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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 090423: NIR photometry and evidence for spectral break
  2. GRB 090422: Swift-XRT refined analysis
  3. GRB090423, RIMOTS optical upper limits
  4. GRB 090423: UKIRT data further analysis
  5. GRB 090423: Enhanced Swift-XRT position
  6. GRB 090423: Swift-BAT refined analysis
  7. GRB 090422: Swift/UVOT Upper Limits
  8. GRB 090423: UKIRT K-band observations
  9. GRB 090423: P60 Observations
  10. GRB 090423: Faulkes Telescope South observations
  11. GRB 090418A: R and I band observation
  12. GRB 090423: Swift detection of a burst
  13. GRB 090422: Liverpool Telescope possible candidate
  14. GRB 090418A: Konus-Wind and Swift/BAT joint spectral analysis
  15. GRB 090422: Swift-BAT refined analysis
  16. GRB 090422: Enhanced Swift-XRT position
  17. GRB 090410: Erratum in GCN 9189
  18. GRB 090408A: Erratum in GCN 9188
  19. GRB 090418B: RTT150 optical observations
  20. GRB 090418A: RTT150 optical observations
  21. GRB 080410: GAO 150cm telescope Optical Observation
  22. GRB 080408A: GAO 150cm telescope Optical Observation
  23. GRB 090422: Liverpool Telescope observations
  24. GRB 090418B: Suzaku WAM observation of the prompt emission
  25. GRB 090422: Swift detection of a burst
  26. GRB 090418C: Fermi GBM Detection
  27. GRB 090418A: Swift/UVOT Detection of the Neighbouring Galaxy
  28. Swift-BAT trigger 349718 is not a burst
  29. GRB 090418B: GRAS002 observatios
  30. GRB 090417B: Optical observation
  31. GRB 090418A: optical observations
  32. GRB 090418B: GROND observations
  33. GRB 090419: Swift/UVOT Observations
  34. GRB 090418B: Faulkes Telescope North observations
  35. GRB 090418A: Swift/UVOT Observations
  36. GRB 090417B: Swift/UVOT Upper Limits
  37. GRB 090417B Correction to the BAT refined analysis position
  38. GRB 090419: Swift-XRT refined analysis
  39. Konus-Wind observation of GRB 090418B
  40. GRB 090418: Erratum in GCN 9168
  41. GRB 090419: GROND detection of afterglow candidate
  42. GRB 090418: Optical observations with MITSuME Okayama and Ishigaki 1m telescope
  43. GRB 090419: Swift-BAT refined analysis
  44. VLA radio detection of GRB 090418
  45. VLA radio upper limit on GRB 090417B
  46. GRB 090419: Enhanced Swift-XRT position
  47. GRB 090418: Swift XRT refined analysis
  48. GRB 090418A: ROTSE-III Refined Analysis
  49. GRB 090419: Swift detection of a burst
  50. VLA observations of short burst GRB 090417A
  51. GRB 090418B: Detection of a bright burst from Swift-BAT slew data
  52. GRB 090417B: Gemini imaging
  53. GRB 090418: Swift-BAT refined analysis
  54. GRB 090417B: Galaxy redshift
  55. GRB 090417B: Swift-XRT refined analysis
  56. GRB 090418: Enhanced Swift-XRT position
  57. GRB 090417B: Swift-BAT further refined analysis
  58. GRB 090418: PAIRITEL NIR detection
  59. GRB 090418 Lick Redshift
  60. GRB 090418: ROTSE-III Confirmation of Optical Counterpart
  61. GRB 090418: Swift detection of a burst with optical afterglow
  62. GRB 090418 OA candidate
  63. GRB 090411B: Suzaku WAM observation of the prompt emission
  64. GRB 090411A: Suzaku WAM observation of the prompt emission
  65. GRB 090417B: Subaru NIR Observations
  66. GRB 090417B: Liverpool Telescope observations
  67. GRB 090417B: MITSuME Okayama optical upper limits
  68. GRB090417B: Xinglong TNT optical upper limit
  69. GRB 090417B: optical observations
  70. GRB090417B: optical observations
  71. GRB 090417B: Swift-BAT refined analysis
  72. GRB 090417A: Swift-BAT refined analysis
  73. GRB 090417A: Early-type nature of the putative host
  74. GRB 090417A: nearby galaxy redshift
  75. GRB 090417B: Swift detection of a burst
  76. GRB 090417: 2MASS galaxy within BAT Localization
  77. GRB 090417: Swift detection of a short burst
  78. GRB 090412: Fermi GBM detection
  79. GRB 090411B: Fermi GBM detection
  80. GRB 090411A: Fermi GBM detection
  81. GRB 090410: Suzaku WAM observation of the prompt emission
  82. GRB 090410: GROND upper limits
  83. Fermi GBM trigger 261106787 is not a GRB
  84. GRB 090410: MITSuME optical upper limits
  85. GRB 090408b: IPN Triangulation
  86. GRB 090328b: IPN Triangulation
  87. GRB 090410: Swift-BAT refined analysis
  88. GRB 090410: Swift detection of a burst
  89. Konus-Wind and Konus-RF observations of GRB 090408b
  90. GRB090408 : TAOS optical observations
  91. GRB 090409: Fermi GBM detection
  92. Swift-BAT Trigger 348781 is not a GRB
  93. Swift-BAT Trigger 348720 is not a GRB
  94. GRB 090406: pseudo-z= 0.91 from prompt emission spectrum
  95. GRB090408, RIMOTS optical upper limits
  96. GRB 090408: Xinglong TNT optical Upper Limit
  97. Swift-BAT trigger 348781: almost certainly not a burst
  98. Fermi GBM Detection of a weak source
  99. GRB 090408B: MASTER II-Kourovka optical observations
  100. GRB 090408: Swift detection of a burst

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