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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. Konus-Wind observation of GRB 090929B
  2. GRB 090927: Fermi GBM observation
  3. GRB 090929B: Swift-XRT refined analysis
  4. GRB 090926A: Fermi LAT and GBM refined analysis
  5. GRB 090929B: Gemini-N upper limits
  6. GRB 090929B: Skynet/DSO Observations
  7. GRB 090929B: Swift/UVOT Observations
  8. Konus-RF observation of GRB 090929A
  9. GRB 090929B: RAPTOR Discovery of Optical Counterpart
  10. GRB 090929A BAT location of the Fermi GBM burst
  11. Correction: GRB 090929B: Enhanced Swift-XRT position
  12. GRB 090929: Enhanced Swift-XRT position
  13. GRB 090929B: Swift detection of a burst
  14. GRB 090929A: Fermi GBM detection
  15. GRB090926A: Swift-XRT refined analysis
  16. GRB 090927: Faulkes Telescope South Detection of the Optical Afterglow
  17. Konus-Wind and Konus-RF observations of GRB 090926A
  18. GRB 090927: VLT redshift
  19. GRB 090926B: Fermi GBM detection
  20. GRB 090927: Zadko Telescope observations
  21. GRB 090927, Swift-BAT refined analysis of the possibly short burst
  22. Swift/UVOT observations of GRB 090927
  23. GRB 090926A: Skynet/PROMPT Continued Observations
  24. GRB 090927: Swift XRT refined analysis
  25. GRB 090926A: Suzaku WAM observation of the prompt emission
  26. GRB 090927: Enhanced Swift-XRT position
  27. GRB090926B: Swift/UVOT Upper Limits
  28. GRB090926A: Swift/UVOT observations
  29. GRB 090926B: VLT spectroscopy
  30. GRB 090927: Swift/UVOT detection of an optical afterglow
  31. GRB 090927: Swift detection of a short burst
  32. GRB 090926B: optical object in error circle
  33. GRB 090926B: MAXI GSC detection
  34. GRB 090926A: VLT/X-shooter redshift
  35. GRB 090926B: NOT optical observation
  36. GRB 090926B: Swift XRT refined analysis
  37. GRB 090926B: Swift-BAT refined analysis
  38. GRB 090926A: Swift/UVOT detection of an optical afterglow
  39. GRB 090926A: Skynet/PROMPT Discovery of the Optical Afterglow
  40. GRB090926A: UVOT-enhanced XRT position
  41. GRB 090926B: Swift detection of a burst
  42. GRB 090926: Fermi LAT detection
  43. GRB 090926: Fermi GBM detection
  44. GRB 090925: Fermi GBM detection
  45. GRB090904B : IRSF NIR upper limit
  46. GRB090922A: correction to Fermi location
  47. GRB 090922A: Fermi GBM detection
  48. Swift returns to normal operations
  49. GRB 090715B: Skynet/PROMPT Detections
  50. GRB 090726: Skynet/GORT Observations
  51. GRB 090916: Swift-XRT upper limit
  52. GRB 090807: Skynet/DSO Observations
  53. GRB 090915: GROND upper limits
  54. Swift-BAT temporarily off-line for a few days
  55. Short-Duration GRB 090916: Skynet/PROMPT Observations
  56. GRB 090915: SARA detection of afterglow candidate
  57. GRB 090912: optical observation
  58. GRB 090915: Swift/UVOT detection of an optical afterglow candidate
  59. GRB 090702: Skynet/GORT Observations
  60. GRB 090902B: Skynet/PROMPT Observations
  61. GRB 090916, Swift-BAT refined analysis
  62. GRB 090915: Swift-XRT detection of a fading X-ray counterpart
  63. GRB 090916: Swift detection of a short burst
  64. GRB 090915 Swift-BAT detection of a burst in ground analysis
  65. GRB 090827: Confirmation of the X-ray afterglow
  66. GRB 090912: Swift-XRT refined analysis
  67. GRB 090912, Swift-BAT refined analysis
  68. GRB 090912: Swift/UVOT Upper Limits
  69. GRB 090912 optical upper limit
  70. GRB 090912: Enhanced Swift-XRT position
  71. GRB 090912: Swift detection of a burst
  72. GRB 090910: Fermi GBM detection
  73. GRB 090814A: Skynet/DSO & GORT Observations
  74. GRB 090823: Swift XRT confirmation of the X-ray afterglow
  75. GRB 090904B: GROND detection of the optical afterglow
  76. GRB 090831A: Suzaku WAM observation of the prompt emission
  77. GRB 090904A: Swift/UVOT Refined Analysis
  78. GRB 090904B: Swift/UVOT Refined Analysis
  79. GRB 090902B: Suzaku WAM observation of the prompt emission
  80. GRB 090829A: Suzaku WAM observation of the prompt emission
  81. GRB 090904B: Fermi GBM detection
  82. GRB 090904A: Swift-XRT refined analysis
  83. GRB 090904B: Swift XRT Refined Analysis
  84. GRB 090904B: MOA-II Optical observation
  85. GRB 090904A: Enhanced Swift XRT position
  86. GRB 090904B: Swift-BAT refined analysis
  87. GRB 090902B: VLA radio detection
  88. GRB 090904A: Swift-BAT refined analysis
  89. GRB 090904B: Enhanced Swift-XRT position
  90. GRB090904A: Correction to enhanced XRT position
  91. GRB 090904A: Enhanced Swift-XRT position
  92. GRB 090904A: NOT observations
  93. GRB 090902B: WSRT Radio Observation
  94. GRB090904B: REM observations
  95. GRB 090904B: Swift detection of a burst
  96. GRB 090904A: ROTSE-III Optical Limits
  97. GRB 090904: Swift detection of a burst
  98. GRB 090902B: ROTSE-III Detection of Optical Afterglow
  99. GRB 090902B: Swift/UVOT refined analysis
  100. GRB090902B: Swift XRT refined analysis

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