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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: SVOM/MXT refined analysis and potential detection
  2. GRB 260504B: EP-FXT upper limit
  3. GRB 260502A: SVOM/GRM observation of a short GRB
  4. GRB 260503A: SVOM/GRM observation of a GRB
  5. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  6. Konus-Wind detection of GRB 260415C
  7. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  8. Konus-Wind detection of GRB 260411C
  9. GRB 260504B: REM optical/NIR observations
  10. IPN triangulation of GRB 260429A
  11. IPN triangulation of GRB 260428A
  12. GRB 260504B: AST3-2 i-band upper limit
  13. GRB 260504B: LCO z-band upper limit
  14. SVOM GRB 260504B: MASTER-OAFA optical observations
  15. GRB 260504B: SVOM detection of a short burst
  16. Fermi GRB 260504A: Global MASTER-Net observations report
  17. GRB 260504A: Fermi GBM Final Real-time Localization
  18. GRB 260503A: Fermi GBM Final Real-time Localization
  19. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  20. GRB 260502A: GECAM-B observation of a short burst
  21. IPN triangulation of a bright burst from SGR 1E1841-045
  22. GRB 260502A: Fermi GBM Final Localization
  23. The EP-WXT trigger 01709261576 is likely a flaring star
  24. GRB 260429B / EP260429a: EP-FXT follow-up observation
  25. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  26. GRB 260429B / EP260429a: AstroSat CZTI detection
  27. EP260502a: BOOTES-7: early optical upper limit
  28. EP260502a: Las Cumbres upper limit
  29. EP260502a: Einstein Probe detection of an X-ray transient
  30. GRB 260429A: SVOM/GRM observation of a short burst
  31. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  32. EP260429a: Global MASTER-Net observations report
  33. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  34. GRB 260424B: AstroSat CZTI detection
  35. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  36. EP260429a: LCO optical upper limits
  37. EP260430a: LCO optical upper limits
  38. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  39. GRB 260429A: Fermi GBM Detection
  40. Fermi GRB 260429A: Global MASTER-Net observations report
  41. EP260430a: Global MASTER-Net observations report
  42. EP260430a: Einstein Probe detection of an X-ray transient
  43. EP260429a: EP-WXT detection of a fast X-ray transient
  44. GRB 260429A: Fermi GBM Final Real-time Localization
  45. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  46. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  47. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  48. GRB 260428A: AstroSat CZTI detection
  49. Fermi GRB 260428A: Global MASTER-Net observations report
  50. EP260416a: Mondy and Terskol optical upper limits
  51. GRB 260424B: Glowbug gamma-ray detection of a short burst
  52. GRB 260424B: COLIBRÍ optical upper limit
  53. Konus-Wind detection of GRB 260424B
  54. GRB 260428A: Fermi GBM Final Real-time Localization
  55. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  56. GRB 260424C: Fermi GBM Final Localization
  57. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  58. IPN triangulation of GRB 260424B (short)
  59. GRB 260424B: SVOM/GRM detection of a short burst
  60. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  61. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  62. IceCube Alert 260425A: Global MASTER-Net observations report
  63. Fermi trigger No 798737427: Global MASTER-Net observations report
  64. GRB 260401A: cubesat Avion detection
  65. GRB 260424A: AstroSat CZTI detection of a long burst
  66. EP260321a: Upper limits from ATCA radio observations
  67. GRB 260421B: Kilonova-Catcher optical afterglow detection
  68. GRB 260421B: Insight-HXMT/HE detection
  69. The EP-WXT trigger 01709258652: Mondy optical observations
  70. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  71. EP260416a: Mondy optical observations
  72. GRB 260421B: SVOM/ECLAIRs refined analysis
  73. GRB 260421B: 3.6m DOT optical observation
  74. EP260416a: ZTSh R band observations
  75. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  76. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  77. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  78. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  79. GRB 260419A: AstroSat CZTI detection
  80. GRB 260421B: SVOM/GRM observation
  81. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  82. GRB 260421B: EP-FXT follow-up observation
  83. The EP-WXT trigger 01709260362 is likely a flaring star
  84. GOTO26djh/AT2026jpw: ATCA radio detection
  85. GRB 260421B: J-band upper limit with WINTER
  86. GRB 260421B: LCO optical counterpart detection
  87. GRB 260421B: Fermi GBM Observation
  88. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  89. GRB 260421A: AstroSat CZTI detection
  90. GOTO26djh/AT2026jpw: radio detection at 15GHz
  91. GRB 260412A: SVOM/ECLAIRs refined analysis
  92. GRB 260421B: SVOM/VT optical observations
  93. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  94. GRB 260310A: Late-time Chandra X-ray Detection
  95. GRB 260418A: Insight-HXMT/HE detection
  96. EP260416a: 1.3m DFOT optical observation
  97. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  98. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  99. Fermi GRB 260421C: Global MASTER-Net observations report
  100. GRB 260421C: Fermi GBM Final Real-time Localization

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