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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"

28047 results found.

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

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