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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"

19603 results found.

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

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