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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"

19590 results found.

  1. EP250911a: Swift-XRT observations
  2. GRB 250911A: Swift/UVOT Detection
  3. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  4. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  5. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  6. GRB 250911A: Enhanced Swift-XRT position
  7. GRB 250911A: Swift-XRT observations
  8. GRB 250911A: COLIBRÍ optical counterpart candidate
  9. GRB 250911A: Swift detection of a burst
  10. GRB 250702B: Late time Chandra observations
  11. EP250908b/EP#01709240653: Swift/UVOT Detection
  12. EP#01709240653: Swift-XRT observations
  13. GRB 250905A: Swift-BAT refined analysis
  14. GRB 250903A: Swift-XRT afterglow detection
  15. GRB 250905A: Swift-XRT refined Analysis
  16. GRB 250904A: Swift-BAT refined analysis
  17. GRB 250905A: Swift/UVOT Upper Limits
  18. GRB 250905A: Enhanced Swift-XRT position
  19. GRB 250904A: Swift/UVOT Detection
  20. GRB 250903A: Swift/UVOT detection
  21. GRB 250904A: Swift-XRT refined Analysis
  22. GRB 250905A: KAIT optical upper limit
  23. GRB 250905A: Swift detection of a burst
  24. Swift GRB250905.09: Global MASTER-Net observations report
  25. Swift GRB 250904A: Global MASTER-Net observations report
  26. GRB 250904A: Enhanced Swift-XRT position
  27. GRB 250904A: TRT optical counterpart detection
  28. GRB 250904A: Prompt enhanced Swift-XRT position
  29. GRB 250904A: Swift detection of a burst
  30. GRB 250903A: Swift-XRT observations
  31. EP250903a: Swift-XRT observations
  32. EP#01709201209: Swift-XRT observations
  33. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  34. EP250901a: Mondy, Assy and SAO RAS optical limits
  35. GRB 250901A: Swift/UVOT Upper Limit
  36. GRB 250830B: Swift-XRT afterglow detection
  37. GRB 250901A: EP-FXT follow-up observation
  38. GRB 250901A: SVOM/VT optical afterglow with VHF data
  39. GRB 250901A: Swift-XRT afterglow detection
  40. EP250901a: Swift-XRT observations
  41. GRB 250901A: LCO optical upper limit
  42. EP250827b: Swift observations of AT 2025wkm
  43. GRB 250901A: SVOM detection of a burst
  44. EP250831a: EP-FXT follow-up observation
  45. EP250831a: Swift-XRT observations
  46. GRB 250831A: Swift-XRT counterpart detection
  47. GRB 250830B: Swift-XRT observations
  48. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  49. GRB 250830B: Swift ToO observations
  50. GRB 250830B: MAXI/GSC detection
  51. GRB 250828B: Swift-BAT refined analysis
  52. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  53. Swift GRB 250828B: Global MASTER-Net observations report
  54. EP250827a: Swift/UVOT Detection
  55. GRB 250828B: Swift detection of a burst
  56. EP250827a: confirmation of optical rebrightening with LCO
  57. EP250827a: Swift-XRT counterpart detection
  58. GRB 250823A: Swift-BAT refined analysis
  59. GRB 250823A: Swift-XRT refined Analysis
  60. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  61. GRB 250823A: COLIBRÍ optical observations
  62. GRB 250823A: SVOM/VT optical observation
  63. GRB 250823A: Swift/UVOT Detection
  64. GRB 250823A: NOT optical observations
  65. GRB 250823A: Fermi GBM Observation
  66. GRB 250818B: MeerKAT Detection
  67. GRB 250823A: Enhanced Swift-XRT position
  68. GRB 250823A: LCOGT Optical Detection
  69. GRB 250823A: BOOTES6/DPRT early optical detection
  70. GRB 250823A: Liverpool Telescope optical detection
  71. GRB 250823A: Swift detection of a burst
  72. Swift GRB250823.84: Global MASTER-Net observations report
  73. GRB 250821A: Kilonova-Catcher optical upper limits
  74. EP250821a: Swift/XRT counterpart fading
  75. GRB 250821A: Swift-BAT refined analysis
  76. EP250821a: Swift/UVOT further observations.
  77. GRB 250821A: VLT/FORS2 Optical Observation
  78. GRB 250821A: GECAM-B detection
  79. EP250821a: SVOM/VT optical observation
  80. GRB 250821A: NOT z-band upper limit
  81. GRB 250821A: Swift-XRT refined Analysis
  82. Swift GRB 250821A: Global MASTER-Net observations report
  83. GRB 250821A: Enhanced Swift-XRT position
  84. GRB 250821A: Swift/UVOT Upper Limits
  85. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  86. EP250821a: Swift XRT and UVOT counterpart detection
  87. GRB 250821A: LCOGT Optical Upper Limits
  88. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  89. GRB 250821A: Prompt enhanced Swift-XRT position
  90. GRB 250821A: Swift detection of a burst
  91. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  92. GRB 250814A: Swift/UVOT Upper Limits
  93. GRB 250813B: Swift/UVOT Upper Limit
  94. IPN triangulation of GRB 250814C (short)
  95. IPN triangulation of GRB 250804B (short)
  96. GRB 250818B: Kilonova-Catcher optical afterglow detection
  97. GRB 250818A: AstroSat CZTI detection
  98. GRB 250818B: Swift/UVOT Detection
  99. GRB 250818B: SAO RAS optical observations
  100. Swift GRB 250818A: Global MASTER-Net observations report

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