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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 090406: pseudo-z= 0.91 from prompt emission spectrum
  2. GRB090408, RIMOTS optical upper limits
  3. GRB 090408: Xinglong TNT optical Upper Limit
  4. Swift-BAT trigger 348781: almost certainly not a burst
  5. Fermi GBM Detection of a weak source
  6. GRB 090408B: MASTER II-Kourovka optical observations
  7. GRB 090408: Swift detection of a burst
  8. GRB 090407: GROND upper limits
  9. GRB 090407: VLT observations
  10. GRB 090407: Swift-XRT refined analysis
  11. GRB 090407: Swift UVOT Upper Limits
  12. GRB 090407: Enhanced Swift-XRT position
  13. GRB 090407: Swift-BAT refined analysis
  14. Konus-Wind and Konus-RF observations of GRB 090406
  15. GRB 090407: ROTSE-III Optical Limits
  16. GRB 090407: Swift detection of a burst
  17. GRB 090404: millimeter detection
  18. GRB 090404: nIR observations at Calar Alto
  19. GRB 090405: Fermi GBM Detection
  20. GRB 090403: Fermi GBM detection
  21. GRB 090404: GROND upper limits
  22. GRB 090404: further NOT observations
  23. Swift/UVOT observations of GRB090404
  24. GRB 090404: NOT observations
  25. GRB 090404: optical observations at BOOTES-3 and 1.5-m OSN
  26. GRB 090404: Swift-XRT Team refined analysis
  27. GRB 090404: Xinglong TNT optical Upper Limit
  28. GRB 090404: Swift-BAT refined analysis
  29. GRB 090404: Enhanced Swift-XRT position
  30. Fermi Gamma-ray Burst Monitor trigger 260428446 is not a GRB
  31. GRB 090404: Swift detection of a burst
  32. GRB 090401A: Suzaku WAM observation of the prompt emission
  33. GRB 090401B: Suzaku WAM observation of the prompt emission
  34. Konus-Wind observation of GRB 090401B
  35. GRB 090401B: Xinglong TNT optical Upper Limit
  36. GRB 090401B: VLA radio upper limit
  37. GRB 090401B: Upper limits of MITSuME optical observation
  38. GRB090401B, RIMOTS optical upper limits
  39. GRB 090401B: NOT optical observations
  40. GRB 090328: Fermi-LAT refined analysis
  41. Swift/UVOT observations of GRB090401B
  42. GRB 090401B: AGILE refined analysis
  43. Swift/UVOT observations of GRB090401B
  44. GRB 090401B: Swift XRT Refined Analysis
  45. GRB 090331: Fermi GBM detection
  46. Konus-Wind observation of GRB 090401A
  47. GRB 090401B: Enhanced Swift-XRT position
  48. AGILE Gamma-ray detection of GRB 090401B
  49. GRB 090401B: Swift-BAT refined analysis
  50. Swift/UVOT detection of GRB090401B
  51. GRB 090401B: Swift detection of a burst
  52. GRB 090328B: MASTER-Irkutsk prompt optical short burst observations
  53. GRB 090401, Swift-BAT refined analysis
  54. GRB 090323: Further TLS detections - a break?
  55. GRB 090401: Swift detection of a burst
  56. GRB 090324: Suzaku WAM observation of the prompt emission
  57. GRB 090328: Radio afterglow detection
  58. GRB 090326: Fermi GBM detection
  59. GRB 090328: BOOTES-3 optical observations
  60. GRB 090328: Fermi GBM Spectral Analysis
  61. GRB 090328B: Fermi GBM Detection
  62. GRB 090330: Fermi GBM detection
  63. GRB 090328: GROND Detection of the Optical/NIR Afterglow
  64. GRB 090328: Gemini South Redshift
  65. GRB 090328: Swift XRT refined analysis
  66. GRB090323: Optical observations from NOT
  67. Konus-Wind observation of GRB 090328
  68. GRB 090328: IPN Triangulation
  69. GRB 090328: Swift UVOT observations
  70. GRB 090323: WSRT Radio Detection
  71. GRB 090328: Updated position/optical afterglow candidate
  72. GRB 090328: Possible Swift/XRT detection
  73. Fermi LAT and GBM detections of GRB090328
  74. GRB 090323: Radio afterglow detection
  75. GRB 090323: Additional Lick observations
  76. GRB 090323: TLS detection at 5 days, no break
  77. GRB 090327: Fermi GBM detection
  78. GRB 090323: Faulkes Telescope South Observations
  79. GRB 090320B: MASTER-Net prompt optical observations
  80. GRB 090323: RTT150 optical observations
  81. GRB 090323: Lick observations
  82. GRB 090323: Fermi GBM Spectral Analysis
  83. GRB 090323: Optical observation of xinglong TNT
  84. GRB 090323 TLS detection - still bright
  85. GRB 090323: UVOT Detection of Afterglow
  86. GRB 090323: Swift-XRT refined analysis
  87. Konus-Wind observation of GRB 090323
  88. GRB 090324: SuperAGILE Localization of a Long GRB
  89. GRB 090323 Gemini-South Redshift
  90. GRB 090323: P60 Afterglow Confirmation
  91. GRB 090323: GROND Detection of the Afterglow and Photo-z
  92. SGR J1550-5418: two Fermi GBM triggers on March 22
  93. GRB 090323: Possible XRT Counterpart
  94. IPN triangulation of GRB090323
  95. GRB 090320C: Fermi GBM Detection
  96. Fermi GBM and LAT detections of GRB 090323
  97. GRB 090320B: Fermi GBM detection.
  98. GRB 090319: Fermi GBM detection
  99. GRB 090320A: Fermi GBM detection
  100. Further 15GHz observations of GRB090313

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