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

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