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

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