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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 260111A: Swift/BAT-GUANO arcminute localization of a burst
  2. GRB 260112A: Fermi GBM Final Real-time Localization
  3. EP260110a: SVOM/VT optical upper limits
  4. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  5. IceCube Alert 260111.84: Global MASTER-Net observations report
  6. EP260110a: Global MASTER-Net observations report
  7. Fermi GRB 260111A: Global MASTER-Net observations report
  8. GRB 260111A: Fermi GBM Final Real-time Localization
  9. Swift trigger 1436759 is not an astrophysical event
  10. EP260110a: KAIT optical upper limit
  11. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  12. EP 260110a: COLIBRÍ optical observations
  13. EP260110a: SVOM/C-GFT upper limit
  14. EP260110a: BOOTES-5/JGU optical upper limit
  15. EP260110a: Einstein Probe detection of an X-ray transient
  16. GRB 260109C: LCO optical upper limits
  17. GRB 260109C: Kilonova-Catcher optical upper limit
  18. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  19. Swift Trigger 1434591: possible GRB 260109C
  20. GRB 260109B: Fermi GBM Final Real-time Localization
  21. GRB 260102A: Swift-XRT afterglow detection
  22. GRB 260109A: Fermi GBM Final Real-time Localization
  23. GRB 260104A: Swift-BAT refined analysis
  24. GRB 260101A: Swift-BAT refined analysis
  25. Swift GRB 251230A: Global MASTER-Net OT detection
  26. Fermi GRB 260107A: Global MASTER-Net observations report
  27. GRB 260102A: AbAO optical observations
  28. GRB 260107A: Fermi GBM Final Real-time Localization
  29. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  30. The EP-WXT trigger 01709251112 is likely a flaring star
  31. Fermi GRB 260105A: Global MASTER-Net observations report
  32. GRB 260105B: Fermi GBM Detection
  33. EP260105a: FTW optical observations
  34. EP260104a: FTW optical observations
  35. GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
  36. GRB 260105A: SVOM/GRM observation
  37. GRB 260105B: SVOM/GRM observation
  38. The EP-WXT trigger 01709251028 is likely a flaring star
  39. FRB 20251229A: COLIBRÍ optical upper limits
  40. Fermi GRB 260105B: Global MASTER-Net observations report
  41. EP260105a: SVOM/VT optical upperlimit
  42. GRB 260105B: Fermi GBM Final Real-time Localization
  43. GRB 260105A: Fermi GBM Final Real-time Localization
  44. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  45. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  46. EP260105a: LCO Optical Upper limit
  47. EP260104a: Global MASTER-Net observations report
  48. EP260104a: Einstein Probe detection of a fast X-ray transient
  49. GRB 260101A: COLIBRÍ optical upper limits
  50. EP260105a: Global MASTER-Net observations report
  51. EP260105a: Einstein Probe detection of an X-ray transient
  52. GRB 260103A: Insight-HXMT/HE detection
  53. GRB 260104A: COLIBRÍ optical upper limits
  54. GRB 260104C: Fermi GBM Final Real-time Localization
  55. Fermi GRB 260104B: Global MASTER-Net observations report
  56. Swift GRB 260104A: Global MASTER-Net observations report
  57. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  58. GRB 260104A: Swift-XRT refined Analysis
  59. GRB 260104A: Enhanced Swift-XRT position
  60. GRB 260101A: Swift/UVOT Detection
  61. GRB 260103A: GECAM-B observation of a burst
  62. GRB 260104B: Fermi GBM Final Localization
  63. GRB 260104A: Swift detection of a burst
  64. GRB 260103A: SVOM/GRM observation of a possible GRB
  65. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  66. GRB 260101A: COLIBRÍ optical observations
  67. SVOM GRB260103.08: Global MASTER-Net observations report
  68. GRB 260102B: Fermi GBM Final Real-time Localization
  69. SVOM GRB260102A: Global MASTER-Net observations report
  70. Fermi GBM Sub-Threshold Detection of GRB 260102A
  71. GRB 260102A: EP-FXT follow-up observation
  72. EP260101a: Global MASTER-Net observations report
  73. GRB 260102A: LCO optical upper limits
  74. GRB 260102A: Swift-XRT observations
  75. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  76. Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
  77. GRB 251230A / EP251230a: GECAM-B detection
  78. GRB 260102A: SVOM/VT optical counterpart
  79. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  80. GRB 260102A: Swift ToO observations
  81. GRB 260101A: Fermi GBM Observation
  82. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  83. GRB 260102A: SVOM detection of a burst
  84. GRB 260101A: GECAM-B detection
  85. GRB 260101A: NOT spectroscopic observations
  86. GRB 260101A: SVOM/GRM observation
  87. GRB 260101A: Swift-XRT refined Analysis
  88. Swift GRB 260101A: Global MASTER-Net observations report
  89. GRB 260101A: Enhanced Swift-XRT position
  90. EP260101a: Einstein Probe detection of an X-ray transient
  91. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  92. GRB 260101A: LCO detection of the optical counterpart
  93. GRB 260101A: Swift detection of a burst with an optical counterpart
  94. GRB 260101A: Fermi GBM Final Real-time Localization
  95. SVOM GRB251231.57: Global MASTER-Net observations report
  96. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  97. GRB 251230A: GRANDMA/TAROT Early Detection
  98. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  99. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  100. EP251229a: Optical upper limit with Kinder observations

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