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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 050803: RTT150 optical observations
  2. GRB050801: Radio Observation
  3. GRB050730: Radio Detection
  4. GRB050803: CrAO optical observations, possible OT candidate
  5. GRB050803: Optical/UV Upper Limits from Swift-UVOT
  6. GRB 050803: Keck Observations
  7. GRB 050803: Swift-BAT refined analysis
  8. GRB 050802.422: Fading of the afterglow and detection of the host
  9. GRB050803: MASTER further analys
  10. GRB 050803, optical observations
  11. GRB 050803: Magellan Observations
  12. GRB 050803: early Swift XRT analysis results
  13. GRB 050803: TAROT optical limits
  14. GRB050803: MASTER optical observations
  15. GRB050802: Tentative absorption redshift
  16. GRB050803: Swift-BAT detection of a very long burst
  17. GCN GRB observation 050713A
  18. GRB050730: FORS1 and UVES/VLT low- and high-resolution spectroscopy
  19. GRB 050802: Swift/UVOT optical and UV detections
  20. GRB050802: CrAO optical observations
  21. GRB050801: Unchanged decay slope
  22. GRB050802 radio non-detection
  23. GRB 050730: OHP optical observations
  24. GRB 050802: early Swift XRT analysis results
  25. GRB 050802: Swift/UVOT observations
  26. GRB 050802 : Lulin Optical follow-up observation
  27. GRB 050802: Swift-BAT refined analysis
  28. GRB050801: Optical photometry and decay index
  29. GRB 050802: XRT position
  30. GRB 050802: Swift Gamma-ray Burst
  31. GRB050801: Swift/UVOT Optical and UV detections
  32. GRB 050730: Preliminary Analysis of MIKE Spectrum
  33. GCN 050801: early Swift XRT analysis results
  34. GRB 050801: Swift-BAT refined analysis
  35. GRB 050801, SMARTS optical/IR afterglow observations
  36. GRB 050801, afterglow observations
  37. GRB 050730, corrected photometry and break?
  38. GRB 050801: ROTSE-III Early Afterglow Break
  39. GRB050801: Swift-BAT detection of a burst
  40. GRB050801: GCN XRT position is incorrect
  41. GRB 050801: ROTSE-III Detection of Possible Counterpart
  42. GRB 050730: XRT refined analysis
  43. Correction to GCN Circ 3476 on GRB050525A
  44. GRB 050730: early TAROT optical observations
  45. GRB 050726: PROMPT Rc Observations
  46. GRB 050730: RTT150 optical observations
  47. Swift/UVOT photometry of GRB050730
  48. GRB 050730, spectra and optical photometry
  49. GRB050730: Refined BAT analysis of the Swift-BAT burst
  50. GRB 050730: Swift XRT afterglow observations
  51. GRB 050730 XMM-Newton observation
  52. GRB 050730: PROMPT VRcIc Observations
  53. GRB050730, afterglow observations
  54. GRB050730: confirmation of redshift
  55. GRB 050730: Redshift Measurement based on Magellan/MIKE Observations
  56. GRB 050730, SMARTS optical/IR afterglow observations
  57. GRB 050730 : Planned XMM-Newton observation
  58. GRB050730: Liverpool Telescope optical observations
  59. GRB 050730, optical candidate
  60. GRB050730: Swift-BAT detection of a weak burst
  61. GRB 050713A: Swift XRT extended light curve
  62. GRB 050709: PROMPT Rc Observations
  63. GRB050713b: Maidanak optical observations
  64. GRB 050724: Secure Host Redshift from Keck
  65. GRB 050724: WHT optical observations
  66. GRB050726: Swift UVOT observations
  67. GRB 050724: Chandra Observations of the X-ray Afterglow
  68. GRB050724: Refined Radio Position
  69. GRB050713: analysis of the XMM-Newton observation
  70. GRB 050724, SMARTS optical/IR afterglow observations
  71. GRB 050726, SMARTS optical/IR observations
  72. Swift-BAT trigger 147918 is not a real GRB
  73. GRB 050727: RTT150 optical observations
  74. GRB050724: VLT observations of the variable source
  75. GRB050727: KAIT optical limit
  76. GRB050709: Second Epoch Chandra Observation
  77. GRB 050726: PROMPT Rc Observations
  78. GRB050709: Second Epoch Chandra Observation
  79. GRB 050724: dust-scattered X-ray halo detected in SWIFT/XRT observation
  80. GRB050724: Further Radio Observations
  81. GRB 050726: early Swift XRT analysis results
  82. GRB050726: Swift-BAT detection of a weak burst
  83. GRB 050724: Optical Variability in Nearby Galaxy
  84. GRB 050724: J-band observations
  85. GRB 050724: GMOS Imaging and Spectroscopy
  86. GRB 050724: SWIFT XRT refined position
  87. RXTE ASM Detection of GRB050724
  88. GRB050724: Radio Observation
  89. GRB 050724: spectroscopy of object in the XRT error circle
  90. GRB 050724: Optical limit
  91. GRB 050724: optical and near-IR observations
  92. GRB 050724: Optical imaging/astrometry
  93. GRB 050724: RTT150 optical observations
  94. GRB 050724: Swift/UVOT Upper Limit
  95. GRB 050724: early Swift XRT analysis results
  96. GRB 050724 : Lulin early R-band monitoring observations
  97. GRB050724: Refined analysis of the Swift-BAT possible short burst
  98. GRB 050724: possible host galaxy in DSS
  99. GRB050724: a short-burst detected by Swift
  100. Swift-BAT trigger 147325 is not due to a real GRB

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