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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. GRB 250521C: Fermi GBM Final Localization
  2. GRB 250521A: DDOTI Optical Upper Limit
  3. GRB 250521B: SVOM detection of a burst through offline search
  4. Konus-Wind detection of GRB 250520A (short/hard)
  5. GRB 250520A: VLT/FORS2 Optical Observation
  6. GRB 250502A: Tautenburg observations
  7. GRB 250520A: Swift/UVOT Upper Limits
  8. GRB 250521A: Fermi GBM Final Real-time Localization
  9. Konus-Wind detection of GRB 250516B
  10. IPN triangulation of GRB 250516B
  11. GRB 250520A: J-band observations with WINTER
  12. GRB 250520A: Gemini-South optical observations
  13. GRB 250520A: Swift-XRT refined Analysis
  14. GRB 250520A: REM optical/NIR early observations
  15. GRB 250520B: Fermi GBM Final Real-time Localization
  16. GRB 250520A:SVOM/VT optical candidate
  17. GRB 250520A: COLIBRÍ optical upper limit
  18. GRB 250520A: DDOTI Optical Upper Limit
  19. GRB 250520A: AstroSat CZTI detection of a short burst
  20. GRB 250516B: GRBAlpha detection
  21. GRB 250520A: SVOM/GRM observation
  22. GRB 250520A: Enhanced Swift-XRT position
  23. GRB 250520A: GOTO optical upper limit
  24. GRB 250520A: Prompt enhanced Swift-XRT position
  25. GRB 250520A: Swift detection of a burst
  26. Swift GRB 250520A: Global MASTER-Net observations report
  27. GRB 250516B: Insight-HXMT detection
  28. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  29. GRB 250516A: Swift-BAT refined analysis
  30. GRB 250516A: COLIBRÍ optical upper limit
  31. Konus-Wind detection of GRB 250516A
  32. GRB 250516B: NuSTAR Detection of the Prompt Emission
  33. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  34. Fermi GRB 250516A: Global MASTER-Net observations report
  35. GRB 250515A: Swift-XRT observations
  36. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  37. Fermi Gamma-ray Burst Monitor trigger 769160489/250517320 is not a GRB
  38. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  39. Swift GRB 250516A: Global MASTER-Net observations report
  40. GRB 250515A: 1.6m Mephisto optical detection
  41. GRB 250516A: AstroSat CZTI detection
  42. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  43. GRB 250516A: Fermi GBM Observation
  44. GRB 250516A: Swift-XRT refined Analysis
  45. GRB 250516A: Swift/UVOT Detection
  46. GRB 250515A: Swift ToO observations
  47. GRB 250516B: GECAM-B detection of a bright long burst
  48. GRB 250516A: Enhanced Swift-XRT position
  49. GRB 250516A: Swift detection of a burst
  50. GRB 250516A: Fermi GBM Final Real-time Localization
  51. GRB 250512B / EP250512a: SVOM/GRM analysis
  52. GRB 250515A: GOTO candidate optical counterpart
  53. MAXI GRB250515.65: Global MASTER-Net observations report
  54. GRB 250515A: Fermi GBM Final Localization
  55. GRB 250424A: COLIBRÍ detection of the associated supernova
  56. Konus-Wind detection of GRB 250512B / EP250512a
  57. GRB 250502A: TESS observations
  58. Fermi trigger No 768922089: Global MASTER-Net observations report
  59. GRB 250511A: GECAM-A detection of a short burst
  60. GRB 250509A: Swift-BAT refined analysis
  61. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  62. Fermi GRB 250512A: Global MASTER-Net observations report
  63. Konus-Wind detection of GRB 250506A
  64. EP250512a/GRB 250512B: REM optical/NIR observations
  65. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  66. GRB 250507B: AstroSat CZTI detection
  67. EP250511a: Gemini optical counterpart observation
  68. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  69. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  70. EP250512a: Global MASTER-Net observations report
  71. EP250511a: FTW optical and NIR observations
  72. GRB 250512B/EP250512a: SVOM/VT optical fading
  73. GRB 250512B/EP250512a:SVOM/VT bright optical counterpart
  74. EP250511a: Mephisto optical upper limits
  75. GRB 250507B: GRBAlpha detection
  76. GRB 250506A: GRBAlpha detection
  77. GRB 250512B: SVOM detection of a burst
  78. GRB 250507B: SVOM/GRM observation of a burst
  79. EP250512a: Einstein Probe detection of an X-ray transient
  80. GRB 250512A: Fermi GBM Final Real-time Localization
  81. EP250511a: REM optical/NIR observations
  82. EP250511a: Einstein Probe follow-up obsevation and refined analysis
  83. EP250511a: SVOM/VT optical candidate comfirmation
  84. EP250511a: Global MASTER-Net observations report
  85. EP250511a: COLIBRÍ optical counterpart candidate
  86. EP250511a: BOOTES-5 optical upper limit
  87. EP250511a: Einstein Probe detection of an X-ray transient
  88. EP250508a: Gemini NIR upper limits
  89. GRB 250510B: Fermi GBM Observation
  90. Fermi GRB 250510C: Global MASTER-Net observations report
  91. Fermi GRB 250510B: Global MASTER-Net observations report
  92. GRB 250510C: Fermi GBM Final Real-time Localization
  93. GRB 250510A: Swift-XRT observations
  94. GRB 250509A: Fermi GBM Observation
  95. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  96. GRB 250510A: follow-up observation with EP-FXT
  97. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  98. GRB 250510B: Fermi GBM Final Localization
  99. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  100. GRB 250509A: Swift-XRT refined Analysis

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