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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"

36319 results found.

  1. GRB 260111A: COLIBRÍ optical afterglow candidate
  2. GRB 260111A: GECAM-B observation of a burst
  3. GRB 260111A: Fermi GBM Observation
  4. Swift Trigger 1434591 is not a GRB
  5. GRB 260111A: GOTO optical upper limits
  6. GRB 260112B: Fermi GBM Final Real-time Localization
  7. GRB 260111A: Swift ToO observations
  8. GRB 251230A: Mondy Optical Observations
  9. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  10. GRB 260112A: Fermi GBM Final Real-time Localization
  11. Fermi GRB 260111A: Global MASTER-Net observations report
  12. GRB 260111A: Fermi GBM Final Real-time Localization
  13. EP260110a: KAIT optical upper limit
  14. EP260110a: BOOTES-5/JGU optical upper limit
  15. GRB 260109C: LCO optical upper limits
  16. GRB 260109C: Kilonova-Catcher optical upper limit
  17. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  18. Swift Trigger 1434591: possible GRB 260109C
  19. GRB 260109B: Fermi GBM Final Real-time Localization
  20. GRB 260102A: Swift-XRT afterglow detection
  21. GRB 260109A: Fermi GBM Final Real-time Localization
  22. GRB 260104A: Swift-BAT refined analysis
  23. GRB 260101A: Swift-BAT refined analysis
  24. Swift GRB 251230A: Global MASTER-Net OT detection
  25. Fermi GRB 260107A: Global MASTER-Net observations report
  26. GRB 260102A: AbAO optical observations
  27. GRB 260107A: Fermi GBM Final Real-time Localization
  28. Fermi GRB 260105A: Global MASTER-Net observations report
  29. GRB 260105B: Fermi GBM Detection
  30. GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
  31. GRB 260105A: SVOM/GRM observation
  32. GRB 260105B: SVOM/GRM observation
  33. Fermi GRB 260105B: Global MASTER-Net observations report
  34. GRB 260105B: Fermi GBM Final Real-time Localization
  35. GRB 260105A: Fermi GBM Final Real-time Localization
  36. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  37. GRB 260101A: COLIBRÍ optical upper limits
  38. GRB 260103A: Insight-HXMT/HE detection
  39. GRB 260104A: COLIBRÍ optical upper limits
  40. GRB 260104C: Fermi GBM Final Real-time Localization
  41. Fermi GRB 260104B: Global MASTER-Net observations report
  42. Swift GRB 260104A: Global MASTER-Net observations report
  43. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  44. GRB 260104A: Swift-XRT refined Analysis
  45. GRB 260104A: Enhanced Swift-XRT position
  46. GRB 260101A: Swift/UVOT Detection
  47. GRB 260103A: GECAM-B observation of a burst
  48. GRB 260104B: Fermi GBM Final Localization
  49. GRB 260104A: Swift detection of a burst
  50. GRB 260103A: SVOM/GRM observation of a possible GRB
  51. GRB 260101A: COLIBRÍ optical observations
  52. GRB 260102B: Fermi GBM Final Real-time Localization
  53. Fermi GBM Sub-Threshold Detection of GRB 260102A
  54. GRB 260102A: EP-FXT follow-up observation
  55. GRB 260102A: LCO optical upper limits
  56. GRB 260102A: Swift-XRT observations
  57. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  58. Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
  59. GRB 251230A / EP251230a: GECAM-B detection
  60. GRB 260102A: SVOM/VT optical counterpart
  61. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  62. GRB 260102A: Swift ToO observations
  63. GRB 260101A: Fermi GBM Observation
  64. GRB 260102A: SVOM detection of a burst
  65. GRB 260101A: GECAM-B detection
  66. GRB 260101A: NOT spectroscopic observations
  67. GRB 260101A: SVOM/GRM observation
  68. GRB 260101A: Swift-XRT refined Analysis
  69. Swift GRB 260101A: Global MASTER-Net observations report
  70. GRB 260101A: Enhanced Swift-XRT position
  71. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  72. GRB 260101A: LCO detection of the optical counterpart
  73. GRB 260101A: Swift detection of a burst with an optical counterpart
  74. GRB 260101A: Fermi GBM Final Real-time Localization
  75. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  76. GRB 251230A: GRANDMA/TAROT Early Detection
  77. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  78. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  79. EP251229a: Optical upper limit with Kinder observations
  80. GRB 251230A: 1.3m DFOT optical upper limit
  81. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  82. GRB 251230A: Swift-XRT refined Analysis
  83. GRB 251231A: Fermi GBM Final Real-time Localization
  84. GRB 251222A: Mondy Optical Observations
  85. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  86. GRB 251230A: Swift/UVOT detection
  87. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  88. GRB 251230A: GOTO optical upper limit
  89. GRB 251230A / EP251230a: SVOM/VT optical observation
  90. GRB 251230A: Enhanced Swift-XRT position
  91. GRB 251230A: Early optical counterpart detection by LCO.
  92. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  93. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  94. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  95. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  96. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  97. Swift GRB 251230A: Global MASTER-Net observations report
  98. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  99. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  100. GRB 251226A: Glowbug gamma-ray detection

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