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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"

19173 results found.

  1. GRB 250905A: KAIT optical upper limit
  2. GRB 250905A: Swift detection of a burst
  3. Swift GRB250905.09: Global MASTER-Net observations report
  4. Swift GRB 250904A: Global MASTER-Net observations report
  5. GRB 250904A: Enhanced Swift-XRT position
  6. GRB 250904A: TRT optical counterpart detection
  7. GRB 250904A: Prompt enhanced Swift-XRT position
  8. GRB 250904A: Swift detection of a burst
  9. GRB 250903A: Swift-XRT observations
  10. EP250903a: Swift-XRT observations
  11. EP#01709201209: Swift-XRT observations
  12. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  13. EP250901a: Mondy, Assy and SAO RAS optical limits
  14. GRB 250901A: Swift/UVOT Upper Limit
  15. GRB 250830B: Swift-XRT afterglow detection
  16. GRB 250901A: EP-FXT follow-up observation
  17. GRB 250901A: SVOM/VT optical afterglow with VHF data
  18. GRB 250901A: Swift-XRT afterglow detection
  19. EP250901a: Swift-XRT observations
  20. GRB 250901A: LCO optical upper limit
  21. EP250827b: Swift observations of AT 2025wkm
  22. GRB 250901A: SVOM detection of a burst
  23. EP250831a: EP-FXT follow-up observation
  24. EP250831a: Swift-XRT observations
  25. GRB 250831A: Swift-XRT counterpart detection
  26. GRB 250830B: Swift-XRT observations
  27. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  28. GRB 250830B: Swift ToO observations
  29. GRB 250830B: MAXI/GSC detection
  30. GRB 250828B: Swift-BAT refined analysis
  31. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  32. Swift GRB 250828B: Global MASTER-Net observations report
  33. EP250827a: Swift/UVOT Detection
  34. GRB 250828B: Swift detection of a burst
  35. EP250827a: confirmation of optical rebrightening with LCO
  36. EP250827a: Swift-XRT counterpart detection
  37. GRB 250823A: Swift-BAT refined analysis
  38. GRB 250823A: Swift-XRT refined Analysis
  39. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  40. GRB 250823A: COLIBRÍ optical observations
  41. GRB 250823A: SVOM/VT optical observation
  42. GRB 250823A: Swift/UVOT Detection
  43. GRB 250823A: NOT optical observations
  44. GRB 250823A: Fermi GBM Observation
  45. GRB 250818B: MeerKAT Detection
  46. GRB 250823A: Enhanced Swift-XRT position
  47. GRB 250823A: LCOGT Optical Detection
  48. GRB 250823A: BOOTES6/DPRT early optical detection
  49. GRB 250823A: Liverpool Telescope optical detection
  50. GRB 250823A: Swift detection of a burst
  51. Swift GRB250823.84: Global MASTER-Net observations report
  52. GRB 250821A: Kilonova-Catcher optical upper limits
  53. EP250821a: Swift/XRT counterpart fading
  54. GRB 250821A: Swift-BAT refined analysis
  55. EP250821a: Swift/UVOT further observations.
  56. GRB 250821A: VLT/FORS2 Optical Observation
  57. GRB 250821A: GECAM-B detection
  58. EP250821a: SVOM/VT optical observation
  59. GRB 250821A: NOT z-band upper limit
  60. GRB 250821A: Swift-XRT refined Analysis
  61. Swift GRB 250821A: Global MASTER-Net observations report
  62. GRB 250821A: Enhanced Swift-XRT position
  63. GRB 250821A: Swift/UVOT Upper Limits
  64. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  65. EP250821a: Swift XRT and UVOT counterpart detection
  66. GRB 250821A: LCOGT Optical Upper Limits
  67. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  68. GRB 250821A: Prompt enhanced Swift-XRT position
  69. GRB 250821A: Swift detection of a burst
  70. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  71. GRB 250814A: Swift/UVOT Upper Limits
  72. GRB 250813B: Swift/UVOT Upper Limit
  73. IPN triangulation of GRB 250814C (short)
  74. IPN triangulation of GRB 250804B (short)
  75. GRB 250818B: Kilonova-Catcher optical afterglow detection
  76. GRB 250818A: AstroSat CZTI detection
  77. GRB 250818B: Swift/UVOT Detection
  78. GRB 250818B: SAO RAS optical observations
  79. Swift GRB 250818A: Global MASTER-Net observations report
  80. GRB 250818A: Swift-XRT refined Analysis
  81. GRB 250818A: Swift-BAT refined analysis
  82. GRB 250818B: Keck redshift of the optical afterglow
  83. GRB 250818A: Swift/UVOT Upper Limits
  84. GRB 250818A: Enhanced Swift-XRT position
  85. GRB 250818A: Fermi GBM Observation
  86. GRB 250818B: SVOM/VT optical observation
  87. GRB 250814A: Further GRAWITA TNG NIR observations
  88. GRB 250818B: Swift-XRT afterglow detection
  89. GRB 250818A: Swift detection of a burst
  90. sb25081602: Swift-XRT observations
  91. GRB 250814A: Swift-BAT refined analysis
  92. GRB 250814A: Further COLIBRÍ optical upper limit
  93. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  94. GRB 250814A: GRAWITA TNG NIR observations
  95. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  96. GRB250814A: TRT optical upper limits
  97. GRB 250814C: SVOM/GRM observation of a short burst
  98. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  99. GRB 250813B: SVOM/GRM observation
  100. GRB 250814A: P200/WIRC observations of the afterglow candidate

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