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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').
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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"

11532 results found.

  1. GRB 250512A: Fermi GBM Final Real-time Localization
  2. GRB 250510B: Fermi GBM Observation
  3. Fermi GRB 250510C: Global MASTER-Net observations report
  4. Fermi GRB 250510B: Global MASTER-Net observations report
  5. GRB 250510C: Fermi GBM Final Real-time Localization
  6. GRB 250509A: Fermi GBM Observation
  7. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  8. GRB 250510B: Fermi GBM Final Localization
  9. Fermi GRB 250509A: Global MASTER-Net observations report
  10. GRB 250509A: Fermi GBM Final Real-time Localization
  11. GRB 250506A: NOT optical upper limits
  12. GRB 250506A: GECAM detection
  13. GRB 250506A: SVOM/VT optical upper limit
  14. GRB 250506A: Swift/UVOT Upper Limits
  15. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  16. GRB 250506A: Mephisto optical upper limits
  17. GRB 250504A: EIRSAT-1 GMOD Detection
  18. IceCube-250506A - IceCube observation of a high-energy neutrino candidate track-like event
  19. GRB 250506A: Xinglong 2.16m optical upper limit
  20. GRB 250506A: REM optical/NIR upper limits
  21. GRB 250506A: Fermi GBM Observation
  22. GRB 250506A: Swift XRT observations and possible counterpart detection
  23. GRB 250506A: TRT optical observations
  24. GRB 250506A: Fermi GBM Final Real-time Localization
  25. GRB 250504A: VLT/X-shooter upper limits
  26. Fermi GRB 250505A: Global MASTER-Net observations report
  27. GRB 250504A: SVOM/VT upper limit
  28. GRB 250504A: REM optical/NIR observations
  29. GRB 250505A: Fermi GBM Final Real-time Localization
  30. GRB 250504A: Fermi GBM Observation
  31. Fermi GRB 250504A: Global MASTER-Net observations report
  32. GRB 250504A: Fermi GBM Final Real-time Localization
  33. Fermi trigger No 767975731: Global MASTER-Net observations report
  34. GRB 250502B: AstroSat CZTI detection
  35. GRB 250502C: Fermi GBM Final Localization
  36. GRB 250407A: VZLUSAT-2 detection
  37. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  38. GRB 250502B: DDOTI Optical Observations
  39. Fermi GRB 250502B: Global MASTER-Net observations report
  40. GRB 250502B: Fermi GBM Final Real-time Localization
  41. EP 250427A: Optical counterpart detection by LCO.
  42. EP250427a/GRB250427A: HCT optical follow-up
  43. Fermi trigger No 767623859: Global MASTER-Net observations report
  44. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  45. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  46. EP250427a: EP-FXT follow-up observations
  47. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  48. GRB250427A/EP250427a GIT optical afterglow detection:
  49. EP250427a / GRB 250427A: LCO optical counterpart detection
  50. EP250427a: REM optical/NIR afterglow detection
  51. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  52. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  53. Fermi-LAT gamma-ray observations of IceCube-250421A
  54. GRB 250407A: GRBAlpha detection
  55. GRB 250404A / EP250404a: GRBAlpha detection
  56. GRB 250330B: GRBAlpha detection
  57. EP250421a: Upper limits from Fermi-GBM Observations
  58. GRB 250421A: AstroSat CZTI detection
  59. Fermi GRB 250421A: Global MASTER-Net observations report
  60. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  61. GRB 250421A: Fermi GBM Final Real-time Localization
  62. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  63. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  64. Konus-Wind detection of GRB 250403A
  65. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  66. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  67. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  68. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  69. GRB 250416B: Fermi GBM Final Real-time Localization
  70. GRB 250416A: Fermi GBM Final Real-time Localization
  71. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  72. GRB 250412A: AstroSat CZTI detection
  73. Fermi trigger No 766148493: Global MASTER-Net observations report
  74. Fermi trigger No 766173972: Global MASTER-Net observations report
  75. GRB 250411A: DDOTI Optical Observations
  76. Fermi GRB 250411A: Global MASTER-Net observations report
  77. GRB 250411A: Fermi GBM Final Real-time Localization
  78. GRB 250407A: Mondy and AbAO Optical Observations
  79. GRB 250320B: cubesat Avion detection
  80. IPN triangulation of GRB 250407A
  81. GRB 250407A: LCO detection of a fading optical counterpart
  82. Fermi-LAT gamma-ray observations of IceCube-250406A
  83. Konus-Wind detection of GRB 250407A
  84. GRB 250407A: SVOM/GRM observation of a bright long burst
  85. GRB 250407A: EP-WXT afterglow detection
  86. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  87. GRB 250407A: KAIT Optical Afterglow Candidate
  88. GRB 250407A: Fermi GBM Detection
  89. GRB 250407A: Swift-XRT afterglow detection
  90. Fermi GRB 250407A: Global MASTER-Net observations report
  91. GRB 250407A: Swift ToO observations
  92. GRB 250407A: SRG/ART-XC afterglow detection
  93. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  94. GRB 250407A: Fermi GBM Final Real-time Localization
  95. GRB 250406A: AstroSat CZTI detection
  96. Fermi trigger No 765663719: Global MASTER-Net observations report
  97. Fermi GRB 250406A: Global MASTER-Net observations report
  98. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  99. GRB 250406A: Fermi GBM Final Real-time Localization
  100. EP250404a / GRB 250404A: Montarrenti Observatory optical observations

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