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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 210822A: AstroSat CZTI detection
  2. GRB 210822A: NOT photometry and spectroscopy
  3. GRB 210822A: Swift-XRT refined Analysis
  4. Fermi trigger No 651306769: Global MASTER-Net observations report
  5. GRB 210822A: Swift-BAT refined analysis
  6. GRB 210820A: NUTTelA-TAO / BSTI Early Optical Limits (Preliminary)
  7. GRB 210822A: Fermi-LAT detection
  8. GRB 210820A: Swift/UVOT Detection
  9. Fermi GRB 210822B: Global MASTER-Net observations report
  10. GRB 210822A: Nanshan/NEXT optical observations
  11. GRB 210822B: Fermi GBM Final Real-time Localization
  12. GRB 210822A: Enhanced Swift-XRT position
  13. Swift GRB 210822A: Global MASTER-Net observations report
  14. GRB 210822A: RATIR Optical Detections
  15. GRB 210822A: KAIT Optical Afterglow Confirmation
  16. GRB 210822A: GECAM detection
  17. GRB 210822A: Swift detection of a burst with an optical afterglow
  18. Fermi GRB 210821A: Global MASTER-Net observations report
  19. GRB 210820A: Swift-BAT refined analysis
  20. GRB 210820A: LT optical upper limit
  21. GRB 210820A: LCO Optical Upper Limit
  22. GRB 210820A: RATIR Optical Detections
  23. GRB 210821A: Fermi GBM Final Real-time Localization
  24. GRB 210820A: NOT optical upper limit
  25. GRB 210820A: Nanshan/NEXT optical upper limit
  26. GRB 210820A: Swift-XRT refined Analysis
  27. GRB 210820A: Enhanced Swift-XRT position
  28. Swift GRB 210820A: Global MASTER-Net observations report
  29. GRB 210820B: Fermi GBM Final Localization
  30. GRB 210820A: Swift detection of a burst with an optical counterpart
  31. Fermi trigger No 651110719: Global MASTER-Net observations report
  32. Swift GRB210818.68: Global MASTER-Net observations report
  33. Swift GRB 210818A: Global MASTER-Net observations report
  34. GRB 210818A: Swift-XRT refined Analysis
  35. GRB 210818A: Swift-BAT refined analysis
  36. GRB 210726A: VLA radio afterglow detection
  37. Konus-Wind detection of GRB 210818A
  38. Swift Trigger 1069242 is Cyg X-1
  39. GRB 210818A: AstroSat CZTI detection
  40. GRB 210818A: AGILE detection
  41. GRB 210818A: Enhanced Swift-XRT position
  42. GRB 210818A: Swift detection of a burst with an optical counterpart
  43. IceCube-210811A: Upper limits from a search for additional neutrino events in IceCube
  44. IceCube-210730A: not observable by Fermi-GBM
  45. IceCube-210811A: Upper limits from Fermi-GBM Observations
  46. GRB 210815A: BALROG localization (Fermi Trigger 650687034 / GRB 210815100)
  47. GRB 210815A: Fermi GBM Final Real-time Localization
  48. Fermi trigger No 650687034: Global MASTER-Net observations report
  49. GRB 210812A is consistent with being a lensed GRB
  50. IceCube-210811A: No Candidate Counterparts from the Zwicky Transient Facility
  51. GRB 210712A: Fermi GBM observation
  52. GRB 210813A: BALROG localization (Fermi Trigger 650508868 / GRB 210813038)
  53. Fermi GRB 210813A: Global MASTER-Net observations report
  54. GRB 210813A: Fermi GBM Final Real-time Localization
  55. Fermi-LAT Gamma-ray Observations of IceCube-210811A
  56. Retraction of Fermi GBM GCN 30630 and GCN 30632
  57. GRB 210807A: continued Assy, AbAO and Mondy observations
  58. Fermi GRB 210812A: Global MASTER-Net observations report
  59. GRB 210812B: Fermi GBM Final Real-time Localization
  60. GRB 210812A: BALROG localization (Fermi Trigger 650479626 / GRB 210812699)
  61. GRB 210812A: Fermi GBM Final Real-time Localization
  62. GRB 080102A: Fermi GBM Final Real-time Localization
  63. SGR 1935+2154: SPI INTEGRAL observations on 2021 August 5
  64. GRB 080101A: Fermi GBM Final Real-time Localization
  65. GRB 210730A: Tautenburg observations
  66. GRB 210807A: Tautenburg observations
  67. IceCube-210811A - IceCube observation of a high-energy neutrino candidate track-like event
  68. IceCube Alert 210811.09: Global MASTER-Net observations report
  69. GRB 210807C: Swift-BAT refined analysis
  70. GRB 210807A: Detection by GRBAlpha
  71. GRB 210807A: Swift-BAT refined analysis
  72. GRB 210802A: Further Swift/XRT observation and afterglow confirmation
  73. GRB 210807C: Swift-XRT refined Analysis
  74. GRB 210807C: Fermi GBM detection
  75. GRB 210807C: Swift/UVOT Upper Limits
  76. GRB 210807A: Swift/UVOT Detection
  77. GRB 210807A: Swift-XRT refined Analysis
  78. GRB 210807A: correction to the GCN Circ. #30614 Assy optical observations
  79. GRB 210807C: Enhanced Swift-XRT position
  80. GRB 210610B: Assy optical observations
  81. Swift GRB210807.74: Global MASTER-Net observations report
  82. Fermi GRB 210807C: Global MASTER-Net observations report
  83. Swift GRB210807.96: Global MASTER-Net observations report
  84. GRB 210807C: Swift detection of a burst
  85. GRB 210807C: Fermi GBM Final Real-time Localization
  86. Fermi GRB 210807B: Global MASTER-Net observations report
  87. Swift GRB 210807A: Global MASTER-Net observations report
  88. Swift GRB210807.79: Global MASTER-Net observations report
  89. Swift GRB210807.78: Global MASTER-Net observations report
  90. Fermi trigger No 650046564: Global MASTER-Net observations report
  91. GRB 210807A: Enhanced Swift-XRT position
  92. GRB 210807A: BOOTES-5/JGT optical afterglow detection
  93. GRB 210807B: Fermi GBM Final Real-time Localization
  94. GRB 210807A: Swift detection of a burst with an optical counterpart
  95. Konus-Wind detection of a burst from SGR 1935+2154 on 2021 August 5
  96. IPN Triangulation of a bright burst from SGR 1935+2154
  97. Fermi trigger No 649814537: Global MASTER-Net observations report
  98. GRB 210802A: MITSuME Okayama optical upper limits
  99. GRB 210803A: Fermi GBM observation
  100. Fermi trigger No 649684549: Global MASTER-Net observations report

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