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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"

28044 results found.

  1. GRB 260114A: NOT optical observations
  2. GRB 260114A: SVOM/GRM observation of a short burst
  3. Swift GRB 260114A: Global MASTER-Net observations report
  4. GRB 260114A: Mondy optical observations
  5. GRB 260114A: GMG Optical Observation
  6. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  7. GRB 260114A: Swift detection of a short burst
  8. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  9. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  10. Swift GRB260113.43: Global MASTER-Net observations report
  11. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  12. EP260110a: TRT optical upper limits
  13. Konus-Wind detection of GRB 260101A
  14. GRB 260111A: Swift-XRT observations
  15. Swift Trigger 1439093: is probably not GRB 260113A
  16. GRB 260111A: COLIBRÍ optical afterglow candidate
  17. GRB 260111A: Fermi GBM Observation
  18. GRB 251230A: Mondy Optical Observations
  19. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  20. IceCube Alert 260111A: Global MASTER-Net observations report
  21. EP260110a: Global MASTER-Net observations report
  22. Fermi GRB 260111A: Global MASTER-Net observations report
  23. Swift trigger 1436759 is not an astrophysical event
  24. EP260110a: KAIT optical upper limit
  25. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  26. EP 260110a: COLIBRÍ optical observations
  27. EP260110a: SVOM/C-GFT upper limit
  28. EP260110a: Einstein Probe detection of an X-ray transient
  29. GRB 260109C: LCO optical upper limits
  30. GRB 260109C: Kilonova-Catcher optical upper limit
  31. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  32. Swift Trigger 1434591: possible GRB 260109C
  33. GRB 260102A: Swift-XRT afterglow detection
  34. GRB 260104A: Swift-BAT refined analysis
  35. GRB 260101A: Swift-BAT refined analysis
  36. Swift GRB 251230A: Global MASTER-Net OT detection
  37. Fermi GRB 260107A: Global MASTER-Net observations report
  38. GRB 260102A: AbAO optical observations
  39. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  40. Fermi GRB 260105A: Global MASTER-Net observations report
  41. GRB 260105B: Fermi GBM Detection
  42. GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
  43. GRB 260105A: SVOM/GRM observation
  44. GRB 260105B: SVOM/GRM observation
  45. FRB 20251229A: COLIBRÍ optical upper limits
  46. Fermi GRB 260105B: Global MASTER-Net observations report
  47. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  48. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  49. EP260105a: LCO Optical Upper limit
  50. EP260104a: Global MASTER-Net observations report
  51. EP260104a: Einstein Probe detection of a fast X-ray transient
  52. GRB 260101A: COLIBRÍ optical upper limits
  53. EP260105a: Global MASTER-Net observations report
  54. EP260105a: Einstein Probe detection of an X-ray transient
  55. GRB 260104A: COLIBRÍ optical upper limits
  56. Fermi GRB 260104B: Global MASTER-Net observations report
  57. Swift GRB 260104A: Global MASTER-Net observations report
  58. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  59. GRB 260104A: Swift-XRT refined Analysis
  60. GRB 260104A: Enhanced Swift-XRT position
  61. GRB 260101A: Swift/UVOT Detection
  62. GRB 260103A: GECAM-B observation of a burst
  63. GRB 260104A: Swift detection of a burst
  64. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  65. GRB 260101A: COLIBRÍ optical observations
  66. SVOM GRB260103.08: Global MASTER-Net observations report
  67. SVOM GRB260102A: Global MASTER-Net observations report
  68. Fermi GBM Sub-Threshold Detection of GRB 260102A
  69. GRB 260102A: EP-FXT follow-up observation
  70. EP260101a: Global MASTER-Net observations report
  71. GRB 260102A: LCO optical upper limits
  72. GRB 260102A: Swift-XRT observations
  73. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  74. GRB 260101A: Fermi GBM Observation
  75. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  76. GRB 260102A: SVOM detection of a burst
  77. GRB 260101A: NOT spectroscopic observations
  78. GRB 260101A: SVOM/GRM observation
  79. GRB 260101A: Swift-XRT refined Analysis
  80. Swift GRB 260101A: Global MASTER-Net observations report
  81. GRB 260101A: Enhanced Swift-XRT position
  82. EP260101a: Einstein Probe detection of an X-ray transient
  83. GRB 260101A: LCO detection of the optical counterpart
  84. GRB 260101A: Swift detection of a burst with an optical counterpart
  85. GRB 260101A: Fermi GBM Final Real-time Localization
  86. SVOM GRB251231.57: Global MASTER-Net observations report
  87. GRB 251230A: GRANDMA/TAROT Early Detection
  88. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  89. EP251229a: Optical upper limit with Kinder observations
  90. GRB 251230A: 1.3m DFOT optical upper limit
  91. GRB 251230A: Swift-XRT refined Analysis
  92. GRB 251222A: Mondy Optical Observations
  93. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  94. GRB 251230A: Swift/UVOT detection
  95. GRB251230A: 7DT optical upper limits
  96. GRB 251230A: GOTO optical upper limit
  97. EP251229a: NOT optical upper limits
  98. GRB 251230A / EP251230a: SVOM/VT optical observation
  99. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  100. GRB 251230A: Enhanced Swift-XRT position

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