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

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