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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 260516D: SVOM possible detection of a burst
  2. Konus-Wind detection of GRB 260515A
  3. GRB 260515A: Liverpool Telescope optical detection
  4. GRB 260515A: LCO optical counterpart detection
  5. Fermi Gamma-ray Burst Monitor trigger 800627191/260516518 is not a GRB
  6. GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
  7. EP260514a: TRT optical counterpart candidate
  8. Fermi GRB 260516B: Global MASTER-Net observations report
  9. GRB 260516B: Fermi GBM Final Real-time Localization
  10. Fermi Gamma-ray Burst Monitor trigger 800592653/260516119 is not a GRB
  11. GRB 260515A: OHP/T193 optical observations
  12. EP260514a: COLIBRÍ optical upper limits
  13. GRB 260516A: Fermi GBM Final Real-time Localization
  14. GRB 260515A: GTC/OSIRIS+ spectroscopic redshift z = 0.764
  15. SVOM GRB 260515A: Global MASTER-Net observations report
  16. GRB 260515A: SVOM/VT optical candidate from VHF data
  17. GRB 260515A: JinShan optical counterpart candidate
  18. GRB 260515A: SVOM detection of a burst
  19. GRB 260511B: NOT optical observations
  20. Konus-Wind detection of GRB 260512A
  21. IPN triangulation of GRB 260512A
  22. GRB 260511B: Mephisto multi-band optical followup
  23. GRB 260512A: AstroSat CZTI detection
  24. The EP-WXT trigger 01709262077 is likely a flaring star
  25. EP260507a: Xinglong Schmidt optical counterpart detection
  26. GRB 260514A: Fermi GBM Final Real-time Localization
  27. Fermi GRB 260513A: Global MASTER-Net observations report
  28. Fermi GRB 260512A: Global MASTER-Net observations report
  29. GRB 260511B: further SAO RAS optical observations
  30. GRB 260513A: Fermi GBM Final Real-time Localization
  31. The EP-WXT trigger 01709262036 is likely a flaring star
  32. EP260512a: COLIBRÍ optical upper limits
  33. GRB 260509A: Infrared J and Hs observations with MDM/MIRAGE
  34. Konus-Wind detection of GRB 260511A
  35. MASS-Cube (GRID 2.0) detection of GRB 260511A
  36. GRB 260510D: Glowbug gamma-ray detection of a likely short burst
  37. GRB 260511B: FRAM-ORM optical detection
  38. GRB 260511A: EP-FXT follow-up observation
  39. GRB 260511B: LCO optical counterpart detection
  40. GRB260511B: MAO/AZT-22 optical observations
  41. GRB 260511A: SVOM/VT optical observations
  42. GRB 260511B: GOTO optical counterpart detection
  43. GRB 260511B: Xinglong 2.16m/BEFOSC redshift confirmation
  44. GRB 260510B: EP-FXT follow-up observation
  45. GRB 260510C: Fermi GBM Observation
  46. GRB 260511B: GROWTH-India Telescope optical observations
  47. GRB 260511B: AstroSat CZTI detection
  48. GRB 260506A: Glowbug gamma-ray detection of a short burst
  49. GRB 260511C: Fermi GBM Final Real-time Localization
  50. GRB 260510B: SVOM/ECLAIRs refined analysis
  51. GRB 260511A: Fermi GBM Detection
  52. EP260509a: LCO optical upper limits
  53. GRB 260510C: AstroSat CZTI detection
  54. GRB 260511B: SVOM detection of a burst
  55. GRB 260510C: SVOM/VT optical counterpart confirmation
  56. EP260509a: EP-FXT non-detection and upper limit
  57. GRB 260511A: SVOM/VT optical observation with VHF data
  58. Fermi GRB 260511A: Global MASTER-Net observations report
  59. GRB 260511A: KAIT optical afterglow observations
  60. GRB 260511A: LCO optical afterglow detection
  61. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  62. GRB 260511A: TRT optical counterpart detection
  63. GRB 260511A: SVOM detection of a bright burst
  64. GRB 260511A: BALROG localization (Fermi Trigger 800172815 / GRB 260511259)
  65. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  66. GRB 260511A: Fermi GBM Final Real-time Localization
  67. GRB 260510B: SVOM/VT optical upper limits
  68. EP260509a: Global MASTER-Net observations report
  69. Fermi GBM Sub-Threshold Detection of GRB 260510B
  70. GRB 260510C: SVOM detection of a burst
  71. GRB 260510A: GECAM-B observation
  72. GRB 260510B: LCO optical upper limits
  73. EP260509a: Einstein Probe detection of an X-ray transient
  74. GRB 260509A: Liverpool Telescope optical observations
  75. GRB 260510B: SVOM detection of a burst
  76. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  77. SVOM GRB 260509A: MASTER-OAFA optical observation
  78. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  79. GRB 260510A: Fermi GBM Final Real-time Localization
  80. GRB 260509A: SVOM/VT optical candidate with VHF data
  81. GRB 260509A: LCO optical counterpart detection
  82. GRB 260509A: GOTO optical counterpart candidate
  83. GRB 260509A: SVOM detection of a burst
  84. GRB 260506B: AstroSat CZTI detection
  85. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  86. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  87. EP260507a: COLIBRÍ optical observations
  88. EP260507a: SVOM/VT optical observations
  89. EP260507a: NOT optical observations
  90. EP260507a: further Liverpool Telescope observations
  91. EP260507a: TRT optical counterpart detection
  92. GRB 260506B: Fermi GBM Final Real-time Localization
  93. EP260502a is likely a flaring star
  94. Fermi GRB 260506A: Global MASTER-Net observations report
  95. GRB 260506A: Fermi GBM Final Real-time Localization
  96. GRB 260503A: GECAM-B observation of a burst
  97. GRB 260430B: Glowbug gamma-ray detection
  98. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  99. Konus-Wind detection of GRB 260504B (short/hard)
  100. GRB 260504B: GECAM-B detection

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