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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"

19539 results found.

  1. Konus-Wind detection of GRB 250911A
  2. GRB 250916A: Swift/UVOT Detection
  3. GRB 250920B: Glowbug gamma-ray detection
  4. GRB 250920C: Swift-XRT refined Analysis
  5. GRB 250920B: Kitab-ISON optical upper limit
  6. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  7. GRB 250920C: SVOM/GRM observation
  8. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  9. GRB 250917B: KAIT optical upper limit
  10. GRB 250920C: GROWTH-India Telescope optical observations
  11. GRB 250920C: Swift-BAT refined analysis
  12. GRB 250920B: Swift-BAT refined analysis
  13. GRB 250920C: Enhanced Swift-XRT position
  14. GRB 250920C: Swift/UVOT Detection
  15. GRB 250920B: Fermi GBM Observation
  16. GRB 250920C: Fermi GBM Observation
  17. Swift GRB 250920C: Global MASTER-Net observations report
  18. GRB 250920B: Swift/UVOT Detection
  19. GRB 250920C: Optical counterpart detection by LCO
  20. GRB250920C: LCOGT Optical Detection
  21. GRB 250920B: Enhanced Swift-XRT position
  22. GRB 250920B: Swift-XRT refined Analysis
  23. GRB 250920B: SVOM/C-GFT optical observations
  24. GRB 250920C: GOTO optical counterpart candidate
  25. GRB 250920C: Swift detection of a burst
  26. Swift GRB 250920B: Global MASTER-Net observations report
  27. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  28. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  29. GRB 250916A: Mondy R-band optical observations
  30. GRB 250919A: Fermi GBM Observation
  31. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  32. GRB 250919A: Swift-XRT afterglow detection
  33. GRB 250917B: Swift-BAT refined analysis
  34. GRB 250917B: Swift/UVOT Upper Limits
  35. GRB 250916A: Swift-XRT observations
  36. GRB250917B: WFST optical observations
  37. GRB 250916A: Swift ToO observations
  38. GRB 250917B: Fermi GBM Observation
  39. GRB 250917B: Swift-XRT observations
  40. GRB 250917B: Swift detection of a short burst
  41. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  42. GRB 250912A: Swift-XRT observations
  43. GRB 250911A: Insight-HXMT detection
  44. GRB 250911A: GECAM-B detection
  45. GRB 250911A: Swift-BAT refined analysis
  46. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  47. EP250911a: SVOM/VT optical observation
  48. GRB 250911A: MASTER optical counterpart observations
  49. GRB 250911A: Swift-XRT refined Analysis
  50. EP250911a: Swift-XRT observations
  51. GRB 250911A: Swift/UVOT Detection
  52. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  53. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  54. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  55. GRB 250911A: Enhanced Swift-XRT position
  56. GRB 250911A: Swift-XRT observations
  57. GRB 250911A: COLIBRÍ optical counterpart candidate
  58. GRB 250911A: Swift detection of a burst
  59. GRB 250702B: Late time Chandra observations
  60. EP250908b/EP#01709240653: Swift/UVOT Detection
  61. EP#01709240653: Swift-XRT observations
  62. GRB 250905A: Swift-BAT refined analysis
  63. GRB 250903A: Swift-XRT afterglow detection
  64. GRB 250905A: Swift-XRT refined Analysis
  65. GRB 250904A: Swift-BAT refined analysis
  66. GRB 250905A: Swift/UVOT Upper Limits
  67. GRB 250905A: Enhanced Swift-XRT position
  68. GRB 250904A: Swift/UVOT Detection
  69. GRB 250903A: Swift/UVOT detection
  70. GRB 250904A: Swift-XRT refined Analysis
  71. GRB 250905A: KAIT optical upper limit
  72. GRB 250905A: Swift detection of a burst
  73. Swift GRB250905.09: Global MASTER-Net observations report
  74. Swift GRB 250904A: Global MASTER-Net observations report
  75. GRB 250904A: Enhanced Swift-XRT position
  76. GRB 250904A: TRT optical counterpart detection
  77. GRB 250904A: Prompt enhanced Swift-XRT position
  78. GRB 250904A: Swift detection of a burst
  79. GRB 250903A: Swift-XRT observations
  80. EP250903a: Swift-XRT observations
  81. EP#01709201209: Swift-XRT observations
  82. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  83. EP250901a: Mondy, Assy and SAO RAS optical limits
  84. GRB 250901A: Swift/UVOT Upper Limit
  85. GRB 250830B: Swift-XRT afterglow detection
  86. GRB 250901A: EP-FXT follow-up observation
  87. GRB 250901A: SVOM/VT optical afterglow with VHF data
  88. GRB 250901A: Swift-XRT afterglow detection
  89. EP250901a: Swift-XRT observations
  90. GRB 250901A: LCO optical upper limit
  91. EP250827b: Swift observations of AT 2025wkm
  92. GRB 250901A: SVOM detection of a burst
  93. EP250831a: EP-FXT follow-up observation
  94. EP250831a: Swift-XRT observations
  95. GRB 250831A: Swift-XRT counterpart detection
  96. GRB 250830B: Swift-XRT observations
  97. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  98. GRB 250830B: Swift ToO observations
  99. GRB 250830B: MAXI/GSC detection
  100. GRB 250828B: Swift-BAT refined analysis

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Download all Circulars as a .tar.gz archive (updated once a day):
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