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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. Fermi Gamma-ray Burst Monitor trigger 230203275 / 697098930 is not a GRB
  2. Fermi trigger No 697098930: Global MASTER-Net observations report
  3. IceCube-230201A: Upper limits from a search for additional neutrino events in IceCube
  4. ZTF23aabmzlp/AT2023azs: Lulin 1m LOT optical observations
  5. GRB 221216A: Swift-BAT refined analysis
  6. ZTF23aabmzlp/AT2023azs: VLA radio detection
  7. ZTF23aaarlti/AT2023avj: AMI-LA radio detection
  8. ZTF23aabmzlp/AT2023azs: AMI-LA radio upper limit
  9. IceCube Alert 230201.26: Global MASTER-Net observations report
  10. Fermi GRB 230201B: Global MASTER-Net observations report
  11. Fermi-LAT gamma-ray observations of IceCube-230201A
  12. GRB 230201B: Fermi GBM Final Real-time Localization
  13. GRB 230126A: Detection by VZLUSAT-2
  14. Fermi GRB 230201A: Global MASTER-Net observations report
  15. IceCube-230201A - IceCube observation of a high-energy neutrino candidate track-like event
  16. GRB 221009A: radio afterglow detection with the EVN
  17. GRB 230201A: Fermi GBM Final Real-time Localization
  18. ZTF23aabmzlp/AT2023azs: LCOGT Optical Detection
  19. ZTF23aaarlti/AT2023avj: Assy continued optical observations
  20. ZTF23aabmzlp/AT2023azs: Mondy and AbAO optical observations
  21. AT2023avj: X-ray Detection with Swift/XRT
  22. ZTF23aabmzlp/AT2023azs: 1.3m DFOT optical observations
  23. GRB 230129A: AstroSat CZTI detection
  24. GRB 230128A: AstroSat CZTI detection
  25. GRB 230130A: Fermi GBM Final Real-time Localization
  26. ZTF23aaarlti/AT2023avj: VLA radio detection
  27. GRB 230129A: Fermi GBM Final Real-time Localization
  28. GRB 230128A: Fermi GBM Final Real-time Localization
  29. ZTF23aabmzlp/AT2023azs: GIT confirmation of the likely afterglow
  30. ZTF23aabmzlp/AT2023azs: Zwicky Transient Facility discovery of a fast optical transient
  31. IceCube-230122A: BOOTES-2/TELMA Optical Upper Limit
  32. AT2023avj ZTF Candidate: Assy optical observations
  33. ZTF and LT Observations of AT2023avj, a Candidate Optical Afterglow
  34. GRB 230126A: Fermi GBM Final Real-time Localization
  35. Swift-XRT observations of NuEm-230125A
  36. Trigger 1150965: Swift detection of LS V +44 17
  37. GRB 230124A: Fermi GBM Observation
  38. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230125A
  39. GRB 230124A: Swift/BAT-GUANO detection outside the coded FOV
  40. IceCube-230122A: Upper limits from a search for additional neutrino events in IceCube
  41. GRB 230114B: Detection by VZLUSAT-2
  42. GRB 230123A: LCOGT Optical Upper Limits
  43. Fermi GRB 230124A: Global MASTER-Net observations report
  44. GRB 230124A: Fermi GBM Final Real-time Localization
  45. GRB 230123A: Swift-BAT refined analysis
  46. GRB 230122A: Swift/BAT-GUANO detection
  47. Fermi-LAT gamma-ray observations of IceCube-230122A
  48. GRB 230123A: Swift/UVOT Upper Limits
  49. GRB 230123A: Swift-XRT refined Analysis
  50. GRB 230123A: Enhanced Swift-XRT position
  51. GRB 230123A: Zadko observatory - Gingin optical observations
  52. GRB 230116C: Swift-XRT observations
  53. GRB 230123A: Swift detection of a burst
  54. IceCube Alert 230122.16: Global MASTER-Net observations report
  55. IceCube-230122A - IceCube observation of a high-energy neutrino candidate track-like event
  56. GRB 230116B: Fermi GBM observation
  57. Trigger 1150107: Swift detection of LS V +44 17
  58. GRB 230120A: AstroSat CZTI detection
  59. IPN triangulation of GRB 230116B (short)
  60. GRB 230119A: CALET Gamma-Ray Burst Monitor detection
  61. GRB 230116D: 3.6m DOT optical upper limit
  62. GRB 230119A: Fermi GBM Final Real-time Localization
  63. Fermi GRB 230118A: Global MASTER-Net observations report
  64. GRB 230118A: Fermi GBM Final Real-time Localization
  65. GRB 230116D: Swift-BAT refined analysis
  66. GRB 230116C: Swift-BAT refined analysis
  67. GRB 230116D: SAO RAS further observations
  68. GRB 230116D: SAO RAS photometry
  69. GRB 230116D: KGO RC-25 optical observations
  70. GRB 230116D: Sintez-Newton/CrAO optical observations
  71. GRB 230116D: LCOGT Optical Upper Limit
  72. GRB 230116D: SAO RAS redshift
  73. Fermi trigger No 695569700: Global MASTER-Net observations report
  74. GRB 230116D: Swift-XRT refined Analysis
  75. Fermi GRB 230117A: Global MASTER-Net observations report
  76. GRB 230117A: Fermi GBM Final Real-time Localization
  77. GRB 230116D: GIT optical follow-up
  78. GRB 230116D: GIT optical follow-up
  79. GRB 230116D: Enhanced Swift-XRT position
  80. GRB 230116D: SAO RAS observations of OT brightening
  81. GRB 230116D: Sintez-Newton/CrAO optical afterglow detection
  82. GRB 230116D: Nanshan/NEXT optical afterglow detection
  83. GRB 230116D: Swift detection of a burst
  84. Swift GRB230116.88: Global MASTER-Net observations report
  85. IceCube-230112A: No Candidate Counterparts from the Zwicky Transient Facility
  86. GRB 230116C: Swift detection of a burst
  87. GRB 230116B: Fermi GBM Final Real-time Localization
  88. GRB 230116A: Fermi GBM Final Real-time Localization
  89. GRB 230114A: Detection by VZLUSAT-2
  90. Fermi-LAT gamma-ray observations of IceCube-230112A
  91. GRB 230114A: Fermi GBM Final Real-time Localization
  92. Fermi-LAT Gamma-ray Observations of IceCube-Cascade-230109A
  93. Fermi-LAT Gamma-ray Observations of IceCube-Cascade-221229A
  94. IceCube-230112A: Upper limits from a search for additional neutrino events in IceCube
  95. IceCube-230112A: BOOTES-4/MET Optical Upper Limit
  96. Trigger 1148770: Swift detection of Cyg X-1 due to Star Tracker loss of lock
  97. GRB 230111A: Fermi GBM Observation
  98. IceCube-230112A - IceCube observation of a high-energy neutrino candidate track-like event
  99. Fermi GRB 230112A: Global MASTER-Net observations report
  100. IceCube Alert 230112.28: Global MASTER-Net observations report

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