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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 260114A: Swift detection of a short burst
  2. GRB 260114A: Fermi GBM Final Real-time Localization
  3. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  4. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  5. Swift GRB260113.43: Global MASTER-Net observations report
  6. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  7. EP260110a: TRT optical upper limits
  8. Konus-Wind detection of GRB 260101A
  9. GRB 260111A: Swift-XRT observations
  10. Swift Trigger 1439093: is probably not GRB 260113A
  11. GRB 260111A: COLIBRÍ optical afterglow candidate
  12. GRB 260111A: GECAM-B observation of a burst
  13. GRB 260111A: Fermi GBM Observation
  14. The EP-WXT trigger 01709251266 is likely a flaring star
  15. Swift Trigger 1434591 is not a GRB
  16. GRB 260111A: GOTO optical upper limits
  17. GRB 260112B: Fermi GBM Final Real-time Localization
  18. GRB 260111A: Swift ToO observations
  19. GRB 251230A: Mondy Optical Observations
  20. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  21. GRB 260112A: Fermi GBM Final Real-time Localization
  22. EP260110a: SVOM/VT optical upper limits
  23. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  24. IceCube Alert 260111A: Global MASTER-Net observations report
  25. EP260110a: Global MASTER-Net observations report
  26. Fermi GRB 260111A: Global MASTER-Net observations report
  27. GRB 260111A: Fermi GBM Final Real-time Localization
  28. Swift trigger 1436759 is not an astrophysical event
  29. EP260110a: KAIT optical upper limit
  30. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  31. EP 260110a: COLIBRÍ optical observations
  32. EP260110a: SVOM/C-GFT upper limit
  33. EP260110a: BOOTES-5/JGU optical upper limit
  34. EP260110a: Einstein Probe detection of an X-ray transient
  35. GRB 260109C: LCO optical upper limits
  36. GRB 260109C: Kilonova-Catcher optical upper limit
  37. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  38. Swift Trigger 1434591: possible GRB 260109C
  39. GRB 260109B: Fermi GBM Final Real-time Localization
  40. GRB 260102A: Swift-XRT afterglow detection
  41. GRB 260109A: Fermi GBM Final Real-time Localization
  42. GRB 260104A: Swift-BAT refined analysis
  43. GRB 260101A: Swift-BAT refined analysis
  44. Swift GRB 251230A: Global MASTER-Net OT detection
  45. Fermi GRB 260107A: Global MASTER-Net observations report
  46. GRB 260102A: AbAO optical observations
  47. GRB 260107A: Fermi GBM Final Real-time Localization
  48. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  49. The EP-WXT trigger 01709251112 is likely a flaring star
  50. Fermi GRB 260105A: Global MASTER-Net observations report
  51. GRB 260105B: Fermi GBM Detection
  52. EP260105a: FTW optical observations
  53. EP260104a: FTW optical observations
  54. GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
  55. GRB 260105A: SVOM/GRM observation
  56. GRB 260105B: SVOM/GRM observation
  57. The EP-WXT trigger 01709251028 is likely a flaring star
  58. FRB 20251229A: COLIBRÍ optical upper limits
  59. Fermi GRB 260105B: Global MASTER-Net observations report
  60. EP260105a: SVOM/VT optical upperlimit
  61. GRB 260105B: Fermi GBM Final Real-time Localization
  62. GRB 260105A: Fermi GBM Final Real-time Localization
  63. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  64. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  65. EP260105a: LCO Optical Upper limit
  66. EP260104a: Global MASTER-Net observations report
  67. EP260104a: Einstein Probe detection of a fast X-ray transient
  68. GRB 260101A: COLIBRÍ optical upper limits
  69. EP260105a: Global MASTER-Net observations report
  70. EP260105a: Einstein Probe detection of an X-ray transient
  71. GRB 260103A: Insight-HXMT/HE detection
  72. GRB 260104A: COLIBRÍ optical upper limits
  73. GRB 260104C: Fermi GBM Final Real-time Localization
  74. Fermi GRB 260104B: Global MASTER-Net observations report
  75. Swift GRB 260104A: Global MASTER-Net observations report
  76. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  77. GRB 260104A: Swift-XRT refined Analysis
  78. GRB 260104A: Enhanced Swift-XRT position
  79. GRB 260101A: Swift/UVOT Detection
  80. GRB 260103A: GECAM-B observation of a burst
  81. GRB 260104B: Fermi GBM Final Localization
  82. GRB 260104A: Swift detection of a burst
  83. GRB 260103A: SVOM/GRM observation of a possible GRB
  84. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  85. GRB 260101A: COLIBRÍ optical observations
  86. SVOM GRB260103.08: Global MASTER-Net observations report
  87. GRB 260102B: Fermi GBM Final Real-time Localization
  88. SVOM GRB260102A: Global MASTER-Net observations report
  89. Fermi GBM Sub-Threshold Detection of GRB 260102A
  90. GRB 260102A: EP-FXT follow-up observation
  91. EP260101a: Global MASTER-Net observations report
  92. GRB 260102A: LCO optical upper limits
  93. GRB 260102A: Swift-XRT observations
  94. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  95. Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
  96. GRB 251230A / EP251230a: GECAM-B detection
  97. GRB 260102A: SVOM/VT optical counterpart
  98. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  99. GRB 260102A: Swift ToO observations
  100. GRB 260101A: Fermi GBM Observation

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