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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"

28095 results found.

  1. EP250427A/GRB250427A: Keck/LRIS redshift
  2. EP250427a: REM optical/NIR afterglow detection
  3. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  4. EP250427A: COLIBRÍ Optical Detection
  5. EP250427a: TRT optical counterpart detection
  6. EP 250427a: BOOTES-7 optical afterglow candidate
  7. EP250427a: Einstein Probe detection of a fast X-ray transient
  8. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  9. GRB 250424A: PRIME near-infrared detection
  10. GRB 250424A: WINTER J-band detection
  11. GRB 250424A: EIRSAT-1 GMOD Detection
  12. GRB 250424A: Swift/UVOT Detection
  13. Konus-Wind detection of GRB 250424A
  14. GRB 250424A: Skynet Optical Observations
  15. GRB 250424A: Kilonova-Catcher optical afterglow detection
  16. GRB 250419a: Continued Liverpool Telescope observations
  17. GRB 250419A: Liverpool Telescope optical upper limit
  18. GRB 250407A: GRBAlpha detection
  19. GRB 250404A / EP250404a: GRBAlpha detection
  20. GRB 250330B: GRBAlpha detection
  21. GRB 250424A: Swift-XRT refined Analysis
  22. GRB 250424A: Enhanced Swift-XRT position
  23. GRB 250424A: AstroSat CZTI detection of a bright long burst
  24. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  25. GRB 250424A: BlackGEM optical afterglow detection
  26. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  27. GRB 250424A: likely host galaxy
  28. GRB 250424A: DDOTI Afterglow Detection
  29. GRB 250424A: REM optical/NIR afterglow detection
  30. GRB 250424A: Swift detection of a burst with an optical counterpart
  31. Swift GRB 250424A: Global MASTER-Net OT detection
  32. EP250421a: Nickel optical upper limit
  33. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  34. SVOM/sb25042207: XRT observations
  35. SVOM/sb25042207: BOOTES-2 early optical upper limit
  36. GRB 250421A: AstroSat CZTI detection
  37. SVOM/sb25042207: SVOM detection of an X-ray transient
  38. GRB250419A: VLA radio detection
  39. IceCube-250421A: DDOTI Detection of the LAST Candidate
  40. GRB 250419A: Mephisto Multi-band Optical Detection
  41. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  42. EP250421a: NOT optical observations
  43. GRB 250419A: Optical Observations via Virtual Telescope Project
  44. EP250421a: REM optical upper limit
  45. EP250421a: Swift/XRT counterpart detection
  46. GRB 250421B: AstroSat CZTI detection of a bright long burst
  47. EP250421a: Einstein Probe detection of an X-ray transient
  48. EP250421a: Mephisto optical counterpart confirmation
  49. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  50. GRB 250421A: Fermi GBM Final Real-time Localization
  51. GRB 250419A: Liverpool Telescope observations
  52. GRB 250419A: JinShan optical observations
  53. GRB 250419A: LCO optical afterglow multi-band observations
  54. GRB 250419A: AKO Optical Afterglow Detection
  55. GRB 250419A: MASTER optical afterglow observation
  56. GRB 250419A: Swift-XRT localisation
  57. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  58. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  59. GRB 250419A: Swift-XRT refined Analysis
  60. GRB 250419A: GOTO optical counterpart detection
  61. GRB 250419A: KAIT optical afterglow observations
  62. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  63. GRB 250419A: SVOM detection of a soft burst
  64. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  65. EP250416a: Swift/XRT counterpart fading
  66. EP250416a: refined EP-WXT and EP-FXT analysis
  67. Konus-Wind detection of GRB 250403A
  68. EP20250416a: Swift/XRT counterpart detection
  69. EP250416a: Gemini South-GMOS optical counterpart
  70. EP250416a: GSP optical upper limit
  71. EP250416a: Einstein Probe detection of an X-ray transient
  72. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  73. GRB 250416B: Fermi GBM Final Real-time Localization
  74. GRB 250416A: Fermi GBM Final Real-time Localization
  75. SVOM/sb25041603: SVOM detection of an X-ray transient
  76. GRB 250413A: AstroSat CZTI detection
  77. GRB 250412A: AstroSat CZTI detection
  78. EP250404a: Nanshan 0.43m Telescope optical observatios
  79. GRB 250411A: Fermi GBM Final Real-time Localization
  80. GRB 250407A: Continued KAIT/Nickel optical observations
  81. GRB 250320B: cubesat Avion detection
  82. IceCube-250406A: Swift-XRT observations
  83. IPN triangulation of GRB 250407A
  84. GRB 250407A: LCO detection of a fading optical counterpart
  85. EP250407a: Swift-XRT observations
  86. Konus-Wind detection of GRB 250407A
  87. GRB 250407A: SVOM/GRM observation of a bright long burst
  88. GRB 250407A: EP-WXT afterglow detection
  89. EP250407a: EP-WXT detection of a fast X-ray transient
  90. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  91. GRB 250407A: KAIT Optical Afterglow Candidate
  92. GRB 250407A: Fermi GBM Detection
  93. GRB 250407A: Swift-XRT afterglow detection
  94. GRB 250407A: Swift ToO observations
  95. GRB 250407A: SRG/ART-XC afterglow detection
  96. Konus-Wind detection of GRB 250406B (short/hard)
  97. GRB 250407A: Fermi GBM Final Real-time Localization
  98. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  99. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  100. GRB 250406A: AstroSat CZTI detection

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