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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. Swift-BAT trigger 155072 ground analysis
  2. Swift-BAT trigger 155072 is probably not a GRB
  3. GRB050914: XRT position probably due to cosmic ray
  4. GRB 050911: LCO limits on a variable source
  5. GRB 050908: DEIMOS spectrum and further analysis
  6. Swift is in normal operation
  7. GRB050911: Swift UVOT followup observations
  8. GRB 050911, optical content of Swift/XRT error box
  9. GRB050911: Swift-XRT position
  10. GRB 050911: LCO observations
  11. GRB 050911, optical observations
  12. GRB 050911: Swift-BAT refined analysis
  13. Later Swift-BAT triggers 154632 and 154633 RETRACTION
  14. GRB 050911: z~0.16 cluster in the field
  15. GRB050911: Swift-BAT detection of a long burst
  16. GRB050908: detection of Swift/UVOT optical counterpart
  17. GRB 050910a: TAROT early optical limits
  18. RBO GRB 050908 observations
  19. WIRO observations in I of GRB 050908
  20. GRB 050906: Possible X-ray Counterpart
  21. GRB 050906: RTT150 optical observations
  22. GRB050908: Swift/UVOT Early upper limits
  23. GRB050908: VLT R-band decay index.
  24. GRB050908 : Swift-XRT refined analysis
  25. GRB 050908: Swift-BAT refined analysis
  26. GRB 050908: Optical observations
  27. Gemini Spectroscopy of GRB 050908
  28. GRB 050908: spectroscopic redshift
  29. GRB 050908: Prompt PROMPT Observations
  30. GRB 050908 : Swift XRT position
  31. GRB 050908: KAIT observations
  32. GRB 050908: P60 Confirmation of Optical Afterglow
  33. GRB 050908: Optical Observations
  34. GRB 050908: Swift detection of a burst
  35. Swift trigger 154073 is not a GRB
  36. GRB 050906: Optical observations at the Very Large Telescope
  37. GRB050904: CrAO optical observations
  38. GRB 050904 BAT refined analysis of complete data set
  39. GRB 050904: Subaru Optical Spectroscopy
  40. GRB 050906: MARGE Optical Limits
  41. GRB 050906: Swift-BAT refined analysis
  42. GRB 050906: Swift XRT upper limit
  43. GRB 050906: Radio Observations
  44. GRB 050904: Keck I-band Imaging
  45. GRB050906: P60 Observations
  46. GRB 050904: more VLT NIR observations
  47. GRB 050904: BOOTES early R-band observation
  48. GRB 050904: Did SWIFT/XRT see the prompt GRB emission ?
  49. GRB 050906: Bright galaxy in BAT error box
  50. GRB 050906: Swift/BAT Detection of a possible burst
  51. GRB 050904: More SOAR
  52. GRB 050904: photometric redshift
  53. GRB 050904: Swift/UVOT observations
  54. GRB 050904: Afterglow Astrometry
  55. GRB 050904: NIR object inside the XRT error box
  56. GRB 050904: early Swift XRT analysis results
  57. GRB 050904: SOAR YJ and PROMPT Ic Observations
  58. GRB 050904: BAT refined analysis of partial data set
  59. GRB 050904: TAROT optical measurements
  60. GRB050904: Optical Observations
  61. GRB 050904: Environmental Constraints
  62. GRB 050904: Possible High-Redshift GRB
  63. GRB 050904: SOAR/PROMPT Observations
  64. GRB050904: P60 Observations
  65. GRB 050904: TAROT optical limits
  66. GRB050904: Swift-BAT detection of a probable burst
  67. Swift-BAT triggers 153461-153465 are not GRBs
  68. Retraction of Swift-BAT trigger #153355
  69. GRB 050824: MDM Observations
  70. GRB 050827: Swift XRT preliminary analysis results
  71. IBAS Alerts 2641 and 2642: not a real GRB
  72. Swift Trigger #152652 is not a GRB
  73. GRB 050827 : OSN 1.5m optical observations
  74. GRB 050827: P200 NIR Observations
  75. GRB050827: Swift/UVOT upper limits
  76. GRB 050827: Optical Limit
  77. GRB 050827: XRT possible afterglow detection
  78. GRB 050826 : Lulin R band observation
  79. GRB050824: Maidanak optical limits
  80. GRB050820A: RTT150 optical observations
  81. GRB050827: RTT150 optical observations
  82. GRB 050827: Swift-BAT refined analysis
  83. GRB050827: Swift-BAT detection of a burst
  84. Subaru Observations of GRB050724
  85. GRB 050826: Optical Candidate
  86. GRB050824, HETE-2 Observation
  87. GRB 050826: Swift XRT preliminary analysis results
  88. GRB 050826: BAT refined analysis
  89. GRB050826: Swift/UVOT early upper limits
  90. GRB050824: First 2 hours of power low optical decay?
  91. GRB 050826: Swift XRT position
  92. GRB050826: Swift-BAT detection of a long burst
  93. GRB050824: MASTER final analysis of the OT observations
  94. Possible GRB050825:MASTER optical observations
  95. Swift-BAT trigger 152038 is definitely not a GRB
  96. GRB050824: CORRECTION to UVOT observing times
  97. Swift-BAT trigger 152038 is probably not a GRB
  98. GRB050824: Swift/UVOT detection of fading afterglow
  99. GRB050824: decay of the XRT light curve and updated X-ray spectrum
  100. GRB050824, I-band imaging

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