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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. IceCube Alert 260115.73: Global MASTER-Net observations report
  2. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  3. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  4. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  5. Fermi GRB 260115A: Global MASTER-Net observations report
  6. GRB 260115A: Fermi GBM Final Real-time Localization
  7. GRB260114A: STEP/T80S optical limits
  8. GRB 251222A: radio detection with the VLA
  9. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  10. Konus-Wind detection of GRB 260114A
  11. GRB 260114A: Swift-XRT refined Analysis
  12. GRB 260114A: 6 GHz VLA observations
  13. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  14. GRB 260114A : MITSuME Akeno optical upper limits
  15. GRB 260114A: COLIBRÍ optical upper limits
  16. GRB 260114A: TNG NIR upper limit
  17. GRB 260114A: NOT optical observations
  18. Konus-Wind detection of GRB 251230A / EP251230a
  19. GRB 260114A: SVOM/GRM observation of a short burst
  20. Swift GRB 260114A: Global MASTER-Net observations report
  21. GRB 260114A: GECAM-B observation of a short burst
  22. GRB 260114A: Mondy optical observations
  23. GRB 260114A: Fermi GBM observation
  24. GRB 260112B: GECAM-B observation
  25. GRB 260114A: GMG Optical Observation
  26. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  27. GRB 260114A: Swift detection of a short burst
  28. GRB 260114A: Fermi GBM Final Real-time Localization
  29. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  30. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  31. Swift GRB260113.43: Global MASTER-Net observations report
  32. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  33. EP260110a: TRT optical upper limits
  34. Konus-Wind detection of GRB 260101A
  35. GRB 260111A: Swift-XRT observations
  36. Swift Trigger 1439093: is probably not GRB 260113A
  37. GRB 260111A: COLIBRÍ optical afterglow candidate
  38. GRB 260111A: GECAM-B observation of a burst
  39. GRB 260111A: Fermi GBM Observation
  40. The EP-WXT trigger 01709251266 is likely a flaring star
  41. Swift Trigger 1434591 is not a GRB
  42. GRB 260111A: GOTO optical upper limits
  43. GRB 260112B: Fermi GBM Final Real-time Localization
  44. GRB 260111A: Swift ToO observations
  45. GRB 251230A: Mondy Optical Observations
  46. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  47. GRB 260112A: Fermi GBM Final Real-time Localization
  48. EP260110a: SVOM/VT optical upper limits
  49. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  50. IceCube Alert 260111A: Global MASTER-Net observations report
  51. EP260110a: Global MASTER-Net observations report
  52. Fermi GRB 260111A: Global MASTER-Net observations report
  53. GRB 260111A: Fermi GBM Final Real-time Localization
  54. Swift trigger 1436759 is not an astrophysical event
  55. EP260110a: KAIT optical upper limit
  56. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  57. EP 260110a: COLIBRÍ optical observations
  58. EP260110a: SVOM/C-GFT upper limit
  59. EP260110a: BOOTES-5/JGU optical upper limit
  60. EP260110a: Einstein Probe detection of an X-ray transient
  61. GRB 260109C: LCO optical upper limits
  62. GRB 260109C: Kilonova-Catcher optical upper limit
  63. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  64. Swift Trigger 1434591: possible GRB 260109C
  65. GRB 260109B: Fermi GBM Final Real-time Localization
  66. GRB 260102A: Swift-XRT afterglow detection
  67. GRB 260109A: Fermi GBM Final Real-time Localization
  68. GRB 260104A: Swift-BAT refined analysis
  69. GRB 260101A: Swift-BAT refined analysis
  70. Swift GRB 251230A: Global MASTER-Net OT detection
  71. Fermi GRB 260107A: Global MASTER-Net observations report
  72. GRB 260102A: AbAO optical observations
  73. GRB 260107A: Fermi GBM Final Real-time Localization
  74. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  75. The EP-WXT trigger 01709251112 is likely a flaring star
  76. Fermi GRB 260105A: Global MASTER-Net observations report
  77. GRB 260105B: Fermi GBM Detection
  78. EP260105a: FTW optical observations
  79. EP260104a: FTW optical observations
  80. GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
  81. GRB 260105A: SVOM/GRM observation
  82. GRB 260105B: SVOM/GRM observation
  83. The EP-WXT trigger 01709251028 is likely a flaring star
  84. FRB 20251229A: COLIBRÍ optical upper limits
  85. Fermi GRB 260105B: Global MASTER-Net observations report
  86. EP260105a: SVOM/VT optical upperlimit
  87. GRB 260105B: Fermi GBM Final Real-time Localization
  88. GRB 260105A: Fermi GBM Final Real-time Localization
  89. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  90. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  91. EP260105a: LCO Optical Upper limit
  92. EP260104a: Global MASTER-Net observations report
  93. EP260104a: Einstein Probe detection of a fast X-ray transient
  94. GRB 260101A: COLIBRÍ optical upper limits
  95. EP260105a: Global MASTER-Net observations report
  96. EP260105a: Einstein Probe detection of an X-ray transient
  97. GRB 260103A: Insight-HXMT/HE detection
  98. GRB 260104A: COLIBRÍ optical upper limits
  99. GRB 260104C: Fermi GBM Final Real-time Localization
  100. Fermi GRB 260104B: Global MASTER-Net observations report

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