroSat CZTI detection
  42. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  43. EP260429a: LCO optical upper limits
  44. EP260430a: LCO optical upper limits
  45. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  46. GRB 260429A: Fermi GBM Detection
  47. Fermi GRB 260429A: Global MASTER-Net observations report
  48. EP260430a: Global MASTER-Net observations report
  49. EP260430a: Einstein Probe detection of an X-ray transient
  50. EP260429a: EP-WXT detection of a fast X-ray transient
  51. GRB 260429A: Fermi GBM Final Real-time Localization
  52. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  53. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  54. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  55. GRB 260428A: AstroSat CZTI detection
  56. Fermi GRB 260428A: Global MASTER-Net observations report
  57. EP260416a: Mondy and Terskol optical upper limits
  58. GRB 260424B: Glowbug gamma-ray detection of a short burst
  59. GRB 260424B: COLIBRÍ optical upper limit
  60. Konus-Wind detection of GRB 260424B
  61. GRB 260428A: Fermi GBM Final Real-time Localization
  62. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  63. GRB 260424C: Fermi GBM Final Localization
  64. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  65. IPN triangulation of GRB 260424B (short)
  66. GRB 260424B: SVOM/GRM detection of a short burst
  67. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  68. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  69. IceCube Alert 260425A: Global MASTER-Net observations report
  70. Fermi trigger No 798737427: Global MASTER-Net observations report
  71. GRB 260401A: cubesat Avion detection
  72. GRB 260424A: AstroSat CZTI detection of a long burst
  73. EP260321a: Upper limits from ATCA radio observations
  74. GRB 260421B: Kilonova-Catcher optical afterglow detection
  75. GRB 260421B: Insight-HXMT/HE detection
  76. The EP-WXT trigger 01709258652: Mondy optical observations
  77. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  78. EP260416a: Mondy optical observations
  79. GRB 260421B: SVOM/ECLAIRs refined analysis
  80. GRB 260421B: 3.6m DOT optical observation
  81. EP260416a: ZTSh R band observations
  82. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  83. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  84. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  85. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  86. GRB 260419A: AstroSat CZTI detection
  87. GRB 260421B: SVOM/GRM observation
  88. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  89. GRB 260421B: EP-FXT follow-up observation
  90. The EP-WXT trigger 01709260362 is likely a flaring star
  91. GOTO26djh/AT2026jpw: ATCA radio detection
  92. GRB 260421B: J-band upper limit with WINTER
  93. GRB 260421B: LCO optical counterpart detection
  94. GRB 260421B: Fermi GBM Observation
  95. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  96. GRB 260421A: AstroSat CZTI detection
  97. GOTO26djh/AT2026jpw: radio detection at 15GHz
  98. GRB 260412A: SVOM/ECLAIRs refined analysis
  99. GRB 260421B: SVOM/VT optical observations
  100. EP260416a: J band upper limit by SYSU 80cm infrared telescope

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