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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 230414B: Nanshan/HMT optical afterglow detection
  2. GRB 230414A: Mondy optical afterglow candidate
  3. Swift GRB 230414B: Global MASTER-Net observations report
  4. GRB 230414B: Prompt enhanced Swift-XRT position
  5. GRB 230414B: Swift detection of a burst
  6. IceCube-230405A: BOOTES-4/MET Optical Upper Limits
  7. GRB 230414A: Fermi GBM Final Real-time Localization
  8. GRB 230328B: redshift lower limit estimating
  9. GRB 230409B: Mondy optical upper limit
  10. GRB 230409B: OHP/T193 optical upper limit
  11. GRB 230410B: VZLUSAT-2 detection
  12. GRB 230409D: VZLUSAT-2 detection
  13. GRB 230410B: AGILE detection of a burst
  14. GRB 230410A: Fermi GBM Final Real-time Localization
  15. Fermi GRB 230409C: Global MASTER-Net observations report
  16. Fermi GRB 230409A: Global MASTER-Net observations report
  17. GRB 230409C: Fermi GBM Final Real-time Localization
  18. GRB 230409B: Swift-XRT refined Analysis
  19. GRB 230409B: Swift-BAT refined analysis
  20. Fermi trigger No 702745263: Global MASTER-Net observations report
  21. Swift GRB 230409B: Global MASTER-Net observations report
  22. GRB 230409B: Swift/UVOT Detection
  23. GRB 230409B: Enhanced Swift-XRT position
  24. MAXI GRB230408.82: Global MASTER-Net observations report
  25. GRB 230409B: Swift detection of a burst
  26. GRB 230409A: Fermi GBM Final Real-time Localization
  27. GRB 230405B: VZLUSAT-2 detection
  28. IceCube-230405A: Upper limits from a search for additional neutrino events in IceCube
  29. Fermi-LAT gamma-ray observations of IceCube-230405A
  30. Konus-Wind detection of GRB 230405B
  31. GRB 230405B: AGILE detection
  32. GRB 230405B: Swift-XRT refined Analysis
  33. GRB 230405B: Fermi GBM Observation
  34. GRB 230405B: MeerLICHT upper limits
  35. IceCube Alert 230405.56: Global MASTER-Net observations report
  36. GRB 230307A: JWST NIRSpec observations, possible higher redshift
  37. GRB 230307A: further analysis of the Konus-Wind detection and rest-frame energetics
  38. GRB 230307A: good match with kilonova models
  39. GRB 230307A: short mininum variability timescale compatible with a merger origin
  40. GRB 230405B: Swift/UVOT Upper Limits
  41. GRB 230405B: AstroSat CZTI detection
  42. GRB 230405B: Enhanced Swift-XRT position
  43. Swift GRB 230405B: Global MASTER-Net observations report
  44. GRB 230405B: Prompt enhanced Swift-XRT position
  45. GRB 230405B: Swift detection of a burst
  46. GRB 230405B: Fermi GBM Final Real-time Localization
  47. GRB 230307A: JWST observations consistent with the presence of a kilonova
  48. Fermi GRB 230405A: Global MASTER-Net observations report
  49. IceCube-230405A: IceCube observation of a high-energy neutrino candidate
  50. GRB 230405A: Fermi GBM Final Real-time Localization
  51. GRB 230404A: AstroSat CZTI detection
  52. GRB 230404A: Fermi GBM Final Real-time Localization
  53. GRB 230402A: CALET Gamma-Ray Burst Monitor detection
  54. GRB 230402A: AstroSat CZTI detection
  55. Fermi-LAT gamma-ray observations of IceCube-230401A and detection of Fermi J0030.2+0005
  56. IceCube-230401A: Upper limits from a search for additional neutrino events in IceCube
  57. GRB 230328B: Multa observatory optical afterglow observation
  58. GRB 230307A: Chandra late-time detection of the X-ray afterglow
  59. GRB 230228A: detection by GTC of the potential host galaxy
  60. GRB 230328B: Swift/UVOT Detection
  61. GRB 230402A: AGILE detection
  62. Fermi GRB 230402A: Global MASTER-Net observations report
  63. GRB 230402A: Fermi GBM Final Real-time Localization
  64. IceCube-230401A: IceCube observation of a high-energy neutrino candidate
  65. GRB 230307A: Bad Time Intervals for Fermi GBM data
  66. GRB 230328B : GRANDMA/Kilonova-Catcher optical detection
  67. GRB 230328B: CAHA 2.2m/CAFOS detection
  68. IceCube-Cascade 230329A: Upper limits from a search for additional neutrino events in IceCube
  69. GRB 230328B: 3.6m DOT multiband optical observation
  70. Fermi trigger No 701883729: Global MASTER-Net observations report
  71. GRB 230330B: Fermi GBM Final Localization
  72. Konus-Wind detection of GRB 230328B
  73. GRB 230328B: GRBAlpha detection
  74. GRB 230330A: Fermi GBM Final Real-time Localization
  75. GRB 230328B: Swift-BAT refined analysis
  76. GRB 230328B: Nanshan/NEXT 2nd optical observation
  77. GRB 230328B NUTTelA-TAO / BSTI Early Measurements
  78. GRB 230328B: Liverpool Telescope afterglow detection
  79. GRB 230328B: OHP/T120 optical observations
  80. GRB 230328B: GIT optical follow-up
  81. GRB 230328B: OASDG optical observations
  82. GRB 230328B: Nanshan/NEXT optical upper limit
  83. GRB 230328B: Swift-XRT refined Analysis
  84. GRB 230328B: AstroSat CZTI detection
  85. GRB 230328B: Fermi GBM observation
  86. GRB 230328B: Mondy, AbAO and Kitab optical observations
  87. GRB 230328B: Enhanced Swift-XRT position
  88. GRB 230328B: Mondy optical afterglow confirmation
  89. GRB 230328B: Swift detection of a burst with an optical afterglow
  90. GRB 230328B: Fermi GBM Final Real-time Localization
  91. Fermi GRB 230328A: Global MASTER-Net observations report
  92. GRB 230328A: Fermi GBM Final Real-time Localization
  93. GRB 230325A: Swift-BAT refined analysis
  94. GRB 230325A: Swift/UVOT Upper Limits
  95. GRB 230325A: X-shooter optical afterglow and redshift
  96. GRB 230325A: Swift-XRT refined Analysis
  97. GRB 230322B: Swift-BAT refined analysis
  98. GRB 230325A: Enhanced Swift-XRT position
  99. GRB 230325A: Prompt enhanced Swift-XRT position
  100. GRB 230325A: Swift detection of a burst

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