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

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