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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"

14326 results found.

  1. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  2. GRB 260105B: Fermi GBM Detection
  3. EP260105a: FTW optical observations
  4. EP260104a: FTW optical observations
  5. GRB 260105B: Fermi GBM Final Real-time Localization
  6. GRB 260105A: Fermi GBM Final Real-time Localization
  7. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  8. EP260104a: Einstein Probe detection of a fast X-ray transient
  9. GRB 260101A: COLIBRÍ optical upper limits
  10. EP260105a: Einstein Probe detection of an X-ray transient
  11. GRB 260103A: Insight-HXMT/HE detection
  12. GRB 260104C: Fermi GBM Final Real-time Localization
  13. GRB 260101A: Swift/UVOT Detection
  14. GRB 260104B: Fermi GBM Final Localization
  15. GRB 260104A: Swift detection of a burst
  16. GRB 260102B: Fermi GBM Final Real-time Localization
  17. Fermi GBM Sub-Threshold Detection of GRB 260102A
  18. GRB 251230A / EP251230a: GECAM-B detection
  19. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  20. GRB 260102A: SVOM detection of a burst
  21. GRB 260101A: GECAM-B detection
  22. EP260101a: Einstein Probe detection of an X-ray transient
  23. GRB 260101A: LCO detection of the optical counterpart
  24. GRB 260101A: Swift detection of a burst with an optical counterpart
  25. GRB 260101A: Fermi GBM Final Real-time Localization
  26. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  27. GRB 251230A: GRANDMA/TAROT Early Detection
  28. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  29. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  30. EP251229a: Optical upper limit with Kinder observations
  31. GRB 251230A: 1.3m DFOT optical upper limit
  32. GRB 251231A: Fermi GBM Final Real-time Localization
  33. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  34. GRB 251230A: Swift/UVOT detection
  35. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  36. EP251229a: BOOTES-2 early optical upper limit
  37. GRB 251230A: Early optical counterpart detection by LCO.
  38. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  39. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  40. EP251229a: Einstein Probe detection of an X-ray transient
  41. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  42. GRB 251226A: Glowbug gamma-ray detection
  43. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  44. GRB 251228A: Fermi GBM Final Real-time Localization
  45. GRB 251226A: SVOM/GRM observation
  46. GRB 251226A: GECAM-B detection
  47. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  48. GRB 251222A/EP251222b: Optical detection with Kinder observations
  49. EP251222a: Optical upper limit with Kinder observations
  50. GRB 251205A: Kilonova-Catcher optical afterglow detection
  51. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  52. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  53. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  54. GRB 251222A: Continued 1.3m DFOT optical observation
  55. EP251220a: 3.6m DOT optical afterglow detection
  56. Konus-Wind detection of GRB 251222A / EP251222b
  57. GRB 251222A: Swift-XRT afterglow detection
  58. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  59. GRB 251222A / EP251222b: GOTO optical counterpart detection
  60. GRB 251222A: 1.3m DFOT optical detection
  61. EP251222a: GSP Optical Counterpart Detection
  62. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  63. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  64. EP251222a: Einstein Probe detection of an X-ray transient
  65. GRB 251222A: PRIME near-infrared detection
  66. EP251221a: NOT optical upper limit
  67. IPN triangulation of GRB 251220B (short)
  68. GRB 251222A: SVOM detection of a long burst
  69. GRB 251222A: Fermi GBM Final Real-time Localization
  70. GRB 251221A: PRIME near-infrared observation
  71. EP251221a: Einstein Probe detection of a fast X-ray transient
  72. GRB 251221B: Fermi GBM Final Real-time Localization
  73. EP251220a: EP-FXT follow-up observation
  74. EP 251220a: GOTO optical counterpart detection
  75. GRB 251221A: COLIBRÍ detection of the optical counterpart
  76. EP 251220a: COLIBRÍ detection of the optical counterpart
  77. GRB 251221A: Swift detection of a burst
  78. GRB 251221A: Fermi GBM Final Real-time Localization
  79. EP251220a: EP detection of a fast X-ray transient
  80. GRB 251220B: Fermi GBM Final Real-time Localization
  81. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  82. GRB 251220A: MAXI/GSC detection
  83. GRB 251215A: Swift-XRT afterglow detection
  84. IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
  85. GRB 251214B: VIRT Optical Upper Limit
  86. GRB 251217A: Fermi GBM Final Real-time Localization
  87. GRB 251216A: Fermi GBM Final Real-time Localization
  88. EP251214a: Optical upper limit with Kinder observations
  89. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  90. GRB 251215A: Glowbug gamma-ray detection
  91. GRB 251213A: GRID-10B observation
  92. GRB 251202A: radio detection with the VLA
  93. EP251214b : Einstein Probe detection of a fast X-ray transient
  94. EP251214b : Einstein Probe detection of a fast X-ray transient
  95. GRB 251214B: LCO detection of the optical counterpart
  96. GRB 251209A: GECAM-B observation of a long burst
  97. GRB 251209A: Insight-HXMT/HE detection
  98. EP251214b (EP trigger 01709250023): LCO optical limits
  99. GRID detection of GRB 251213A
  100. GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst

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