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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"

21459 results found.

  1. GRB 250919A: Swift-XRT afterglow detection
  2. GRB 250917B: Swift-BAT refined analysis
  3. GRB 250917B: Swift/UVOT Upper Limits
  4. GRB 250916A: Swift-XRT observations
  5. GRB250917B: WFST optical observations
  6. GRB 250916A: Swift ToO observations
  7. GRB 250917B: Fermi GBM Observation
  8. GRB 250917B: Swift-XRT observations
  9. GRB 250917B: Swift detection of a short burst
  10. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  11. GRB 250912A: Swift-XRT observations
  12. GRB 250911A: Insight-HXMT detection
  13. GRB 250911A: GECAM-B detection
  14. GRB 250911A: Swift-BAT refined analysis
  15. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  16. EP250911a: SVOM/VT optical observation
  17. GRB 250911A: MASTER optical counterpart observations
  18. GRB 250911A: Swift-XRT refined Analysis
  19. EP250911a: Swift-XRT observations
  20. GRB 250911A: Swift/UVOT Detection
  21. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  22. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  23. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  24. GRB 250911A: Enhanced Swift-XRT position
  25. GRB 250911A: Swift-XRT observations
  26. GRB 250911A: COLIBRÍ optical counterpart candidate
  27. GRB 250911A: Swift detection of a burst
  28. GRB 250702B: Late time Chandra observations
  29. EP250908b/EP#01709240653: Swift/UVOT Detection
  30. EP#01709240653: Swift-XRT observations
  31. GRB 250905A: Swift-BAT refined analysis
  32. GRB 250903A: Swift-XRT afterglow detection
  33. GRB 250905A: Swift-XRT refined Analysis
  34. GRB 250904A: Swift-BAT refined analysis
  35. GRB 250905A: Swift/UVOT Upper Limits
  36. GRB250904A: Liverpool Telescope upper limits
  37. GRB 250905A: Enhanced Swift-XRT position
  38. GRB 250904A: Swift/UVOT Detection
  39. GRB 250903A: Swift/UVOT detection
  40. GRB 250904A: Swift-XRT refined Analysis
  41. GRB 250905A: KAIT optical upper limit
  42. GRB 250905A: Swift detection of a burst
  43. Swift GRB250905.09: Global MASTER-Net observations report
  44. Swift GRB 250904A: Global MASTER-Net observations report
  45. GRB 250904A: Enhanced Swift-XRT position
  46. GRB 250904A: TRT optical counterpart detection
  47. GRB 250904A: Prompt enhanced Swift-XRT position
  48. GRB 250904A: Swift detection of a burst
  49. GRB 250903A: Swift-XRT observations
  50. EP250903a: Swift-XRT observations
  51. EP#01709201209: Swift-XRT observations
  52. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  53. EP250901a: Mondy, Assy and SAO RAS optical limits
  54. GRB 250901A: Swift/UVOT Upper Limit
  55. GRB 250830B: Swift-XRT afterglow detection
  56. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  57. GRB 250901A: EP-FXT follow-up observation
  58. GRB 250901A: SVOM/VT optical afterglow with VHF data
  59. GRB 250901A: Swift-XRT afterglow detection
  60. EP250901a: Swift-XRT observations
  61. GRB 250901A: LCO optical upper limit
  62. EP250827b: Swift observations of AT 2025wkm
  63. GRB 250901A: SVOM detection of a burst
  64. EP250831a: EP-FXT follow-up observation
  65. EP250831a: Swift-XRT observations
  66. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  67. GRB 250831A: Swift-XRT counterpart detection
  68. GRB 250830B: Swift-XRT observations
  69. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  70. GRB 250830B: Swift ToO observations
  71. GRB 250830B: MAXI/GSC detection
  72. GRB 250828B: Swift-BAT refined analysis
  73. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  74. Swift GRB 250828B: Global MASTER-Net observations report
  75. EP250827a: Swift/UVOT Detection
  76. GRB 250828B: Swift detection of a burst
  77. EP250827a: confirmation of optical rebrightening with LCO
  78. EP250827a: Swift-XRT counterpart detection
  79. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  80. GRB 250823A: Swift-BAT refined analysis
  81. GRB 250823A: Swift-XRT refined Analysis
  82. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  83. GRB 250823A: COLIBRÍ optical observations
  84. GRB 250823A: SVOM/VT optical observation
  85. GRB 250823A: Swift/UVOT Detection
  86. GRB 250823A: NOT optical observations
  87. GRB 250823A: Fermi GBM Observation
  88. GRB 250818B: MeerKAT Detection
  89. GRB 250823A: Enhanced Swift-XRT position
  90. GRB 250823A: LCOGT Optical Detection
  91. GRB 250823A: BOOTES6/DPRT early optical detection
  92. GRB 250823A: Liverpool Telescope optical detection
  93. GRB 250823A: Swift detection of a burst
  94. Swift GRB250823.84: Global MASTER-Net observations report
  95. GRB 250821A: Kilonova-Catcher optical upper limits
  96. EP250821a: Swift/XRT counterpart fading
  97. GRB 250821A: Swift-BAT refined analysis
  98. EP250821a: Swift/UVOT further observations.
  99. GRB 250821A: VLT/FORS2 Optical Observation
  100. GRB 250821A: GECAM-B detection

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