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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. GRB051008: Swift XRT refined analysis
  2. GRB051008 - Swift UVOT upper limits
  3. Konus-Wind observation of GRB 051008
  4. GRB051008: Final refined analysis of the Swift-BAT burst
  5. GRB 051008: R-band upper limit
  6. GRB051008: Refined analysis of the Swift-BAT burst
  7. GRB051008: Radio Observation
  8. GRB 051008: Swift XRT position
  9. GRB 051008, optical observations
  10. GRB 051008: early Swift XRT analysis
  11. GRB 051008: Swift UVOT Candidate
  12. GRB051008: Swift-BAT detection of a bright burst
  13. GRB 051006: P60 Observations
  14. grb test
  15. GRB 051006: XRT refined analysis
  16. Swift-BAT trigger 158700 is a probable Cosmic Ray Shower Event
  17. GRB 051006: optical observations at Sierra Nevada
  18. GRB051006: Refined analysis of the Swift-BAT burst
  19. GRB 051006: XRT position
  20. GRB051006: Swift detection of a burst
  21. GRB 050906, summary of radio observations
  22. Swift-BAT triggers 158261 and 158262 Retraction
  23. GRB051001: Swift UVOT Upper Limits
  24. GRB 050925: Second Epoch WSRT Radio Observations
  25. GRB 051001: Swift XRT refined analysis
  26. GRB 051001, optical observations at Mt. John
  27. GRB 051001: I-band limit
  28. GRB 051001: AAT infra-red observations
  29. GRB 051001: Swift-BAT refined analysis
  30. GRB 051001: Swift Detection of a Burst
  31. GRB 051001: ROTSE-III Optical Limits
  32. GRB050908: optical observations
  33. GRB050922C: optical observation
  34. GRB050922B: optical limit
  35. GRB 050922C: further VLT observations
  36. GRB 050820A: NIR photometry at the TNG
  37. GRB050922C: UVES/VLT high resolution spectroscopy
  38. GRB050925: Swift/XRT limits
  39. GRB/SGR 050925: IR Observations
  40. GRB050922C - Swift UVOT preliminary analysis
  41. GRB 050922C: break in the lightcurve
  42. GRB 050925: WSRT Radio Observations
  43. GRB050925: Swift UVOT upper limits
  44. Refined analysis of the Swift-BAT soft short burst
  45. GRB 050925 : I-band observation at Xinglong observatory
  46. GRB050925: Faulkes Telescope North R-band limit
  47. GRB050925: Swift-BAT detection of a short burst
  48. GRB 050922B: Correction to BAT refined analysis, longer burst
  49. GRB050922C: TNG spectroscopic observations
  50. GRB050922B: refined XRT analysis
  51. Konus-Wind observation of GRB 050922C
  52. GRB 050922C: Refined redshift
  53. GRB050922B: Swift UVOT early upper limits.
  54. GRB OT observation
  55. GRB050922C: observation at MonteBoo
  56. INT 2.5m limit for GRB050922B
  57. GRB 050922B: optical limit
  58. GRB050922C: Optical Observations
  59. GRB 050922C: Swift XRT refined analysis
  60. HETE Fregate observations of GRB 050922C
  61. GRB 050922C: Swift-BAT refined analysis
  62. GRB 050922B: Swift-BAT refined analysis
  63. GRB050922C: optical observations
  64. GRB 050922C: Absorption redshift from the Nordic Optical Telescope
  65. GRB 050922C: optical obserations
  66. GRB 050922C: NOT optical observations
  67. GRB 050922A: Analysis of Swift/XRT TOO observation
  68. GRB 050922C: Swift detection of a bright burst
  69. GRB 050922C: ROTSE-IIId Refined Analysis
  70. GRB 050922C: ROTSE-III Detection of Possible Counterpart
  71. GRB 050922B: ROTSE-III Optical Limits
  72. GRB 050922B,optical observation
  73. GRB050922B: Swift-BAT detection of a weak long burst
  74. Possible GRB 050922 detected by INTEGRAL
  75. GRB050918: Possible Swift/XRT detected afterglow
  76. GRB050820B: analysis of the XMM-Newton observation
  77. GRB050916: Swift/UVOT Upper Limits
  78. GRB 050916: Swift-BAT refined analysis
  79. GRB 050918 - A long GRB detected by INTEGRAL
  80. GRB 050915a: Radio Observations
  81. Swift-BAT trigger 155764 is not a GRB
  82. Swift-BAT trigger 155764 is probably not a GRB
  83. Swift trigger 155764: bad XRT centroid
  84. Swift-BAT trigger 155535 is definitely not a GRB
  85. GRB050916 : Swift-XRT refined analysis
  86. GRB 050916: XRT position
  87. GRB 050915b, SMARTS optical/IR observations of the XRT position
  88. GRB 050915B: Swift-BAT refined analysis
  89. GRB 050915B: Swift/UVOT Upper Limits
  90. GRB050916: Swift-BAT detection of a long weak burst
  91. GRB 050915a: IR Transient
  92. GRB 050915B: XRT position
  93. GRB 050915b, SMARTS optical/IR observations
  94. GRB050915B: Swift-BAT detection of a long bright burst
  95. GRB050915: Swift/UVOT upper limits
  96. GRB 050915: KAIT optical limit
  97. GRB 050915: IR Observations
  98. GRB 050915: Swift XRT refined analysis
  99. GRB 050915: Swift-BAT refined analysis
  100. GRB050915: P60 Optical Observations

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