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

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