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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"

27558 results found.

  1. GRB 090423: Swift detection of a burst
  2. GRB 090422: Liverpool Telescope possible candidate
  3. GRB 090422: Enhanced Swift-XRT position
  4. GRB 090418A: RTT150 optical observations
  5. GRB 090422: Liverpool Telescope observations
  6. GRB 090422: Swift detection of a burst
  7. GRB 090418C: Fermi GBM Detection
  8. GRB 090418A: Swift/UVOT Detection of the Neighbouring Galaxy
  9. Swift-BAT trigger 349718 is not a burst
  10. GRB 090417B: Optical observation
  11. GRB 090418A: optical observations
  12. GRB 090419: Swift/UVOT Observations
  13. GRB 090418A: Swift/UVOT Observations
  14. GRB 090417B: Swift/UVOT Upper Limits
  15. GRB 090417B Correction to the BAT refined analysis position
  16. GRB 090419: Swift-XRT refined analysis
  17. GRB 090419: GROND detection of afterglow candidate
  18. GRB 090418: Optical observations with MITSuME Okayama and Ishigaki 1m telescope
  19. VLA radio detection of GRB 090418
  20. VLA radio upper limit on GRB 090417B
  21. GRB 090419: Enhanced Swift-XRT position
  22. GRB 090418: Swift XRT refined analysis
  23. GRB 090418A: ROTSE-III Refined Analysis
  24. GRB 090419: Swift detection of a burst
  25. GRB 090418B: Detection of a bright burst from Swift-BAT slew data
  26. GRB 090417B: Gemini imaging
  27. GRB 090417B: Galaxy redshift
  28. GRB 090417B: Swift-XRT refined analysis
  29. GRB 090418: Enhanced Swift-XRT position
  30. GRB 090418: PAIRITEL NIR detection
  31. GRB 090418 Lick Redshift
  32. GRB 090418: Swift detection of a burst with optical afterglow
  33. GRB 090417B: Subaru NIR Observations
  34. GRB 090417B: Liverpool Telescope observations
  35. GRB 090417B: MITSuME Okayama optical upper limits
  36. GRB090417B: Xinglong TNT optical upper limit
  37. GRB 090417B: optical observations
  38. GRB090417B: optical observations
  39. GRB 090417B: Swift detection of a burst
  40. GRB 090417: Swift detection of a short burst
  41. GRB 090412: Fermi GBM detection
  42. GRB 090411B: Fermi GBM detection
  43. GRB 090411A: Fermi GBM detection
  44. GRB 090410: Swift detection of a burst
  45. GRB 090409: Fermi GBM detection
  46. Swift-BAT Trigger 348781 is not a GRB
  47. Swift-BAT Trigger 348720 is not a GRB
  48. Swift-BAT trigger 348781: almost certainly not a burst
  49. Fermi GBM Detection of a weak source
  50. GRB 090408: Swift detection of a burst
  51. GRB 090407: GROND upper limits
  52. GRB 090407: Swift-XRT refined analysis
  53. GRB 090407: Swift UVOT Upper Limits
  54. GRB 090407: Enhanced Swift-XRT position
  55. GRB 090407: ROTSE-III Optical Limits
  56. GRB 090407: Swift detection of a burst
  57. GRB 090404: millimeter detection
  58. GRB 090404: nIR observations at Calar Alto
  59. GRB 090405: Fermi GBM Detection
  60. GRB 090403: Fermi GBM detection
  61. GRB 090404: GROND upper limits
  62. GRB 090404: further NOT observations
  63. Swift/UVOT observations of GRB090404
  64. GRB 090404: NOT observations
  65. GRB 090404: optical observations at BOOTES-3 and 1.5-m OSN
  66. GRB 090404: Swift-XRT Team refined analysis
  67. GRB 090404: Enhanced Swift-XRT position
  68. GRB 090404: Swift detection of a burst
  69. GRB 090401B: VLA radio upper limit
  70. GRB 090401B: Upper limits of MITSuME optical observation
  71. GRB 090401B: NOT optical observations
  72. Swift/UVOT observations of GRB090401B
  73. GRB 090401B: AGILE refined analysis
  74. Swift/UVOT observations of GRB090401B
  75. GRB 090401B: Swift XRT Refined Analysis
  76. GRB 090331: Fermi GBM detection
  77. GRB 090401B: Enhanced Swift-XRT position
  78. AGILE Gamma-ray detection of GRB 090401B
  79. Swift/UVOT detection of GRB090401B
  80. GRB 090401B: Swift detection of a burst
  81. GRB 090323: Further TLS detections - a break?
  82. GRB 090401: Swift detection of a burst
  83. GRB 090328: Radio afterglow detection
  84. GRB 090326: Fermi GBM detection
  85. GRB 090328: BOOTES-3 optical observations
  86. GRB 090328B: Fermi GBM Detection
  87. GRB 090330: Fermi GBM detection
  88. GRB 090328: GROND Detection of the Optical/NIR Afterglow
  89. GRB 090328: Gemini South Redshift
  90. GRB 090328: Swift XRT refined analysis
  91. GRB090323: Optical observations from NOT
  92. GRB 090328: Swift UVOT observations
  93. GRB 090323: WSRT Radio Detection
  94. GRB 090328: Updated position/optical afterglow candidate
  95. GRB 090328: Possible Swift/XRT detection
  96. Fermi LAT and GBM detections of GRB090328
  97. GRB 090323: Radio afterglow detection
  98. GRB 090323: Additional Lick observations
  99. GRB 090323: TLS detection at 5 days, no break
  100. GRB 090327: Fermi GBM detection

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