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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"

37514 results found.

  1. GRB 250527B: Tiled Swift observations
  2. GRB 250520A: Gemini-South optical afterglow detection
  3. Fermi trigger No 770058372: Global MASTER-Net observations report
  4. Fermi trigger No 770047117: Global MASTER-Net observations report
  5. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  6. GRB 250527A: Fermi GBM Final Localization
  7. GRB 250314A: CIDER NB1008 upper limit
  8. GRB 250520A: 3 GHz MeerKAT Detection
  9. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  10. Fermi GRB 250523A: Global MASTER-Net observations report
  11. Fermi trigger No 769611916: Global MASTER-Net observations report
  12. GRB 250521A: GRBAlpha detection
  13. GRB 250520A: GRBAlpha detection
  14. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  15. GRB 250523A: Fermi GBM Final Real-time Localization
  16. GRB 250521B: SVOM/VT optical upper limit
  17. Fermi GRB 250522B: Global MASTER-Net observations report
  18. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  19. GRB 250522B: Fermi GBM Final Localization
  20. GRB 250521D: SVOM/VT optical observations
  21. GRB 250522A: Fermi GBM Final Real-time Localization
  22. Fermi GRB 250521D: Global MASTER-Net observations report
  23. Fermi trigger No 769533898: Global MASTER-Net observations report
  24. Fermi trigger No 769499303: Global MASTER-Net observations report
  25. GRB 250521D: DDOTI Optical Upper Limit
  26. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  27. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  28. GRB 250521D: LAST tentative optical counterpart candidate
  29. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  30. GRB 250520A: 10 GHz VLA radio source
  31. GRB 250521B: Swift ToO observations
  32. GRB 250521D: Fermi GBM Final Real-time Localization
  33. GRB 250521C: Fermi GBM Final Localization
  34. GRB 250521A: DDOTI Optical Upper Limit
  35. GRB 250521B: SVOM detection of a burst through offline search
  36. Konus-Wind detection of GRB 250520A (short/hard)
  37. GRB 250520A: VLT/FORS2 Optical Observation
  38. GRB 250502A: Tautenburg observations
  39. GRB 250520A: Swift/UVOT Upper Limits
  40. GRB 250521A: Fermi GBM Final Real-time Localization
  41. Konus-Wind detection of GRB 250516B
  42. IPN triangulation of GRB 250516B
  43. GRB 250520A: J-band observations with WINTER
  44. GRB 250520A: Gemini-South optical observations
  45. GRB 250520A: Swift-XRT refined Analysis
  46. GRB 250520A: REM optical/NIR early observations
  47. GRB 250520B: Fermi GBM Final Real-time Localization
  48. GRB 250520A：SVOM/VT optical candidate
  49. GRB 250520A: COLIBRÍ optical upper limit
  50. GRB 250520A: DDOTI Optical Upper Limit
  51. GRB 250520A: AstroSat CZTI detection of a short burst
  52. GRB 250516B: GRBAlpha detection
  53. GRB 250520A: SVOM/GRM observation
  54. GRB 250520A: Enhanced Swift-XRT position
  55. GRB 250520A: GOTO optical upper limit
  56. GRB 250520A: Prompt enhanced Swift-XRT position
  57. GRB 250520A: Swift detection of a burst
  58. Swift GRB 250520A: Global MASTER-Net observations report
  59. GRB 250516B: Insight-HXMT detection
  60. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  61. GRB 250516A: Swift-BAT refined analysis
  62. GRB 250516A: COLIBRÍ optical upper limit
  63. Konus-Wind detection of GRB 250516A
  64. GRB 250516B: NuSTAR Detection of the Prompt Emission
  65. Fermi GRB 250516A: Global MASTER-Net observations report
  66. GRB 250515A: Swift-XRT observations
  67. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  68. Fermi Gamma-ray Burst Monitor trigger 769160489/250517320 is not a GRB
  69. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  70. Swift GRB 250516A: Global MASTER-Net observations report
  71. GRB 250515A: 1.6m Mephisto optical detection
  72. GRB 250516A: AstroSat CZTI detection
  73. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  74. GRB 250516A: Fermi GBM Observation
  75. GRB 250516A: Swift-XRT refined Analysis
  76. GRB 250516A: Swift/UVOT Detection
  77. GRB 250515A: Swift ToO observations
  78. GRB 250516B: GECAM-B detection of a bright long burst
  79. GRB 250516A: Enhanced Swift-XRT position
  80. GRB 250516A: Swift detection of a burst
  81. GRB 250516A: Fermi GBM Final Real-time Localization
  82. GRB 250512B / EP250512a: SVOM/GRM analysis
  83. GRB 250515A: GOTO candidate optical counterpart
  84. GRB 250515A: Fermi GBM Final Localization
  85. GRB 250424A: COLIBRÍ detection of the associated supernova
  86. Konus-Wind detection of GRB 250512B / EP250512a
  87. GRB 250502A: TESS observations
  88. Fermi trigger No 768922089: Global MASTER-Net observations report
  89. GRB 250511A: GECAM-A detection of a short burst
  90. GRB 250509A: Swift-BAT refined analysis
  91. Fermi GRB 250512A: Global MASTER-Net observations report
  92. Konus-Wind detection of GRB 250506A
  93. EP250512a/GRB 250512B: REM optical/NIR observations
  94. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  95. GRB 250507B: AstroSat CZTI detection
  96. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  97. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  98. GRB 250512B/EP250512a: SVOM/VT optical fading
  99. GRB 250512B/EP250512a：SVOM/VT bright optical counterpart
  100. GRB 250507B: GRBAlpha detection

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