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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"

11051 results found.

  1. GRB 250521D: DDOTI Optical Upper Limit
  2. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  3. GRB 250521D: LAST tentative optical counterpart candidate
  4. GRB 250521D: Fermi GBM Final Real-time Localization
  5. GRB 250521C: Fermi GBM Final Localization
  6. GRB 250521A: DDOTI Optical Upper Limit
  7. GRB 250521A: Fermi GBM Final Real-time Localization
  8. GRB 250520B: Fermi GBM Final Real-time Localization
  9. GRB 250520A: DDOTI Optical Upper Limit
  10. GRB 250520A: AstroSat CZTI detection of a short burst
  11. GRB 250516A: COLIBRÍ optical upper limit
  12. Konus-Wind detection of GRB 250516A
  13. Fermi GRB 250516A: Global MASTER-Net observations report
  14. GRB 250515A: Swift-XRT observations
  15. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  16. Fermi Gamma-ray Burst Monitor trigger 769160489/250517320 is not a GRB
  17. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  18. GRB 250515A: 1.6m Mephisto optical detection
  19. GRB 250516A: AstroSat CZTI detection
  20. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  21. GRB 250516A: Fermi GBM Observation
  22. GRB 250515A: Swift ToO observations
  23. GRB 250516A: Fermi GBM Final Real-time Localization
  24. GRB 250515A: GOTO candidate optical counterpart
  25. GRB 250515A: Fermi GBM Final Localization
  26. Fermi trigger No 768922089: Global MASTER-Net observations report
  27. Fermi GRB 250512A: Global MASTER-Net observations report
  28. Konus-Wind detection of GRB 250506A
  29. GRB 250506A: GRBAlpha detection
  30. GRB 250512A: Fermi GBM Final Real-time Localization
  31. GRB 250510B: Fermi GBM Observation
  32. Fermi GRB 250510C: Global MASTER-Net observations report
  33. Fermi GRB 250510B: Global MASTER-Net observations report
  34. GRB 250510C: Fermi GBM Final Real-time Localization
  35. GRB 250509A: Fermi GBM Observation
  36. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  37. GRB 250510B: Fermi GBM Final Localization
  38. Fermi GRB 250509A: Global MASTER-Net observations report
  39. GRB 250509A: Fermi GBM Final Real-time Localization
  40. GRB 250506A: NOT optical upper limits
  41. GRB 250506A: GECAM detection
  42. GRB 250506A: SVOM/VT optical upper limit
  43. GRB 250506A: Swift/UVOT Upper Limits
  44. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  45. GRB 250506A: Mephisto optical upper limits
  46. GRB 250504A: EIRSAT-1 GMOD Detection
  47. IceCube-250506A - IceCube observation of a high-energy neutrino candidate track-like event
  48. GRB 250506A: Xinglong 2.16m optical upper limit
  49. GRB 250506A: REM optical/NIR upper limits
  50. GRB 250506A: Fermi GBM Observation
  51. GRB 250506A: Swift XRT observations and possible counterpart detection
  52. GRB 250506A: TRT optical observations
  53. GRB 250506A: Fermi GBM Final Real-time Localization
  54. GRB 250504A: VLT/X-shooter upper limits
  55. Fermi GRB 250505A: Global MASTER-Net observations report
  56. GRB 250504A: SVOM/VT upper limit
  57. GRB 250504A: REM optical/NIR observations
  58. GRB 250505A: Fermi GBM Final Real-time Localization
  59. GRB 250504A: Fermi GBM Observation
  60. Fermi GRB 250504A: Global MASTER-Net observations report
  61. GRB 250504A: Fermi GBM Final Real-time Localization
  62. Fermi trigger No 767975731: Global MASTER-Net observations report
  63. GRB 250502B: AstroSat CZTI detection
  64. GRB 250502C: Fermi GBM Final Localization
  65. GRB 250407A: VZLUSAT-2 detection
  66. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  67. GRB 250502B: DDOTI Optical Observations
  68. Fermi GRB 250502B: Global MASTER-Net observations report
  69. GRB 250502B: Fermi GBM Final Real-time Localization
  70. EP 250427A: Optical counterpart detection by LCO.
  71. EP250427a/GRB250427A: HCT optical follow-up
  72. Fermi trigger No 767623859: Global MASTER-Net observations report
  73. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  74. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  75. EP250427a: EP-FXT follow-up observations
  76. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  77. GRB250427A/EP250427a GIT optical afterglow detection:
  78. EP250427a / GRB 250427A: LCO optical counterpart detection
  79. EP250427a: REM optical/NIR afterglow detection
  80. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  81. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  82. Fermi-LAT gamma-ray observations of IceCube-250421A
  83. GRB 250407A: GRBAlpha detection
  84. GRB 250404A / EP250404a: GRBAlpha detection
  85. GRB 250330B: GRBAlpha detection
  86. EP250421a: Upper limits from Fermi-GBM Observations
  87. GRB 250421A: AstroSat CZTI detection
  88. Fermi GRB 250421A: Global MASTER-Net observations report
  89. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  90. GRB 250421A: Fermi GBM Final Real-time Localization
  91. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  92. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  93. Konus-Wind detection of GRB 250403A
  94. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  95. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  96. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  97. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  98. GRB 250416B: Fermi GBM Final Real-time Localization
  99. GRB 250416A: Fermi GBM Final Real-time Localization
  100. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB

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