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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 230207B: Detection by GRBAlpha
  2. GRB 230205A: possible host galaxy detection with the Schmidt - Asiago telescope
  3. GRB 230204B: MASTER early OT detection
  4. GRB 230208A: Fermi GBM Final Real-time Localization
  5. Fermi Gamma-ray Burst Monitor triggers 230206723/697396830 and 230206797/697403223 are not GRBs
  6. GRB 230207B: Swift/BAT-GUANO detection outside the coded FOV
  7. ZTF23aabmzlp/AT2023azs: Neil Gehrels Swift Observatory X-ray observations
  8. GRB 230207B: AGILE detection of a burst
  9. Fermi GRB 230207A: Global MASTER-Net observations report
  10. GRB 230207A: Fermi GBM Final Real-time Localization
  11. GRB 230204B: LCOGT Optical Upper Limits
  12. GRB 230204B: Swift/UVOT Upper Limits
  13. Fermi trigger No 697403223: Global MASTER-Net observations report
  14. Fermi trigger No 697396830: Global MASTER-Net observations report
  15. GRB 230205A: Swift/UVOT Upper Limits
  16. GRB 230204B: Fermi GBM detection
  17. Fermi Gamma-ray Burst Monitor triggers due to recent activity of RX J0440.9+4431 (LS V +44 17)
  18. GRB 230205A: LCOGT Optical Upper Limits
  19. GRB 230204B: Swift-XRT afterglow detection
  20. GRB 230204B: 3.6m DOT optical observation
  21. GRB 230205A: SVOM/C-GFT optical upper limit
  22. GRB 230205A: OHP/T193 optical observations
  23. GRB 230204B: VLT/X-shooter redshift
  24. GRB 230205A: Swift-BAT refined analysis (T90 = 2.3 s)
  25. GRB 230204A: Swift-BAT refined analysis
  26. GRB 230204B: ATLAS detection of the optical afterglow and a projected location in a nearby galaxy group
  27. GRB 230205A: Swift-XRT refined Analysis
  28. GRB 230204B: Swift ToO observations
  29. GRB 230205A: Enhanced Swift-XRT position
  30. GRB 230205A: BOOTES-5/JGT early optical upper limit
  31. GRB 230204B: Detection by GRBAlpha
  32. GRB 230204B: AGILE detection
  33. GRB 230205A: Swift detection of a burst
  34. IceCube-230201A: BOOTES-4/MET Optical Upper Limits
  35. GRB 230204B: GIT discovery of the likely optical afterglow
  36. GRB 230204B: AstroSat CZTI detection
  37. GRB 230204B: Swift/BAT-GUANO detection outside the coded FOV
  38. GRB 230204A: Swift/UVOT Upper Limits
  39. GRB 230204B: MAXI/GSC detection
  40. GRB 230204A: Swift-XRT refined Analysis
  41. GRB 230204A/Swift J1552.8-5055: LCOGT Optical Counterpart Candidate
  42. Fermi trigger No 697208885: Global MASTER-Net observations report
  43. GRB 230204A: Enhanced Swift-XRT position
  44. GRB 230204A: Swift detection of a possible burst (or possible transient Swift J1552.8-5055)
  45. GRB 230201B: TURBO Optical Upper Limits
  46. Fermi Gamma-ray Burst Monitor trigger 230203275 / 697098930 is not a GRB
  47. Fermi trigger No 697098930: Global MASTER-Net observations report
  48. IceCube-230201A: Upper limits from a search for additional neutrino events in IceCube
  49. ZTF23aabmzlp/AT2023azs: Lulin 1m LOT optical observations
  50. GRB 221216A: Swift-BAT refined analysis
  51. ZTF23aabmzlp/AT2023azs: VLA radio detection
  52. ZTF23aaarlti/AT2023avj: AMI-LA radio detection
  53. ZTF23aabmzlp/AT2023azs: AMI-LA radio upper limit
  54. IceCube Alert 230201.26: Global MASTER-Net observations report
  55. Fermi GRB 230201B: Global MASTER-Net observations report
  56. Fermi-LAT gamma-ray observations of IceCube-230201A
  57. GRB 230201B: Fermi GBM Final Real-time Localization
  58. GRB 230126A: Detection by VZLUSAT-2
  59. Fermi GRB 230201A: Global MASTER-Net observations report
  60. IceCube-230201A - IceCube observation of a high-energy neutrino candidate track-like event
  61. GRB 221009A: radio afterglow detection with the EVN
  62. GRB 230201A: Fermi GBM Final Real-time Localization
  63. ZTF23aabmzlp/AT2023azs: LCOGT Optical Detection
  64. ZTF23aaarlti/AT2023avj: Assy continued optical observations
  65. ZTF23aabmzlp/AT2023azs: Mondy and AbAO optical observations
  66. AT2023avj: X-ray Detection with Swift/XRT
  67. ZTF23aabmzlp/AT2023azs: 1.3m DFOT optical observations
  68. GRB 230129A: AstroSat CZTI detection
  69. GRB 230128A: AstroSat CZTI detection
  70. GRB 230130A: Fermi GBM Final Real-time Localization
  71. ZTF23aaarlti/AT2023avj: VLA radio detection
  72. GRB 230129A: Fermi GBM Final Real-time Localization
  73. GRB 230128A: Fermi GBM Final Real-time Localization
  74. ZTF23aabmzlp/AT2023azs: GIT confirmation of the likely afterglow
  75. ZTF23aabmzlp/AT2023azs: Zwicky Transient Facility discovery of a fast optical transient
  76. IceCube-230122A: BOOTES-2/TELMA Optical Upper Limit
  77. AT2023avj ZTF Candidate: Assy optical observations
  78. ZTF and LT Observations of AT2023avj, a Candidate Optical Afterglow
  79. GRB 230126A: Fermi GBM Final Real-time Localization
  80. Swift-XRT observations of NuEm-230125A
  81. Trigger 1150965: Swift detection of LS V +44 17
  82. GRB 230124A: Fermi GBM Observation
  83. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230125A
  84. GRB 230124A: Swift/BAT-GUANO detection outside the coded FOV
  85. IceCube-230122A: Upper limits from a search for additional neutrino events in IceCube
  86. GRB 230114B: Detection by VZLUSAT-2
  87. GRB 230123A: LCOGT Optical Upper Limits
  88. Fermi GRB 230124A: Global MASTER-Net observations report
  89. GRB 230124A: Fermi GBM Final Real-time Localization
  90. GRB 230123A: Swift-BAT refined analysis
  91. GRB 230122A: Swift/BAT-GUANO detection
  92. Fermi-LAT gamma-ray observations of IceCube-230122A
  93. GRB 230123A: Swift/UVOT Upper Limits
  94. GRB 230123A: Swift-XRT refined Analysis
  95. GRB 230123A: Enhanced Swift-XRT position
  96. GRB 230123A: Zadko observatory - Gingin optical observations
  97. GRB 230116C: Swift-XRT observations
  98. GRB 230123A: Swift detection of a burst
  99. IceCube Alert 230122.16: Global MASTER-Net observations report
  100. IceCube-230122A - IceCube observation of a high-energy neutrino candidate track-like event

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