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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"

19941 results found.

  1. GRB 250917B: Swift detection of a short burst
  2. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  3. GRB 250912A: Swift-XRT observations
  4. GRB 250911A: Insight-HXMT detection
  5. GRB 250911A: GECAM-B detection
  6. GRB 250911A: Swift-BAT refined analysis
  7. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  8. EP250911a: SVOM/VT optical observation
  9. GRB 250911A: MASTER optical counterpart observations
  10. GRB 250911A: Swift-XRT refined Analysis
  11. EP250911a: Swift-XRT observations
  12. GRB 250911A: Swift/UVOT Detection
  13. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  14. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  15. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  16. GRB 250911A: Enhanced Swift-XRT position
  17. GRB 250911A: Swift-XRT observations
  18. GRB 250911A: COLIBRÍ optical counterpart candidate
  19. GRB 250911A: Swift detection of a burst
  20. GRB 250702B: Late time Chandra observations
  21. EP250908b/EP#01709240653: Swift/UVOT Detection
  22. EP#01709240653: Swift-XRT observations
  23. GRB 250905A: Swift-BAT refined analysis
  24. GRB 250903A: Swift-XRT afterglow detection
  25. GRB 250905A: Swift-XRT refined Analysis
  26. GRB 250904A: Swift-BAT refined analysis
  27. GRB 250905A: Swift/UVOT Upper Limits
  28. GRB 250905A: Enhanced Swift-XRT position
  29. GRB 250904A: Swift/UVOT Detection
  30. GRB 250903A: Swift/UVOT detection
  31. GRB 250904A: Swift-XRT refined Analysis
  32. GRB 250905A: KAIT optical upper limit
  33. GRB 250905A: Swift detection of a burst
  34. Swift GRB250905.09: Global MASTER-Net observations report
  35. Swift GRB 250904A: Global MASTER-Net observations report
  36. GRB 250904A: Enhanced Swift-XRT position
  37. GRB 250904A: TRT optical counterpart detection
  38. GRB 250904A: Prompt enhanced Swift-XRT position
  39. GRB 250904A: Swift detection of a burst
  40. GRB 250903A: Swift-XRT observations
  41. EP250903a: Swift-XRT observations
  42. EP#01709201209: Swift-XRT observations
  43. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  44. EP250901a: Mondy, Assy and SAO RAS optical limits
  45. GRB 250901A: Swift/UVOT Upper Limit
  46. GRB 250830B: Swift-XRT afterglow detection
  47. GRB 250901A: EP-FXT follow-up observation
  48. GRB 250901A: SVOM/VT optical afterglow with VHF data
  49. GRB 250901A: Swift-XRT afterglow detection
  50. EP250901a: Swift-XRT observations
  51. GRB 250901A: LCO optical upper limit
  52. EP250827b: Swift observations of AT 2025wkm
  53. GRB 250901A: SVOM detection of a burst
  54. EP250831a: EP-FXT follow-up observation
  55. EP250831a: Swift-XRT observations
  56. GRB 250831A: Swift-XRT counterpart detection
  57. GRB 250830B: Swift-XRT observations
  58. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  59. GRB 250830B: Swift ToO observations
  60. GRB 250830B: MAXI/GSC detection
  61. GRB 250828B: Swift-BAT refined analysis
  62. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  63. Swift GRB 250828B: Global MASTER-Net observations report
  64. EP250827a: Swift/UVOT Detection
  65. GRB 250828B: Swift detection of a burst
  66. EP250827a: confirmation of optical rebrightening with LCO
  67. EP250827a: Swift-XRT counterpart detection
  68. GRB 250823A: Swift-BAT refined analysis
  69. GRB 250823A: Swift-XRT refined Analysis
  70. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  71. GRB 250823A: COLIBRÍ optical observations
  72. GRB 250823A: SVOM/VT optical observation
  73. GRB 250823A: Swift/UVOT Detection
  74. GRB 250823A: NOT optical observations
  75. GRB 250823A: Fermi GBM Observation
  76. GRB 250818B: MeerKAT Detection
  77. GRB 250823A: Enhanced Swift-XRT position
  78. GRB 250823A: LCOGT Optical Detection
  79. GRB 250823A: BOOTES6/DPRT early optical detection
  80. GRB 250823A: Liverpool Telescope optical detection
  81. GRB 250823A: Swift detection of a burst
  82. Swift GRB250823.84: Global MASTER-Net observations report
  83. GRB 250821A: Kilonova-Catcher optical upper limits
  84. EP250821a: Swift/XRT counterpart fading
  85. GRB 250821A: Swift-BAT refined analysis
  86. EP250821a: Swift/UVOT further observations.
  87. GRB 250821A: VLT/FORS2 Optical Observation
  88. GRB 250821A: GECAM-B detection
  89. EP250821a: SVOM/VT optical observation
  90. GRB 250821A: NOT z-band upper limit
  91. GRB 250821A: Swift-XRT refined Analysis
  92. Swift GRB 250821A: Global MASTER-Net observations report
  93. GRB 250821A: Enhanced Swift-XRT position
  94. GRB 250821A: Swift/UVOT Upper Limits
  95. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  96. EP250821a: Swift XRT and UVOT counterpart detection
  97. GRB 250821A: LCOGT Optical Upper Limits
  98. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  99. GRB 250821A: Prompt enhanced Swift-XRT position
  100. GRB 250821A: Swift detection of a burst

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