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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"

11100 results found.

  1. GRB 250506A: TRT optical observations
  2. GRB 250506A: Fermi GBM Final Real-time Localization
  3. GRB 250504A: VLT/X-shooter upper limits
  4. Fermi GRB 250505A: Global MASTER-Net observations report
  5. GRB 250504A: SVOM/VT upper limit
  6. GRB 250504A: REM optical/NIR observations
  7. GRB 250505A: Fermi GBM Final Real-time Localization
  8. GRB 250504A: Fermi GBM Observation
  9. Fermi GRB 250504A: Global MASTER-Net observations report
  10. GRB 250504A: Fermi GBM Final Real-time Localization
  11. Fermi trigger No 767975731: Global MASTER-Net observations report
  12. GRB 250502B: AstroSat CZTI detection
  13. GRB 250502C: Fermi GBM Final Localization
  14. GRB 250407A: VZLUSAT-2 detection
  15. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  16. GRB 250502B: DDOTI Optical Observations
  17. Fermi GRB 250502B: Global MASTER-Net observations report
  18. GRB 250502B: Fermi GBM Final Real-time Localization
  19. EP 250427A: Optical counterpart detection by LCO.
  20. EP250427a/GRB250427A: HCT optical follow-up
  21. Fermi trigger No 767623859: Global MASTER-Net observations report
  22. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  23. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  24. EP250427a: EP-FXT follow-up observations
  25. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  26. GRB250427A/EP250427a GIT optical afterglow detection:
  27. EP250427a / GRB 250427A: LCO optical counterpart detection
  28. EP250427a: REM optical/NIR afterglow detection
  29. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  30. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  31. Fermi-LAT gamma-ray observations of IceCube-250421A
  32. GRB 250407A: GRBAlpha detection
  33. GRB 250404A / EP250404a: GRBAlpha detection
  34. GRB 250330B: GRBAlpha detection
  35. EP250421a: Upper limits from Fermi-GBM Observations
  36. GRB 250421A: AstroSat CZTI detection
  37. Fermi GRB 250421A: Global MASTER-Net observations report
  38. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  39. GRB 250421A: Fermi GBM Final Real-time Localization
  40. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  41. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  42. Konus-Wind detection of GRB 250403A
  43. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  44. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  45. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  46. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  47. GRB 250416B: Fermi GBM Final Real-time Localization
  48. GRB 250416A: Fermi GBM Final Real-time Localization
  49. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  50. GRB 250412A: AstroSat CZTI detection
  51. Fermi trigger No 766148493: Global MASTER-Net observations report
  52. Fermi trigger No 766173972: Global MASTER-Net observations report
  53. GRB 250411A: DDOTI Optical Observations
  54. Fermi GRB 250411A: Global MASTER-Net observations report
  55. GRB 250411A: Fermi GBM Final Real-time Localization
  56. GRB 250407A: Mondy and AbAO Optical Observations
  57. GRB 250320B: cubesat Avion detection
  58. IPN triangulation of GRB 250407A
  59. GRB 250407A: LCO detection of a fading optical counterpart
  60. Fermi-LAT gamma-ray observations of IceCube-250406A
  61. Konus-Wind detection of GRB 250407A
  62. GRB 250407A: SVOM/GRM observation of a bright long burst
  63. GRB 250407A: EP-WXT afterglow detection
  64. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  65. GRB 250407A: KAIT Optical Afterglow Candidate
  66. GRB 250407A: Fermi GBM Detection
  67. GRB 250407A: Swift-XRT afterglow detection
  68. Fermi GRB 250407A: Global MASTER-Net observations report
  69. GRB 250407A: Swift ToO observations
  70. GRB 250407A: SRG/ART-XC afterglow detection
  71. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  72. GRB 250407A: Fermi GBM Final Real-time Localization
  73. GRB 250406A: AstroSat CZTI detection
  74. Fermi trigger No 765663719: Global MASTER-Net observations report
  75. Fermi GRB 250406A: Global MASTER-Net observations report
  76. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  77. GRB 250406A: Fermi GBM Final Real-time Localization
  78. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  79. Fermi trigger No 765619921: Global MASTER-Net observations report
  80. Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
  81. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  82. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  83. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  84. Konus-Wind detection of GRB 250404A / EP250404a
  85. GRB 250404A / EP250404a: Mondy optical observations
  86. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  87. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  88. GRB 250404A / EP250404a: NOT optical observations
  89. GRB 250403A: AstroSat CZTI detection
  90. EP250404a: REM optical/NIR observations
  91. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  92. EP250404a: LCO optical counterpart detection
  93. Fermi GRB 250404A: Global MASTER-Net observations report
  94. GRB 250403A: Montarrenti Observatory optical detection
  95. GRB 250404A: Fermi GBM Detection
  96. GRB 250403A: KAIT optical observations
  97. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  98. EP250404a: Xinglong-2.16m spectroscopic redshift
  99. GRB 250403A: Fermi GBM observations
  100. EP250404a: Mephisto multi-band optical detection

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