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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 230228A: Fermi GBM Observation
  2. Fermi trigger No 699294715: Global MASTER-Net observations report
  3. GRB 230228A: OSN optical upper limit
  4. Fermi trigger No 699311646: Global MASTER-Net observations report
  5. GRB 230301A: Fermi GBM Final Real-time Localization
  6. GRB 230228A: Swift-XRT refined Analysis
  7. GRB 230228A: Mondy optical upper limit
  8. GRB 230228A: Enhanced Swift-XRT position
  9. GRB 230228A: Nanshan/NEXT optical upper limit
  10. GRB 230228A: Miryang Arirang Astronomical Observatory (MAAO) 0.7-m telescope optical upper limit
  11. GRB 230228A: Prompt enhanced Swift-XRT position
  12. GRB 230228A: Swift detection of a possibly short burst
  13. Fermi GRB 230227A: Global MASTER-Net observations report
  14. GRB 230227A: Fermi GBM Final Real-time Localization
  15. Fermi trigger No 699029364: Global MASTER-Net observations report
  16. GRB 230217A: VLT/FORS2 optical observations and candidate counterpart
  17. GRB 230216A Mondy Observations
  18. GRB 230205A: VLA radio afterglow confirmation
  19. IceCube-230220A: Upper limits from a search for additional neutrino events in IceCube
  20. GRB 230217A: Swift/UVOT Upper Limits
  21. GRB 230216A: Swift/UVOT Upper Limits
  22. GRB 230217A: Continued Gemini Observations
  23. GRB 230220A: Correction to GCN 33352
  24. GRB 230222A: Fermi GBM Final Real-time Localization
  25. GRB 230217A: Swift-XRT afterglow detection
  26. Fermi-LAT gamma-ray observations of IceCube-230220A
  27. GRB 230217A: Swift-BAT refined analysis
  28. Fermi GRB 230220B: Global MASTER-Net observations report
  29. GRB 230217A: AstroSat CZTI detection
  30. GRB 230217A: Gemini South optical upper limits
  31. GRB 230216B: CALET Gamma-Ray Burst Monitor detection
  32. GRB 230217A: 6 GHz VLA observations
  33. GRB 230220B: Fermi GBM Final Real-time Localization
  34. GRB 230217A: Gemini-South Optical Observation
  35. IceCube-230217A: Upper limits from a search for additional neutrino events in IceCube
  36. IceCube-230220A - IceCube observation of a high-energy neutrino candidate
  37. GRB 230217A: Fermi GBM observation
  38. GRB 230220A: MAXI/GSC detection
  39. IceCube-230217A: BOOTES-4/MET Optical Observations
  40. Fermi-LAT gamma-ray observations of IceCube-230217A
  41. Konus-Wind detection of GRB 230217A
  42. GRB 230217A: Swift-XRT observations
  43. Fermi trigger No 698427992: Global MASTER-Net observations report
  44. IceCube Alert 230217.87: Global MASTER-Net observations report
  45. GRB 230218A is not a GRB
  46. GRB 230218A: Fermi GBM Final Real-time Localization
  47. GRB 230217A: AGILE/MCAL detection
  48. GRB 230207B: CALET Gamma-Ray Burst Monitor detection
  49. GRB 230216B: AstroSat CZTI detection
  50. GRB 230216A: SVOM/C-GFT optical upper limit
  51. GRB 230217A: Swift detection of a short burst
  52. GRB 230217A: Fermi GBM Final Real-time Localization
  53. IceCube-230217A - IceCube observation of a high-energy neutrino candidate track-like event
  54. GRB 230216A: Swift-BAT refined analysis
  55. GRB 230216A: Swift-XRT refined Analysis
  56. GRB 230205A: Lowell Discovery Telescope Observations
  57. GRB 230204B: Lowell Discovery Telescope Observations
  58. Swift GRB 230216A: Global MASTER-Net observations report
  59. GRB 230216A: Enhanced Swift-XRT position
  60. GRB 230216A: AKO Upper Limit
  61. GRB 230216A: Zadko observatory - Gingin optical observations
  62. GRB 230216A: Swift detection of a burst
  63. Fermi GRB 230215A: Global MASTER-Net observations report
  64. GRB 230215A: Fermi GBM Final Real-time Localization
  65. GRB 230209B: AGILE detection
  66. GRB 230209B: Fermi GBM Observation
  67. IPN triangulation of GRB 230209B
  68. GRB 230204B: CALET Gamma-Ray Burst Monitor detection
  69. GRB 230204B: ATCA radio detection
  70. Outburst from LS V +44 17 / RX J0440.9+4431: Transient detection by GRBAlpha
  71. Fermi trigger No 697926015: Global MASTER-Net observations report
  72. Fermi trigger No 697904388: Global MASTER-Net observations report
  73. 230211A is not a GRB
  74. GRB 230211A: Fermi GBM Final Real-time Localization
  75. GRB 230209B: Swift/BAT-GUANO detection outside the coded FOV
  76. Fermi trigger No 697678542: Global MASTER-Net observations report
  77. Swift Trigger 1153670 is probably not a GRB
  78. GRB 230210A: Fermi GBM Final Real-time Localization
  79. Fermi GRB 230209B: Global MASTER-Net observations report
  80. GRB 230209B: Fermi GBM Final Real-time Localization
  81. GRB 230205A: 6 GHz VLA observations
  82. GRB 230209A is not a GRB
  83. GRB 230205A: SUBARU HSC pre-imaging for host galaxy search
  84. GRB 230209A: Fermi GBM Final Real-time Localization
  85. GRB 221009A: Continued Swift Observations
  86. Fermi Gamma-ray Burst Monitor trigger 230208382/697540213 is not a GRB
  87. GRB 230207B: Detection by GRBAlpha
  88. GRB 230205A: possible host galaxy detection with the Schmidt - Asiago telescope
  89. GRB 230204B: MASTER early OT detection
  90. GRB 230208A: Fermi GBM Final Real-time Localization
  91. Fermi Gamma-ray Burst Monitor triggers 230206723/697396830 and 230206797/697403223 are not GRBs
  92. GRB 230207B: Swift/BAT-GUANO detection outside the coded FOV
  93. ZTF23aabmzlp/AT2023azs: Neil Gehrels Swift Observatory X-ray observations
  94. GRB 230207B: AGILE detection of a burst
  95. Fermi GRB 230207A: Global MASTER-Net observations report
  96. GRB 230207A: Fermi GBM Final Real-time Localization
  97. GRB 230204B: LCOGT Optical Upper Limits
  98. GRB 230204B: Swift/UVOT Upper Limits
  99. Fermi trigger No 697403223: Global MASTER-Net observations report
  100. Fermi trigger No 697396830: Global MASTER-Net observations report

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