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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"

27783 results found.

  1. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  2. Swift Trigger 1434591: possible GRB 260109C
  3. GRB 260109B: Fermi GBM Final Real-time Localization
  4. GRB 260102A: Swift-XRT afterglow detection
  5. GRB 260109A: Fermi GBM Final Real-time Localization
  6. GRB 260104A: Swift-BAT refined analysis
  7. GRB 260101A: Swift-BAT refined analysis
  8. Swift GRB 251230A: Global MASTER-Net OT detection
  9. GRB 260107A: Fermi GBM Final Real-time Localization
  10. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  11. GRB 260105B: Fermi GBM Detection
  12. EP260105a: FTW optical observations
  13. EP260104a: FTW optical observations
  14. GRB 260105B: Fermi GBM Final Real-time Localization
  15. GRB 260105A: Fermi GBM Final Real-time Localization
  16. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  17. EP260104a: Einstein Probe detection of a fast X-ray transient
  18. GRB 260101A: COLIBRÍ optical upper limits
  19. EP260105a: Einstein Probe detection of an X-ray transient
  20. GRB 260103A: Insight-HXMT/HE detection
  21. GRB 260104C: Fermi GBM Final Real-time Localization
  22. Swift GRB 260104A: Global MASTER-Net observations report
  23. GRB 260104A: Swift-XRT refined Analysis
  24. GRB 260104A: Enhanced Swift-XRT position
  25. GRB 260101A: Swift/UVOT Detection
  26. GRB 260104B: Fermi GBM Final Localization
  27. GRB 260104A: Swift detection of a burst
  28. GRB 260102B: Fermi GBM Final Real-time Localization
  29. Fermi GBM Sub-Threshold Detection of GRB 260102A
  30. GRB 260102A: LCO optical upper limits
  31. GRB 260102A: Swift-XRT observations
  32. GRB 251230A / EP251230a: GECAM-B detection
  33. GRB 260102A: SVOM/VT optical counterpart
  34. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  35. GRB 260102A: Swift ToO observations
  36. GRB 260101A: Fermi GBM Observation
  37. GRB 260102A: SVOM detection of a burst
  38. GRB 260101A: GECAM-B detection
  39. GRB 260101A: NOT spectroscopic observations
  40. GRB 260101A: SVOM/GRM observation
  41. GRB 260101A: Swift-XRT refined Analysis
  42. Swift GRB 260101A: Global MASTER-Net observations report
  43. GRB 260101A: Enhanced Swift-XRT position
  44. EP260101a: Einstein Probe detection of an X-ray transient
  45. GRB 260101A: LCO detection of the optical counterpart
  46. GRB 260101A: Swift detection of a burst with an optical counterpart
  47. GRB 260101A: Fermi GBM Final Real-time Localization
  48. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  49. GRB 251230A: GRANDMA/TAROT Early Detection
  50. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  51. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  52. EP251229a: Optical upper limit with Kinder observations
  53. GRB 251230A: 1.3m DFOT optical upper limit
  54. GRB 251230A: Swift-XRT refined Analysis
  55. GRB 251231A: Fermi GBM Final Real-time Localization
  56. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  57. GRB 251230A: Swift/UVOT detection
  58. GRB251230A: 7DT optical upper limits
  59. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  60. EP251229a: BOOTES-2 early optical upper limit
  61. GRB 251230A: GOTO optical upper limit
  62. GRB 251230A / EP251230a: SVOM/VT optical observation
  63. GRB 251230A: Enhanced Swift-XRT position
  64. GRB 251230A: Early optical counterpart detection by LCO.
  65. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  66. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  67. Swift GRB 251230A: Global MASTER-Net observations report
  68. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  69. EP251229a: Einstein Probe detection of an X-ray transient
  70. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  71. GRB 251226A: Glowbug gamma-ray detection
  72. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  73. GRB 251228A: Fermi GBM Final Real-time Localization
  74. GRB 251226A: GECAM-B detection
  75. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  76. GRB 251222A/EP251222b: Optical detection with Kinder observations
  77. EP251222a: Optical upper limit with Kinder observations
  78. GRB 251221A: Swift-BAT refined analysis
  79. GRB 251205A: Kilonova-Catcher optical afterglow detection
  80. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  81. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  82. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  83. GRB 251222A: Continued 1.3m DFOT optical observation
  84. EP251220a: 3.6m DOT optical afterglow detection
  85. GRB 251222A: Fermi GBM Observation
  86. Konus-Wind detection of GRB 251222A / EP251222b
  87. GRB 251222A: Swift-XRT afterglow detection
  88. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  89. GRB 251222A / EP251222b: GOTO optical counterpart detection
  90. GRB 251222A: 1.3m DFOT optical detection
  91. GRB251221A: 7DT optical upper limits
  92. EP251222a: GSP Optical Counterpart Detection
  93. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  94. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  95. EP251222a: Einstein Probe detection of an X-ray transient
  96. GRB 251222A: PRIME near-infrared detection
  97. IPN triangulation of GRB 251220B (short)
  98. GRB 251222A: Swift ToO observations
  99. GRB 251222A: SVOM detection of a long burst
  100. GRB 251222A: Fermi GBM Final Real-time Localization

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