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

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