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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"

34170 results found.

  1. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  2. GRB 250522B: Fermi GBM Final Localization
  3. GRB 250521D: SVOM/VT optical observations
  4. GRB 250522A: Fermi GBM Final Real-time Localization
  5. Fermi GRB 250521D: Global MASTER-Net observations report
  6. GRB 250521D: DDOTI Optical Upper Limit
  7. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  8. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  9. GRB 250521D: LAST tentative optical counterpart candidate
  10. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  11. GRB 250520A: 10 GHz VLA radio source
  12. GRB 250521B: Swift ToO observations
  13. GRB 250521D: Fermi GBM Final Real-time Localization
  14. GRB 250521C: Fermi GBM Final Localization
  15. GRB 250521A: DDOTI Optical Upper Limit
  16. GRB 250521B: SVOM detection of a burst through offline search
  17. Konus-Wind detection of GRB 250520A (short/hard)
  18. GRB 250520A: VLT/FORS2 Optical Observation
  19. GRB 250502A: Tautenburg observations
  20. GRB 250520A: Swift/UVOT Upper Limits
  21. GRB 250521A: Fermi GBM Final Real-time Localization
  22. Konus-Wind detection of GRB 250516B
  23. IPN triangulation of GRB 250516B
  24. GRB 250520A: J-band observations with WINTER
  25. GRB 250520A: Gemini-South optical observations
  26. GRB 250520A: Swift-XRT refined Analysis
  27. GRB 250520A: REM optical/NIR early observations
  28. GRB 250520B: Fermi GBM Final Real-time Localization
  29. GRB 250520A：SVOM/VT optical candidate
  30. GRB 250520A: COLIBRÍ optical upper limit
  31. GRB 250520A: DDOTI Optical Upper Limit
  32. GRB 250520A: AstroSat CZTI detection of a short burst
  33. GRB 250516B: GRBAlpha detection
  34. GRB 250520A: SVOM/GRM observation
  35. GRB 250520A: Enhanced Swift-XRT position
  36. GRB 250520A: GOTO optical upper limit
  37. GRB 250520A: Prompt enhanced Swift-XRT position
  38. GRB 250520A: Swift detection of a burst
  39. Swift GRB 250520A: Global MASTER-Net observations report
  40. GRB 250516B: Insight-HXMT detection
  41. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  42. GRB 250516A: Swift-BAT refined analysis
  43. GRB 250516A: COLIBRÍ optical upper limit
  44. Konus-Wind detection of GRB 250516A
  45. GRB 250516B: NuSTAR Detection of the Prompt Emission
  46. Fermi GRB 250516A: Global MASTER-Net observations report
  47. GRB 250515A: Swift-XRT observations
  48. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  49. Fermi Gamma-ray Burst Monitor trigger 769160489/250517320 is not a GRB
  50. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  51. Swift GRB 250516A: Global MASTER-Net observations report
  52. GRB 250515A: 1.6m Mephisto optical detection
  53. GRB 250516A: AstroSat CZTI detection
  54. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  55. GRB 250516A: Fermi GBM Observation
  56. GRB 250516A: Swift-XRT refined Analysis
  57. GRB 250516A: Swift/UVOT Detection
  58. GRB 250515A: Swift ToO observations
  59. GRB 250516B: GECAM-B detection of a bright long burst
  60. GRB 250516A: Enhanced Swift-XRT position
  61. GRB 250516A: Swift detection of a burst
  62. GRB 250516A: Fermi GBM Final Real-time Localization
  63. GRB 250512B / EP250512a: SVOM/GRM analysis
  64. GRB 250515A: GOTO candidate optical counterpart
  65. GRB 250515A: Fermi GBM Final Localization
  66. GRB 250424A: COLIBRÍ detection of the associated supernova
  67. Konus-Wind detection of GRB 250512B / EP250512a
  68. GRB 250502A: TESS observations
  69. GRB 250511A: GECAM-A detection of a short burst
  70. GRB 250509A: Swift-BAT refined analysis
  71. Fermi GRB 250512A: Global MASTER-Net observations report
  72. Konus-Wind detection of GRB 250506A
  73. EP250512a/GRB 250512B: REM optical/NIR observations
  74. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  75. GRB 250507B: AstroSat CZTI detection
  76. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  77. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  78. GRB 250512B/EP250512a: SVOM/VT optical fading
  79. GRB 250512B/EP250512a：SVOM/VT bright optical counterpart
  80. GRB 250507B: GRBAlpha detection
  81. GRB 250506A: GRBAlpha detection
  82. GRB 250512B: SVOM detection of a burst
  83. GRB 250507B: SVOM/GRM observation of a burst
  84. GRB 250512A: Fermi GBM Final Real-time Localization
  85. EP250511a: REM optical/NIR observations
  86. GRB 250510B: Fermi GBM Observation
  87. Fermi GRB 250510C: Global MASTER-Net observations report
  88. Fermi GRB 250510B: Global MASTER-Net observations report
  89. GRB 250510C: Fermi GBM Final Real-time Localization
  90. GRB 250510A: Swift-XRT observations
  91. GRB 250509A: Fermi GBM Observation
  92. GRB 250510A: follow-up observation with EP-FXT
  93. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  94. GRB 250510B: Fermi GBM Final Localization
  95. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  96. GRB 250509A: Swift-XRT refined Analysis
  97. GRB 250510A: SVOM possible detection of a burst
  98. GRB 250507A: J-band observations with WINTER (duplicate submission)
  99. GRB 250507A: J-band observations with WINTER
  100. GRB 250509A: Enhanced Swift-XRT position

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