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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 051021A: RTT150 optical observations
  2. GRB051028 SARA Observation
  3. GRB051028: optical observations
  4. GRB051028: Swift/UVOT upper limits
  5. GRB051028: confirmation of the afterglow
  6. GRB051028: WHT optical candidate
  7. GRB051028: Swift XRT Position
  8. GRB051028:MASTER observations
  9. GRB 051028 (=H3951): A GRB localized by HETE
  10. GRB051028:MASTER optical observations
  11. GRB 051022: XRT Refined Spectral and Temporal Analysis--Correction
  12. GRB051022: Swift XRT measurement of jet break
  13. SGR 1806-20: continued moderate activity seen with INTEGRAL
  14. GRB051021B: Swift/UVOT Upper limits
  15. GRB 051021, Optical Observations
  16. GRB 051022: XRT Refined Spectral and Temporal Analysis
  17. GRB 051022, refined optical astrometry
  18. Chandra Observations of GRB 051022
  19. GRB051012: Swift-XRT analysis
  20. GRB 051022 Chandra Observations scheduled
  21. GRB051021B: Swift XRT refined analysis
  22. GRB051021a: optical observations
  23. GRB 051022: WSRT Radio Detection
  24. GRB 051022, mm counterpart
  25. GRB051022: host galaxy redshift
  26. GRB 051022: Swift/UVOT Upper Limits
  27. GRB051022: Radio Counterpart
  28. GRB051022: IR observations
  29. GRB 051022: SOAR JKs Observations
  30. GRB051021A: Swift XRT refined analysis
  31. Konus-Wind observation of GRB 051022
  32. GRB051022: Optical Observations
  33. GRB 051022: Magellan NIR imaging
  34. GRB 051021: PROMPT RcIc Observations
  35. GRB051021b: Magellan IR Imaging
  36. GRB 051022: Spectral Analysis Indicates That The Spectrum Is Absorbed
  37. GRB 051021: Correction
  38. GRB 051022, J & K-band observation
  39. GRB 051021, SMARTS optical/IR observations
  40. GRB051022: Swift XRT Position
  41. GRB 051021: P200 Ks Observations
  42. IPN triangulation of GRB051022 (=H3950)
  43. GRB 051021: MDM Upper Limit
  44. GRB 051022 (=H3950): SXC Flight Localization is Valid
  45. GRB051021: Swift/UVOT Upper Limits
  46. GRB 051021B: Refined analysis of the Swift-BAT burst
  47. GRB 051022: SSO40 Optical Observations
  48. GRB051022,optical observation
  49. GRB 051022A: ROTSE-III Optical Limits
  50. GRB051022 (=H3590), A GRB Detected By HETE
  51. GRB 051022: Optical observations
  52. GRB 051021,optical observation
  53. GRB051021B: Swift XRT Position
  54. GRB 051021: SOAR NIR Observations
  55. GRB 051021B: Swift detection of a burst
  56. GRB051021: Swift XRT analysis
  57. GRB051021 (=H3947): Refined Analysis
  58. GRB 051021 : optical afterglow observation at Lulin
  59. GRB 051021: Optical observations
  60. GRB 051021: ROTSE-III Confirmation of Optical Counterpart
  61. GRB 051021: Optical observations and candidate afterglow
  62. GRB051021.63
  63. GRB051021.6: MASTER optical observation
  64. Swift-BAT trigger 160640 is not a real GRB
  65. GRB051021: A GRB Localized by HETE
  66. Swift-BAT trigger 160619 is not a GRB
  67. Swift-BAT triggered on a posible CR Shower or possible GRB
  68. GRB 050502b: Optical limit
  69. GRB 051016b: Optical limit
  70. Afterglow candidate of GRB 051016B observed at Lulin
  71. GRB 051016b: Gemini Near IR Observations
  72. GRB 051016A: Swift/UVOT upper limits
  73. GRB 051016B: refined analysis of the Swift/XRT data
  74. GRB 051016B: Swift/UVOT detection
  75. GRB 051016B,optical observation
  76. GRB 051016B : Optical follow-up at Lulin
  77. GRB 051016B: Refined analysis of the Swift-BAT burst
  78. GRB 051016B: Swift detection of a soft burst
  79. GRB 051016: Swift-BAT refined analysis
  80. GRB051016 XMM-Newton observation
  81. GRB051016: Swift XRT refined analysis.
  82. GRB051016: Planned XMM-Newton observation
  83. GRB 051016: LCO optical and near-IR imaging
  84. GRB 051016: PROMPT Observations
  85. GRB051016: Swift detection of a burst
  86. Photometric calibration of Swift/UVOT and Re-analysis of Swift/UVOT GRB 050922C data
  87. GRB051006: optical observations
  88. GRB 051012: Swift-BAT detection of burst yesterday
  89. Swift trigger 159578 is not a burst
  90. Swift-BAT Trigger 159578 is a possible burst
  91. GRB050805A: Rc optical observations
  92. GRB 051006: Swift/UVOT Upper Limits
  93. IBAS Alert 2675 : not a GRB
  94. GRB051008: optical candidate
  95. GRB 051008: - a high redshift high-luminosity burst?
  96. GRB 051008 - a low redshift low-luminosity burst?
  97. IBAS Alert 2673: not a real GRB
  98. GRB051011: bright nebulae near error box
  99. GRB051011: MASTER optical observation
  100. GRB051008: optical observation

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