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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

19663 results found.

  1. GRB 250504A: Enhanced Swift-XRT position
  2. GRB 250504A: Swift detection of a burst
  3. Swift GRB250504.98: Global MASTER-Net observations report
  4. GRB 250502A: Swift/UVOT Follow up
  5. GRB 250502A: Swift-XRT afterglow detection
  6. GRB 250502A: Swift ToO observations
  7. GRB 250430A: Swift-XRT refined Analysis
  8. GRB 250430A: Swift/UVOT Detection
  9. GRB 250430A: Enhanced Swift-XRT position
  10. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  11. GRB 250430A: DDOTI Optical Observations
  12. GRB 250430A: Leavitt Observatory optical upper limit
  13. GRB 250430A: Bassano Bresciano Observatory upper limit
  14. GRB 250430A : MITSuME Akeno optical upper limits
  15. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  16. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  17. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  18. GRB 250430A: AKO Optical Afterglow Detection
  19. GRB 250430A: Swift detection of a burst with optical counterpart
  20. Swift GRB250430.73: Global MASTER-Net observations report
  21. GRB 250427A: Swift/UVOT Detection
  22. EP250427a: EP-FXT follow-up observations
  23. GRB 250427A: Swift-XRT refined Analysis
  24. GRB 250424A: LCO optical observation
  25. GRB 250424A: Swift-BAT refined analysis
  26. GRB 250424A: SVOM/GRM observation of a long burst
  27. GRB 250424A: PRIME near-infrared detection
  28. GRB 250424A: WINTER J-band detection
  29. GRB 250424A: EIRSAT-1 GMOD Detection
  30. GRB 250424A: Swift/UVOT Detection
  31. Konus-Wind detection of GRB 250424A
  32. GRB 250424A: Skynet Optical Observations
  33. GRB 250424A: Kilonova-Catcher optical afterglow detection
  34. GRB 250424A: Swift-XRT refined Analysis
  35. GRB 250424A: Enhanced Swift-XRT position
  36. GRB 250424A: AstroSat CZTI detection of a bright long burst
  37. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  38. GRB 250424A: BlackGEM optical afterglow detection
  39. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  40. GRB 250424A: likely host galaxy
  41. GRB 250424A: DDOTI Afterglow Detection
  42. GRB 250424A: REM optical/NIR afterglow detection
  43. GRB 250424A: Swift detection of a burst with an optical counterpart
  44. Swift GRB 250424A: Global MASTER-Net observations report
  45. Swift GRB 250424A: Global MASTER-Net OT detection
  46. SVOM/sb25042207: XRT observations
  47. EP250421a: NOT optical observations
  48. EP250421a: Swift/XRT counterpart detection
  49. GRB 250419A: Swift/UVOT Follow up
  50. GRB 250419A: LCO optical afterglow multi-band observations
  51. GRB 250419A: Mondy and AbAO Optical Observations
  52. GRB 250419A: Swift-XRT localisation
  53. GRB 250419A: Swift-XRT refined Analysis
  54. EP250416a: Swift/XRT counterpart fading
  55. EP20250416a: Swift/XRT counterpart detection
  56. GRB 250407A: Mondy and AbAO Optical Observations
  57. IceCube-250406A: Swift-XRT observations
  58. IPN triangulation of GRB 250407A
  59. GRB 250407A: LCO detection of a fading optical counterpart
  60. EP250407a: Swift-XRT observations
  61. Konus-Wind detection of GRB 250407A
  62. GRB 250407A: SVOM/GRM observation of a bright long burst
  63. GRB 250407A: EP-WXT afterglow detection
  64. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  65. GRB 250407A: Fermi GBM Detection
  66. GRB 250407A: Swift-XRT afterglow detection
  67. GRB 250407A: Swift ToO observations
  68. GRB 250407A: SRG/ART-XC afterglow detection
  69. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  70. IPN triangulation of GRB 250406B (short/hard)
  71. GRB 250331D: Swift-XRT afterglow detection
  72. GRB 250403A: Montarrenti Observatory optical detection
  73. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  74. GRB 250331C Swift-BAT refined analysis
  75. GRB 250331B Swift-BAT refined analysis
  76. GRB 250330A Swift-BAT refined analysis
  77. EP250321A: J band upper limit by SYSU 80cm telescope
  78. GRB 250403A: Swift/UVOT Detection
  79. GRB 250402A: Swift/UVOT Upper Limits
  80. GRB 250403A: LCO optical counterpart detection
  81. GRB 250402A: EP-FXT afterglow detection
  82. GRB 250403A: Swift-XRT observations
  83. GRB 250402A: Swift-XRT observations
  84. GRB 250225B: VLT host galaxy redshift z = 0.950
  85. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  86. GRB 250329B: Swift/UVOT Upper Limit
  87. GRB 250329A: Swift/UVOT Upper Limit
  88. GRB 250327B: Swift/UVOT Detection
  89. GRB 250327A: Swift/UVOT Upper Limits
  90. GRB250331D: AbAO optical observations
  91. GRB 250331D: Fermi GBM observation
  92. GRB 250331C: Swift/UVOT Upper Limits
  93. GRB 250331B: Swift/UVOT Upper Limits
  94. GRB 250331D: Swift-XRT observations
  95. GRB 250331C: Swift-XRT refined Analysis
  96. GRB 250331B: Swift-XRT refined Analysis
  97. GRB 250331B: Swift-XRT refined Analysis
  98. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  99. GRB 250327A Swift-BAT refined analysis
  100. GRB 250329B: CAHA 2.2m telescope optical limit

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