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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 050525A: BOOTES simultaneous optical observations
  2. GRB 050525A: Swift-BAT refined analysis
  3. GRB050525: Optical observations
  4. GRB 050525B: INTEGRAL shows it is unrelated to GRB050525A
  5. Subject : GRB 050525: pseudo-redshift
  6. Swift/UVOT UV and optical detections of GRB 050525
  7. Konus-Wind observation of GRB 050525
  8. GRB 050525: TAROT observations of the early afterglow
  9. INTEGRAL detection of GRB 050525
  10. GRB 050525, infrared observations
  11. GRB 050525: Optical observation
  12. GRB 050525: observatons of the optical afterglow
  13. GRB050525: ROTSE-III Refined Analysis
  14. GRB 050525 - Very Bright, Not Short
  15. GRB 050525: Swift Detection of a Bright, Possibly Short Burst
  16. GRB 050525A: ROTSE-III Detection of Possible Counterpart
  17. XRF050522: NIR observations of XRT candidate
  18. XRF 050522: Swift XRT refined analysis
  19. XRF050522: Radio Observations
  20. Swift/UVOT observation of XRF 050522
  21. GRB 050509A: Further I-band imaging
  22. GRB050522,optical observation
  23. GRB050520,optical observation
  24. XRF 050522: Continued NIR P200 Monitoring
  25. RBO Observations of GRB050522
  26. GRB050509b: optical observations
  27. Recent GRB BVRcIc field photometry
  28. GRB050520: Radio Observations
  29. XRF 050522: Swift XRT observation
  30. XRF050522, BVRcIc field photometry
  31. XRF 050522 : Lulin observations
  32. XRF050522: Optical Observations
  33. XRF050522: Near-infrared Observations
  34. XRF 050522: KAIT observations
  35. XRF 050522 detected with INTEGRAL
  36. GRB 050520: VLT/ULTRACAM observations
  37. Swift UVOT Observations of GRB 050520
  38. GRB 050520: Swift XRT refined analysis
  39. XRF050509C: Chandra Afterglow Detection
  40. XRF 050509c: Swift XRT Upper Limit
  41. XRF050509c: Radio Observations
  42. RBO Observations of GRB050520
  43. GRB 050520: P200 Observations
  44. GRB050520: Liverpool Telescope follow-up
  45. RBO Observations of GRB050520
  46. GRB 050520: TAROT optical limit
  47. GRB 050520: Swift XRT position
  48. GRB 050520: VLT/ULTRACAM observations
  49. GRB 050520: OSN optical observations
  50. GRB 050520: BART optical limit
  51. GRB 050520 - A long GRB detected with INTEGRAL
  52. No Swift-BAT Lightcurves in real-time for next 3 weeks
  53. Swift-BAT trigger 122203 is not a real GRB
  54. XRF 050509C: REM NIR and Optical refined analysis
  55. GRB 050504: Swift XRT afterglow candidate has faded
  56. XRF 050509c optical afterglow
  57. GRB 050509B and short GRB-SN association? (corrected)
  58. GRB 050509B and short GRB-SN association?
  59. GRB 050509B: Subaru Optical Observations
  60. GRB050502b: Early Observation
  61. GRB050509b, Bok telescope B-band imaging
  62. Refined Chandra analysis of GRB 050509b
  63. GRB050509b, SDSS pre-burst observations
  64. GRB 050509b: Keck/Chandra Cross-Correlation
  65. GRB 050509b: Keck/Chandra Cross-Correlation
  66. Chandra observation of GRB 050509b
  67. GRB 050509b: RAPTOR deep, early limits.
  68. GRB050509B: Optical/Infared observations
  69. GRB 050509b: Swift/UVOT follow-up measurements
  70. GRB 050509b Milagro GeV/TeV Observations
  71. GRB050509B: Optical observations at the Very Large Telescope
  72. GRB 050509b: No Optical Variability in XRT Error Circle
  73. GRB050416: Afterglow detection at 188 nm with Swift UVOT
  74. GRB 050509a: Swift-BAT refined analysis
  75. GRB 050509c: ROTSE-III Optical Limits
  76. GRB 050509B: WSRT Radio Observations
  77. GRB050509c: REM NIR and Optical observations (errata corrige to GCN 3400)
  78. GRB 050505, early TAROT observation
  79. GRB050509c (=H3751): An X-Ray Flash Localized By HETE
  80. GRB 050509b: Further Analysis of Keck LRIS Images
  81. GRB050509c: REM NIR and Optical observations
  82. GRB 050509b: Physical Properties of the Candidate Host galaxy
  83. GRB 050505: SARA Observations
  84. Swift UVOT Follow-up Observations of GRB 050509B
  85. GRB 050509B, Optical Observations
  86. GRB 050509B: Swift/XRT refined analysis
  87. GRB050509a: Swift UVOT observations
  88. GRB 050509b: Optical observations
  89. GRB 050509b: Precision Astrometry
  90. GRB 050509b: Possible Optical Counterpart
  91. Keck/DEIMOS Spectrum of Possible Host Galaxy for GRB050509b
  92. GRB 050509A: Optical observations
  93. GRB 050509b: Optical Counterpart Candidate
  94. GRB050509b: Radio Observations
  95. GRB 050509b: PAIRITEL and WIYN Observations
  96. GRB 050509b: Swift-BAT refined analysis of the short hard burst
  97. GRB 050509b: optical observations
  98. GRB 050509b: Swift XRT Position
  99. GRB 050509B: ROTSE-III Optical Limits
  100. Swift Detection of GRB050509b: A short duration burst

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