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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. GRB050528: BOOTES optical candidate
  2. Possible GRB050528: no candidate from Liverpool Telescope
  3. Swift-BAT detection of possible GRB 050528
  4. GRB050525a: Radio Observations
  5. GRB 050509b: refined XRT/Chandra afterglow position analysis
  6. GRB 050525: RTT150, Optical observations
  7. GRB050525a: optical upper limits
  8. GRB 050525a: SARA Observations
  9. GRB 050525B: Swift-BAT observations
  10. GRB 050525: MITSuME Optical Observation in VRI
  11. GRB 050525a: MDM Observations
  12. GRB050525A,optical observation
  13. GRB 050525 : Lulin optical afterglow observations
  14. GRB050525: Super-LOTIS observations
  15. GRB 050525, spectral lag pseudo-redshift
  16. GRB 050525a: Gemini/GMOS Spectra
  17. GRB050306: optical afterglow not confirmed
  18. GRB 050525: BART optical observation
  19. GRB 050525A: BOOTES simultaneous optical observations
  20. GRB 050525A: Swift-BAT refined analysis
  21. GRB050525: Optical observations
  22. GRB 050525B: INTEGRAL shows it is unrelated to GRB050525A
  23. GRB 050525: pseudo-redshift
  24. Swift/UVOT UV and optical detections of GRB 050525
  25. Konus-Wind observation of GRB 050525
  26. GRB 050525: TAROT observations of the early afterglow
  27. INTEGRAL detection of GRB 050525
  28. GRB 050525, infrared observations
  29. GRB 050525: Optical observation
  30. GRB 050525: observatons of the optical afterglow
  31. GRB050525: ROTSE-III Refined Analysis
  32. GRB 050525 - Very Bright, Not Short
  33. GRB 050525: Swift Detection of a Bright, Possibly Short Burst
  34. GRB 050525A: ROTSE-III Detection of Possible Counterpart
  35. XRF050522: NIR observations of XRT candidate
  36. XRF 050522: Swift XRT refined analysis
  37. XRF050522: Radio Observations
  38. Swift/UVOT observation of XRF 050522
  39. GRB 050509A: Further I-band imaging
  40. GRB050522,optical observation
  41. GRB050520,optical observation
  42. XRF 050522: Continued NIR P200 Monitoring
  43. RBO Observations of GRB050522
  44. GRB050509b: optical observations
  45. Recent GRB BVRcIc field photometry
  46. GRB050520: Radio Observations
  47. XRF 050522: Swift XRT observation
  48. XRF050522, BVRcIc field photometry
  49. XRF 050522 : Lulin observations
  50. XRF050522: Optical Observations
  51. XRF050522: Near-infrared Observations
  52. XRF 050522: KAIT observations
  53. XRF 050522 detected with INTEGRAL
  54. GRB 050520: VLT/ULTRACAM observations
  55. Swift UVOT Observations of GRB 050520
  56. GRB 050520: Swift XRT refined analysis
  57. XRF050509C: Chandra Afterglow Detection
  58. XRF 050509c: Swift XRT Upper Limit
  59. XRF050509c: Radio Observations
  60. RBO Observations of GRB050520
  61. GRB 050520: P200 Observations
  62. GRB050520: Liverpool Telescope follow-up
  63. RBO Observations of GRB050520
  64. GRB 050520: TAROT optical limit
  65. GRB 050520: Swift XRT position
  66. GRB 050520: VLT/ULTRACAM observations
  67. GRB 050520: OSN optical observations
  68. GRB 050520: BART optical limit
  69. GRB 050520 - A long GRB detected with INTEGRAL
  70. No Swift-BAT Lightcurves in real-time for next 3 weeks
  71. Swift-BAT trigger 122203 is not a real GRB
  72. XRF 050509C: REM NIR and Optical refined analysis
  73. GRB 050504: Swift XRT afterglow candidate has faded
  74. XRF 050509c optical afterglow
  75. GRB 050509B and short GRB-SN association? (corrected)
  76. GRB 050509B and short GRB-SN association?
  77. GRB 050509B: Subaru Optical Observations
  78. GRB050502b: Early Observation
  79. GRB050509b, Bok telescope B-band imaging
  80. Refined Chandra analysis of GRB 050509b
  81. GRB050509b, SDSS pre-burst observations
  82. GRB 050509b: Keck/Chandra Cross-Correlation
  83. GRB 050509b: Keck/Chandra Cross-Correlation
  84. Chandra observation of GRB 050509b
  85. GRB 050509b: RAPTOR deep, early limits.
  86. GRB050509B: Optical/Infared observations
  87. GRB 050509b: Swift/UVOT follow-up measurements
  88. GRB 050509b Milagro GeV/TeV Observations
  89. GRB050509B: Optical observations at the Very Large Telescope
  90. GRB 050509b: No Optical Variability in XRT Error Circle
  91. GRB050416: Afterglow detection at 188 nm with Swift UVOT
  92. GRB 050509a: Swift-BAT refined analysis
  93. GRB 050509c: ROTSE-III Optical Limits
  94. GRB 050509B: WSRT Radio Observations
  95. GRB050509c: REM NIR and Optical observations (errata corrige to GCN 3400)
  96. GRB 050505, early TAROT observation
  97. GRB050509c (=H3751): An X-Ray Flash Localized By HETE
  98. GRB 050509b: Further Analysis of Keck LRIS Images
  99. GRB050509c: REM NIR and Optical observations
  100. GRB 050509b: Physical Properties of the Candidate Host galaxy

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