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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 051227: Magellan r'-band Imaging/Astrometry
  2. GRB 051227: refined analysis of VLT images
  3. GRB 051227: P60 Observations
  4. GRB 051227: MDM Observation
  5. GRB 051227: R-band object in the XRT error circle
  6. GRB 051227: Joint Swift-HETE Spectral Analysis
  7. GRB 051227: XRT refined analysis
  8. GRB 051227: Further analysis of the Swift-BAT burst
  9. GRB 051227: Refined analysis of the Swift-BAT burst
  10. GRB051227: SDSS pre-burst observations
  11. GRB 051227, optical observation
  12. GRB 051227: Swift detection of a burst
  13. GRB051117B: optical observation
  14. IBAS_alert n. 2719 : not a real GRB
  15. Konus-Wind observation of GRB 051221A
  16. GRB051221A: Suzaku WAM observation of the prompt emission
  17. GRB 051221A: MDM Optical Observations
  18. GRB051016: analysis of the XMM-Newton observation
  19. GRB 051221A: Detection at 251nm with Swift UVOT
  20. GRB 051221A: Chandra Afterglow Position
  21. GRB 051221A: Refined spectral and temporal analysis of the Swift-BAT short hard burst
  22. GRB 051221B: ROTSE-III Optical Limits
  23. GRB 051221B: TAROT optical limits
  24. GRB 051221A: WSRT Radio Observations
  25. GRB 051221: Redshift from Gemini
  26. GRB 051221: Continued fading of optical afterglow
  27. GRB 051221B: Refined analysis of the Swift-BAT burst
  28. Possible GRB 051221B: MDM Optical Detection
  29. GRB 051221A: RAPTOR Fading Counterpart Constraint
  30. GRB 051221B: BOOTES optical observations.
  31. Possible GRB 051221B: Swift XRT position
  32. GRB 051211A: Evidence This Is a Short Burst from Analysis of Spectral
  33. Swift-BAT detection of a possible burst
  34. GRB 051221: Discovery of fading optical afterglow
  35. GRB 051221: Swift XRT refined analysis
  36. GRB 051221: Swift/UVOT upper limits
  37. GRB 051221: Possible nearby cluster
  38. GRB 051221: No variability in Gemini data
  39. GRB 051221: Correction to GCN #4368
  40. GRB 051221: Gemini observations
  41. GRB 051221: Improved astrometry of the IR counterpart
  42. GRB051221: K-band source
  43. GRB 051221: XRT position
  44. GRB 051221: Refined analysis of the Swift-BAT short hard burst
  45. GRB 051221: IR Observations at GRB+1hr
  46. GRB 051221: Swift detection of a bright short burst
  47. Refined analysis of the SWIFT J1626.6-5156
  48. Swift-BAT discovery of hard x-ray transient SWIFT J1626.6-5156
  49. Refined analysis of the Swift-BAT detection of the RS CVn star II Peg
  50. GRB051211A (=H3979): Refined Analysis
  51. GRB 051211B: optical afterglow
  52. Swift detection of an RS CVn flare star
  53. GRB051211A: possible optical candidate
  54. Swift Trigger 172767 is not a GRB
  55. GRB 051215: near-infrared observations
  56. GRB051215 - SDSS pre-burst observations
  57. GRB 051215: Swift detection of a possible burst
  58. GRB 051215: A short GRB in a cluster?
  59. GRB051211B: Probable radio afterglow
  60. GRB051105: optical observations
  61. GRB 051213: Swift-BAT refined analysis
  62. GRB051211B: XRT refined analysis
  63. GRB 051211B, optical observation
  64. GRB 051213: Swift-BAT detection of a burst
  65. GRB 051211a: RTT150 optical observations
  66. GRB051211B, RBO optical observations
  67. GRB 051211A: Swift/UVOT upper limits
  68. GRB 051211B: Swift/UVOT upper limits - correction
  69. GRB 051211B: Swift/UVOT upper limits
  70. GRB 051211A,optical observation
  71. GRB 051211B: Swift XRT confirmation of the afterglow
  72. GRB051211B: Liverpool Telescope observation
  73. GRB 051211b: RTT150 optical observations
  74. GRB051211b: P60 Observations
  75. GRB 051211A and GRB051211B: BOOTES simultaneous observations
  76. GRB 051211B: Swift XRT Observations
  77. GRB 051210: Swift/UVOT upper limits
  78. GRB 051210: Magellan Imaging
  79. GRB 051211: TAROT optical limits
  80. GRB 051211B: a possible optical detection by TAROT
  81. GRB 051211B: a long GRB detected by INTEGRAL
  82. GRB 051211: Swift XRT upper limit
  83. GRB 051211:IAC80 optical observations
  84. HETE SXC localization of GRB 051211 (=H3979)
  85. GRB 051210: Optical imaging from Las Campanas
  86. GRB 051210: SALT detection limit
  87. GRB 051210: BAT further refined analysis of the short burst
  88. GRB 051210: Swift XRT refined analysis
  89. GRB 051210: FRAM early limit
  90. GRB 051210: Swift-BAT refined analysis of a short burst
  91. GRB051210: Swift UVOT Observation
  92. GRB 051210: A short GRB in a cluster?
  93. GRB 051210: Swift detection of a burst
  94. IPN observations of SGR1806-20
  95. Swift XRT positions
  96. An extraordinary long burst on December 3 from SGR1806-20
  97. IBAS Alert 2706 : not a real GRB
  98. Possible resuming of the SGR 1806-20 activity
  99. Swift UVOT Calibration Documentation
  100. GRB051117B: optical observation

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