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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"

12320 results found.

  1. GRB 260127A: SVOM/C-GFT optical observations
  2. Fermi GRB 260127B: Global MASTER-Net observations report
  3. Swift GRB 260127A: Global MASTER-Net observations report
  4. GRB 260125A: Swift-XRT observations
  5. EP260126a: Optical upper limit with Kinder observations
  6. EP260126a: Liverpool Telescope optical upper limits
  7. EP260126a: Further NOT optical upper limits
  8. EP260126a: COLIBRÍ optical upper limits
  9. EP260126a: NOT optical observations
  10. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  11. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  12. Fermi GRB 260125B: Global MASTER-Net observations report
  13. GRB 260114A: SVOM/VT optical upper limits
  14. Swift GRB260122.97: Global MASTER-Net observations report
  15. EP260119a: Mondy and SAO RAS optical upper limits
  16. EP260119a: Xinglong optical upper limit
  17. Fermi GRB 260120C: Global MASTER-Net observations report
  18. GRB 260120B: Swift/UVOT Detection
  19. GRB 260120B: COLIBRÍ optical upper limits
  20. SVOM GRB260121.06: Global MASTER-Net observations report
  21. Swift GRB260120B: Global MASTER-Net observations report
  22. Fermi trigger No 790601190: Global MASTER-Net observations report
  23. Fermi trigger No 790570272: Global MASTER-Net observations report
  24. GRB 260114A: Swift/UVOT Upper Limits
  25. SVOM GRB260119.92: Global MASTER-Net observations report
  26. SVOM GRB260119.92: Global MASTER-Net observations report
  27. SVOM GRB260119.90: Global MASTER-Net observations report
  28. EP260119a: Global MASTER-Net observations report
  29. GRB 260117A: ZTSh optical upper limit
  30. Swift GRB260118.48: Global MASTER-Net observations report
  31. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  32. SVOM GRB260117.82: Global MASTER-Net observations report
  33. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  34. GRB 260117A: SVOM/C-GFT upper limit
  35. GRB 260117A: Swift-XRT observations
  36. EP 260116a: COLIBRÍ optical upper limit
  37. EP260116a: Liverpool Telescope upper limits
  38. EP260116A: 1.3m DFOT optical upper limit
  39. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  40. EP260116a: Global MASTER-Net observations report
  41. EP260116a: Xinglong optical upper limit
  42. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  43. IceCube Alert 260115.73: Global MASTER-Net observations report
  44. Fermi GRB 260115A: Global MASTER-Net observations report
  45. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  46. Konus-Wind detection of GRB 260114A
  47. GRB 260114A: 6 GHz VLA observations
  48. GRB 260114A : MITSuME Akeno optical upper limits
  49. GRB 260114A: COLIBRÍ optical upper limits
  50. GRB 260114A: TNG NIR upper limit
  51. GRB 260114A: NOT optical observations
  52. Konus-Wind detection of GRB 251230A / EP251230a
  53. Swift GRB 260114A: Global MASTER-Net observations report
  54. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  55. GRB 260114A: Swift detection of a short burst
  56. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  57. Swift GRB260113.43: Global MASTER-Net observations report
  58. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  59. EP260110a: TRT optical upper limits
  60. GRB 260111A: Swift-XRT observations
  61. Swift Trigger 1439093: is probably not GRB 260113A
  62. GRB 260111A: COLIBRÍ optical afterglow candidate
  63. GRB 260111A: GOTO optical upper limits
  64. GRB 251230A: Mondy Optical Observations
  65. EP260110a: SVOM/VT optical upper limits
  66. IceCube Alert 260111A: Global MASTER-Net observations report
  67. EP260110a: Global MASTER-Net observations report
  68. Fermi GRB 260111A: Global MASTER-Net observations report
  69. Swift trigger 1436759 is not an astrophysical event
  70. EP260110a: KAIT optical upper limit
  71. EP 260110a: COLIBRÍ optical observations
  72. EP260110a: SVOM/C-GFT upper limit
  73. EP260110a: BOOTES-5/JGU optical upper limit
  74. GRB 260109C: LCO optical upper limits
  75. GRB 260109C: Kilonova-Catcher optical upper limit
  76. Swift Trigger 1434591: possible GRB 260109C
  77. Swift GRB 251230A: Global MASTER-Net OT detection
  78. Fermi GRB 260107A: Global MASTER-Net observations report
  79. GRB 260102A: AbAO optical observations
  80. Fermi GRB 260105A: Global MASTER-Net observations report
  81. EP260105a: FTW optical observations
  82. EP260104a: FTW optical observations
  83. FRB 20251229A: COLIBRÍ optical upper limits
  84. Fermi GRB 260105B: Global MASTER-Net observations report
  85. EP260105a: LCO Optical Upper limit
  86. EP260104a: Global MASTER-Net observations report
  87. GRB 260101A: COLIBRÍ optical upper limits
  88. EP260105a: Global MASTER-Net observations report
  89. GRB 260104A: COLIBRÍ optical upper limits
  90. Fermi GRB 260104B: Global MASTER-Net observations report
  91. Swift GRB 260104A: Global MASTER-Net observations report
  92. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  93. GRB 260101A: Swift/UVOT Detection
  94. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  95. SVOM GRB260103.08: Global MASTER-Net observations report
  96. SVOM GRB260102A: Global MASTER-Net observations report
  97. GRB 260102A: EP-FXT follow-up observation
  98. EP260101a: Global MASTER-Net observations report
  99. GRB 260102A: LCO optical upper limits
  100. GRB 260102A: Swift-XRT observations

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