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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

19605 results found.

  1. GRB 250916A: Swift-XRT observations
  2. GRB250917B: WFST optical observations
  3. GRB 250916A: Swift ToO observations
  4. GRB 250917B: Fermi GBM Observation
  5. GRB 250917B: Swift-XRT observations
  6. GRB 250917B: Swift detection of a short burst
  7. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  8. GRB 250912A: Swift-XRT observations
  9. GRB 250911A: Insight-HXMT detection
  10. GRB 250911A: GECAM-B detection
  11. GRB 250911A: Swift-BAT refined analysis
  12. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  13. EP250911a: SVOM/VT optical observation
  14. GRB 250911A: MASTER optical counterpart observations
  15. GRB 250911A: Swift-XRT refined Analysis
  16. EP250911a: Swift-XRT observations
  17. GRB 250911A: Swift/UVOT Detection
  18. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  19. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  20. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  21. GRB 250911A: Enhanced Swift-XRT position
  22. GRB 250911A: Swift-XRT observations
  23. GRB 250911A: COLIBRÍ optical counterpart candidate
  24. GRB 250911A: Swift detection of a burst
  25. GRB 250702B: Late time Chandra observations
  26. EP250908b/EP#01709240653: Swift/UVOT Detection
  27. EP#01709240653: Swift-XRT observations
  28. GRB 250905A: Swift-BAT refined analysis
  29. GRB 250903A: Swift-XRT afterglow detection
  30. GRB 250905A: Swift-XRT refined Analysis
  31. GRB 250904A: Swift-BAT refined analysis
  32. GRB 250905A: Swift/UVOT Upper Limits
  33. GRB 250905A: Enhanced Swift-XRT position
  34. GRB 250904A: Swift/UVOT Detection
  35. GRB 250903A: Swift/UVOT detection
  36. GRB 250904A: Swift-XRT refined Analysis
  37. GRB 250905A: KAIT optical upper limit
  38. GRB 250905A: Swift detection of a burst
  39. Swift GRB250905.09: Global MASTER-Net observations report
  40. Swift GRB 250904A: Global MASTER-Net observations report
  41. GRB 250904A: Enhanced Swift-XRT position
  42. GRB 250904A: TRT optical counterpart detection
  43. GRB 250904A: Prompt enhanced Swift-XRT position
  44. GRB 250904A: Swift detection of a burst
  45. GRB 250903A: Swift-XRT observations
  46. EP250903a: Swift-XRT observations
  47. EP#01709201209: Swift-XRT observations
  48. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  49. EP250901a: Mondy, Assy and SAO RAS optical limits
  50. GRB 250901A: Swift/UVOT Upper Limit
  51. GRB 250830B: Swift-XRT afterglow detection
  52. GRB 250901A: EP-FXT follow-up observation
  53. GRB 250901A: SVOM/VT optical afterglow with VHF data
  54. GRB 250901A: Swift-XRT afterglow detection
  55. EP250901a: Swift-XRT observations
  56. GRB 250901A: LCO optical upper limit
  57. EP250827b: Swift observations of AT 2025wkm
  58. GRB 250901A: SVOM detection of a burst
  59. EP250831a: EP-FXT follow-up observation
  60. EP250831a: Swift-XRT observations
  61. GRB 250831A: Swift-XRT counterpart detection
  62. GRB 250830B: Swift-XRT observations
  63. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  64. GRB 250830B: Swift ToO observations
  65. GRB 250830B: MAXI/GSC detection
  66. GRB 250828B: Swift-BAT refined analysis
  67. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  68. Swift GRB 250828B: Global MASTER-Net observations report
  69. EP250827a: Swift/UVOT Detection
  70. GRB 250828B: Swift detection of a burst
  71. EP250827a: confirmation of optical rebrightening with LCO
  72. EP250827a: Swift-XRT counterpart detection
  73. GRB 250823A: Swift-BAT refined analysis
  74. GRB 250823A: Swift-XRT refined Analysis
  75. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  76. GRB 250823A: COLIBRÍ optical observations
  77. GRB 250823A: SVOM/VT optical observation
  78. GRB 250823A: Swift/UVOT Detection
  79. GRB 250823A: NOT optical observations
  80. GRB 250823A: Fermi GBM Observation
  81. GRB 250818B: MeerKAT Detection
  82. GRB 250823A: Enhanced Swift-XRT position
  83. GRB 250823A: LCOGT Optical Detection
  84. GRB 250823A: BOOTES6/DPRT early optical detection
  85. GRB 250823A: Liverpool Telescope optical detection
  86. GRB 250823A: Swift detection of a burst
  87. Swift GRB250823.84: Global MASTER-Net observations report
  88. GRB 250821A: Kilonova-Catcher optical upper limits
  89. EP250821a: Swift/XRT counterpart fading
  90. GRB 250821A: Swift-BAT refined analysis
  91. EP250821a: Swift/UVOT further observations.
  92. GRB 250821A: VLT/FORS2 Optical Observation
  93. GRB 250821A: GECAM-B detection
  94. EP250821a: SVOM/VT optical observation
  95. GRB 250821A: NOT z-band upper limit
  96. GRB 250821A: Swift-XRT refined Analysis
  97. Swift GRB 250821A: Global MASTER-Net observations report
  98. GRB 250821A: Enhanced Swift-XRT position
  99. GRB 250821A: Swift/UVOT Upper Limits
  100. EP250821a: Rapidly fading optical source detected in Las Cumbres followup

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