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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. Possible GRB 051221B: MDM Optical Detection
  2. GRB 051221A: RAPTOR Fading Counterpart Constraint
  3. GRB 051221B: BOOTES optical observations.
  4. Possible GRB 051221B: Swift XRT position
  5. GRB 051211A: Evidence This Is a Short Burst from Analysis of Spectral
  6. Swift-BAT detection of a possible burst
  7. GRB 051221: Discovery of fading optical afterglow
  8. GRB 051221: Swift XRT refined analysis
  9. GRB 051221: Swift/UVOT upper limits
  10. GRB 051221: Possible nearby cluster
  11. GRB 051221: No variability in Gemini data
  12. GRB 051221: Correction to GCN #4368
  13. GRB 051221: Gemini observations
  14. GRB 051221: Improved astrometry of the IR counterpart
  15. GRB051221: K-band source
  16. GRB 051221: XRT position
  17. GRB 051221: Refined analysis of the Swift-BAT short hard burst
  18. GRB 051221: IR Observations at GRB+1hr
  19. GRB 051221: Swift detection of a bright short burst
  20. Refined analysis of the SWIFT J1626.6-5156
  21. Swift-BAT discovery of hard x-ray transient SWIFT J1626.6-5156
  22. Refined analysis of the Swift-BAT detection of the RS CVn star II Peg
  23. GRB051211A (=H3979): Refined Analysis
  24. GRB 051211B: optical afterglow
  25. Swift detection of an RS CVn flare star
  26. GRB051211A: possible optical candidate
  27. Swift Trigger 172767 is not a GRB
  28. GRB 051215: near-infrared observations
  29. GRB051215 - SDSS pre-burst observations
  30. GRB 051215: Swift detection of a possible burst
  31. GRB 051215: A short GRB in a cluster?
  32. GRB051211B: Probable radio afterglow
  33. GRB051105: optical observations
  34. GRB 051213: Swift-BAT refined analysis
  35. GRB051211B: XRT refined analysis
  36. GRB 051211B, optical observation
  37. GRB 051213: Swift-BAT detection of a burst
  38. GRB 051211a: RTT150 optical observations
  39. GRB051211B, RBO optical observations
  40. GRB 051211A: Swift/UVOT upper limits
  41. GRB 051211B: Swift/UVOT upper limits - correction
  42. GRB 051211B: Swift/UVOT upper limits
  43. GRB 051211A,optical observation
  44. GRB 051211B: Swift XRT confirmation of the afterglow
  45. GRB051211B: Liverpool Telescope observation
  46. GRB 051211b: RTT150 optical observations
  47. GRB051211b: P60 Observations
  48. GRB 051211A and GRB051211B: BOOTES simultaneous observations
  49. GRB 051211B: Swift XRT Observations
  50. GRB 051210: Swift/UVOT upper limits
  51. GRB 051210: Magellan Imaging
  52. GRB 051211: TAROT optical limits
  53. GRB 051211B: a possible optical detection by TAROT
  54. GRB 051211B: a long GRB detected by INTEGRAL
  55. GRB 051211: Swift XRT upper limit
  56. GRB 051211:IAC80 optical observations
  57. HETE SXC localization of GRB 051211 (=H3979)
  58. GRB 051210: Optical imaging from Las Campanas
  59. GRB 051210: SALT detection limit
  60. GRB 051210: BAT further refined analysis of the short burst
  61. GRB 051210: Swift XRT refined analysis
  62. GRB 051210: FRAM early limit
  63. GRB 051210: Swift-BAT refined analysis of a short burst
  64. GRB051210: Swift UVOT Observation
  65. GRB 051210: A short GRB in a cluster?
  66. GRB 051210: Swift detection of a burst
  67. IPN observations of SGR1806-20
  68. Swift XRT positions
  69. An extraordinary long burst on December 3 from SGR1806-20
  70. IBAS Alert 2706 : not a real GRB
  71. Possible resuming of the SGR 1806-20 activity
  72. Swift UVOT Calibration Documentation
  73. GRB051117B: optical observation
  74. GRB051111: optical observaion
  75. Swift-BAT trigger 165579 is not a GRB
  76. GRB 051127: Swift-BAT detection of a possible burst
  77. GRB051117B: Swift XRT refined analysis
  78. GRB051117b: No Swift/UVOT Detection
  79. GRB051111: Rc optical observations: correction
  80. GRB 051117A: Swift/UVOT Detection of an Afterglow: Correction
  81. GRB 051117A: Swift/UVOT Detection of an Afterglow
  82. GRB051111: Suzaku WAM observation of the prompt emission
  83. GRB051111: Rc optical observations
  84. GRB051008: Suzaku WAM observation of the prompt emission
  85. GRB 051109B: GAO 150cm telescope Optical limit
  86. GRB 051109A : GAO 150cm telescope Rc-band detection
  87. GRB 051021 Optical Observations
  88. GRB 051117B: MARGE Optical Limits
  89. GRB 051117A and B: Radio Observations
  90. GRB 051117B: R and I observations of possible host galaxy
  91. GRB 051117b: NIR observations
  92. GRB 051117A: Refined analysis of the Swift-BAT burst
  93. GRB 051117B: Refined analysis of the Swift-BAT burst
  94. GRB051117A : XRT refined analysis
  95. GRB 051117B,optical observation
  96. GRB 051117B: Lulin R and I band observation
  97. GRB 051117B: Optical observations
  98. GRB 051117B: ROTSE-III Optical Limits
  99. GRB051117B: Swift XRT position
  100. GRB 051117B: Swift detection of a burst

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