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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"

19165 results found.

  1. GRB 250904A: Enhanced Swift-XRT position
  2. GRB 250904A: TRT optical counterpart detection
  3. GRB 250904A: Prompt enhanced Swift-XRT position
  4. GRB 250904A: Swift detection of a burst
  5. GRB 250903A: Swift-XRT observations
  6. EP250903a: Swift-XRT observations
  7. EP#01709201209: Swift-XRT observations
  8. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  9. EP250901a: Mondy, Assy and SAO RAS optical limits
  10. GRB 250901A: Swift/UVOT Upper Limit
  11. GRB 250830B: Swift-XRT afterglow detection
  12. GRB 250901A: EP-FXT follow-up observation
  13. GRB 250901A: SVOM/VT optical afterglow with VHF data
  14. GRB 250901A: Swift-XRT afterglow detection
  15. EP250901a: Swift-XRT observations
  16. GRB 250901A: LCO optical upper limit
  17. EP250827b: Swift observations of AT 2025wkm
  18. GRB 250901A: SVOM detection of a burst
  19. EP250831a: EP-FXT follow-up observation
  20. EP250831a: Swift-XRT observations
  21. GRB 250831A: Swift-XRT counterpart detection
  22. GRB 250830B: Swift-XRT observations
  23. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  24. GRB 250830B: Swift ToO observations
  25. GRB 250830B: MAXI/GSC detection
  26. GRB 250828B: Swift-BAT refined analysis
  27. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  28. Swift GRB 250828B: Global MASTER-Net observations report
  29. EP250827a: Swift/UVOT Detection
  30. GRB 250828B: Swift detection of a burst
  31. EP250827a: confirmation of optical rebrightening with LCO
  32. EP250827a: Swift-XRT counterpart detection
  33. GRB 250823A: Swift-BAT refined analysis
  34. GRB 250823A: Swift-XRT refined Analysis
  35. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  36. GRB 250823A: COLIBRÍ optical observations
  37. GRB 250823A: SVOM/VT optical observation
  38. GRB 250823A: Swift/UVOT Detection
  39. GRB 250823A: NOT optical observations
  40. GRB 250823A: Fermi GBM Observation
  41. GRB 250818B: MeerKAT Detection
  42. GRB 250823A: Enhanced Swift-XRT position
  43. GRB 250823A: LCOGT Optical Detection
  44. GRB 250823A: BOOTES6/DPRT early optical detection
  45. GRB 250823A: Liverpool Telescope optical detection
  46. GRB 250823A: Swift detection of a burst
  47. Swift GRB250823.84: Global MASTER-Net observations report
  48. GRB 250821A: Kilonova-Catcher optical upper limits
  49. EP250821a: Swift/XRT counterpart fading
  50. GRB 250821A: Swift-BAT refined analysis
  51. EP250821a: Swift/UVOT further observations.
  52. GRB 250821A: VLT/FORS2 Optical Observation
  53. GRB 250821A: GECAM-B detection
  54. EP250821a: SVOM/VT optical observation
  55. GRB 250821A: NOT z-band upper limit
  56. GRB 250821A: Swift-XRT refined Analysis
  57. Swift GRB 250821A: Global MASTER-Net observations report
  58. GRB 250821A: Enhanced Swift-XRT position
  59. GRB 250821A: Swift/UVOT Upper Limits
  60. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  61. EP250821a: Swift XRT and UVOT counterpart detection
  62. GRB 250821A: LCOGT Optical Upper Limits
  63. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  64. GRB 250821A: Prompt enhanced Swift-XRT position
  65. GRB 250821A: Swift detection of a burst
  66. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  67. GRB 250814A: Swift/UVOT Upper Limits
  68. GRB 250813B: Swift/UVOT Upper Limit
  69. IPN triangulation of GRB 250814C (short)
  70. IPN triangulation of GRB 250804B (short)
  71. GRB 250818B: Kilonova-Catcher optical afterglow detection
  72. GRB 250818A: AstroSat CZTI detection
  73. GRB 250818B: Swift/UVOT Detection
  74. GRB 250818B: SAO RAS optical observations
  75. Swift GRB 250818A: Global MASTER-Net observations report
  76. GRB 250818A: Swift-XRT refined Analysis
  77. GRB 250818A: Swift-BAT refined analysis
  78. GRB 250818B: Keck redshift of the optical afterglow
  79. GRB 250818A: Swift/UVOT Upper Limits
  80. GRB 250818A: Enhanced Swift-XRT position
  81. GRB 250818A: Fermi GBM Observation
  82. GRB 250818B: SVOM/VT optical observation
  83. GRB 250814A: Further GRAWITA TNG NIR observations
  84. GRB 250818B: Swift-XRT afterglow detection
  85. GRB 250818A: Swift detection of a burst
  86. sb25081602: Swift-XRT observations
  87. GRB 250814A: Swift-BAT refined analysis
  88. GRB 250814A: Further COLIBRÍ optical upper limit
  89. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  90. GRB 250814A: GRAWITA TNG NIR observations
  91. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  92. GRB250814A: TRT optical upper limits
  93. GRB 250814C: SVOM/GRM observation of a short burst
  94. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  95. GRB 250813B: SVOM/GRM observation
  96. GRB 250814A: P200/WIRC observations of the afterglow candidate
  97. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  98. GRB 250814A: KAIT optical upper limit
  99. GRB 250814A: Swift-XRT refined Analysis
  100. GRB 240814A: Fermi GBM Observation

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