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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. Swift GRB 210824A: Global MASTER-Net observations report
  2. GRB 210824A: BOOTES-5/JGT optical upper limit
  3. GRB 210824A: Fermi GBM Observation
  4. Fermi GRB 210824A: Global MASTER-Net observations report
  5. GRB 210824A: Nanshan/NEXT optical upper limit
  6. GRB 210824A: Swift-XRT refined Analysis
  7. GRB 210822A: GROND observations
  8. GRB 210824A: Enhanced Swift-XRT position
  9. GRB 210822A: Abbey Ridge Observatory optical afterglow observation
  10. GRB 210824A: Swift detection of a burst
  11. GRB 210824A: Fermi GBM Final Real-time Localization
  12. GRB 210822B: DDOTI Upper Limits on the Afterglow
  13. GRB 210822A: Detection by GRBAlpha
  14. GRB 210822A: GECAM refined analysis
  15. GRB 210820A: GROND observations
  16. Konus-Wind detection of GRB 210822A
  17. GRB 210822A: AstroSat CZTI detection
  18. GRB 210822A: NOT photometry and spectroscopy
  19. GRB 210822A: Swift-XRT refined Analysis
  20. Fermi trigger No 651306769: Global MASTER-Net observations report
  21. GRB 210822A: Swift-BAT refined analysis
  22. GRB 210820A: NUTTelA-TAO / BSTI Early Optical Limits (Preliminary)
  23. GRB 210822A: Fermi-LAT detection
  24. GRB 210820A: Swift/UVOT Detection
  25. Fermi GRB 210822B: Global MASTER-Net observations report
  26. GRB 210822A: Nanshan/NEXT optical observations
  27. GRB 210822B: Fermi GBM Final Real-time Localization
  28. GRB 210822A: Enhanced Swift-XRT position
  29. Swift GRB 210822A: Global MASTER-Net observations report
  30. GRB 210822A: RATIR Optical Detections
  31. GRB 210822A: KAIT Optical Afterglow Confirmation
  32. GRB 210822A: GECAM detection
  33. GRB 210822A: Swift detection of a burst with an optical afterglow
  34. Fermi GRB 210821A: Global MASTER-Net observations report
  35. GRB 210820A: Swift-BAT refined analysis
  36. GRB 210820A: LT optical upper limit
  37. GRB 210820A: LCO Optical Upper Limit
  38. GRB 210820A: RATIR Optical Detections
  39. GRB 210821A: Fermi GBM Final Real-time Localization
  40. GRB 210820A: NOT optical upper limit
  41. GRB 210820A: Nanshan/NEXT optical upper limit
  42. GRB 210820A: Swift-XRT refined Analysis
  43. GRB 210820A: Enhanced Swift-XRT position
  44. Swift GRB 210820A: Global MASTER-Net observations report
  45. GRB 210820B: Fermi GBM Final Localization
  46. GRB 210820A: Swift detection of a burst with an optical counterpart
  47. Fermi trigger No 651110719: Global MASTER-Net observations report
  48. Swift GRB210818.68: Global MASTER-Net observations report
  49. Swift GRB 210818A: Global MASTER-Net observations report
  50. GRB 210818A: Swift-XRT refined Analysis
  51. GRB 210818A: Swift-BAT refined analysis
  52. GRB 210726A: VLA radio afterglow detection
  53. Konus-Wind detection of GRB 210818A
  54. Swift Trigger 1069242 is Cyg X-1
  55. GRB 210818A: AstroSat CZTI detection
  56. GRB 210818A: AGILE detection
  57. GRB 210818A: Enhanced Swift-XRT position
  58. GRB 210818A: Swift detection of a burst with an optical counterpart
  59. IceCube-210811A: Upper limits from a search for additional neutrino events in IceCube
  60. IceCube-210730A: not observable by Fermi-GBM
  61. IceCube-210811A: Upper limits from Fermi-GBM Observations
  62. GRB 210815A: BALROG localization (Fermi Trigger 650687034 / GRB 210815100)
  63. GRB 210815A: Fermi GBM Final Real-time Localization
  64. Fermi trigger No 650687034: Global MASTER-Net observations report
  65. GRB 210812A is consistent with being a lensed GRB
  66. IceCube-210811A: No Candidate Counterparts from the Zwicky Transient Facility
  67. GRB 210712A: Fermi GBM observation
  68. GRB 210813A: BALROG localization (Fermi Trigger 650508868 / GRB 210813038)
  69. Fermi GRB 210813A: Global MASTER-Net observations report
  70. GRB 210813A: Fermi GBM Final Real-time Localization
  71. Fermi-LAT Gamma-ray Observations of IceCube-210811A
  72. Retraction of Fermi GBM GCN 30630 and GCN 30632
  73. GRB 210807A: continued Assy, AbAO and Mondy observations
  74. Fermi GRB 210812A: Global MASTER-Net observations report
  75. GRB 210812B: Fermi GBM Final Real-time Localization
  76. GRB 210812A: BALROG localization (Fermi Trigger 650479626 / GRB 210812699)
  77. GRB 210812A: Fermi GBM Final Real-time Localization
  78. GRB 080102A: Fermi GBM Final Real-time Localization
  79. SGR 1935+2154: SPI INTEGRAL observations on 2021 August 5
  80. GRB 080101A: Fermi GBM Final Real-time Localization
  81. GRB 210730A: Tautenburg observations
  82. GRB 210807A: Tautenburg observations
  83. IceCube-210811A - IceCube observation of a high-energy neutrino candidate track-like event
  84. IceCube Alert 210811.09: Global MASTER-Net observations report
  85. GRB 210807C: Swift-BAT refined analysis
  86. GRB 210807A: Detection by GRBAlpha
  87. GRB 210807A: Swift-BAT refined analysis
  88. GRB 210802A: Further Swift/XRT observation and afterglow confirmation
  89. GRB 210807C: Swift-XRT refined Analysis
  90. GRB 210807C: Fermi GBM detection
  91. GRB 210807C: Swift/UVOT Upper Limits
  92. GRB 210807A: Swift/UVOT Detection
  93. GRB 210807A: Swift-XRT refined Analysis
  94. GRB 210807A: correction to the GCN Circ. #30614 Assy optical observations
  95. GRB 210807C: Enhanced Swift-XRT position
  96. GRB 210610B: Assy optical observations
  97. Swift GRB210807.74: Global MASTER-Net observations report
  98. Fermi GRB 210807C: Global MASTER-Net observations report
  99. Swift GRB210807.96: Global MASTER-Net observations report
  100. GRB 210807C: Swift detection of a burst

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