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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').
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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"

11533 results found.

  1. GRB 260511B: LCO optical observations
  2. GRB 260511B: OHP/T193 spectroscopic observations
  3. GRB 260511B: GOTO optical counterpart detection
  4. GRB 260511B: Xinglong 2.16m/BEFOSC redshift confirmation
  5. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
  6. GRB 260511B: SVOM/VT optical observations
  7. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  8. GRB 260511B: OSIRIS+/GTC redshift z=2.006
  9. GRB 260510C: Fermi GBM Observation
  10. GRB 260511A: REM near-infrared detection
  11. GRB 260511B: GROWTH-India Telescope optical observations
  12. GRB 260511B: AstroSat CZTI detection
  13. GRB 260506B: Glowbug gamma-ray detection
  14. GRB 260506A: Glowbug gamma-ray detection of a short burst
  15. GRB 260511B: J-band observations by the SYSU 80 cm infrared telescope
  16. GRB 260511B: NuSTAR detection of prompt emission
  17. GRB 260511A: NuSTAR detection of prompt emission
  18. GRB 260511B: Fermi GBM Detection
  19. GRB 260511C: Fermi GBM Final Real-time Localization
  20. GRB 260511B: SVOM/VT optical observation with VHF data
  21. GRB 260511B: TRT optical observation
  22. GRB 260511A: Fermi GBM Detection
  23. GRB 260511A: UTGO H50 optical afterglow observation
  24. GRB 260510C: AstroSat CZTI detection
  25. GRB 260511B: SVOM detection of a burst
  26. GRB 260511B: Fermi GBM Final Real-time Localization
  27. GRB 260510C: EP-FXT follow-up observation
  28. GRB 260510C: SVOM/VT optical counterpart confirmation
  29. GRB 260511A: SVOM/VT optical observation with VHF data
  30. Fermi GRB 260511A: Global MASTER-Net observations report
  31. GRB 260511A: KAIT optical afterglow observations
  32. GRB 260511A: LCO optical afterglow detection
  33. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  34. GRB 260511A: TRT optical counterpart detection
  35. GRB 260511A: SVOM detection of a bright burst
  36. GRB 260511A: BALROG localization (Fermi Trigger 800172815 / GRB 260511259)
  37. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  38. GRB 260511A: Fermi GBM Final Real-time Localization
  39. GRB 260510B: SVOM/VT optical upper limits
  40. GRB 260510C: SVOM/VT optical upper limits
  41. GRB 260510C: MAXI/GSC detection
  42. Fermi GBM Sub-Threshold Detection of GRB 260510B
  43. GRB 260510D: Fermi GBM Final Real-time Localization
  44. GRB 260510C: SVOM detection of a burst
  45. GRB 260510C: Fermi GBM Final Real-time Localization
  46. GRB 260510A: GECAM-B observation
  47. Fermi GRB 260510A: Global MASTER-Net observations report
  48. GRB 260510A: Fermi GBM Final Real-time Localization
  49. GRB 260506B: AstroSat CZTI detection
  50. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  51. GRB 260507A: Fermi GBM Final Real-time Localization
  52. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  53. GRB 260506B: Fermi GBM Final Real-time Localization
  54. Fermi GRB 260506A: Global MASTER-Net observations report
  55. GRB 260506A: Fermi GBM Final Real-time Localization
  56. GRB 260503A: GECAM-B observation of a burst
  57. GRB 260421B: radio observation with the VLA
  58. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  59. GRB 260502A: SVOM/GRM observation of a short GRB
  60. GRB 260503A: SVOM/GRM observation of a GRB
  61. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  62. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  63. IPN triangulation of GRB 260429A
  64. IPN triangulation of GRB 260428A
  65. Fermi GRB 260504A: Global MASTER-Net observations report
  66. GRB 260504A: Fermi GBM Final Real-time Localization
  67. GRB 260503A: Fermi GBM Final Real-time Localization
  68. GRB 260502A: GECAM-B observation of a short burst
  69. GRB 260502A: Fermi GBM Final Localization
  70. GRB 260429A: SVOM/GRM observation of a short burst
  71. GRB 260429A: Fermi GBM Detection
  72. Fermi GRB 260429A: Global MASTER-Net observations report
  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. GRB 260428A: AstroSat CZTI detection
  77. Fermi GRB 260428A: Global MASTER-Net observations report
  78. GRB 260424B: COLIBRÍ optical upper limit
  79. GRB 260428A: Fermi GBM Final Real-time Localization
  80. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  81. GRB 260424C: Fermi GBM Final Localization
  82. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  83. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  84. Fermi trigger No 798737427: Global MASTER-Net observations report
  85. GRB 260401A: cubesat Avion detection
  86. GRB 260421B: Kilonova-Catcher optical afterglow detection
  87. GRB 260421B: Insight-HXMT/HE detection
  88. GRB 260421B: SVOM/ECLAIRs refined analysis
  89. GRB 260421B: 3.6m DOT optical observation
  90. GRB 260419A: AstroSat CZTI detection
  91. GRB 260421B: SVOM/GRM observation
  92. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  93. GRB 260421B: EP-FXT follow-up observation
  94. GRB 260421B: J-band upper limit with WINTER
  95. GRB 260421B: LCO optical counterpart detection
  96. GRB 260421B: Fermi GBM Observation
  97. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  98. GRB 260421A: AstroSat CZTI detection
  99. GRB 260412A: SVOM/ECLAIRs refined analysis
  100. GRB 260421B: SVOM/VT optical observations

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