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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 240209A: Fermi GBM Final Localization
  2. Fermi trigger No 729152364: Global MASTER-Net observations report
  3. IPN triangulation of GRB 240205A (short)
  4. Fermi-LAT gamma-ray observations of IceCube-240204A
  5. GRB 240205B: PRIME near infrared detection
  6. GRB 240205A (short): Glowbug gamma-ray detection
  7. Swift Trigger 1213872 is not an astrophysical event
  8. GRB240204A: Swift/UVOT Upper Limits
  9. GRB 240205B: AstroSat CZTI detection
  10. Fermi trigger No 729012023: Global MASTER-Net observations report
  11. GRB 240205B: Swift-BAT refined analysis
  12. Konus-Wind detection of GRB 240205B (long / very soft)
  13. GRB 240207A: Fermi GBM Final Real-time Localization
  14. Konus-Wind detection of GRB 240125A
  15. GRB 240205B: VLT/X-shooter redshift
  16. GRB 240205B: CALET Gamma-Ray Burst Monitor detection
  17. GRB 240205B: BOOTES-6 optical afterglow follow-up
  18. GRB 240205B: ATCA detection of radio counterpart
  19. GRB 240205B: REM detection of the optical/NIR afterglow
  20. GRB 240205B: Fermi GBM Observation
  21. GRB 240204A: AstroSat CZTI detection
  22. GRB 240204A: Mondy optical afterglow observations
  23. GRB 240204A : OHP/T193/T120 optical afterglow fading detection
  24. GRB 240205B: GECAM detection of a long burst
  25. GRB 240204A: Swift-BAT refined analysis
  26. GRB 240205B: Skynet Optical Afterglow Observations
  27. GRB 240205B: BOOTES-7 optical afterglow follow-up
  28. Fermi trigger No 728749569: Global MASTER-Net observations report
  29. GRB 240205B: MASTER OT J232550.14-550704.6 counterpart detection
  30. GRB 240205B: Swift detection of a burst
  31. GRB 240205B: Fermi GBM Final Real-time Localization
  32. Swift GRB240205.93: Global MASTER-Net observations report
  33. GRB 240204A: Fermi GBM Observation
  34. GRB 240205A: Fermi GBM Final Real-time Localization
  35. GRB 240204a: Liverpool Telescope optical afterglow detection
  36. GRB 240204A: Osservatorio Astronomico Nastro Verde upper limit
  37. IceCube-240204A: Upper limits from a search for additional neutrino events in IceCube
  38. Fermi Gamma-ray Burst Monitor trigger 728740048/240204491 is not a GRB
  39. Fermi trigger No 728796365: Global MASTER-Net observations report
  40. GRB 240204A: optical afterglow detection with LCOGT 1m telescopes at Sutherland and Teide Observatories
  41. GRB 240204A: Montarrenti Observatory optical observations
  42. GRB 240204A: Enhanced Swift-XRT position
  43. GRB 240204A: Mondy optical afterglow candidate
  44. Fermi Gamma-ray Burst Monitor trigger 728706420/240204102 is not a GRB
  45. Fermi GRB 240204A: Global MASTER-Net observations report
  46. Fermi trigger No 728706420: Global MASTER-Net observations report
  47. GRB 240204A: Swift detection of a burst
  48. IceCube-240204A - IceCube observation of a high-energy neutrino candidate track-like event
  49. GRB 240204A: Fermi GBM Final Real-time Localization
  50. IceCube Alert 240204.38: Global MASTER-Net observations report
  51. Swift Trigger 1212791 is not an astrophysical event.
  52. Swift-BAT triggers 1212787, 1212789 are not astrophysical.
  53. GRB 230812B: Update on Bad Time Intervals for Fermi GBM data
  54. Konus-Wind detection of GRB 240124B
  55. Konus-Wind detection of GRB 240123C
  56. IPN triangulation of GRB 240124B
  57. GRB 240201A: AstroSat CZTI detection
  58. GRB 240129A: Fermi GBM Observation
  59. IPN triangulation of GRB 240125B (short)
  60. GRB 240129A: Swift/BAT-GUANO detection of a burst outside the coded FOV
  61. IPN triangulation of GRB 240125A (short)
  62. GRB 240128A: Glowbug gamma-ray detection
  63. GRB 240128A: Swift-XRT observations
  64. GRB 240128A: GRBAlpha detection
  65. GRB 240128A: Tiled Swift observations
  66. GRB 240128A: CALET Gamma-Ray Burst Monitor detection
  67. GRB 240128A: MAXI/GSC detection
  68. GRB 240125A: GRBAlpha detection
  69. Fermi GRB 240127A: Global MASTER-Net observations report
  70. GRB 240123C: GRBAlpha detection
  71. GRB 240122A: ATCA detection of radio counterpart
  72. GRB 240127A: Fermi GBM Final Real-time Localization
  73. IceCube-240123A: Upper limits from a search for additional neutrino events in IceCube
  74. GRB 240125A: CALET Gamma-Ray Burst Monitor detection
  75. Swift Trigger 1211211 and 1211212 are not astrophysical
  76. GRB 240125A: AstroSat CZTI detection of a short burst
  77. GRB 240124B: AstroSat CZTI detection
  78. GRB 240123C: AstroSat CZTI detection
  79. GRB 240125B: Fermi GBM Final Localization
  80. GRB240122A: PRIME near infrared detection
  81. GRB 240123B: Fermi GBM Observation
  82. GRB 240123A: Glowbug gamma-ray detection
  83. GRB 240125A (short): Glowbug gamma-ray detection
  84. GRB 240123B: Swift/BAT-GUANO detection of a long burst
  85. GRB 240123A: GRBAlpha detection
  86. IPN triangulation of GRB 240123C (short)
  87. Swift trigger 1210856 is not astrophysical
  88. Fermi-LAT gamma-ray observations of IceCube-240123A
  89. GRB 240123A: further SAO RAS optical observations
  90. GRB 240122B: CALET Gamma-Ray Burst Monitor detection
  91. GRB 240123A: Swift-BAT refined analysis
  92. IceCube Alert 240123.48: Global MASTER-Net observations report
  93. GRB 240123A: Mondy continued optical observations and the PL decay index
  94. GRB 240123A: SAO RAS optical observations
  95. GRB 240123A : MITSuME Akeno optical afterglow candidate detection
  96. Fermi/GBM trigger 727752941: BALROG analysis retraction
  97. GRB 240123A: Enhanced Swift-XRT position
  98. GRB 240124A?: BALROG localization (Fermi Trigger 727752941 / GRB 240124066)
  99. Fermi GRB 240123B: Global MASTER-Net observations report
  100. GRB 240122A: Swift/UVOT Upper Limits

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