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

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