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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 061201: Coincidence with a Galaxy Cluster
  2. GRB 061122: GETS observation
  3. GRB 061121, SMARTS optical/IR observations
  4. GRB 061121: flattening of the decay
  5. INT+WFC observations of GRB 061126
  6. GRB 061126: Possible Jet Break
  7. GRB 061121: Second Epoch ATCA Radio Observations
  8. GRB 061126: RAPTOR Optical Detection During Gamma-Ray Emission
  9. Swift XRT on-board boresight update
  10. GRB 061121: ATCA & WSRT Radio Observations
  11. GRB061121: optical observations
  12. GRB 061126: Early Super-LOTIS Observations
  13. GRB 061126: optical observation
  14. RHESSI Spectrum of GRB061126
  15. GRB 061126: Tautenburg afterglow observations
  16. GRB061126: Optical afterglow observations from MIRO
  17. GRB061126: Optical afterglow observations from MIRO
  18. GRB 061126 : SDSS Pre-Burst Observations
  19. GRB 061126: Swift-XRT refined analysis
  20. GRB 061126: Swift/UVOT Observations
  21. GRB 061126, Swift-BAT refined analysis
  22. GRB 061126: SARA Observations
  23. GRB 061126: Early Detection of the IR Afterglow
  24. GRB 061126: Faulkes Telescope North Optical Observations
  25. GRB 061126: Swift/UVOT Afterglow Detection
  26. GRB 061126: XRT position
  27. GRB 061126: Swift detection of a burst
  28. GRB 061121: MDM Continued Monitoring
  29. GRB 061122: Confirmation of X-ray/Optical Afterglow
  30. GRB 061121: MDM Continuing Optical Decay
  31. GRB061121: optical observations
  32. GRB 061122: Candidate Optical Afterglow
  33. GRB 061121: Ep,i - Eiso correlation
  34. GRB 061121: MDM Optical Decay
  35. GRB061122: Swift/UVOT Optical Observations
  36. GRB 061121: ART detection in Ic
  37. GRB061121: P60 Observations
  38. Radio detection of GRB 061121
  39. GRB061122: Swift-XRT position
  40. Konus-Wind observation of GRB 061122
  41. GRB 061121: MDM Optical Observations
  42. GRB 061121 declared "Burst of Interest" by Swift team
  43. RHESSI Spectrum of GRB061121
  44. Konus-Wind and Konus-A observations of GRB 061121
  45. INTEGRAL results on GRB 061122
  46. Swift-BAT trigger 239987 is not a GRB
  47. GRB 061122A: a long GRB detected by INTEGRAL
  48. GRB 061121: Swift/UVOT Observations
  49. GRB 061121: Swift-XRT Team Refined Analysis
  50. GRB 061121, Swift-BAT refined analysis
  51. GRB061121, optical observation
  52. GRB 061121 : Planned XMM-Newton observation
  53. GRB 061121: Optical observation at the KANATA 1.5m telescope
  54. GRB 061121: Faulkes Telescope North Optical Observation
  55. GRB061121: Spectroscopic Redshift
  56. GRB061121: Keck spectroscopic observations
  57. GRB 061121: ROTSE-III Confirmation of Optical Counterpart
  58. GRB 061121: Swift detection of a bright burst with an optical counterpart
  59. GRB 060605: NIR Observations
  60. GRB 050915B: optical afterglow
  61. GRB 060111B: Swift UVOT Refined Magnitudes
  62. Swift-BAT triggers 238544 and 238546 are not GRBs
  63. GRB061110A: Correction to GCN5817
  64. GRB 061110A: refined R-band analysis
  65. GRB 061110B: NIR Observations
  66. Swift TOO observations of GRB061110A
  67. Swift/UVOT Upper Limits for GRB061110b
  68. Swift/UVOT Upper Limits for GRB061110a
  69. GRB 061110A - VLT tentative redshift
  70. GRB 061110B: Swift XRT refined analysis
  71. GRB 061110B, Swift-BAT refined analysis
  72. GRB 061110B: VLT redshift
  73. GRB061110B: Optical observations at Crni Vrh
  74. GRB 061110B: NOT optical observations
  75. GRB 061110A: Swift XRT refined analysis
  76. GRB 061110B: Swift/XRT position
  77. GRB 061110B : Liverpool Telescope Optical Afterglow Detection
  78. GRB 061110B: Swift-UVOT Initial Observation
  79. GRB 061110A, Swift-BAT refined analysis
  80. GRB 061110B: TAROT Calern observatory optical observations
  81. GRB 061110B: Swift detection of a burst
  82. GRB 061110: NOT observations
  83. GRB 061110: Candidate confirmed
  84. GRB 061110 : Optical afterglow candidate
  85. GRB 061110: ROTSE-III Optical Limits
  86. GRB 061110: Swift detection of a burst
  87. GRB061110A - Optical Non-detection
  88. Swift-BAT Trigger 237821 is a Cosmic Ray Shower event
  89. GRB 061109: optical observation
  90. GRB 061109: TAROT Calern observatory optical observations
  91. GRB 061109: Swift detection of a possible burst
  92. GRB061028: MAGIC telescope GeV observation
  93. GRB 061027: TAROT La Silla observatory optical observations
  94. GRB 061007: Third Epoch ATCA Radio Observations
  95. GRB061019: second epoch CrAO observations
  96. GRB 061028: Swift/XRT Astrometry Correction
  97. GRB 061102: Swift/UVOT Magnitude Upper Limits
  98. GRB 061102, XRT refined analysis
  99. GRB 061004: Further VLT/NTT observations
  100. Swift-BAT Trigger 236481 is a Cosmic Ray Shower event

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