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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. Fermi GRB 260115A: Global MASTER-Net observations report
  2. GRB 260115A: Fermi GBM Final Real-time Localization
  3. GRB260114A: STEP/T80S optical limits
  4. GRB 251222A: radio detection with the VLA
  5. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  6. Konus-Wind detection of GRB 260114A
  7. GRB 260114A: Swift-XRT refined Analysis
  8. GRB 260114A: 6 GHz VLA observations
  9. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  10. GRB 260114A : MITSuME Akeno optical upper limits
  11. GRB 260114A: COLIBRÍ optical upper limits
  12. GRB 260114A: TNG NIR upper limit
  13. GRB 260114A: NOT optical observations
  14. Konus-Wind detection of GRB 251230A / EP251230a
  15. GRB 260114A: SVOM/GRM observation of a short burst
  16. Swift GRB 260114A: Global MASTER-Net observations report
  17. GRB 260114A: GECAM-B observation of a short burst
  18. GRB 260114A: Mondy optical observations
  19. GRB 260114A: Fermi GBM observation
  20. GRB 260112B: GECAM-B observation
  21. GRB 260114A: GMG Optical Observation
  22. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  23. GRB 260114A: Swift detection of a short burst
  24. GRB 260114A: Fermi GBM Final Real-time Localization
  25. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  26. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  27. Swift GRB260113.43: Global MASTER-Net observations report
  28. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  29. EP260110a: TRT optical upper limits
  30. Konus-Wind detection of GRB 260101A
  31. GRB 260111A: Swift-XRT observations
  32. Swift Trigger 1439093: is probably not GRB 260113A
  33. GRB 260111A: COLIBRÍ optical afterglow candidate
  34. GRB 260111A: GECAM-B observation of a burst
  35. GRB 260111A: Fermi GBM Observation
  36. The EP-WXT trigger 01709251266 is likely a flaring star
  37. Swift Trigger 1434591 is not a GRB
  38. GRB 260111A: GOTO optical upper limits
  39. GRB 260112B: Fermi GBM Final Real-time Localization
  40. GRB 260111A: Swift ToO observations
  41. GRB 251230A: Mondy Optical Observations
  42. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  43. GRB 260112A: Fermi GBM Final Real-time Localization
  44. EP260110a: SVOM/VT optical upper limits
  45. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  46. IceCube Alert 260111A: Global MASTER-Net observations report
  47. EP260110a: Global MASTER-Net observations report
  48. Fermi GRB 260111A: Global MASTER-Net observations report
  49. GRB 260111A: Fermi GBM Final Real-time Localization
  50. Swift trigger 1436759 is not an astrophysical event
  51. EP260110a: KAIT optical upper limit
  52. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  53. EP 260110a: COLIBRÍ optical observations
  54. EP260110a: SVOM/C-GFT upper limit
  55. EP260110a: BOOTES-5/JGU optical upper limit
  56. EP260110a: Einstein Probe detection of an X-ray transient
  57. GRB 260109C: LCO optical upper limits
  58. GRB 260109C: Kilonova-Catcher optical upper limit
  59. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  60. Swift Trigger 1434591: possible GRB 260109C
  61. GRB 260109B: Fermi GBM Final Real-time Localization
  62. GRB 260102A: Swift-XRT afterglow detection
  63. GRB 260109A: Fermi GBM Final Real-time Localization
  64. GRB 260104A: Swift-BAT refined analysis
  65. GRB 260101A: Swift-BAT refined analysis
  66. Swift GRB 251230A: Global MASTER-Net OT detection
  67. Fermi GRB 260107A: Global MASTER-Net observations report
  68. GRB 260102A: AbAO optical observations
  69. GRB 260107A: Fermi GBM Final Real-time Localization
  70. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  71. The EP-WXT trigger 01709251112 is likely a flaring star
  72. Fermi GRB 260105A: Global MASTER-Net observations report
  73. GRB 260105B: Fermi GBM Detection
  74. EP260105a: FTW optical observations
  75. EP260104a: FTW optical observations
  76. GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
  77. GRB 260105A: SVOM/GRM observation
  78. GRB 260105B: SVOM/GRM observation
  79. The EP-WXT trigger 01709251028 is likely a flaring star
  80. FRB 20251229A: COLIBRÍ optical upper limits
  81. Fermi GRB 260105B: Global MASTER-Net observations report
  82. EP260105a: SVOM/VT optical upperlimit
  83. GRB 260105B: Fermi GBM Final Real-time Localization
  84. GRB 260105A: Fermi GBM Final Real-time Localization
  85. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  86. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  87. EP260105a: LCO Optical Upper limit
  88. EP260104a: Global MASTER-Net observations report
  89. EP260104a: Einstein Probe detection of a fast X-ray transient
  90. GRB 260101A: COLIBRÍ optical upper limits
  91. EP260105a: Global MASTER-Net observations report
  92. EP260105a: Einstein Probe detection of an X-ray transient
  93. GRB 260103A: Insight-HXMT/HE detection
  94. GRB 260104A: COLIBRÍ optical upper limits
  95. GRB 260104C: Fermi GBM Final Real-time Localization
  96. Fermi GRB 260104B: Global MASTER-Net observations report
  97. Swift GRB 260104A: Global MASTER-Net observations report
  98. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  99. GRB 260104A: Swift-XRT refined Analysis
  100. GRB 260104A: Enhanced Swift-XRT position

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