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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 050520: P200 Observations
  2. GRB050520: Liverpool Telescope follow-up
  3. RBO Observations of GRB050520
  4. GRB 050520: TAROT optical limit
  5. GRB 050520: Swift XRT position
  6. GRB 050520: VLT/ULTRACAM observations
  7. GRB 050520: OSN optical observations
  8. GRB 050520: BART optical limit
  9. GRB 050520 - A long GRB detected with INTEGRAL
  10. No Swift-BAT Lightcurves in real-time for next 3 weeks
  11. Swift-BAT trigger 122203 is not a real GRB
  12. XRF 050509C: REM NIR and Optical refined analysis
  13. GRB 050504: Swift XRT afterglow candidate has faded
  14. XRF 050509c optical afterglow
  15. GRB 050509B and short GRB-SN association? (corrected)
  16. GRB 050509B and short GRB-SN association?
  17. GRB 050509B: Subaru Optical Observations
  18. GRB050502b: Early Observation
  19. GRB050509b, Bok telescope B-band imaging
  20. Refined Chandra analysis of GRB 050509b
  21. GRB050509b, SDSS pre-burst observations
  22. GRB 050509b: Keck/Chandra Cross-Correlation
  23. GRB 050509b: Keck/Chandra Cross-Correlation
  24. Chandra observation of GRB 050509b
  25. GRB 050509b: RAPTOR deep, early limits.
  26. GRB050509B: Optical/Infared observations
  27. GRB 050509b: Swift/UVOT follow-up measurements
  28. GRB 050509b Milagro GeV/TeV Observations
  29. GRB050509B: Optical observations at the Very Large Telescope
  30. GRB 050509b: No Optical Variability in XRT Error Circle
  31. GRB050416: Afterglow detection at 188 nm with Swift UVOT
  32. GRB 050509a: Swift-BAT refined analysis
  33. GRB 050509c: ROTSE-III Optical Limits
  34. GRB 050509B: WSRT Radio Observations
  35. GRB050509c: REM NIR and Optical observations (errata corrige to GCN 3400)
  36. GRB 050505, early TAROT observation
  37. GRB050509c (=H3751): An X-Ray Flash Localized By HETE
  38. GRB 050509b: Further Analysis of Keck LRIS Images
  39. GRB050509c: REM NIR and Optical observations
  40. GRB 050509b: Physical Properties of the Candidate Host galaxy
  41. GRB 050505: SARA Observations
  42. Swift UVOT Follow-up Observations of GRB 050509B
  43. GRB 050509B, Optical Observations
  44. GRB 050509B: Swift/XRT refined analysis
  45. GRB050509a: Swift UVOT observations
  46. GRB 050509b: Optical observations
  47. GRB 050509b: Precision Astrometry
  48. GRB 050509b: Possible Optical Counterpart
  49. Keck/DEIMOS Spectrum of Possible Host Galaxy for GRB050509b
  50. GRB 050509A: Optical observations
  51. GRB 050509b: Optical Counterpart Candidate
  52. GRB050509b: Radio Observations
  53. GRB 050509b: PAIRITEL and WIYN Observations
  54. GRB 050509b: Swift-BAT refined analysis of the short hard burst
  55. GRB 050509b: optical observations
  56. GRB 050509b: Swift XRT Position
  57. GRB 050509B: ROTSE-III Optical Limits
  58. Swift Detection of GRB050509b: A short duration burst
  59. GRB 050509a: Swift XRT Position
  60. Swift Detection of the Burst GRB050509
  61. Swift-BAT detection of GRB 050507
  62. GRB 050505: Keck I-band Magnitude
  63. GRB 050505: early time observations
  64. GRB 050505 - Faulkes Telescope North observations
  65. GRB 050502a: Swift XRT Upper Limit
  66. GRB 050505, simultaneous optical observation
  67. GRB050505: Infrared observations
  68. GRB 050505: Further Swift UVOT observations.
  69. GRB050505: AAVSO observations
  70. GRB050416A : 1 GHz limit from GMRT
  71. GRB 050505: Keck absorption spectrum and redshift (z=4.27)
  72. GRB 050505 UVOT
  73. GRB050505: Optical Afterglow Candidate
  74. GRB 050505: Swift XRT Position
  75. GRB050505 Swift-BAT refined analysis
  76. GRB 050502a: Optical Observations
  77. GRB 050416b:Swift XRT afterglow upper limits
  78. GRB 050416b:Swift XRT afterglow upper limits
  79. Swift-BAT detection of GRB050505
  80. GRB 050504: Swift XRT position
  81. GRB050502b: Afterglow Confirmation: Correction to OT Coordinates
  82. GRB050502b: Afterglow Confirmation
  83. GRB050502: P200 Observations (Correction)
  84. GRB050502: P200 Observations
  85. GRB 050504 : R band observation at Lulin observatory
  86. Swift UVOT observation of GRB 050504
  87. GRB 050504, R band Observations
  88. GRB050504: Faulkes North optical robotic limit
  89. GRB 050502b, V band Observations
  90. GRB050504: P60 Observations
  91. GRB 050504: A long GRB detected with INTEGRAL
  92. GRB (?) 050504: IR Observations, Intriguing Source
  93. GRB 050502b, Optical observations
  94. GRB050502a: P60 Observations (Correction)
  95. GRB050502a: P60 Observations
  96. Renewal of SGR 1806-20 activity
  97. GRB 050502a: RBO Observations
  98. GRB 050502A: WSRT Radio Observations
  99. GRB050502A: Optical Observations
  100. GRB050502B Swift-BAT refined analysis

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