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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. GRB050410: P60 Observations
  2. GRB 050410: Early Optical/Ultraviolet Observations with Swift/UVOT
  3. GRB 050410, optical observations
  4. GRB 050408: PROMPT VRcIc Observations
  5. GRB 050408: Early Optical/Ultraviolet Observations with Swift/UVOT
  6. GRB 050410 R band Optical Observations
  7. GRB050410 : Null detection report
  8. GRB 050410, optical observations
  9. GRB050410: Radio Observations
  10. GRB 050408: Swift XRT measurement of possible jet break
  11. GRB050410: MASTER optical observations
  12. GRB 050410: Early observations with Swift-UVOT
  13. Swift-BAT detection of GRB 050410
  14. GRB 050410: Swift XRT Position
  15. GRB 050408: Retraction of Proposed Host Galaxy
  16. GRB 050408: Inconsistency of host galaxy identification
  17. GRB 050408: Subaru Observations
  18. GRB 050408: WIDGET simultaneous optical observations
  19. GRB 050408: SOAR UBVRc Observations
  20. GRB 050408: Properties of the Host Galaxy
  21. GRB 050408: Mercator Optical Observations
  22. GRB050408: Radio Observations
  23. GRB 050408: Swift XRT analysis
  24. GRB 050408, SMARTS optical/IR afterglow observations
  25. GRB 050408: Optical limit at 20 min after the burst
  26. GRB 050408, optical observations
  27. GRB050408: REM NIR and Optical observation
  28. GRB 050408: Moderate-resolution Gemini Spectroscopy
  29. GRB 050408,optical observation
  30. GRB 050408 Optical Observations
  31. GRB 050408: Emission and absorption redshift
  32. GRB 050408: Mercator Optical Observations
  33. GRB 050408: Magellan astrometry and photometry
  34. GRB 050408: First Optical observations with TFOSC at the RTT150
  35. GRB 050408: steepening of the optical decay
  36. GRB 050408: Optical afterglow confirmed
  37. GRB 050408: opitcal observation
  38. GRB 050408, optical observations
  39. GRB 050408 optical candidate
  40. GRB 050408: Swift XRT Position
  41. GRB 050408: ROTSE-III Optical Limits
  42. GRB 050408 (=H3711): A Long X-Ray-Rich GRB Detected by HETE
  43. GRB050408: MASTER optical observations
  44. GRB050401: Radio Detection
  45. Swift-UVOT Optical Counterpart Candidate to XRF 050406
  46. GRB 050406: Magellan optical observations
  47. GRB 050406: early Swift XRT analysis results
  48. GRB 050406 BAT refined analysis
  49. GRB 050406: Early observations with Swift-UVOT
  50. GRB 050406: Swift XRT Position
  51. Swift-BAT detection of GRB 050406
  52. Konus-Wind observation of GRB 050401
  53. GRB050401: Radio observation at 610 MHz with GMRT
  54. GRB050401, radio observation at 4.8 GHz and 8.64 GHz
  55. GRB 050401: VLT spectroscopic redshift
  56. GRB 050401 Optical Observations
  57. GRB050401: Maidanak optical observation
  58. GRB 050401 BAT refined analysis
  59. Very questionable identity of Swift-BAT GRB050402 (Trig=113225)
  60. GRB050401: TNG R-band observation
  61. GRB 050402A: IR Analysis
  62. GRB050402: XDSS counterpart
  63. GRB 050402A: IR Observations
  64. GRB 050402: Early observations with Swift-UVOT
  65. Swift Trigger 113225: P60 Observations
  66. GRB050401: ROTSE-III Detection of Prompt Optical Counterpart
  67. GRB 050401: Optical afterglow confirmed
  68. GRB 050401: Optical afterglow candidate
  69. Swift-BAT detection of GRB 050401
  70. GRB 050401: Prompt XRT position
  71. Retraction of three Swift GRB triggers
  72. GRB050331: No Afterglow Detected
  73. Swift-BAT detection of GRB 050331b
  74. GRB 050331: Swift UVOT Source
  75. Swift-BAT detection of GRB 050331
  76. GRB 050331: Swift XRT Position
  77. Swift Data Publicly Available Starting April 5, 2005
  78. GRB050319: radio observation
  79. Konus-Wind observation of GRB 050326
  80. GRB050326: optical limit
  81. GRB 050326: Early observations with Swift-UVOT
  82. GRB 050326 XMM-Newton observation
  83. GRB 050326 : Planned XMM-Newton observation
  84. GRB 050326: Swift XRT Position
  85. GRB050326: optical limit 33min before GRB
  86. GRB 050326 BAT refined analysis
  87. GRB050326: delayed XRT observation
  88. Swift-BAT detection of a bright GRB 050326
  89. GRB050319, optical observations
  90. GRB050319, color indices
  91. GRB050319: optical observation, March 20-22
  92. GRB050319: RTT150 Optical Observations
  93. Swift-BAT detection of a bright outburst from SGR1806-20
  94. Swift-BAT trigger 112060 is not a real GRB
  95. GRB 050319: Absorption redshift from the Nordic Optical Telescope
  96. GRB 050319: ROTSE-III Refined Analysis
  97. GRB 050318: Swift-BAT refined analysis
  98. Refined Swift XRT positions for GRB050315, GRB050318 and GRB050319
  99. GRB050319: VLA Observations
  100. GRB050319: radio observation

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