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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 050730: Preliminary Analysis of MIKE Spectrum
  2. GCN 050801: early Swift XRT analysis results
  3. GRB 050801: Swift-BAT refined analysis
  4. GRB 050801, SMARTS optical/IR afterglow observations
  5. GRB 050801, afterglow observations
  6. GRB 050730, corrected photometry and break?
  7. GRB 050801: ROTSE-III Early Afterglow Break
  8. GRB050801: Swift-BAT detection of a burst
  9. GRB050801: GCN XRT position is incorrect
  10. GRB 050801: ROTSE-III Detection of Possible Counterpart
  11. GRB 050730: XRT refined analysis
  12. Correction to GCN Circ 3476 on GRB050525A
  13. GRB 050730: early TAROT optical observations
  14. GRB 050726: PROMPT Rc Observations
  15. GRB 050730: RTT150 optical observations
  16. Swift/UVOT photometry of GRB050730
  17. GRB 050730, spectra and optical photometry
  18. GRB050730: Refined BAT analysis of the Swift-BAT burst
  19. GRB 050730: Swift XRT afterglow observations
  20. GRB 050730 XMM-Newton observation
  21. GRB 050730: PROMPT VRcIc Observations
  22. GRB050730, afterglow observations
  23. GRB050730: confirmation of redshift
  24. GRB 050730: Redshift Measurement based on Magellan/MIKE Observations
  25. GRB 050730, SMARTS optical/IR afterglow observations
  26. GRB 050730 : Planned XMM-Newton observation
  27. GRB050730: Liverpool Telescope optical observations
  28. GRB 050730, optical candidate
  29. GRB050730: Swift-BAT detection of a weak burst
  30. GRB 050713A: Swift XRT extended light curve
  31. GRB 050709: PROMPT Rc Observations
  32. GRB050713b: Maidanak optical observations
  33. GRB 050724: Secure Host Redshift from Keck
  34. GRB 050724: WHT optical observations
  35. GRB050726: Swift UVOT observations
  36. GRB 050724: Chandra Observations of the X-ray Afterglow
  37. GRB050724: Refined Radio Position
  38. GRB050713: analysis of the XMM-Newton observation
  39. GRB 050724, SMARTS optical/IR afterglow observations
  40. GRB 050726, SMARTS optical/IR observations
  41. Swift-BAT trigger 147918 is not a real GRB
  42. GRB 050727: RTT150 optical observations
  43. GRB050724: VLT observations of the variable source
  44. GRB050727: KAIT optical limit
  45. GRB050709: Second Epoch Chandra Observation
  46. GRB 050726: PROMPT Rc Observations
  47. GRB050709: Second Epoch Chandra Observation
  48. GRB 050724: dust-scattered X-ray halo detected in SWIFT/XRT observation
  49. GRB050724: Further Radio Observations
  50. GRB 050726: early Swift XRT analysis results
  51. GRB050726: Swift-BAT detection of a weak burst
  52. GRB 050724: Optical Variability in Nearby Galaxy
  53. GRB 050724: J-band observations
  54. GRB 050724: GMOS Imaging and Spectroscopy
  55. GRB 050724: SWIFT XRT refined position
  56. RXTE ASM Detection of GRB050724
  57. GRB050724: Radio Observation
  58. GRB 050724: spectroscopy of object in the XRT error circle
  59. GRB 050724: Optical limit
  60. GRB 050724: optical and near-IR observations
  61. GRB 050724: Optical imaging/astrometry
  62. GRB 050724: RTT150 optical observations
  63. GRB 050724: Swift/UVOT Upper Limit
  64. GRB 050724: early Swift XRT analysis results
  65. GRB 050724 : Lulin early R-band monitoring observations
  66. GRB050724: Refined analysis of the Swift-BAT possible short burst
  67. GRB 050724: possible host galaxy in DSS
  68. GRB050724: a short-burst detected by Swift
  69. Swift-BAT trigger 147325 is not due to a real GRB
  70. GRB050723: XRT distributed coordinates are not related to the burst
  71. GRB 050721: early afterglow light curve
  72. GRB 050721A: Swift-BAT refined analysis
  73. Correction to GCN Circ 3474 on GRB050525A
  74. GRB 050721A: Early Swift XRT analysis results
  75. GRB050721A: optical decay
  76. GRB 050721: optical afterglow confirmed
  77. Swift BAT Trigger 146986 is SWIFT J1753.5-0127
  78. GRB 050721a: Optical Observations
  79. GRB050721A: Swift-BAT detection of a weak burst
  80. GRB 050709: Refined Spectral and Temporal Properties
  81. GRB 050717: PROMPT RcIc Observations
  82. GRB050714b: Radio Observation
  83. GRB050712: Radio Observations
  84. GRB 050714a: Refined XRT analysis and afterglow confirmation
  85. GRB050713a: Radio Observation
  86. Swift-BAT trigger 146731 is not a real GRB
  87. GRB 050712, Tautenburg optical afterglow observations
  88. Swift-BAT detection of a possible GRB
  89. GRB 050714B: VLT R-band observations
  90. GRB 050717: Additional LCO observations
  91. GRB050717
  92. GRB 050716; J-band observations
  93. Konus-Wind observation of GRB 050717
  94. GRB 050717: LCO near-IR observations
  95. Swift/UVOT Observations of GRB 050717
  96. GRB 050717: Swift-BAT refined analysis
  97. GRB 050717: Refined XRT analysis.
  98. GRB050712: optical limits
  99. GRB050717: Swift XRT position
  100. Swift detection of GRB 050717

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