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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"

19670 results found.

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

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