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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. IceCube-230201A: BOOTES-4/MET Optical Upper Limits
  2. GRB 230204B: GIT discovery of the likely optical afterglow
  3. GRB 230204B: AstroSat CZTI detection
  4. GRB 230204B: Swift/BAT-GUANO detection outside the coded FOV
  5. GRB 230204A: Swift/UVOT Upper Limits
  6. GRB 230204B: MAXI/GSC detection
  7. GRB 230204A: Swift-XRT refined Analysis
  8. GRB 230204A/Swift J1552.8-5055: LCOGT Optical Counterpart Candidate
  9. Fermi trigger No 697208885: Global MASTER-Net observations report
  10. GRB 230204A: Enhanced Swift-XRT position
  11. GRB 230204A: Swift detection of a possible burst (or possible transient Swift J1552.8-5055)
  12. GRB 230201B: TURBO Optical Upper Limits
  13. Fermi Gamma-ray Burst Monitor trigger 230203275 / 697098930 is not a GRB
  14. Fermi trigger No 697098930: Global MASTER-Net observations report
  15. IceCube-230201A: Upper limits from a search for additional neutrino events in IceCube
  16. ZTF23aabmzlp/AT2023azs: Lulin 1m LOT optical observations
  17. GRB 221216A: Swift-BAT refined analysis
  18. ZTF23aabmzlp/AT2023azs: VLA radio detection
  19. ZTF23aaarlti/AT2023avj: AMI-LA radio detection
  20. ZTF23aabmzlp/AT2023azs: AMI-LA radio upper limit
  21. IceCube Alert 230201.26: Global MASTER-Net observations report
  22. Fermi GRB 230201B: Global MASTER-Net observations report
  23. Fermi-LAT gamma-ray observations of IceCube-230201A
  24. GRB 230201B: Fermi GBM Final Real-time Localization
  25. GRB 230126A: Detection by VZLUSAT-2
  26. Fermi GRB 230201A: Global MASTER-Net observations report
  27. IceCube-230201A - IceCube observation of a high-energy neutrino candidate track-like event
  28. GRB 221009A: radio afterglow detection with the EVN
  29. GRB 230201A: Fermi GBM Final Real-time Localization
  30. ZTF23aabmzlp/AT2023azs: LCOGT Optical Detection
  31. ZTF23aaarlti/AT2023avj: Assy continued optical observations
  32. ZTF23aabmzlp/AT2023azs: Mondy and AbAO optical observations
  33. AT2023avj: X-ray Detection with Swift/XRT
  34. ZTF23aabmzlp/AT2023azs: 1.3m DFOT optical observations
  35. GRB 230129A: AstroSat CZTI detection
  36. GRB 230128A: AstroSat CZTI detection
  37. GRB 230130A: Fermi GBM Final Real-time Localization
  38. ZTF23aaarlti/AT2023avj: VLA radio detection
  39. GRB 230129A: Fermi GBM Final Real-time Localization
  40. GRB 230128A: Fermi GBM Final Real-time Localization
  41. ZTF23aabmzlp/AT2023azs: GIT confirmation of the likely afterglow
  42. ZTF23aabmzlp/AT2023azs: Zwicky Transient Facility discovery of a fast optical transient
  43. IceCube-230122A: BOOTES-2/TELMA Optical Upper Limit
  44. AT2023avj ZTF Candidate: Assy optical observations
  45. ZTF and LT Observations of AT2023avj, a Candidate Optical Afterglow
  46. GRB 230126A: Fermi GBM Final Real-time Localization
  47. Swift-XRT observations of NuEm-230125A
  48. Trigger 1150965: Swift detection of LS V +44 17
  49. GRB 230124A: Fermi GBM Observation
  50. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230125A
  51. GRB 230124A: Swift/BAT-GUANO detection outside the coded FOV
  52. IceCube-230122A: Upper limits from a search for additional neutrino events in IceCube
  53. GRB 230114B: Detection by VZLUSAT-2
  54. GRB 230123A: LCOGT Optical Upper Limits
  55. Fermi GRB 230124A: Global MASTER-Net observations report
  56. GRB 230124A: Fermi GBM Final Real-time Localization
  57. GRB 230123A: Swift-BAT refined analysis
  58. GRB 230122A: Swift/BAT-GUANO detection
  59. Fermi-LAT gamma-ray observations of IceCube-230122A
  60. GRB 230123A: Swift/UVOT Upper Limits
  61. GRB 230123A: Swift-XRT refined Analysis
  62. GRB 230123A: Enhanced Swift-XRT position
  63. GRB 230123A: Zadko observatory - Gingin optical observations
  64. GRB 230116C: Swift-XRT observations
  65. GRB 230123A: Swift detection of a burst
  66. IceCube Alert 230122.16: Global MASTER-Net observations report
  67. IceCube-230122A - IceCube observation of a high-energy neutrino candidate track-like event
  68. GRB 230116B: Fermi GBM observation
  69. Trigger 1150107: Swift detection of LS V +44 17
  70. GRB 230120A: AstroSat CZTI detection
  71. IPN triangulation of GRB 230116B (short)
  72. GRB 230119A: CALET Gamma-Ray Burst Monitor detection
  73. GRB 230116D: 3.6m DOT optical upper limit
  74. GRB 230119A: Fermi GBM Final Real-time Localization
  75. Fermi GRB 230118A: Global MASTER-Net observations report
  76. GRB 230118A: Fermi GBM Final Real-time Localization
  77. GRB 230116D: Swift-BAT refined analysis
  78. GRB 230116C: Swift-BAT refined analysis
  79. GRB 230116D: SAO RAS further observations
  80. GRB 230116D: SAO RAS photometry
  81. GRB 230116D: KGO RC-25 optical observations
  82. GRB 230116D: Sintez-Newton/CrAO optical observations
  83. GRB 230116D: LCOGT Optical Upper Limit
  84. GRB 230116D: SAO RAS redshift
  85. Fermi trigger No 695569700: Global MASTER-Net observations report
  86. GRB 230116D: Swift-XRT refined Analysis
  87. Fermi GRB 230117A: Global MASTER-Net observations report
  88. GRB 230117A: Fermi GBM Final Real-time Localization
  89. GRB 230116D: GIT optical follow-up
  90. GRB 230116D: GIT optical follow-up
  91. GRB 230116D: Enhanced Swift-XRT position
  92. GRB 230116D: SAO RAS observations of OT brightening
  93. GRB 230116D: Sintez-Newton/CrAO optical afterglow detection
  94. GRB 230116D: Nanshan/NEXT optical afterglow detection
  95. GRB 230116D: Swift detection of a burst
  96. Swift GRB230116.88: Global MASTER-Net observations report
  97. IceCube-230112A: No Candidate Counterparts from the Zwicky Transient Facility
  98. GRB 230116C: Swift detection of a burst
  99. GRB 230116B: Fermi GBM Final Real-time Localization
  100. GRB 230116A: Fermi GBM Final Real-time Localization

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