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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 210901A: GROND observations
  2. GRB 210903B: Fermi GBM Final Localization
  3. Fermi GBM observation of a burst from SGR J1555.2-5402
  4. GRB 210903A: Fermi GBM Final Real-time Localization
  5. GRB 210901A: Swift-XRT refined Analysis
  6. GRB 210901A: Swift-BAT refined analysis
  7. GRB 210901A: Enhanced Swift-XRT position
  8. GRB 210901A: LCO Optical Upper Limit
  9. Swift GRB 210901A: Global MASTER-Net observations report
  10. GRB 210901A: Swift detection of a burst
  11. GRB 210827A: further Swift-XRT observations
  12. GRB 210822A: CALET Gamma-Ray Burst Monitor detection
  13. GRB 210827A: Swift/UVOT Upper Limits
  14. GRB 210827A: BOOTES-5/JGT optical upper limit
  15. Integral GRB210829.17: Global MASTER-Net observations report
  16. IBAS Alert n. 9366 not a GRB
  17. Integral GRB210829.14: Global MASTER-Net observations report
  18. GRB 210827A: Fermi GBM Observation
  19. GRB 210826A: AstroSat CZTI detection
  20. Fermi GRB 210827A: Global MASTER-Net observations report
  21. Fermi GRB 210827B: Global MASTER-Net observations report
  22. GRB 210827A: Swift-XRT observations
  23. GRB 210827A: Swift ToO observations
  24. GRB 210827A: Swift/BAT-GUANO detection and arcminute localization
  25. GRB 210820A: CAHA 2.2m Optical Detection
  26. GRB 210824A: Swift/UVOT Upper Limits
  27. GRB 210826A: Swift/UVOT Upper Limits
  28. POLAR detection of a SGR-like burst
  29. GRB 210827B: BALROG localization (Fermi Trigger 651751821 / GRB 210827424)
  30. GRB 210827B: Fermi GBM Final Real-time Localization
  31. GRB 210826A: Swift-XRT observations
  32. GRB 210827A: Fermi GBM Final Real-time Localization
  33. GRB 210822A: CAHA 2.2m observations
  34. GRB 210824A: Swift-BAT refined analysis
  35. GRB 210826A: Fermi-LAT detection
  36. Fermi GRB 210826A: Global MASTER-Net observations report
  37. GRB 210826A: Tiled Swift observations
  38. GRB 210824A: MITSuME Akeno optical upper limits
  39. GRB 210826A: BALROG localization (Fermi Trigger 651654110 / GRB 210826293)
  40. GRB 210826A: Fermi GBM Final Real-time Localization
  41. Swift GRB210825.29: Global MASTER-Net observations report
  42. GRB 210822A: TSHAO continued optical observation
  43. GRB 210822A: VLA detection
  44. GRB 210822A: TSHAO optical observation
  45. Swift detection of an outburst from SGR Swift J1555.2-5402
  46. GRB 210822A: Swift/UVOT Detection
  47. Swift GRB 210824A: Global MASTER-Net observations report
  48. GRB 210824A: BOOTES-5/JGT optical upper limit
  49. GRB 210824A: Fermi GBM Observation
  50. Fermi GRB 210824A: Global MASTER-Net observations report
  51. GRB 210824A: Nanshan/NEXT optical upper limit
  52. GRB 210824A: Swift-XRT refined Analysis
  53. GRB 210822A: GROND observations
  54. GRB 210824A: Enhanced Swift-XRT position
  55. GRB 210822A: Abbey Ridge Observatory optical afterglow observation
  56. GRB 210824A: Swift detection of a burst
  57. GRB 210824A: Fermi GBM Final Real-time Localization
  58. GRB 210822B: DDOTI Upper Limits on the Afterglow
  59. GRB 210822A: Detection by GRBAlpha
  60. GRB 210822A: GECAM refined analysis
  61. GRB 210820A: GROND observations
  62. Konus-Wind detection of GRB 210822A
  63. GRB 210822A: AstroSat CZTI detection
  64. GRB 210822A: NOT photometry and spectroscopy
  65. GRB 210822A: Swift-XRT refined Analysis
  66. Fermi trigger No 651306769: Global MASTER-Net observations report
  67. GRB 210822A: Swift-BAT refined analysis
  68. GRB 210820A: NUTTelA-TAO / BSTI Early Optical Limits (Preliminary)
  69. GRB 210822A: Fermi-LAT detection
  70. GRB 210820A: Swift/UVOT Detection
  71. Fermi GRB 210822B: Global MASTER-Net observations report
  72. GRB 210822A: Nanshan/NEXT optical observations
  73. GRB 210822B: Fermi GBM Final Real-time Localization
  74. GRB 210822A: Enhanced Swift-XRT position
  75. Swift GRB 210822A: Global MASTER-Net observations report
  76. GRB 210822A: RATIR Optical Detections
  77. GRB 210822A: KAIT Optical Afterglow Confirmation
  78. GRB 210822A: GECAM detection
  79. GRB 210822A: Swift detection of a burst with an optical afterglow
  80. Fermi GRB 210821A: Global MASTER-Net observations report
  81. GRB 210820A: Swift-BAT refined analysis
  82. GRB 210820A: LT optical upper limit
  83. GRB 210820A: LCO Optical Upper Limit
  84. GRB 210820A: RATIR Optical Detections
  85. GRB 210821A: Fermi GBM Final Real-time Localization
  86. GRB 210820A: NOT optical upper limit
  87. GRB 210820A: Nanshan/NEXT optical upper limit
  88. GRB 210820A: Swift-XRT refined Analysis
  89. GRB 210820A: Enhanced Swift-XRT position
  90. Swift GRB 210820A: Global MASTER-Net observations report
  91. GRB 210820B: Fermi GBM Final Localization
  92. GRB 210820A: Swift detection of a burst with an optical counterpart
  93. Fermi trigger No 651110719: Global MASTER-Net observations report
  94. Swift GRB210818.68: Global MASTER-Net observations report
  95. Swift GRB 210818A: Global MASTER-Net observations report
  96. GRB 210818A: Swift-XRT refined Analysis
  97. GRB 210818A: Swift-BAT refined analysis
  98. GRB 210726A: VLA radio afterglow detection
  99. Konus-Wind detection of GRB 210818A
  100. Swift Trigger 1069242 is Cyg X-1

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