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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 050505, early TAROT observation
  2. GRB050509c (=H3751): An X-Ray Flash Localized By HETE
  3. GRB 050509b: Further Analysis of Keck LRIS Images
  4. GRB050509c: REM NIR and Optical observations
  5. GRB 050509b: Physical Properties of the Candidate Host galaxy
  6. GRB 050505: SARA Observations
  7. Swift UVOT Follow-up Observations of GRB 050509B
  8. GRB 050509B, Optical Observations
  9. GRB 050509B: Swift/XRT refined analysis
  10. GRB050509a: Swift UVOT observations
  11. GRB 050509b: Optical observations
  12. GRB 050509b: Precision Astrometry
  13. GRB 050509b: Possible Optical Counterpart
  14. Keck/DEIMOS Spectrum of Possible Host Galaxy for GRB050509b
  15. GRB 050509A: Optical observations
  16. GRB 050509b: Optical Counterpart Candidate
  17. GRB050509b: Radio Observations
  18. GRB 050509b: PAIRITEL and WIYN Observations
  19. GRB 050509b: Swift-BAT refined analysis of the short hard burst
  20. GRB 050509b: optical observations
  21. GRB 050509b: Swift XRT Position
  22. GRB 050509B: ROTSE-III Optical Limits
  23. Swift Detection of GRB050509b: A short duration burst
  24. GRB 050509a: Swift XRT Position
  25. Swift Detection of the Burst GRB050509
  26. Swift-BAT detection of GRB 050507
  27. GRB 050505: Keck I-band Magnitude
  28. GRB 050505: early time observations
  29. GRB 050505 - Faulkes Telescope North observations
  30. GRB 050502a: Swift XRT Upper Limit
  31. GRB 050505, simultaneous optical observation
  32. GRB050505: Infrared observations
  33. GRB 050505: Further Swift UVOT observations.
  34. GRB050505: AAVSO observations
  35. GRB050416A : 1 GHz limit from GMRT
  36. GRB 050505: Keck absorption spectrum and redshift (z=4.27)
  37. GRB 050505 UVOT
  38. GRB050505: Optical Afterglow Candidate
  39. GRB 050505: Swift XRT Position
  40. GRB050505 Swift-BAT refined analysis
  41. GRB 050502a: Optical Observations
  42. GRB 050416b:Swift XRT afterglow upper limits
  43. GRB 050416b:Swift XRT afterglow upper limits
  44. Swift-BAT detection of GRB050505
  45. GRB 050504: Swift XRT position
  46. GRB050502b: Afterglow Confirmation: Correction to OT Coordinates
  47. GRB050502b: Afterglow Confirmation
  48. GRB050502: P200 Observations (Correction)
  49. GRB050502: P200 Observations
  50. GRB 050504 : R band observation at Lulin observatory
  51. Swift UVOT observation of GRB 050504
  52. GRB 050504, R band Observations
  53. GRB050504: Faulkes North optical robotic limit
  54. GRB 050502b, V band Observations
  55. GRB050504: P60 Observations
  56. GRB 050504: A long GRB detected with INTEGRAL
  57. GRB (?) 050504: IR Observations, Intriguing Source
  58. GRB 050502b, Optical observations
  59. GRB050502a: P60 Observations (Correction)
  60. GRB050502a: P60 Observations
  61. Renewal of SGR 1806-20 activity
  62. GRB 050502a: RBO Observations
  63. GRB 050502A: WSRT Radio Observations
  64. GRB050502A: Optical Observations
  65. GRB050502B Swift-BAT refined analysis
  66. GRB050502B: I band source in XRT error circle
  67. Swift UVOT refined analysis
  68. Retraction of Swift-BAT trigger 116145
  69. GRB 050502a : R band observation at Lulin observatory
  70. GRB 050502b : optical observation at Lulin observatory
  71. GRB 050502b: Swift XRT Position
  72. GRB 050502A: Redshift measurement based on Keck HIRES Observations
  73. GRB050502B: Optical Limits from ANU 1m
  74. Swift Detection of the Bright Burst GRB050502b
  75. GRB 050502: INTEGRAL results
  76. GRB050502: ANU 1m optical Observations
  77. GRB 050502: Confirmed variability of the afterglow candidate +
  78. GRB 050502: PAIRITEL IR Observations
  79. GRB050502 - Correction on the Optical Candidate from the Liverpool
  80. GRB050502 - Optical Candidate from the Liverpool Telescope
  81. GRB 050502 - A long GRB detected with INTEGRAL
  82. GRB 050502: ROTSE-III Detection of Possible Counterpart
  83. Swift-BAT Trigger 115881 is not a real GRB
  84. Swift/BAT possible detection of a weak burst GRB050430
  85. GRB 050401: Rc observation
  86. GRB050416a: Radio Detection
  87. GRB 050422: Swift-UVOT observation
  88. GRB 050422: Swift-BAT refined analysis
  89. GRB 050422: Swift XRT Position
  90. Swift Detection of GRB 050422
  91. GRB 050421: NIR observations
  92. GRB 050416: Optical/NIR observations
  93. GRB 050421: SLOTIS observations
  94. GRB 050421: Further Analysis of IR imaging
  95. GRB050421: Radio Observations
  96. GRB050421: Radio Observations
  97. GRB 050421: Swift-UVOT observation
  98. GRB 050421: IR Observations
  99. GRB 050421: Swift-BAT refined analysis
  100. GRB 050421: ROTSE-III Optical Limits

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Download all Circulars as a .tar.gz archive (updated once a day):
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