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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 230307A: Swift/BAT upper limits on the early afterglow
  2. GRB 230307A: Upper limits from a neutrino search with IceCube
  3. GRB 230307A: Swift-XRT observations
  4. Fermi GRB 230307A: Global MASTER-Net observations report
  5. Konus-Wind detection of GRB 230307A
  6. GRB 230228A: VIRT Optical Upper Limit
  7. Improved IPN localization for GRB 230307A
  8. GRB 230307A: VZLUSAT-2 detection
  9. GRB 230304B: CALET Gamma-Ray Burst Monitor detection
  10. Fermi GRB 230308A: Global MASTER-Net observations report
  11. GRB 230308A: BALROG localization (Fermi Trigger 699975152 / GRB 230308564)
  12. GRB 230308A: Fermi GBM Final Real-time Localization
  13. GRB 230307A: Tiled Swift observations
  14. GRB 230307A: Detection by GRBAlpha
  15. GRB 230305A: Detection by GRBAlpha
  16. GRB 230307A: BALROG localization (Fermi Trigger 699896651/ GRB 230307656)
  17. GRB 230307A: AstroSat CZTI detection
  18. GRB 230307A: possibly the second highest GRB energy fluence ever identified
  19. IPN triangulation of GRB 230307A (long/very bright)
  20. GRB 230307A: AGILE/MCAL detection
  21. GRB 230307A: Fermi GBM Observation of a very bright burst
  22. Solar Orbiter STIX observation of GRB 230307A
  23. IceCube-230306A: Upper limits from a search for additional neutrino events in IceCube
  24. Fermi-LAT gamma-ray observations of IceCube-230306A
  25. GRB 230307A: Fermi GBM detection of a very bright GRB
  26. GRB 230307A: GECAM detection of an extremely bright burst
  27. GRB 230307A: Fermi GBM Final Real-time Localization
  28. Fermi trigger No 699811746: Global MASTER-Net observations report
  29. IceCube-230306A - IceCube observation of a high-energy neutrino candidate
  30. IceCube Alert 230306.46: Global MASTER-Net observations report
  31. GRB 230304C: AstroSat CZTI detection
  32. GRB 230304B: AstroSat CZTI detection
  33. GRB 230304A: AstroSat CZTI detection
  34. GRB 230304B: Detection by GRBAlpha
  35. GRB 230304C: Fermi GBM Final Real-time Localization
  36. GRB 230304B: Fermi GBM Final Real-time Localization
  37. GRB 230304A: Fermi GBM Final Real-time Localization
  38. GRB 230228A: 6 GHz VLA radio upper limit
  39. GRB 230228A: Swift-BAT refined analysis
  40. GRB 230228A: Swift/UVOT Upper Limits
  41. Fermi GRB 230301B: Global MASTER-Net observations report
  42. GRB 230301B: Fermi GBM Final Real-time Localization
  43. GRB 230228A: Fermi GBM Observation
  44. Fermi trigger No 699294715: Global MASTER-Net observations report
  45. GRB 230228A: OSN optical upper limit
  46. Fermi trigger No 699311646: Global MASTER-Net observations report
  47. GRB 230301A: Fermi GBM Final Real-time Localization
  48. GRB 230228A: Swift-XRT refined Analysis
  49. GRB 230228A: Mondy optical upper limit
  50. GRB 230228A: Enhanced Swift-XRT position
  51. GRB 230228A: Nanshan/NEXT optical upper limit
  52. GRB 230228A: Miryang Arirang Astronomical Observatory (MAAO) 0.7-m telescope optical upper limit
  53. GRB 230228A: Prompt enhanced Swift-XRT position
  54. GRB 230228A: Swift detection of a possibly short burst
  55. Fermi GRB 230227A: Global MASTER-Net observations report
  56. GRB 230227A: Fermi GBM Final Real-time Localization
  57. Fermi trigger No 699029364: Global MASTER-Net observations report
  58. GRB 230217A: VLT/FORS2 optical observations and candidate counterpart
  59. GRB 230216A Mondy Observations
  60. GRB 230205A: VLA radio afterglow confirmation
  61. IceCube-230220A: Upper limits from a search for additional neutrino events in IceCube
  62. GRB 230217A: Swift/UVOT Upper Limits
  63. GRB 230216A: Swift/UVOT Upper Limits
  64. GRB 230217A: Continued Gemini Observations
  65. GRB 230220A: Correction to GCN 33352
  66. GRB 230222A: Fermi GBM Final Real-time Localization
  67. GRB 230217A: Swift-XRT afterglow detection
  68. Fermi-LAT gamma-ray observations of IceCube-230220A
  69. GRB 230217A: Swift-BAT refined analysis
  70. Fermi GRB 230220B: Global MASTER-Net observations report
  71. GRB 230217A: AstroSat CZTI detection
  72. GRB 230217A: Gemini South optical upper limits
  73. GRB 230216B: CALET Gamma-Ray Burst Monitor detection
  74. GRB 230217A: 6 GHz VLA observations
  75. GRB 230220B: Fermi GBM Final Real-time Localization
  76. GRB 230217A: Gemini-South Optical Observation
  77. IceCube-230217A: Upper limits from a search for additional neutrino events in IceCube
  78. IceCube-230220A - IceCube observation of a high-energy neutrino candidate
  79. GRB 230217A: Fermi GBM observation
  80. GRB 230220A: MAXI/GSC detection
  81. IceCube-230217A: BOOTES-4/MET Optical Observations
  82. Fermi-LAT gamma-ray observations of IceCube-230217A
  83. Konus-Wind detection of GRB 230217A
  84. GRB 230217A: Swift-XRT observations
  85. Fermi trigger No 698427992: Global MASTER-Net observations report
  86. IceCube Alert 230217.87: Global MASTER-Net observations report
  87. GRB 230218A is not a GRB
  88. GRB 230218A: Fermi GBM Final Real-time Localization
  89. GRB 230217A: AGILE/MCAL detection
  90. GRB 230207B: CALET Gamma-Ray Burst Monitor detection
  91. GRB 230216B: AstroSat CZTI detection
  92. GRB 230216A: SVOM/C-GFT optical upper limit
  93. GRB 230217A: Swift detection of a short burst
  94. GRB 230217A: Fermi GBM Final Real-time Localization
  95. IceCube-230217A - IceCube observation of a high-energy neutrino candidate track-like event
  96. GRB 230216A: Swift-BAT refined analysis
  97. GRB 230216A: Swift-XRT refined Analysis
  98. GRB 230205A: Lowell Discovery Telescope Observations
  99. GRB 230204B: Lowell Discovery Telescope Observations
  100. Swift GRB 230216A: Global MASTER-Net observations report

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