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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"

19938 results found.

  1. GRB 250911A: Insight-HXMT detection
  2. GRB 250911A: GECAM-B detection
  3. GRB 250911A: Swift-BAT refined analysis
  4. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  5. EP250911a: SVOM/VT optical observation
  6. GRB 250911A: MASTER optical counterpart observations
  7. GRB 250911A: Swift-XRT refined Analysis
  8. EP250911a: Swift-XRT observations
  9. GRB 250911A: Swift/UVOT Detection
  10. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  11. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  12. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  13. GRB 250911A: Enhanced Swift-XRT position
  14. GRB 250911A: Swift-XRT observations
  15. GRB 250911A: COLIBRÍ optical counterpart candidate
  16. GRB 250911A: Swift detection of a burst
  17. GRB 250702B: Late time Chandra observations
  18. EP250908b/EP#01709240653: Swift/UVOT Detection
  19. EP#01709240653: Swift-XRT observations
  20. GRB 250905A: Swift-BAT refined analysis
  21. GRB 250903A: Swift-XRT afterglow detection
  22. GRB 250905A: Swift-XRT refined Analysis
  23. GRB 250904A: Swift-BAT refined analysis
  24. GRB 250905A: Swift/UVOT Upper Limits
  25. GRB 250905A: Enhanced Swift-XRT position
  26. GRB 250904A: Swift/UVOT Detection
  27. GRB 250903A: Swift/UVOT detection
  28. GRB 250904A: Swift-XRT refined Analysis
  29. GRB 250905A: KAIT optical upper limit
  30. GRB 250905A: Swift detection of a burst
  31. Swift GRB250905.09: Global MASTER-Net observations report
  32. Swift GRB 250904A: Global MASTER-Net observations report
  33. GRB 250904A: Enhanced Swift-XRT position
  34. GRB 250904A: TRT optical counterpart detection
  35. GRB 250904A: Prompt enhanced Swift-XRT position
  36. GRB 250904A: Swift detection of a burst
  37. GRB 250903A: Swift-XRT observations
  38. EP250903a: Swift-XRT observations
  39. EP#01709201209: Swift-XRT observations
  40. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  41. EP250901a: Mondy, Assy and SAO RAS optical limits
  42. GRB 250901A: Swift/UVOT Upper Limit
  43. GRB 250830B: Swift-XRT afterglow detection
  44. GRB 250901A: EP-FXT follow-up observation
  45. GRB 250901A: SVOM/VT optical afterglow with VHF data
  46. GRB 250901A: Swift-XRT afterglow detection
  47. EP250901a: Swift-XRT observations
  48. GRB 250901A: LCO optical upper limit
  49. EP250827b: Swift observations of AT 2025wkm
  50. GRB 250901A: SVOM detection of a burst
  51. EP250831a: EP-FXT follow-up observation
  52. EP250831a: Swift-XRT observations
  53. GRB 250831A: Swift-XRT counterpart detection
  54. GRB 250830B: Swift-XRT observations
  55. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  56. GRB 250830B: Swift ToO observations
  57. GRB 250830B: MAXI/GSC detection
  58. GRB 250828B: Swift-BAT refined analysis
  59. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  60. Swift GRB 250828B: Global MASTER-Net observations report
  61. EP250827a: Swift/UVOT Detection
  62. GRB 250828B: Swift detection of a burst
  63. EP250827a: confirmation of optical rebrightening with LCO
  64. EP250827a: Swift-XRT counterpart detection
  65. GRB 250823A: Swift-BAT refined analysis
  66. GRB 250823A: Swift-XRT refined Analysis
  67. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  68. GRB 250823A: COLIBRÍ optical observations
  69. GRB 250823A: SVOM/VT optical observation
  70. GRB 250823A: Swift/UVOT Detection
  71. GRB 250823A: NOT optical observations
  72. GRB 250823A: Fermi GBM Observation
  73. GRB 250818B: MeerKAT Detection
  74. GRB 250823A: Enhanced Swift-XRT position
  75. GRB 250823A: LCOGT Optical Detection
  76. GRB 250823A: BOOTES6/DPRT early optical detection
  77. GRB 250823A: Liverpool Telescope optical detection
  78. GRB 250823A: Swift detection of a burst
  79. Swift GRB250823.84: Global MASTER-Net observations report
  80. GRB 250821A: Kilonova-Catcher optical upper limits
  81. EP250821a: Swift/XRT counterpart fading
  82. GRB 250821A: Swift-BAT refined analysis
  83. EP250821a: Swift/UVOT further observations.
  84. GRB 250821A: VLT/FORS2 Optical Observation
  85. GRB 250821A: GECAM-B detection
  86. EP250821a: SVOM/VT optical observation
  87. GRB 250821A: NOT z-band upper limit
  88. GRB 250821A: Swift-XRT refined Analysis
  89. Swift GRB 250821A: Global MASTER-Net observations report
  90. GRB 250821A: Enhanced Swift-XRT position
  91. GRB 250821A: Swift/UVOT Upper Limits
  92. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  93. EP250821a: Swift XRT and UVOT counterpart detection
  94. GRB 250821A: LCOGT Optical Upper Limits
  95. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  96. GRB 250821A: Prompt enhanced Swift-XRT position
  97. GRB 250821A: Swift detection of a burst
  98. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  99. GRB 250814A: Swift/UVOT Upper Limits
  100. GRB 250813B: Swift/UVOT Upper Limit

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