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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 230124A: Fermi GBM Final Real-time Localization
  2. GRB 230123A: Swift-BAT refined analysis
  3. GRB 230122A: Swift/BAT-GUANO detection
  4. Fermi-LAT gamma-ray observations of IceCube-230122A
  5. GRB 230123A: Swift/UVOT Upper Limits
  6. GRB 230123A: Swift-XRT refined Analysis
  7. GRB 230123A: Enhanced Swift-XRT position
  8. GRB 230123A: Zadko observatory - Gingin optical observations
  9. GRB 230116C: Swift-XRT observations
  10. GRB 230123A: Swift detection of a burst
  11. IceCube Alert 230122.16: Global MASTER-Net observations report
  12. IceCube-230122A - IceCube observation of a high-energy neutrino candidate track-like event
  13. GRB 230116B: Fermi GBM observation
  14. Trigger 1150107: Swift detection of LS V +44 17
  15. GRB 230120A: AstroSat CZTI detection
  16. IPN triangulation of GRB 230116B (short)
  17. GRB 230119A: CALET Gamma-Ray Burst Monitor detection
  18. GRB 230116D: 3.6m DOT optical upper limit
  19. GRB 230119A: Fermi GBM Final Real-time Localization
  20. Fermi GRB 230118A: Global MASTER-Net observations report
  21. GRB 230118A: Fermi GBM Final Real-time Localization
  22. GRB 230116D: Swift-BAT refined analysis
  23. GRB 230116C: Swift-BAT refined analysis
  24. GRB 230116D: SAO RAS further observations
  25. GRB 230116D: SAO RAS photometry
  26. GRB 230116D: KGO RC-25 optical observations
  27. GRB 230116D: Sintez-Newton/CrAO optical observations
  28. GRB 230116D: LCOGT Optical Upper Limit
  29. GRB 230116D: SAO RAS redshift
  30. Fermi trigger No 695569700: Global MASTER-Net observations report
  31. GRB 230116D: Swift-XRT refined Analysis
  32. Fermi GRB 230117A: Global MASTER-Net observations report
  33. GRB 230117A: Fermi GBM Final Real-time Localization
  34. GRB 230116D: GIT optical follow-up
  35. GRB 230116D: GIT optical follow-up
  36. GRB 230116D: Enhanced Swift-XRT position
  37. GRB 230116D: SAO RAS observations of OT brightening
  38. GRB 230116D: Sintez-Newton/CrAO optical afterglow detection
  39. GRB 230116D: Nanshan/NEXT optical afterglow detection
  40. GRB 230116D: Swift detection of a burst
  41. Swift GRB230116.88: Global MASTER-Net observations report
  42. IceCube-230112A: No Candidate Counterparts from the Zwicky Transient Facility
  43. GRB 230116C: Swift detection of a burst
  44. GRB 230116B: Fermi GBM Final Real-time Localization
  45. GRB 230116A: Fermi GBM Final Real-time Localization
  46. GRB 230114A: Detection by VZLUSAT-2
  47. Fermi-LAT gamma-ray observations of IceCube-230112A
  48. GRB 230114A: Fermi GBM Final Real-time Localization
  49. Fermi-LAT Gamma-ray Observations of IceCube-Cascade-230109A
  50. Fermi-LAT Gamma-ray Observations of IceCube-Cascade-221229A
  51. IceCube-230112A: Upper limits from a search for additional neutrino events in IceCube
  52. IceCube-230112A: BOOTES-4/MET Optical Upper Limit
  53. Trigger 1148770: Swift detection of Cyg X-1 due to Star Tracker loss of lock
  54. GRB 230111A: Fermi GBM Observation
  55. IceCube-230112A - IceCube observation of a high-energy neutrino candidate track-like event
  56. Fermi GRB 230112A: Global MASTER-Net observations report
  57. IceCube Alert 230112.28: Global MASTER-Net observations report
  58. GRB 230112A: Fermi GBM Final Real-time Localization
  59. GRB 230111A: MAXI/GSC detection
  60. GRB 230111A: Fermi GBM Final Real-time Localization
  61. GRB 230106: AstroSat LAXPC detection
  62. IceCube-Cascade 230109A: Upper limits from a search for additional neutrino events in IceCube
  63. Fermi trigger No 695057654: Global MASTER-Net observations report
  64. IceCube-221223A: JCMT/SCUBA2 observations
  65. GRB 230102A: Fermi GBM Observation
  66. Fermi Gamma-ray Burst Monitor trigger 694043024/221229905 is not a GRB
  67. GRB 221231A: 3.6m DOT optical upper limit
  68. GRB 230104A: AGILE/MCAL detection of a burst
  69. GRB 230102A: Swift/BAT-GUANO detection outside the coded FOV
  70. GRB 221231A: Fermi GBM Observation
  71. GRB 221230A: CALET Gamma-Ray Burst Monitor detection
  72. Fermi Gamma-ray Burst Monitor trigger 694259491/230101411 is not a GRB
  73. GRB 230102A: Detection by GRBAlpha
  74. Fermi Gamma-ray Burst Monitor trigger 694302022/230101903 is not a GRB
  75. GRB 230101A: AstroSat CZTI detection
  76. Fermi trigger No 694259491: Global MASTER-Net observations report
  77. GRB 221231A: Swift-XRT afterglow detection
  78. GRB 230102A: AGILE/MCAL detection
  79. GRB 230102A: Fermi GBM Final Real-time Localization
  80. GRB 221231A: AKO Upper Limit
  81. GRB 221231A: Swift-XRT observations
  82. IceCube-221223A: No Candidate Counterparts from the Zwicky Transient Facility
  83. GRB 221231A: Swift ToO observations
  84. GRB 221231A: Swift/BAT-GUANO arcminute localization of a possibly short burst
  85. Fermi trigger No 694232203: Global MASTER-Net observations report
  86. GRB 230101A: Fermi GBM Final Real-time Localization
  87. GRB 221231A: Fermi GBM Final Real-time Localization
  88. Subject: IceCube-Cascade 221229A: Upper limits from a search for additional neutrino events in IceCube
  89. IceCube-221229A: Upper limits from a search for additional neutrino events in IceCube
  90. Fermi-LAT gamma-ray observations of IceCube-221229A
  91. GRB 221226A: Fermi GBM detection
  92. IceCube-221229A: BOOTES-2/TELMA Optical Upper Limit
  93. IPN triangulation of GRB 221226A
  94. IceCube-221229A - IceCube observation of a high-energy neutrino candidate track-like event
  95. GRB 221226A: Swift/BAT-GUANO detection outside the coded FOV
  96. ZTF22acaruqr/AT2022adzb: Neil Gehrels Swift Observatory X-ray detection
  97. GRB 221226B: LCOGT Optical Upper Limits
  98. IceCube-221224A: Upper limits from a search for additional neutrino events in IceCube
  99. IceCube-221223A: Upper limits from a search for additional neutrino events in IceCube
  100. GRB 221228A: Fermi GBM Final Real-time Localization

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