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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. AT2023avj ZTF Candidate: Assy optical observations
  2. ZTF and LT Observations of AT2023avj, a Candidate Optical Afterglow
  3. GRB 230126A: Fermi GBM Final Real-time Localization
  4. Swift-XRT observations of NuEm-230125A
  5. Trigger 1150965: Swift detection of LS V +44 17
  6. GRB 230124A: Fermi GBM Observation
  7. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230125A
  8. GRB 230124A: Swift/BAT-GUANO detection outside the coded FOV
  9. IceCube-230122A: Upper limits from a search for additional neutrino events in IceCube
  10. GRB 230114B: Detection by VZLUSAT-2
  11. GRB 230123A: LCOGT Optical Upper Limits
  12. Fermi GRB 230124A: Global MASTER-Net observations report
  13. GRB 230124A: Fermi GBM Final Real-time Localization
  14. GRB 230123A: Swift-BAT refined analysis
  15. GRB 230122A: Swift/BAT-GUANO detection
  16. Fermi-LAT gamma-ray observations of IceCube-230122A
  17. GRB 230123A: Swift/UVOT Upper Limits
  18. GRB 230123A: Swift-XRT refined Analysis
  19. GRB 230123A: Enhanced Swift-XRT position
  20. GRB 230123A: Zadko observatory - Gingin optical observations
  21. GRB 230116C: Swift-XRT observations
  22. GRB 230123A: Swift detection of a burst
  23. IceCube Alert 230122.16: Global MASTER-Net observations report
  24. IceCube-230122A - IceCube observation of a high-energy neutrino candidate track-like event
  25. GRB 230116B: Fermi GBM observation
  26. Trigger 1150107: Swift detection of LS V +44 17
  27. GRB 230120A: AstroSat CZTI detection
  28. IPN triangulation of GRB 230116B (short)
  29. GRB 230119A: CALET Gamma-Ray Burst Monitor detection
  30. GRB 230116D: 3.6m DOT optical upper limit
  31. GRB 230119A: Fermi GBM Final Real-time Localization
  32. Fermi GRB 230118A: Global MASTER-Net observations report
  33. GRB 230118A: Fermi GBM Final Real-time Localization
  34. GRB 230116D: Swift-BAT refined analysis
  35. GRB 230116C: Swift-BAT refined analysis
  36. GRB 230116D: SAO RAS further observations
  37. GRB 230116D: SAO RAS photometry
  38. GRB 230116D: KGO RC-25 optical observations
  39. GRB 230116D: Sintez-Newton/CrAO optical observations
  40. GRB 230116D: LCOGT Optical Upper Limit
  41. GRB 230116D: SAO RAS redshift
  42. Fermi trigger No 695569700: Global MASTER-Net observations report
  43. GRB 230116D: Swift-XRT refined Analysis
  44. Fermi GRB 230117A: Global MASTER-Net observations report
  45. GRB 230117A: Fermi GBM Final Real-time Localization
  46. GRB 230116D: GIT optical follow-up
  47. GRB 230116D: GIT optical follow-up
  48. GRB 230116D: Enhanced Swift-XRT position
  49. GRB 230116D: SAO RAS observations of OT brightening
  50. GRB 230116D: Sintez-Newton/CrAO optical afterglow detection
  51. GRB 230116D: Nanshan/NEXT optical afterglow detection
  52. GRB 230116D: Swift detection of a burst
  53. Swift GRB230116.88: Global MASTER-Net observations report
  54. IceCube-230112A: No Candidate Counterparts from the Zwicky Transient Facility
  55. GRB 230116C: Swift detection of a burst
  56. GRB 230116B: Fermi GBM Final Real-time Localization
  57. GRB 230116A: Fermi GBM Final Real-time Localization
  58. GRB 230114A: Detection by VZLUSAT-2
  59. Fermi-LAT gamma-ray observations of IceCube-230112A
  60. GRB 230114A: Fermi GBM Final Real-time Localization
  61. Fermi-LAT Gamma-ray Observations of IceCube-Cascade-230109A
  62. Fermi-LAT Gamma-ray Observations of IceCube-Cascade-221229A
  63. IceCube-230112A: Upper limits from a search for additional neutrino events in IceCube
  64. IceCube-230112A: BOOTES-4/MET Optical Upper Limit
  65. Trigger 1148770: Swift detection of Cyg X-1 due to Star Tracker loss of lock
  66. GRB 230111A: Fermi GBM Observation
  67. IceCube-230112A - IceCube observation of a high-energy neutrino candidate track-like event
  68. Fermi GRB 230112A: Global MASTER-Net observations report
  69. IceCube Alert 230112.28: Global MASTER-Net observations report
  70. GRB 230112A: Fermi GBM Final Real-time Localization
  71. GRB 230111A: MAXI/GSC detection
  72. GRB 230111A: Fermi GBM Final Real-time Localization
  73. GRB 230106: AstroSat LAXPC detection
  74. IceCube-Cascade 230109A: Upper limits from a search for additional neutrino events in IceCube
  75. Fermi trigger No 695057654: Global MASTER-Net observations report
  76. IceCube-221223A: JCMT/SCUBA2 observations
  77. GRB 230102A: Fermi GBM Observation
  78. Fermi Gamma-ray Burst Monitor trigger 694043024/221229905 is not a GRB
  79. GRB 221231A: 3.6m DOT optical upper limit
  80. GRB 230104A: AGILE/MCAL detection of a burst
  81. GRB 230102A: Swift/BAT-GUANO detection outside the coded FOV
  82. GRB 221231A: Fermi GBM Observation
  83. GRB 221230A: CALET Gamma-Ray Burst Monitor detection
  84. Fermi Gamma-ray Burst Monitor trigger 694259491/230101411 is not a GRB
  85. GRB 230102A: Detection by GRBAlpha
  86. Fermi Gamma-ray Burst Monitor trigger 694302022/230101903 is not a GRB
  87. GRB 230101A: AstroSat CZTI detection
  88. Fermi trigger No 694259491: Global MASTER-Net observations report
  89. GRB 221231A: Swift-XRT afterglow detection
  90. GRB 230102A: AGILE/MCAL detection
  91. GRB 230102A: Fermi GBM Final Real-time Localization
  92. GRB 221231A: AKO Upper Limit
  93. GRB 221231A: Swift-XRT observations
  94. IceCube-221223A: No Candidate Counterparts from the Zwicky Transient Facility
  95. GRB 221231A: Swift ToO observations
  96. GRB 221231A: Swift/BAT-GUANO arcminute localization of a possibly short burst
  97. Fermi trigger No 694232203: Global MASTER-Net observations report
  98. GRB 230101A: Fermi GBM Final Real-time Localization
  99. GRB 221231A: Fermi GBM Final Real-time Localization
  100. Subject: IceCube-Cascade 221229A: Upper limits from a search for additional neutrino events in IceCube

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