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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. Fermi LAT Upper Limits on GRB 091010
  2. GRB 091102 : Faulkes Telescope South Upper Limits
  3. GRB 091102A: Fermi GBM observation
  4. GRB 091102: Swift-XRT refined analysis
  5. GRB 091102: Swift/UVOT Upper Limits
  6. GRB 091102: GROND Upper Limits
  7. GRB 091102: BOOTES-3 observations
  8. GRB 091102: Swift-BAT refined analysis
  9. GRB 091102: Swift/XRT localization
  10. GRB 091102: ROTSE-III Optical Limits
  11. GRB 091102: Swift/UVOT Finding Chart Observation
  12. GRB 091102: Swift detection of a burst
  13. GRB 091024: optical observations
  14. GRB 091031: Fermi GBM detection
  15. GRB 091024: Fermi LAT upper limits
  16. GRB 090926a, SMARTS optical/IR afterglow observations
  17. GRB 091018: Skynet/PROMPT Observations of Possible Host Galaxy
  18. GRB 091029, SMARTS optical/IR afterglow observations
  19. GRB 091018, SMARTS optical/IR afterglow observations
  20. GRB 090920: Skynet/DSO Detection
  21. GRB091029: Swift/UVOT observations
  22. GRB 091029: Skynet/PROMPT Continued Observations of Fading
  23. GRB 091029: Swift XRT refined analysis
  24. Fermi Gamma-ray Burst Monitor trigger 091028818 is not a GRB
  25. GRB 091029: BOOTES-3 observations
  26. GRB 091029: Swift-BAT refined analysis
  27. GRB 091029: Enhanced Swift-XRT position
  28. GRB091024 optical observations
  29. GRB 091029: Gemini-South Redshift
  30. GRB 091029: Skynet/PROMPT Observations of Peak and Fading
  31. GRB 091029: GROND Detection of the Optical/NIR Afterglow
  32. GRB 091029: Swift detection of a burst with an optical counterpart
  33. A mistake in testing a new function in Swift
  34. GRB 091020: Fermi GBM observation
  35. GRB 091026: Suzaku WAM observation of the prompt emission
  36. GRB 091024: Keck/LRIS Spectroscopy
  37. GRB 091024: YNAO-GMG observations
  38. GRB 091026: GROND Upper Limits
  39. GRB 091020: Late TLS detection
  40. GRB 091026: Swift-BAT refined analysis
  41. Radio afterglow detection from GRB 091020
  42. GRB 091026: Swift/UVOT Upper Limits
  43. GRB 091024: Burst was outside the Swift-BAT FOV after T0(BAT)+460sec
  44. GRB 091026: Swift-XRT refined analysis
  45. GRB 091026: Enhanced Swift-XRT position
  46. Konus-Wind and Konus-RF observations of GRB 091024
  47. GRB 091026: Updated Swift-XRT position
  48. GRB 091026: Swift detection of a Gamma Ray Burst
  49. GRB 091020 : Xinglong TNT upper limit
  50. Swift-BAT Triggers 373776-373778 are not real
  51. GRB091024 Swift/UVOT Upper Limits
  52. GRB 091024: TLS Upper Limit
  53. GRB 091020: Early TLS Multicolor detections, red afterglow
  54. GRB 091024: KAIT optical afterglow observations
  55. GRB 091024: Super-LOTIS early observations
  56. GRB091024: VRcIc Afterglow Observations
  57. GRB 091024: Swift-BAT refined analysis
  58. Swift-BAT Triggers 373679-373684 are not real
  59. GRB 091024: Fermi GBM Observations
  60. GRB 091024: Swift-XRT team refined analysis
  61. Swift-BAT trigger 373691 is a galactic bulge transient
  62. GRB 091024: Xinglong TNT optical observation
  63. GRB 091024 : Faulkes Telescope North - Afterglow Confirmation
  64. GRB 091024 Gemini-North redshift
  65. GRB 091024: GRAS004 optical observations
  66. GRB 091024: Faulkes Telescope North Afterglow Candidate
  67. GRB 091024: Swift detection of a burst
  68. GRB 091018: Skynet/PROMPT Continued Observations of Fading
  69. GRB 091020: Additional Lick observations
  70. Konus-Wind observations of GRB 091020 (correction to GCN 10057)
  71. GRB 091020: Lick observations
  72. Konus-Wind observations of GRB 091010
  73. GRB 091020: Swift-XRT refined analysis
  74. GRB 091018: Swift XRT refined analysis
  75. GRB091020 Swift/UVOT observations
  76. GRB 091020: NOT spectroscopic redshift
  77. GRB 091020: MASTER optical transient polarimetry
  78. GRB 091020, Swift-BAT refined analysis
  79. GRB 091020: Enhanced Swift-XRT position
  80. GRB 090926A: Late-time Gemini South Observations and Possible Jet Break
  81. GRB 091020: Swift detection of a burst with an optical afterglow
  82. GRB 091018: miniTAO/ANIR Observations
  83. GRB 091018: Skynet/PROMPT Observations of Fading
  84. Konus-RF observation of GRB 091018
  85. GRB 091018 : Faulkes Telescope South Observations
  86. GRB 091018: BOOTES-3 observations
  87. GRB 091018: VLT/X-shooter spectra
  88. GRB091018: Swift/UVOT observations
  89. GRB 091018: Swift-BAT refined analysis
  90. GRB 091018: GROND observations
  91. GRB091018: Magellan Echellette Observations
  92. GRB 091018: Enhanced Swift-XRT position
  93. GRB 091018: ROTSE-III Detection of Optical Counterpart
  94. GRB 091015: Skynet/PROMPT Observations
  95. GRB 091018: Swift detection of a burst with optical afterglow
  96. Fwd: GRB 091003: Possible Supernova Component Retraction
  97. GRB 091003: Possible Supernova Component
  98. GRB 091003: Gemini-N redshift of possible host galaxy
  99. GRB 091010: optical obsevation
  100. GRB 091015: RTT150 optical observations

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