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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"

32796 results found.

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

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