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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').
  1. Fermi GRB 230227A: Global MASTER-Net observations report
  2. GRB 230227A: Fermi GBM Final Real-time Localization
  3. Fermi trigger No 699029364: Global MASTER-Net observations report
  4. GRB 230217A: VLT/FORS2 optical observations and candidate counterpart
  5. GRB 230216A Mondy Observations
  6. GRB 230205A: VLA radio afterglow confirmation
  7. IceCube-230220A: Upper limits from a search for additional neutrino events in IceCube
  8. GRB 230217A: Swift/UVOT Upper Limits
  9. GRB 230216A: Swift/UVOT Upper Limits
  10. GRB 230217A: Continued Gemini Observations
  11. GRB 230220A: Correction to GCN 33352
  12. GRB 230222A: Fermi GBM Final Real-time Localization
  13. GRB 230217A: Swift-XRT afterglow detection
  14. Fermi-LAT gamma-ray observations of IceCube-230220A
  15. GRB 230217A: Swift-BAT refined analysis
  16. Fermi GRB 230220B: Global MASTER-Net observations report
  17. GRB 230217A: AstroSat CZTI detection
  18. GRB 230217A: Gemini South optical upper limits
  19. GRB 230216B: CALET Gamma-Ray Burst Monitor detection
  20. GRB 230217A: 6 GHz VLA observations
  21. GRB 230220B: Fermi GBM Final Real-time Localization
  22. GRB 230217A: Gemini-South Optical Observation
  23. IceCube-230217A: Upper limits from a search for additional neutrino events in IceCube
  24. IceCube-230220A - IceCube observation of a high-energy neutrino candidate
  25. GRB 230217A: Fermi GBM observation
  26. GRB 230220A: MAXI/GSC detection
  27. IceCube-230217A: BOOTES-4/MET Optical Observations
  28. Fermi-LAT gamma-ray observations of IceCube-230217A
  29. Konus-Wind detection of GRB 230217A
  30. GRB 230217A: Swift-XRT observations
  31. Fermi trigger No 698427992: Global MASTER-Net observations report
  32. IceCube Alert 230217.87: Global MASTER-Net observations report
  33. GRB 230218A is not a GRB
  34. GRB 230218A: Fermi GBM Final Real-time Localization
  35. GRB 230217A: AGILE/MCAL detection
  36. GRB 230207B: CALET Gamma-Ray Burst Monitor detection
  37. GRB 230216B: AstroSat CZTI detection
  38. GRB 230216A: SVOM/C-GFT optical upper limit
  39. GRB 230217A: Swift detection of a short burst
  40. GRB 230217A: Fermi GBM Final Real-time Localization
  41. IceCube-230217A - IceCube observation of a high-energy neutrino candidate track-like event
  42. GRB 230216A: Swift-BAT refined analysis
  43. GRB 230216A: Swift-XRT refined Analysis
  44. GRB 230205A: Lowell Discovery Telescope Observations
  45. GRB 230204B: Lowell Discovery Telescope Observations
  46. Swift GRB 230216A: Global MASTER-Net observations report
  47. GRB 230216A: Enhanced Swift-XRT position
  48. GRB 230216A: AKO Upper Limit
  49. GRB 230216A: Zadko observatory - Gingin optical observations
  50. GRB 230216A: Swift detection of a burst
  51. Fermi GRB 230215A: Global MASTER-Net observations report
  52. GRB 230215A: Fermi GBM Final Real-time Localization
  53. GRB 230209B: AGILE detection
  54. GRB 230209B: Fermi GBM Observation
  55. IPN triangulation of GRB 230209B
  56. GRB 230204B: CALET Gamma-Ray Burst Monitor detection
  57. GRB 230204B: ATCA radio detection
  58. Outburst from LS V +44 17 / RX J0440.9+4431: Transient detection by GRBAlpha
  59. Fermi trigger No 697926015: Global MASTER-Net observations report
  60. Fermi trigger No 697904388: Global MASTER-Net observations report
  61. 230211A is not a GRB
  62. GRB 230211A: Fermi GBM Final Real-time Localization
  63. GRB 230209B: Swift/BAT-GUANO detection outside the coded FOV
  64. Fermi trigger No 697678542: Global MASTER-Net observations report
  65. Swift Trigger 1153670 is probably not a GRB
  66. GRB 230210A: Fermi GBM Final Real-time Localization
  67. Fermi GRB 230209B: Global MASTER-Net observations report
  68. GRB 230209B: Fermi GBM Final Real-time Localization
  69. GRB 230205A: 6 GHz VLA observations
  70. GRB 230209A is not a GRB
  71. GRB 230205A: SUBARU HSC pre-imaging for host galaxy search
  72. GRB 230209A: Fermi GBM Final Real-time Localization
  73. GRB 221009A: Continued Swift Observations
  74. Fermi Gamma-ray Burst Monitor trigger 230208382/697540213 is not a GRB
  75. GRB 230207B: Detection by GRBAlpha
  76. GRB 230205A: possible host galaxy detection with the Schmidt - Asiago telescope
  77. GRB 230204B: MASTER early OT detection
  78. GRB 230208A: Fermi GBM Final Real-time Localization
  79. Fermi Gamma-ray Burst Monitor triggers 230206723/697396830 and 230206797/697403223 are not GRBs
  80. GRB 230207B: Swift/BAT-GUANO detection outside the coded FOV
  81. ZTF23aabmzlp/AT2023azs: Neil Gehrels Swift Observatory X-ray observations
  82. GRB 230207B: AGILE detection of a burst
  83. Fermi GRB 230207A: Global MASTER-Net observations report
  84. GRB 230207A: Fermi GBM Final Real-time Localization
  85. GRB 230204B: LCOGT Optical Upper Limits
  86. GRB 230204B: Swift/UVOT Upper Limits
  87. Fermi trigger No 697403223: Global MASTER-Net observations report
  88. Fermi trigger No 697396830: Global MASTER-Net observations report
  89. GRB 230205A: Swift/UVOT Upper Limits
  90. GRB 230204B: Fermi GBM detection
  91. Fermi Gamma-ray Burst Monitor triggers due to recent activity of RX J0440.9+4431 (LS V +44 17)
  92. GRB 230205A: LCOGT Optical Upper Limits
  93. GRB 230204B: Swift-XRT afterglow detection
  94. GRB 230204B: 3.6m DOT optical observation
  95. GRB 230205A: SVOM/C-GFT optical upper limit
  96. GRB 230205A: OHP/T193 optical observations
  97. GRB 230204B: VLT/X-shooter redshift
  98. GRB 230205A: Swift-BAT refined analysis (T90 = 2.3 s)
  99. GRB 230204A: Swift-BAT refined analysis
  100. GRB 230204B: ATLAS detection of the optical afterglow and a projected location in a nearby galaxy group

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