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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 050509b: Possible Optical Counterpart
  2. Keck/DEIMOS Spectrum of Possible Host Galaxy for GRB050509b
  3. GRB 050509A: Optical observations
  4. GRB 050509b: Optical Counterpart Candidate
  5. GRB050509b: Radio Observations
  6. GRB 050509b: PAIRITEL and WIYN Observations
  7. GRB 050509b: Swift-BAT refined analysis of the short hard burst
  8. GRB 050509b: optical observations
  9. GRB 050509b: Swift XRT Position
  10. GRB 050509B: ROTSE-III Optical Limits
  11. Swift Detection of GRB050509b: A short duration burst
  12. GRB 050509a: Swift XRT Position
  13. Swift Detection of the Burst GRB050509
  14. Swift-BAT detection of GRB 050507
  15. GRB 050505: Keck I-band Magnitude
  16. GRB 050505: early time observations
  17. GRB 050505 - Faulkes Telescope North observations
  18. GRB 050502a: Swift XRT Upper Limit
  19. GRB 050505, simultaneous optical observation
  20. GRB050505: Infrared observations
  21. GRB 050505: Further Swift UVOT observations.
  22. GRB050505: AAVSO observations
  23. GRB050416A : 1 GHz limit from GMRT
  24. GRB 050505: Keck absorption spectrum and redshift (z=4.27)
  25. GRB 050505 UVOT
  26. GRB050505: Optical Afterglow Candidate
  27. GRB 050505: Swift XRT Position
  28. GRB050505 Swift-BAT refined analysis
  29. GRB 050502a: Optical Observations
  30. GRB 050416b:Swift XRT afterglow upper limits
  31. GRB 050416b:Swift XRT afterglow upper limits
  32. Swift-BAT detection of GRB050505
  33. GRB 050504: Swift XRT position
  34. GRB050502b: Afterglow Confirmation: Correction to OT Coordinates
  35. GRB050502b: Afterglow Confirmation
  36. GRB050502: P200 Observations (Correction)
  37. GRB050502: P200 Observations
  38. GRB 050504 : R band observation at Lulin observatory
  39. Swift UVOT observation of GRB 050504
  40. GRB 050504, R band Observations
  41. GRB050504: Faulkes North optical robotic limit
  42. GRB 050502b, V band Observations
  43. GRB050504: P60 Observations
  44. GRB 050504: A long GRB detected with INTEGRAL
  45. GRB (?) 050504: IR Observations, Intriguing Source
  46. GRB 050502b, Optical observations
  47. GRB050502a: P60 Observations (Correction)
  48. GRB050502a: P60 Observations
  49. Renewal of SGR 1806-20 activity
  50. GRB 050502a: RBO Observations
  51. GRB 050502A: WSRT Radio Observations
  52. GRB050502A: Optical Observations
  53. GRB050502B Swift-BAT refined analysis
  54. GRB050502B: I band source in XRT error circle
  55. Swift UVOT refined analysis
  56. Retraction of Swift-BAT trigger 116145
  57. GRB 050502a : R band observation at Lulin observatory
  58. GRB 050502b : optical observation at Lulin observatory
  59. GRB 050502b: Swift XRT Position
  60. GRB 050502A: Redshift measurement based on Keck HIRES Observations
  61. GRB050502B: Optical Limits from ANU 1m
  62. Swift Detection of the Bright Burst GRB050502b
  63. GRB 050502: INTEGRAL results
  64. GRB050502: ANU 1m optical Observations
  65. GRB 050502: Confirmed variability of the afterglow candidate +
  66. GRB 050502: PAIRITEL IR Observations
  67. GRB050502 - Correction on the Optical Candidate from the Liverpool
  68. GRB050502 - Optical Candidate from the Liverpool Telescope
  69. GRB 050502 - A long GRB detected with INTEGRAL
  70. GRB 050502: ROTSE-III Detection of Possible Counterpart
  71. Swift-BAT Trigger 115881 is not a real GRB
  72. Swift/BAT possible detection of a weak burst GRB050430
  73. GRB 050401: Rc observation
  74. GRB050416a: Radio Detection
  75. GRB 050422: Swift-UVOT observation
  76. GRB 050422: Swift-BAT refined analysis
  77. GRB 050422: Swift XRT Position
  78. Swift Detection of GRB 050422
  79. GRB 050421: NIR observations
  80. GRB 050416: Optical/NIR observations
  81. GRB 050421: SLOTIS observations
  82. GRB 050421: Further Analysis of IR imaging
  83. GRB050421: Radio Observations
  84. GRB050421: Radio Observations
  85. GRB 050421: Swift-UVOT observation
  86. GRB 050421: IR Observations
  87. GRB 050421: Swift-BAT refined analysis
  88. GRB 050421: ROTSE-III Optical Limits
  89. GRB 050421: NIR observations re-examination
  90. GRB050421
  91. GRB 050421: early Swift XRT analysis results
  92. GRB 050421: NIR observations
  93. GRB050421: P60 Observations
  94. GRB 050421: BOOTES-2 simultaneous optical observations
  95. GRB 050421: Optical observations at the INT
  96. Swift Detection of GRB050421
  97. GRB 050416b: Tentative Swift XRT Position
  98. GRB 050315: potential host galaxy
  99. GRB050326: analysis of the XMM-Newton observation
  100. GRB050418: Null Optical Observations

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