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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 230211A: Fermi GBM Final Real-time Localization
  2. GRB 230209B: Swift/BAT-GUANO detection outside the coded FOV
  3. Fermi trigger No 697678542: Global MASTER-Net observations report
  4. Swift Trigger 1153670 is probably not a GRB
  5. GRB 230210A: Fermi GBM Final Real-time Localization
  6. Fermi GRB 230209B: Global MASTER-Net observations report
  7. GRB 230209B: Fermi GBM Final Real-time Localization
  8. GRB 230205A: 6 GHz VLA observations
  9. GRB 230209A is not a GRB
  10. GRB 230205A: SUBARU HSC pre-imaging for host galaxy search
  11. GRB 230209A: Fermi GBM Final Real-time Localization
  12. GRB 221009A: Continued Swift Observations
  13. Fermi Gamma-ray Burst Monitor trigger 230208382/697540213 is not a GRB
  14. GRB 230207B: Detection by GRBAlpha
  15. GRB 230205A: possible host galaxy detection with the Schmidt - Asiago telescope
  16. GRB 230204B: MASTER early OT detection
  17. GRB 230208A: Fermi GBM Final Real-time Localization
  18. Fermi Gamma-ray Burst Monitor triggers 230206723/697396830 and 230206797/697403223 are not GRBs
  19. GRB 230207B: Swift/BAT-GUANO detection outside the coded FOV
  20. ZTF23aabmzlp/AT2023azs: Neil Gehrels Swift Observatory X-ray observations
  21. GRB 230207B: AGILE detection of a burst
  22. Fermi GRB 230207A: Global MASTER-Net observations report
  23. GRB 230207A: Fermi GBM Final Real-time Localization
  24. GRB 230204B: LCOGT Optical Upper Limits
  25. GRB 230204B: Swift/UVOT Upper Limits
  26. Fermi trigger No 697403223: Global MASTER-Net observations report
  27. Fermi trigger No 697396830: Global MASTER-Net observations report
  28. GRB 230205A: Swift/UVOT Upper Limits
  29. GRB 230204B: Fermi GBM detection
  30. Fermi Gamma-ray Burst Monitor triggers due to recent activity of RX J0440.9+4431 (LS V +44 17)
  31. GRB 230205A: LCOGT Optical Upper Limits
  32. GRB 230204B: Swift-XRT afterglow detection
  33. GRB 230204B: 3.6m DOT optical observation
  34. GRB 230205A: SVOM/C-GFT optical upper limit
  35. GRB 230205A: OHP/T193 optical observations
  36. GRB 230204B: VLT/X-shooter redshift
  37. GRB 230205A: Swift-BAT refined analysis (T90 = 2.3 s)
  38. GRB 230204A: Swift-BAT refined analysis
  39. GRB 230204B: ATLAS detection of the optical afterglow and a projected location in a nearby galaxy group
  40. GRB 230205A: Swift-XRT refined Analysis
  41. GRB 230204B: Swift ToO observations
  42. GRB 230205A: Enhanced Swift-XRT position
  43. GRB 230205A: BOOTES-5/JGT early optical upper limit
  44. GRB 230204B: Detection by GRBAlpha
  45. GRB 230204B: AGILE detection
  46. GRB 230205A: Swift detection of a burst
  47. IceCube-230201A: BOOTES-4/MET Optical Upper Limits
  48. GRB 230204B: GIT discovery of the likely optical afterglow
  49. GRB 230204B: AstroSat CZTI detection
  50. GRB 230204B: Swift/BAT-GUANO detection outside the coded FOV
  51. GRB 230204A: Swift/UVOT Upper Limits
  52. GRB 230204B: MAXI/GSC detection
  53. GRB 230204A: Swift-XRT refined Analysis
  54. GRB 230204A/Swift J1552.8-5055: LCOGT Optical Counterpart Candidate
  55. Fermi trigger No 697208885: Global MASTER-Net observations report
  56. GRB 230204A: Enhanced Swift-XRT position
  57. GRB 230204A: Swift detection of a possible burst (or possible transient Swift J1552.8-5055)
  58. GRB 230201B: TURBO Optical Upper Limits
  59. Fermi Gamma-ray Burst Monitor trigger 230203275 / 697098930 is not a GRB
  60. Fermi trigger No 697098930: Global MASTER-Net observations report
  61. IceCube-230201A: Upper limits from a search for additional neutrino events in IceCube
  62. ZTF23aabmzlp/AT2023azs: Lulin 1m LOT optical observations
  63. GRB 221216A: Swift-BAT refined analysis
  64. ZTF23aabmzlp/AT2023azs: VLA radio detection
  65. ZTF23aaarlti/AT2023avj: AMI-LA radio detection
  66. ZTF23aabmzlp/AT2023azs: AMI-LA radio upper limit
  67. IceCube Alert 230201.26: Global MASTER-Net observations report
  68. Fermi GRB 230201B: Global MASTER-Net observations report
  69. Fermi-LAT gamma-ray observations of IceCube-230201A
  70. GRB 230201B: Fermi GBM Final Real-time Localization
  71. GRB 230126A: Detection by VZLUSAT-2
  72. Fermi GRB 230201A: Global MASTER-Net observations report
  73. IceCube-230201A - IceCube observation of a high-energy neutrino candidate track-like event
  74. GRB 221009A: radio afterglow detection with the EVN
  75. GRB 230201A: Fermi GBM Final Real-time Localization
  76. ZTF23aabmzlp/AT2023azs: LCOGT Optical Detection
  77. ZTF23aaarlti/AT2023avj: Assy continued optical observations
  78. ZTF23aabmzlp/AT2023azs: Mondy and AbAO optical observations
  79. AT2023avj: X-ray Detection with Swift/XRT
  80. ZTF23aabmzlp/AT2023azs: 1.3m DFOT optical observations
  81. GRB 230129A: AstroSat CZTI detection
  82. GRB 230128A: AstroSat CZTI detection
  83. GRB 230130A: Fermi GBM Final Real-time Localization
  84. ZTF23aaarlti/AT2023avj: VLA radio detection
  85. GRB 230129A: Fermi GBM Final Real-time Localization
  86. GRB 230128A: Fermi GBM Final Real-time Localization
  87. ZTF23aabmzlp/AT2023azs: GIT confirmation of the likely afterglow
  88. ZTF23aabmzlp/AT2023azs: Zwicky Transient Facility discovery of a fast optical transient
  89. IceCube-230122A: BOOTES-2/TELMA Optical Upper Limit
  90. AT2023avj ZTF Candidate: Assy optical observations
  91. ZTF and LT Observations of AT2023avj, a Candidate Optical Afterglow
  92. GRB 230126A: Fermi GBM Final Real-time Localization
  93. Swift-XRT observations of NuEm-230125A
  94. Trigger 1150965: Swift detection of LS V +44 17
  95. GRB 230124A: Fermi GBM Observation
  96. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230125A
  97. GRB 230124A: Swift/BAT-GUANO detection outside the coded FOV
  98. IceCube-230122A: Upper limits from a search for additional neutrino events in IceCube
  99. GRB 230114B: Detection by VZLUSAT-2
  100. GRB 230123A: LCOGT Optical Upper Limits

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