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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. Fermi GRB 210909A: Global MASTER-Net observations report
  2. GECAM observation of a burst from SGR J1555.2-5402
  3. GRB 210909A: Fermi GBM Final Real-time Localization
  4. GRB 210905A: Swift/UVOT Upper Limits
  5. GRB 210905A: ATCA detection
  6. GRB 210905A: ALMA detection
  7. GRB 210905A: AstroSat CZTI detection
  8. GRB 210905A, GROND observations
  9. Konus-Wind detection of GRB 210905A
  10. Fermi GBM Sub-Threshold Detection of GRB 210905A
  11. Fermi GBM trigger 652585475 / 210906073 is not a GRB
  12. Fermi trigger No 652585475: Global MASTER-Net observations report
  13. GRB 210905A: Swift-XRT refined Analysis
  14. GRB 210610A: Maidanak and AbAO optical observations
  15. GRB 210827B: GECAM detection
  16. GRB 210905A: DECam Detection
  17. GRB 210905A: REM NIR afterglow detection
  18. GRB 210905A: VLT/X-shooter spectroscopic redshift
  19. GRB 210905A: Continued LCO Optical Observations
  20. GRB 210905A: LCO Optical Detection
  21. GRB 210905A: Enhanced Swift-XRT position
  22. GRB 210901A: Swift/UVOT Upper Limits
  23. Swift GRB 210905A: Global MASTER-Net observations report
  24. GRB 210905A: Swift detection of a burst
  25. Fermi GRB 210904A: Global MASTER-Net observations report
  26. GRB 210904A: Fermi GBM Final Real-time Localization
  27. Swift GRB210903.59: Global MASTER-Net observations report
  28. Swift GRB210903.58: Global MASTER-Net observations report
  29. Swift GRB210903.58: Global MASTER-Net observations report
  30. Fermi GRB 210903A: Global MASTER-Net observations report
  31. GRB 210903C: Fermi GBM Final Real-time Localization
  32. GRB 210820A: TSHAO optical upper limit
  33. Fermi GRB 210903B: Global MASTER-Net observations report
  34. GRB 210901A: GROND observations
  35. GRB 210903B: Fermi GBM Final Localization
  36. Fermi GBM observation of a burst from SGR J1555.2-5402
  37. GRB 210903A: Fermi GBM Final Real-time Localization
  38. GRB 210901A: Swift-XRT refined Analysis
  39. GRB 210901A: Swift-BAT refined analysis
  40. GRB 210901A: Enhanced Swift-XRT position
  41. GRB 210901A: LCO Optical Upper Limit
  42. Swift GRB 210901A: Global MASTER-Net observations report
  43. GRB 210901A: Swift detection of a burst
  44. GRB 210827A: further Swift-XRT observations
  45. GRB 210822A: CALET Gamma-Ray Burst Monitor detection
  46. GRB 210827A: Swift/UVOT Upper Limits
  47. GRB 210827A: BOOTES-5/JGT optical upper limit
  48. Integral GRB210829.17: Global MASTER-Net observations report
  49. IBAS Alert n. 9366 not a GRB
  50. Integral GRB210829.14: Global MASTER-Net observations report
  51. GRB 210827A: Fermi GBM Observation
  52. GRB 210826A: AstroSat CZTI detection
  53. Fermi GRB 210827A: Global MASTER-Net observations report
  54. Fermi GRB 210827B: Global MASTER-Net observations report
  55. GRB 210827A: Swift-XRT observations
  56. GRB 210827A: Swift ToO observations
  57. GRB 210827A: Swift/BAT-GUANO detection and arcminute localization
  58. GRB 210820A: CAHA 2.2m Optical Detection
  59. GRB 210824A: Swift/UVOT Upper Limits
  60. GRB 210826A: Swift/UVOT Upper Limits
  61. POLAR detection of a SGR-like burst
  62. GRB 210827B: BALROG localization (Fermi Trigger 651751821 / GRB 210827424)
  63. GRB 210827B: Fermi GBM Final Real-time Localization
  64. GRB 210826A: Swift-XRT observations
  65. GRB 210827A: Fermi GBM Final Real-time Localization
  66. GRB 210822A: CAHA 2.2m observations
  67. GRB 210824A: Swift-BAT refined analysis
  68. GRB 210826A: Fermi-LAT detection
  69. Fermi GRB 210826A: Global MASTER-Net observations report
  70. GRB 210826A: Tiled Swift observations
  71. GRB 210824A: MITSuME Akeno optical upper limits
  72. GRB 210826A: BALROG localization (Fermi Trigger 651654110 / GRB 210826293)
  73. GRB 210826A: Fermi GBM Final Real-time Localization
  74. Swift GRB210825.29: Global MASTER-Net observations report
  75. GRB 210822A: TSHAO continued optical observation
  76. GRB 210822A: VLA detection
  77. GRB 210822A: TSHAO optical observation
  78. Swift detection of an outburst from SGR Swift J1555.2-5402
  79. GRB 210822A: Swift/UVOT Detection
  80. Swift GRB 210824A: Global MASTER-Net observations report
  81. GRB 210824A: BOOTES-5/JGT optical upper limit
  82. GRB 210824A: Fermi GBM Observation
  83. Fermi GRB 210824A: Global MASTER-Net observations report
  84. GRB 210824A: Nanshan/NEXT optical upper limit
  85. GRB 210824A: Swift-XRT refined Analysis
  86. GRB 210822A: GROND observations
  87. GRB 210824A: Enhanced Swift-XRT position
  88. GRB 210822A: Abbey Ridge Observatory optical afterglow observation
  89. GRB 210824A: Swift detection of a burst
  90. GRB 210824A: Fermi GBM Final Real-time Localization
  91. GRB 210822B: DDOTI Upper Limits on the Afterglow
  92. GRB 210822A: Detection by GRBAlpha
  93. GRB 210822A: GECAM refined analysis
  94. GRB 210820A: GROND observations
  95. Konus-Wind detection of GRB 210822A
  96. GRB 210822A: AstroSat CZTI detection
  97. GRB 210822A: NOT photometry and spectroscopy
  98. GRB 210822A: Swift-XRT refined Analysis
  99. Fermi trigger No 651306769: Global MASTER-Net observations report
  100. GRB 210822A: Swift-BAT refined analysis

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