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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"
  1. Fermi GRB 250522B: Global MASTER-Net observations report
  2. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  3. GRB 250522B: Fermi GBM Final Localization
  4. GRB 250521D: SVOM/VT optical observations
  5. GRB 250522A: Fermi GBM Final Real-time Localization
  6. EP#01709176612: Swift-XRT counterpart detection of flaring star
  7. Fermi GRB 250521D: Global MASTER-Net observations report
  8. Fermi trigger No 769533898: Global MASTER-Net observations report
  9. Fermi trigger No 769499303: Global MASTER-Net observations report
  10. GRB 250521D: DDOTI Optical Upper Limit
  11. The EP-WXT trigger 01709176612 is likely a flaring star
  12. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  13. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  14. GRB 250521D: LAST tentative optical counterpart candidate
  15. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  16. GRB 250520A: 10 GHz VLA radio source
  17. GRB 250521B: Swift ToO observations
  18. GRB 250521D: Fermi GBM Final Real-time Localization
  19. GRB 250521C: Fermi GBM Final Localization
  20. GRB 250521A: DDOTI Optical Upper Limit
  21. GRB 250521B: SVOM detection of a burst through offline search
  22. Konus-Wind detection of GRB 250520A (short/hard)
  23. GRB 250520A: VLT/FORS2 Optical Observation
  24. GRB 250502A: Tautenburg observations
  25. GRB 250520A: Swift/UVOT Upper Limits
  26. GRB 250521A: Fermi GBM Final Real-time Localization
  27. Konus-Wind detection of GRB 250516B
  28. IPN triangulation of GRB 250516B
  29. GRB 250520A: J-band observations with WINTER
  30. GRB 250520A: Gemini-South optical observations
  31. GRB 250520A: Swift-XRT refined Analysis
  32. GRB 250520A: REM optical/NIR early observations
  33. GRB 250520B: Fermi GBM Final Real-time Localization
  34. GRB 250520A：SVOM/VT optical candidate
  35. GRB 250520A: COLIBRÍ optical upper limit
  36. GRB 250520A: DDOTI Optical Upper Limit
  37. GRB 250520A: AstroSat CZTI detection of a short burst
  38. GRB 250516B: GRBAlpha detection
  39. GRB 250520A: SVOM/GRM observation
  40. GRB 250520A: Enhanced Swift-XRT position
  41. GRB 250520A: GOTO optical upper limit
  42. GRB 250520A: Prompt enhanced Swift-XRT position
  43. GRB 250520A: Swift detection of a burst
  44. Swift GRB 250520A: Global MASTER-Net observations report
  45. GRB 250516B: Insight-HXMT detection
  46. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  47. GRB 250516A: Swift-BAT refined analysis
  48. GRB 250516A: COLIBRÍ optical upper limit
  49. Konus-Wind detection of GRB 250516A
  50. GRB 250516B: NuSTAR Detection of the Prompt Emission
  51. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  52. Fermi GRB 250516A: Global MASTER-Net observations report
  53. GRB 250515A: Swift-XRT observations
  54. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  55. Fermi Gamma-ray Burst Monitor trigger 769160489/250517320 is not a GRB
  56. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  57. Swift GRB 250516A: Global MASTER-Net observations report
  58. GRB 250515A: 1.6m Mephisto optical detection
  59. GRB 250516A: AstroSat CZTI detection
  60. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  61. GRB 250516A: Fermi GBM Observation
  62. GRB 250516A: Swift-XRT refined Analysis
  63. GRB 250516A: Swift/UVOT Detection
  64. GRB 250515A: Swift ToO observations
  65. GRB 250516B: GECAM-B detection of a bright long burst
  66. GRB 250516A: Enhanced Swift-XRT position
  67. GRB 250516A: Swift detection of a burst
  68. GRB 250516A: Fermi GBM Final Real-time Localization
  69. GRB 250512B / EP250512a: SVOM/GRM analysis
  70. GRB 250515A: GOTO candidate optical counterpart
  71. MAXI GRB250515.65: Global MASTER-Net observations report
  72. GRB 250515A: Fermi GBM Final Localization
  73. GRB 250424A: COLIBRÍ detection of the associated supernova
  74. Konus-Wind detection of GRB 250512B / EP250512a
  75. GRB 250502A: TESS observations
  76. Fermi trigger No 768922089: Global MASTER-Net observations report
  77. GRB 250511A: GECAM-A detection of a short burst
  78. GRB 250509A: Swift-BAT refined analysis
  79. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  80. Fermi GRB 250512A: Global MASTER-Net observations report
  81. Konus-Wind detection of GRB 250506A
  82. EP250512a/GRB 250512B: REM optical/NIR observations
  83. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  84. GRB 250507B: AstroSat CZTI detection
  85. EP250511a: Gemini optical counterpart observation
  86. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  87. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  88. EP250512a: Global MASTER-Net observations report
  89. EP250511a: FTW optical and NIR observations
  90. GRB 250512B/EP250512a: SVOM/VT optical fading
  91. GRB 250512B/EP250512a：SVOM/VT bright optical counterpart
  92. EP250511a: Mephisto optical upper limits
  93. GRB 250507B: GRBAlpha detection
  94. GRB 250506A: GRBAlpha detection
  95. GRB 250512B: SVOM detection of a burst
  96. GRB 250507B: SVOM/GRM observation of a burst
  97. EP250512a: Einstein Probe detection of an X-ray transient
  98. GRB 250512A: Fermi GBM Final Real-time Localization
  99. EP250511a: REM optical/NIR observations
  100. EP250511a: Einstein Probe follow-up obsevation and refined analysis

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