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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. XRF050509C: Chandra Afterglow Detection
  2. XRF 050509c: Swift XRT Upper Limit
  3. XRF050509c: Radio Observations
  4. RBO Observations of GRB050520
  5. GRB 050520: P200 Observations
  6. GRB050520: Liverpool Telescope follow-up
  7. RBO Observations of GRB050520
  8. GRB 050520: TAROT optical limit
  9. GRB 050520: Swift XRT position
  10. GRB 050520: VLT/ULTRACAM observations
  11. GRB 050520: OSN optical observations
  12. GRB 050520: BART optical limit
  13. GRB 050520 - A long GRB detected with INTEGRAL
  14. No Swift-BAT Lightcurves in real-time for next 3 weeks
  15. Swift-BAT trigger 122203 is not a real GRB
  16. XRF 050509C: REM NIR and Optical refined analysis
  17. GRB 050504: Swift XRT afterglow candidate has faded
  18. XRF 050509c optical afterglow
  19. GRB 050509B and short GRB-SN association? (corrected)
  20. GRB 050509B and short GRB-SN association?
  21. GRB 050509B: Subaru Optical Observations
  22. GRB050502b: Early Observation
  23. GRB050509b, Bok telescope B-band imaging
  24. Refined Chandra analysis of GRB 050509b
  25. GRB050509b, SDSS pre-burst observations
  26. GRB 050509b: Keck/Chandra Cross-Correlation
  27. GRB 050509b: Keck/Chandra Cross-Correlation
  28. Chandra observation of GRB 050509b
  29. GRB 050509b: RAPTOR deep, early limits.
  30. GRB050509B: Optical/Infared observations
  31. GRB 050509b: Swift/UVOT follow-up measurements
  32. GRB 050509b Milagro GeV/TeV Observations
  33. GRB050509B: Optical observations at the Very Large Telescope
  34. GRB 050509b: No Optical Variability in XRT Error Circle
  35. GRB050416: Afterglow detection at 188 nm with Swift UVOT
  36. GRB 050509a: Swift-BAT refined analysis
  37. GRB 050509c: ROTSE-III Optical Limits
  38. GRB 050509B: WSRT Radio Observations
  39. GRB050509c: REM NIR and Optical observations (errata corrige to GCN 3400)
  40. GRB 050505, early TAROT observation
  41. GRB050509c (=H3751): An X-Ray Flash Localized By HETE
  42. GRB 050509b: Further Analysis of Keck LRIS Images
  43. GRB050509c: REM NIR and Optical observations
  44. GRB 050509b: Physical Properties of the Candidate Host galaxy
  45. GRB 050505: SARA Observations
  46. Swift UVOT Follow-up Observations of GRB 050509B
  47. GRB 050509B, Optical Observations
  48. GRB 050509B: Swift/XRT refined analysis
  49. GRB050509a: Swift UVOT observations
  50. GRB 050509b: Optical observations
  51. GRB 050509b: Precision Astrometry
  52. GRB 050509b: Possible Optical Counterpart
  53. Keck/DEIMOS Spectrum of Possible Host Galaxy for GRB050509b
  54. GRB 050509A: Optical observations
  55. GRB 050509b: Optical Counterpart Candidate
  56. GRB050509b: Radio Observations
  57. GRB 050509b: PAIRITEL and WIYN Observations
  58. GRB 050509b: Swift-BAT refined analysis of the short hard burst
  59. GRB 050509b: optical observations
  60. GRB 050509b: Swift XRT Position
  61. GRB 050509B: ROTSE-III Optical Limits
  62. Swift Detection of GRB050509b: A short duration burst
  63. GRB 050509a: Swift XRT Position
  64. Swift Detection of the Burst GRB050509
  65. Swift-BAT detection of GRB 050507
  66. GRB 050505: Keck I-band Magnitude
  67. GRB 050505: early time observations
  68. GRB 050505 - Faulkes Telescope North observations
  69. GRB 050502a: Swift XRT Upper Limit
  70. GRB 050505, simultaneous optical observation
  71. GRB050505: Infrared observations
  72. GRB 050505: Further Swift UVOT observations.
  73. GRB050505: AAVSO observations
  74. GRB050416A : 1 GHz limit from GMRT
  75. GRB 050505: Keck absorption spectrum and redshift (z=4.27)
  76. GRB 050505 UVOT
  77. GRB050505: Optical Afterglow Candidate
  78. GRB 050505: Swift XRT Position
  79. GRB050505 Swift-BAT refined analysis
  80. GRB 050502a: Optical Observations
  81. GRB 050416b:Swift XRT afterglow upper limits
  82. GRB 050416b:Swift XRT afterglow upper limits
  83. Swift-BAT detection of GRB050505
  84. GRB 050504: Swift XRT position
  85. GRB050502b: Afterglow Confirmation: Correction to OT Coordinates
  86. GRB050502b: Afterglow Confirmation
  87. GRB050502: P200 Observations (Correction)
  88. GRB050502: P200 Observations
  89. GRB 050504 : R band observation at Lulin observatory
  90. Swift UVOT observation of GRB 050504
  91. GRB 050504, R band Observations
  92. GRB050504: Faulkes North optical robotic limit
  93. GRB 050502b, V band Observations
  94. GRB050504: P60 Observations
  95. GRB 050504: A long GRB detected with INTEGRAL
  96. GRB (?) 050504: IR Observations, Intriguing Source
  97. GRB 050502b, Optical observations
  98. GRB050502a: P60 Observations (Correction)
  99. GRB050502a: P60 Observations
  100. Renewal of SGR 1806-20 activity

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