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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. GRB050922C: optical observations
  2. GRB 050922C: Absorption redshift from the Nordic Optical Telescope
  3. GRB 050922C: optical obserations
  4. GRB 050922C: NOT optical observations
  5. GRB 050922A: Analysis of Swift/XRT TOO observation
  6. GRB 050922C: Swift detection of a bright burst
  7. GRB 050922C: ROTSE-IIId Refined Analysis
  8. GRB 050922C: ROTSE-III Detection of Possible Counterpart
  9. GRB 050922B: ROTSE-III Optical Limits
  10. GRB 050922B,optical observation
  11. GRB050922B: Swift-BAT detection of a weak long burst
  12. Possible GRB 050922 detected by INTEGRAL
  13. GRB050918: Possible Swift/XRT detected afterglow
  14. GRB050820B: analysis of the XMM-Newton observation
  15. GRB050916: Swift/UVOT Upper Limits
  16. GRB 050916: Swift-BAT refined analysis
  17. GRB 050918 - A long GRB detected by INTEGRAL
  18. GRB 050915a: Radio Observations
  19. Swift-BAT trigger 155764 is not a GRB
  20. Swift-BAT trigger 155764 is probably not a GRB
  21. Swift trigger 155764: bad XRT centroid
  22. Swift-BAT trigger 155535 is definitely not a GRB
  23. GRB050916 : Swift-XRT refined analysis
  24. GRB 050916: XRT position
  25. GRB 050915b, SMARTS optical/IR observations of the XRT position
  26. GRB 050915B: Swift-BAT refined analysis
  27. GRB 050915B: Swift/UVOT Upper Limits
  28. GRB050916: Swift-BAT detection of a long weak burst
  29. GRB 050915a: IR Transient
  30. GRB 050915B: XRT position
  31. GRB 050915b, SMARTS optical/IR observations
  32. GRB050915B: Swift-BAT detection of a long bright burst
  33. GRB050915: Swift/UVOT upper limits
  34. GRB 050915: KAIT optical limit
  35. GRB 050915: IR Observations
  36. GRB 050915: Swift XRT refined analysis
  37. GRB 050915: Swift-BAT refined analysis
  38. GRB050915: P60 Optical Observations
  39. GRB050915, optical observations
  40. GRB050915: XRT position
  41. GRB 050915: ROTSE-III optical limits
  42. GRB 050915: Swift detection of a GRB
  43. GRB050911: Upper limit on X-ray afterglow
  44. Swift-BAT trigger 155072 ground analysis
  45. Swift-BAT trigger 155072 is probably not a GRB
  46. GRB050914: XRT position probably due to cosmic ray
  47. GRB 050911: LCO limits on a variable source
  48. GRB 050908: DEIMOS spectrum and further analysis
  49. Swift is in normal operation
  50. GRB050911: Swift UVOT followup observations
  51. GRB 050911, optical content of Swift/XRT error box
  52. GRB050911: Swift-XRT position
  53. GRB 050911: LCO observations
  54. GRB 050911, optical observations
  55. GRB 050911: Swift-BAT refined analysis
  56. Later Swift-BAT triggers 154632 and 154633 RETRACTION
  57. GRB 050911: z~0.16 cluster in the field
  58. GRB050911: Swift-BAT detection of a long burst
  59. GRB050908: detection of Swift/UVOT optical counterpart
  60. GRB 050910a: TAROT early optical limits
  61. RBO GRB 050908 observations
  62. WIRO observations in I of GRB 050908
  63. GRB 050906: Possible X-ray Counterpart
  64. GRB 050906: RTT150 optical observations
  65. GRB050908: Swift/UVOT Early upper limits
  66. GRB050908: VLT R-band decay index.
  67. GRB050908 : Swift-XRT refined analysis
  68. GRB 050908: Swift-BAT refined analysis
  69. GRB 050908: Optical observations
  70. Gemini Spectroscopy of GRB 050908
  71. GRB 050908: spectroscopic redshift
  72. GRB 050908: Prompt PROMPT Observations
  73. GRB 050908 : Swift XRT position
  74. GRB 050908: KAIT observations
  75. GRB 050908: P60 Confirmation of Optical Afterglow
  76. GRB 050908: Optical Observations
  77. GRB 050908: Swift detection of a burst
  78. Swift trigger 154073 is not a GRB
  79. GRB 050906: Optical observations at the Very Large Telescope
  80. GRB050904: CrAO optical observations
  81. GRB 050904 BAT refined analysis of complete data set
  82. GRB 050904: Subaru Optical Spectroscopy
  83. GRB 050906: MARGE Optical Limits
  84. GRB 050906: Swift-BAT refined analysis
  85. GRB 050906: Swift XRT upper limit
  86. GRB 050906: Radio Observations
  87. GRB 050904: Keck I-band Imaging
  88. GRB050906: P60 Observations
  89. GRB 050904: more VLT NIR observations
  90. GRB 050904: BOOTES early R-band observation
  91. GRB 050904: Did SWIFT/XRT see the prompt GRB emission ?
  92. GRB 050906: Bright galaxy in BAT error box
  93. GRB 050906: Swift/BAT Detection of a possible burst
  94. GRB 050904: More SOAR
  95. GRB 050904: photometric redshift
  96. GRB 050904: Swift/UVOT observations
  97. GRB 050904: Afterglow Astrometry
  98. GRB 050904: NIR object inside the XRT error box
  99. GRB 050904: early Swift XRT analysis results
  100. GRB 050904: SOAR YJ and PROMPT Ic Observations

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