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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 230304A: AstroSat CZTI detection
  2. GRB 230304B: Detection by GRBAlpha
  3. GRB 230304C: Fermi GBM Final Real-time Localization
  4. GRB 230304B: Fermi GBM Final Real-time Localization
  5. GRB 230304A: Fermi GBM Final Real-time Localization
  6. GRB 230228A: 6 GHz VLA radio upper limit
  7. GRB 230228A: Swift-BAT refined analysis
  8. GRB 230228A: Swift/UVOT Upper Limits
  9. Fermi GRB 230301B: Global MASTER-Net observations report
  10. GRB 230301B: Fermi GBM Final Real-time Localization
  11. GRB 230228A: Fermi GBM Observation
  12. Fermi trigger No 699294715: Global MASTER-Net observations report
  13. GRB 230228A: OSN optical upper limit
  14. Fermi trigger No 699311646: Global MASTER-Net observations report
  15. GRB 230301A: Fermi GBM Final Real-time Localization
  16. GRB 230228A: Swift-XRT refined Analysis
  17. GRB 230228A: Mondy optical upper limit
  18. GRB 230228A: Enhanced Swift-XRT position
  19. GRB 230228A: Nanshan/NEXT optical upper limit
  20. GRB 230228A: Miryang Arirang Astronomical Observatory (MAAO) 0.7-m telescope optical upper limit
  21. GRB 230228A: Prompt enhanced Swift-XRT position
  22. GRB 230228A: Swift detection of a possibly short burst
  23. Fermi GRB 230227A: Global MASTER-Net observations report
  24. GRB 230227A: Fermi GBM Final Real-time Localization
  25. Fermi trigger No 699029364: Global MASTER-Net observations report
  26. GRB 230217A: VLT/FORS2 optical observations and candidate counterpart
  27. GRB 230216A Mondy Observations
  28. GRB 230205A: VLA radio afterglow confirmation
  29. IceCube-230220A: Upper limits from a search for additional neutrino events in IceCube
  30. GRB 230217A: Swift/UVOT Upper Limits
  31. GRB 230216A: Swift/UVOT Upper Limits
  32. GRB 230217A: Continued Gemini Observations
  33. GRB 230220A: Correction to GCN 33352
  34. GRB 230222A: Fermi GBM Final Real-time Localization
  35. GRB 230217A: Swift-XRT afterglow detection
  36. Fermi-LAT gamma-ray observations of IceCube-230220A
  37. GRB 230217A: Swift-BAT refined analysis
  38. Fermi GRB 230220B: Global MASTER-Net observations report
  39. GRB 230217A: AstroSat CZTI detection
  40. GRB 230217A: Gemini South optical upper limits
  41. GRB 230216B: CALET Gamma-Ray Burst Monitor detection
  42. GRB 230217A: 6 GHz VLA observations
  43. GRB 230220B: Fermi GBM Final Real-time Localization
  44. GRB 230217A: Gemini-South Optical Observation
  45. IceCube-230217A: Upper limits from a search for additional neutrino events in IceCube
  46. IceCube-230220A - IceCube observation of a high-energy neutrino candidate
  47. GRB 230217A: Fermi GBM observation
  48. GRB 230220A: MAXI/GSC detection
  49. IceCube-230217A: BOOTES-4/MET Optical Observations
  50. Fermi-LAT gamma-ray observations of IceCube-230217A
  51. Konus-Wind detection of GRB 230217A
  52. GRB 230217A: Swift-XRT observations
  53. Fermi trigger No 698427992: Global MASTER-Net observations report
  54. IceCube Alert 230217.87: Global MASTER-Net observations report
  55. GRB 230218A is not a GRB
  56. GRB 230218A: Fermi GBM Final Real-time Localization
  57. GRB 230217A: AGILE/MCAL detection
  58. GRB 230207B: CALET Gamma-Ray Burst Monitor detection
  59. GRB 230216B: AstroSat CZTI detection
  60. GRB 230216A: SVOM/C-GFT optical upper limit
  61. GRB 230217A: Swift detection of a short burst
  62. GRB 230217A: Fermi GBM Final Real-time Localization
  63. IceCube-230217A - IceCube observation of a high-energy neutrino candidate track-like event
  64. GRB 230216A: Swift-BAT refined analysis
  65. GRB 230216A: Swift-XRT refined Analysis
  66. GRB 230205A: Lowell Discovery Telescope Observations
  67. GRB 230204B: Lowell Discovery Telescope Observations
  68. Swift GRB 230216A: Global MASTER-Net observations report
  69. GRB 230216A: Enhanced Swift-XRT position
  70. GRB 230216A: AKO Upper Limit
  71. GRB 230216A: Zadko observatory - Gingin optical observations
  72. GRB 230216A: Swift detection of a burst
  73. Fermi GRB 230215A: Global MASTER-Net observations report
  74. GRB 230215A: Fermi GBM Final Real-time Localization
  75. GRB 230209B: AGILE detection
  76. GRB 230209B: Fermi GBM Observation
  77. IPN triangulation of GRB 230209B
  78. GRB 230204B: CALET Gamma-Ray Burst Monitor detection
  79. GRB 230204B: ATCA radio detection
  80. Outburst from LS V +44 17 / RX J0440.9+4431: Transient detection by GRBAlpha
  81. Fermi trigger No 697926015: Global MASTER-Net observations report
  82. Fermi trigger No 697904388: Global MASTER-Net observations report
  83. 230211A is not a GRB
  84. GRB 230211A: Fermi GBM Final Real-time Localization
  85. GRB 230209B: Swift/BAT-GUANO detection outside the coded FOV
  86. Fermi trigger No 697678542: Global MASTER-Net observations report
  87. Swift Trigger 1153670 is probably not a GRB
  88. GRB 230210A: Fermi GBM Final Real-time Localization
  89. Fermi GRB 230209B: Global MASTER-Net observations report
  90. GRB 230209B: Fermi GBM Final Real-time Localization
  91. GRB 230205A: 6 GHz VLA observations
  92. GRB 230209A is not a GRB
  93. GRB 230205A: SUBARU HSC pre-imaging for host galaxy search
  94. GRB 230209A: Fermi GBM Final Real-time Localization
  95. GRB 221009A: Continued Swift Observations
  96. Fermi Gamma-ray Burst Monitor trigger 230208382/697540213 is not a GRB
  97. GRB 230207B: Detection by GRBAlpha
  98. GRB 230205A: possible host galaxy detection with the Schmidt - Asiago telescope
  99. GRB 230204B: MASTER early OT detection
  100. GRB 230208A: Fermi GBM Final Real-time Localization

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