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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 050209 I-band observation
  2. GRB 050209 Optical observations
  3. GRB050209: P60 Optical Observations
  4. GRB050209 (=U11568): A Long GRB Detected by HETE
  5. GRB 050209: Optical observation
  6. GRB 050128: Radio observations
  7. Further analysis of the short Swift-BAT GRB 050202
  8. GRB 050202: Second epoch radio observations
  9. GRB 050129: Optical observations
  10. GRB050202: Radio Observations
  11. GRB 050202: Optical observations with LCO40
  12. GRB 050202: Short burst detected by Swift-BAT
  13. GRB 050128 Optical observation with REM
  14. GRB 050129: a weak long GRB detected with INTEGRAL
  15. SGR1806-20: Swift-BAT detection of a large normal burst
  16. GRB050128: Faulkes Telescope South observations
  17. GRB 050124: Radio Observations
  18. GRB 050128: near-infrared observations with REM
  19. GRB050128,optical observations
  20. GRB 050126: A NIR afterglow candidate in the revised XRT error circle
  21. GRB050126: Updated Swift XRT Position
  22. SGR 1806-20: GMRT results at 240 MHz band.
  23. SGR 1806-20: low frequency GMRT results of 2005 Jan 16.
  24. GRB 050126: Radio Observations
  25. GRB050128 Swift-BAT observations
  26. GRB 050128: Swift XRT prompt afterglow position
  27. HETE #3667: P60 Observations
  28. GRB 050124: K-band afterglow observations
  29. GRB050126: MASTER optical limit for KECK OT
  30. GRB050126: Burst Parameters Measured by BAT
  31. GRB050126: MASTER optical observations
  32. GRB 050126: Detection of NIR afterglow with Keck/NIRC
  33. GRB 050126: Prompt XRT detection and localization
  34. GRB 050124: NIR afterglow confirmed with Keck/NIRC
  35. GRB050124: No Swift UVOT Detection of Afterglow Emission
  36. GRB 050124, SMARTS optical/IR observations
  37. GRB 050117a: Radio Observations
  38. GRB 050124 I-band observation
  39. GRB 050124: NIR Candidates from Keck/NIRC
  40. GRB050124,optical observation
  41. GRB 050124 : Lulin R-band follow-up observation
  42. GRB050124: Updated Swift XRT Position and Fluxes
  43. GRB 050124: Swift XRT Detection of X-ray Afterglow Emission
  44. GRB050124: Refined BAT position, spectral and fluence information
  45. GRB050124: Swift-BAT position of a double-peaked burst
  46. GRB 050123 : I-band follow-up observation
  47. GRB050123: optical limit 1.8h before GRB
  48. GRB050123,optical observation
  49. GRB 050123: KAIT observations
  50. GRB050123: P60 Observations
  51. GRB 050123(=H3666): A GRB Localized in Real Time by HETE
  52. CFHTLS optical transient unlikely to be a GRB
  53. Unusual optical transient (GRB ???)
  54. GRB050117a: Radio Observations
  55. GRB050117a: Refined analysis
  56. GRB 041224 and GRB 041226: BOOTES-2 simultaneous observations
  57. GRB050117: Palomar WIRC Ks-band observations
  58. GRB050117b: Swift-BAT detection of a weak burst
  59. GRB050117: optical observation
  60. GRB 050117, I-band observations
  61. GRB 050117: Optical observation
  62. GRB050117: Refined XRT position
  63. GRB050117: MASTER optical observations
  64. MASTER:GRB050117 SWIFT
  65. GRB050117: Swift-BAT detection of a long multi-peaked burst
  66. GRB050117: Swift XRT Position
  67. SGR 1806-20: RXTE/PCA pulse frequency during flare
  68. Triangulation of Short Hard GRB050112 (large error box)
  69. SGR 1806-20: Further VLA Observations
  70. SGR 1806-20: Further low frequency GMRT results
  71. SGR 1806-20: Further VLA Observations
  72. SGR1806-20: Swift-BAT observations of two additional bursts
  73. SGR1806: Optical Transient Candidates in SOHO/LASCO Images
  74. Further VLA observations of SGR 1806-20
  75. SGR 1806-20 and extragalactic short-duration GRBs
  76. Further ATCA observations of SGR 1806-20
  77. Fourth Epoch VLA observations of SGR 1806-20
  78. SGR 1806-20: Low frequency GMRT results; submission to GCN circulars
  79. SGR 1806-20: Temporal and Spectral behavior of radio transient
  80. ATCA observations of SGR 1806-20
  81. SGR 1806-20, RHESSI observations of the 041227 giant flare
  82. Third epoch observations of SGR 1806-20 with VLA
  83. Second Epoch VLA observations of SGR 1806-20
  84. Second-epoch VLA observations of SGR 1806-20
  85. SGR1806: Detection of a Sudden Ionospheric Disturbance
  86. DETECTION OF POLARIZATION OF THE RADIO EMISSION FROM SGR 1806-20
  87. VLA observations of SGR 1806-20
  88. SGR1806 VLA Observations
  89. VLA observations of SGR 1806-20
  90. SGR1806-20: RXTE-PCA observation of the 041227 super-flare
  91. GRB 041217: Optical observations
  92. SGR1806-20: Swift-BAT observation of the 041227 super-flare
  93. GRB041219, early time observations
  94. Detection of the SGR 1806-20 giant outburst back-scattered by the
  95. The giant outburst from SGR 1806-20
  96. IPN localization of giant flare from SGR1806-20
  97. Giant flare from SGR 1806-20 detected by INTEGRAL
  98. GRB041228: ROTSE-III Optical Observations
  99. GRB041228: Swift-BAT detection of a burst
  100. GRB041219; RXTE ASM Observations

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