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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 Alert 230217.87: Global MASTER-Net observations report
  2. GRB 230218A is not a GRB
  3. GRB 230218A: Fermi GBM Final Real-time Localization
  4. GRB 230217A: AGILE/MCAL detection
  5. GRB 230207B: CALET Gamma-Ray Burst Monitor detection
  6. GRB 230216B: AstroSat CZTI detection
  7. GRB 230216A: SVOM/C-GFT optical upper limit
  8. GRB 230217A: Swift detection of a short burst
  9. GRB 230217A: Fermi GBM Final Real-time Localization
  10. IceCube-230217A - IceCube observation of a high-energy neutrino candidate track-like event
  11. GRB 230216A: Swift-BAT refined analysis
  12. GRB 230216A: Swift-XRT refined Analysis
  13. GRB 230205A: Lowell Discovery Telescope Observations
  14. GRB 230204B: Lowell Discovery Telescope Observations
  15. Swift GRB 230216A: Global MASTER-Net observations report
  16. GRB 230216A: Enhanced Swift-XRT position
  17. GRB 230216A: AKO Upper Limit
  18. GRB 230216A: Zadko observatory - Gingin optical observations
  19. GRB 230216A: Swift detection of a burst
  20. Fermi GRB 230215A: Global MASTER-Net observations report
  21. GRB 230215A: Fermi GBM Final Real-time Localization
  22. GRB 230209B: AGILE detection
  23. GRB 230209B: Fermi GBM Observation
  24. IPN triangulation of GRB 230209B
  25. GRB 230204B: CALET Gamma-Ray Burst Monitor detection
  26. GRB 230204B: ATCA radio detection
  27. Outburst from LS V +44 17 / RX J0440.9+4431: Transient detection by GRBAlpha
  28. Fermi trigger No 697926015: Global MASTER-Net observations report
  29. Fermi trigger No 697904388: Global MASTER-Net observations report
  30. 230211A is not a GRB
  31. GRB 230211A: Fermi GBM Final Real-time Localization
  32. GRB 230209B: Swift/BAT-GUANO detection outside the coded FOV
  33. Fermi trigger No 697678542: Global MASTER-Net observations report
  34. Swift Trigger 1153670 is probably not a GRB
  35. GRB 230210A: Fermi GBM Final Real-time Localization
  36. Fermi GRB 230209B: Global MASTER-Net observations report
  37. GRB 230209B: Fermi GBM Final Real-time Localization
  38. GRB 230205A: 6 GHz VLA observations
  39. GRB 230209A is not a GRB
  40. GRB 230205A: SUBARU HSC pre-imaging for host galaxy search
  41. GRB 230209A: Fermi GBM Final Real-time Localization
  42. GRB 221009A: Continued Swift Observations
  43. Fermi Gamma-ray Burst Monitor trigger 230208382/697540213 is not a GRB
  44. GRB 230207B: Detection by GRBAlpha
  45. GRB 230205A: possible host galaxy detection with the Schmidt - Asiago telescope
  46. GRB 230204B: MASTER early OT detection
  47. GRB 230208A: Fermi GBM Final Real-time Localization
  48. Fermi Gamma-ray Burst Monitor triggers 230206723/697396830 and 230206797/697403223 are not GRBs
  49. GRB 230207B: Swift/BAT-GUANO detection outside the coded FOV
  50. ZTF23aabmzlp/AT2023azs: Neil Gehrels Swift Observatory X-ray observations
  51. GRB 230207B: AGILE detection of a burst
  52. Fermi GRB 230207A: Global MASTER-Net observations report
  53. GRB 230207A: Fermi GBM Final Real-time Localization
  54. GRB 230204B: LCOGT Optical Upper Limits
  55. GRB 230204B: Swift/UVOT Upper Limits
  56. Fermi trigger No 697403223: Global MASTER-Net observations report
  57. Fermi trigger No 697396830: Global MASTER-Net observations report
  58. GRB 230205A: Swift/UVOT Upper Limits
  59. GRB 230204B: Fermi GBM detection
  60. Fermi Gamma-ray Burst Monitor triggers due to recent activity of RX J0440.9+4431 (LS V +44 17)
  61. GRB 230205A: LCOGT Optical Upper Limits
  62. GRB 230204B: Swift-XRT afterglow detection
  63. GRB 230204B: 3.6m DOT optical observation
  64. GRB 230205A: SVOM/C-GFT optical upper limit
  65. GRB 230205A: OHP/T193 optical observations
  66. GRB 230204B: VLT/X-shooter redshift
  67. GRB 230205A: Swift-BAT refined analysis (T90 = 2.3 s)
  68. GRB 230204A: Swift-BAT refined analysis
  69. GRB 230204B: ATLAS detection of the optical afterglow and a projected location in a nearby galaxy group
  70. GRB 230205A: Swift-XRT refined Analysis
  71. GRB 230204B: Swift ToO observations
  72. GRB 230205A: Enhanced Swift-XRT position
  73. GRB 230205A: BOOTES-5/JGT early optical upper limit
  74. GRB 230204B: Detection by GRBAlpha
  75. GRB 230204B: AGILE detection
  76. GRB 230205A: Swift detection of a burst
  77. IceCube-230201A: BOOTES-4/MET Optical Upper Limits
  78. GRB 230204B: GIT discovery of the likely optical afterglow
  79. GRB 230204B: AstroSat CZTI detection
  80. GRB 230204B: Swift/BAT-GUANO detection outside the coded FOV
  81. GRB 230204A: Swift/UVOT Upper Limits
  82. GRB 230204B: MAXI/GSC detection
  83. GRB 230204A: Swift-XRT refined Analysis
  84. GRB 230204A/Swift J1552.8-5055: LCOGT Optical Counterpart Candidate
  85. Fermi trigger No 697208885: Global MASTER-Net observations report
  86. GRB 230204A: Enhanced Swift-XRT position
  87. GRB 230204A: Swift detection of a possible burst (or possible transient Swift J1552.8-5055)
  88. GRB 230201B: TURBO Optical Upper Limits
  89. Fermi Gamma-ray Burst Monitor trigger 230203275 / 697098930 is not a GRB
  90. Fermi trigger No 697098930: Global MASTER-Net observations report
  91. IceCube-230201A: Upper limits from a search for additional neutrino events in IceCube
  92. ZTF23aabmzlp/AT2023azs: Lulin 1m LOT optical observations
  93. GRB 221216A: Swift-BAT refined analysis
  94. ZTF23aabmzlp/AT2023azs: VLA radio detection
  95. ZTF23aaarlti/AT2023avj: AMI-LA radio detection
  96. ZTF23aabmzlp/AT2023azs: AMI-LA radio upper limit
  97. IceCube Alert 230201.26: Global MASTER-Net observations report
  98. Fermi GRB 230201B: Global MASTER-Net observations report
  99. Fermi-LAT gamma-ray observations of IceCube-230201A
  100. GRB 230201B: Fermi GBM Final Real-time Localization

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