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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"

37639 results found.

  1. GRB 250530C: Swift-XRT refined Analysis
  2. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  3. Swift GRB 250530C: Global MASTER-Net observations report
  4. GRB 250530C: Enhanced Swift-XRT position
  5. GRB 250530C: Swift detection of a burst
  6. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  7. GRB 250530A: EP-FXT counterpart detection
  8. GRB 250530A: SVOM/VT optical upper limit
  9. Fermi Gamma-ray Burst Monitor trigger 770296643/250530470 is not a GRB
  10. GRB 250530B: Fermi GBM Final Real-time Localization
  11. GRB 250530A: Swift-XRT counterpart detection
  12. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  13. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  14. GRB 250530A: SVOM detection of a burst
  15. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  16. GRB 250527C: Swift/UVOT Upper Limits
  17. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  18. GRB 250529B: Fermi GBM Final Real-time Localization
  19. GRB 250527B: Swift-XRT observations
  20. GRB 250529A: Fermi GBM Final Real-time Localization
  21. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  22. GRB 250520A: Swift-BAT refined analysis
  23. GRB 250527C: Swift ToO observations
  24. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  25. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  26. GRB 250527B: Tiled Swift observations
  27. GRB 250520A: Gemini-South optical afterglow detection
  28. Fermi trigger No 770058372: Global MASTER-Net observations report
  29. Fermi trigger No 770047117: Global MASTER-Net observations report
  30. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  31. GRB 250527A: Fermi GBM Final Localization
  32. GRB 250314A: CIDER NB1008 upper limit
  33. GRB 250520A: 3 GHz MeerKAT Detection
  34. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  35. Fermi GRB 250523A: Global MASTER-Net observations report
  36. Fermi trigger No 769611916: Global MASTER-Net observations report
  37. GRB 250521A: GRBAlpha detection
  38. GRB 250520A: GRBAlpha detection
  39. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  40. GRB 250523A: Fermi GBM Final Real-time Localization
  41. GRB 250521B: SVOM/VT optical upper limit
  42. Fermi GRB 250522B: Global MASTER-Net observations report
  43. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  44. GRB 250522B: Fermi GBM Final Localization
  45. GRB 250521D: SVOM/VT optical observations
  46. GRB 250522A: Fermi GBM Final Real-time Localization
  47. Fermi GRB 250521D: Global MASTER-Net observations report
  48. Fermi trigger No 769533898: Global MASTER-Net observations report
  49. Fermi trigger No 769499303: Global MASTER-Net observations report
  50. GRB 250521D: DDOTI Optical Upper Limit
  51. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  52. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  53. GRB 250521D: LAST tentative optical counterpart candidate
  54. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  55. GRB 250520A: 10 GHz VLA radio source
  56. GRB 250521B: Swift ToO observations
  57. GRB 250521D: Fermi GBM Final Real-time Localization
  58. GRB 250521C: Fermi GBM Final Localization
  59. GRB 250521A: DDOTI Optical Upper Limit
  60. GRB 250521B: SVOM detection of a burst through offline search
  61. Konus-Wind detection of GRB 250520A (short/hard)
  62. GRB 250520A: VLT/FORS2 Optical Observation
  63. GRB 250502A: Tautenburg observations
  64. GRB 250520A: Swift/UVOT Upper Limits
  65. GRB 250521A: Fermi GBM Final Real-time Localization
  66. Konus-Wind detection of GRB 250516B
  67. IPN triangulation of GRB 250516B
  68. GRB 250520A: J-band observations with WINTER
  69. GRB 250520A: Gemini-South optical observations
  70. GRB 250520A: Swift-XRT refined Analysis
  71. GRB 250520A: REM optical/NIR early observations
  72. GRB 250520B: Fermi GBM Final Real-time Localization
  73. GRB 250520A：SVOM/VT optical candidate
  74. GRB 250520A: COLIBRÍ optical upper limit
  75. GRB 250520A: DDOTI Optical Upper Limit
  76. GRB 250520A: AstroSat CZTI detection of a short burst
  77. GRB 250516B: GRBAlpha detection
  78. GRB 250520A: SVOM/GRM observation
  79. GRB 250520A: Enhanced Swift-XRT position
  80. GRB 250520A: GOTO optical upper limit
  81. GRB 250520A: Prompt enhanced Swift-XRT position
  82. GRB 250520A: Swift detection of a burst
  83. Swift GRB 250520A: Global MASTER-Net observations report
  84. GRB 250516B: Insight-HXMT detection
  85. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  86. GRB 250516A: Swift-BAT refined analysis
  87. GRB 250516A: COLIBRÍ optical upper limit
  88. Konus-Wind detection of GRB 250516A
  89. GRB 250516B: NuSTAR Detection of the Prompt Emission
  90. Fermi GRB 250516A: Global MASTER-Net observations report
  91. GRB 250515A: Swift-XRT observations
  92. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  93. Fermi Gamma-ray Burst Monitor trigger 769160489/250517320 is not a GRB
  94. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  95. Swift GRB 250516A: Global MASTER-Net observations report
  96. GRB 250515A: 1.6m Mephisto optical detection
  97. GRB 250516A: AstroSat CZTI detection
  98. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  99. GRB 250516A: Fermi GBM Observation
  100. GRB 250516A: Swift-XRT refined Analysis

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