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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. GRB 091120: MAXI GSC detection
  2. GRB 091120: Fermi GBM observation
  3. GRB 091117A: Suzaku WAM observation of the prompt emission
  4. GRB 091117: TNG optical observations
  5. GRB 091117A: Swift/UVOT followup observations
  6. GRB 091117: 2nd epoch of Magellan optical observations
  7. GRB 091117: VLA radio observations
  8. GRB 091117: Swift-XRT observations
  9. GRB 091117 BAT refined analysis
  10. GRB 091117: Evidence for Variability of XRT Source #1
  11. GRB091117: Gemini South Observations
  12. GRB 091117: Swift XRT refined analysis
  13. GRB 091117: Gemini-North spectroscopy of DSS galaxy
  14. Konus-Wind observations of GRB 091117A
  15. GRB 091117: Magellan optical observations
  16. GRB 091117: XRT source coincident with a DSS galaxy
  17. GRB 091117: OSN I-band observations
  18. GRB 091117A Detected in ground analysis of BAT data and IPN triangulation
  19. GRB 091112: Suzaku WAM observation of the prompt emission
  20. GRB 091102A: Suzaku WAM observation of the prompt emission
  21. GRB 091109B: Suzaku WAM observation of the prompt emission
  22. GRB091111: Swift XRT refined analysis
  23. Konus-Wind and Konus-RF observations of GRB 091031
  24. GRB 091112: Swift-BAT refined analysis
  25. GRB 091112: Fermi GBM observation
  26. GRB 091031: Fermi LAT detection of a faint burst
  27. GRB 091112: Swift detection of a possible burst
  28. GRB 091111: BOOTES-3 contemporaneous imaging
  29. GRB 091111: BOOTES-3 observations
  30. GRB 091111: a faint long GRB detected with INTEGRAL
  31. GRB 091109A: GROND and VLT observations
  32. GRB 091109B: Swift/UVOT Upper Limits
  33. GRB 091109B: VLT afterglow confirmation
  34. GRB 091109B: Swift-XRT Team refined analysis
  35. GRB 091109B: VLT observations
  36. GRB 091109b: Magellan Observations
  37. GRB 091109B: Swift-BAT refined analysis
  38. GRB 091109B: Enhanced Swift-XRT position
  39. GRB 091109B: Optical limits from Watcher
  40. GRB 091109B: ROTSE-III Optical Limits
  41. GRB 091109B: Swift detection of a short burst
  42. GRB091109: Correction to GCN 10139
  43. GRB 091030: Fermi GBM detection
  44. GRB 091109: Swift-XRT refined analysis
  45. GRB 091109: BOOTES-3 observations
  46. GRB 091109: Swift/UVOT observations
  47. GRB 091109: Faulkes Telescope South observations
  48. GRB 091109: Swift-BAT refined analysis
  49. GRB 091109: Enhanced Swift-XRT position
  50. GRB091109: REM detection of the NIR afterglow
  51. GRB 091109: Swift detection of a burst with optical afterglow
  52. GRB 091029: Observations from Stardome Observatory
  53. GRB 091104: Swift-BAT refined analysis
  54. GRB 091104: Swift XRT Refined Analysis
  55. GRB 091104: Swift/UVOT Upper Limits
  56. GRB091026 : IRSF NIR upper limit
  57. GRB091102 : MOA optical upper limit
  58. GRB 091104: Enhanced Swift-XRT position
  59. GRB 091104: Swift detection of a burst
  60. GRB 091102: LABOCA/APEX submm observations
  61. Fermi LAT Upper Limits on GRB 091010
  62. GRB 091102 : Faulkes Telescope South Upper Limits
  63. GRB 091102A: Fermi GBM observation
  64. GRB 091102: Swift-XRT refined analysis
  65. GRB 091102: Swift/UVOT Upper Limits
  66. GRB 091102: GROND Upper Limits
  67. GRB 091102: BOOTES-3 observations
  68. GRB 091102: Swift-BAT refined analysis
  69. GRB 091102: Swift/XRT localization
  70. GRB 091102: ROTSE-III Optical Limits
  71. GRB 091102: Swift/UVOT Finding Chart Observation
  72. GRB 091102: Swift detection of a burst
  73. GRB 091024: optical observations
  74. GRB 091031: Fermi GBM detection
  75. GRB 091024: Fermi LAT upper limits
  76. GRB 090926a, SMARTS optical/IR afterglow observations
  77. GRB 091018: Skynet/PROMPT Observations of Possible Host Galaxy
  78. GRB 091029, SMARTS optical/IR afterglow observations
  79. GRB 091018, SMARTS optical/IR afterglow observations
  80. GRB 090920: Skynet/DSO Detection
  81. GRB091029: Swift/UVOT observations
  82. GRB 091029: Skynet/PROMPT Continued Observations of Fading
  83. GRB 091029: Swift XRT refined analysis
  84. Fermi Gamma-ray Burst Monitor trigger 091028818 is not a GRB
  85. GRB 091029: BOOTES-3 observations
  86. GRB 091029: Swift-BAT refined analysis
  87. GRB 091029: Enhanced Swift-XRT position
  88. GRB091024 optical observations
  89. GRB 091029: Gemini-South Redshift
  90. GRB 091029: Skynet/PROMPT Observations of Peak and Fading
  91. GRB 091029: GROND Detection of the Optical/NIR Afterglow
  92. GRB 091029: Swift detection of a burst with an optical counterpart
  93. A mistake in testing a new function in Swift
  94. GRB 091020: Fermi GBM observation
  95. GRB 091026: Suzaku WAM observation of the prompt emission
  96. GRB 091024: Keck/LRIS Spectroscopy
  97. GRB 091024: YNAO-GMG observations
  98. GRB 091026: GROND Upper Limits
  99. GRB 091020: Late TLS detection
  100. GRB 091026: Swift-BAT refined analysis

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