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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"

28072 results found.

  1. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  2. GRB 250424A: BlackGEM optical afterglow detection
  3. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  4. GRB 250424A: likely host galaxy
  5. GRB 250424A: DDOTI Afterglow Detection
  6. GRB 250424A: REM optical/NIR afterglow detection
  7. GRB 250424A: Swift detection of a burst with an optical counterpart
  8. Swift GRB 250424A: Global MASTER-Net OT detection
  9. EP250421a: Nickel optical upper limit
  10. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  11. SVOM/sb25042207: XRT observations
  12. SVOM/sb25042207: BOOTES-2 early optical upper limit
  13. GRB 250421A: AstroSat CZTI detection
  14. SVOM/sb25042207: SVOM detection of an X-ray transient
  15. GRB250419A: VLA radio detection
  16. IceCube-250421A: DDOTI Detection of the LAST Candidate
  17. GRB 250419A: Mephisto Multi-band Optical Detection
  18. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  19. EP250421a: NOT optical observations
  20. GRB 250419A: Optical Observations via Virtual Telescope Project
  21. EP250421a: REM optical upper limit
  22. EP250421a: Swift/XRT counterpart detection
  23. GRB 250421B: AstroSat CZTI detection of a bright long burst
  24. EP250421a: Einstein Probe detection of an X-ray transient
  25. EP250421a: Mephisto optical counterpart confirmation
  26. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  27. GRB 250421A: Fermi GBM Final Real-time Localization
  28. GRB 250419A: Liverpool Telescope observations
  29. GRB 250419A: JinShan optical observations
  30. GRB 250419A: LCO optical afterglow multi-band observations
  31. GRB 250419A: AKO Optical Afterglow Detection
  32. GRB 250419A: MASTER optical afterglow observation
  33. GRB 250419A: Swift-XRT localisation
  34. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  35. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  36. GRB 250419A: Swift-XRT refined Analysis
  37. GRB 250419A: GOTO optical counterpart detection
  38. GRB 250419A: KAIT optical afterglow observations
  39. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  40. GRB 250419A: SVOM detection of a soft burst
  41. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  42. EP250416a: Swift/XRT counterpart fading
  43. EP250416a: refined EP-WXT and EP-FXT analysis
  44. Konus-Wind detection of GRB 250403A
  45. EP20250416a: Swift/XRT counterpart detection
  46. EP250416a: Gemini South-GMOS optical counterpart
  47. EP250416a: GSP optical upper limit
  48. EP250416a: Einstein Probe detection of an X-ray transient
  49. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  50. GRB 250416B: Fermi GBM Final Real-time Localization
  51. GRB 250416A: Fermi GBM Final Real-time Localization
  52. SVOM/sb25041603: SVOM detection of an X-ray transient
  53. GRB 250413A: AstroSat CZTI detection
  54. GRB 250412A: AstroSat CZTI detection
  55. EP250404a: Nanshan 0.43m Telescope optical observatios
  56. GRB 250411A: Fermi GBM Final Real-time Localization
  57. GRB 250407A: Continued KAIT/Nickel optical observations
  58. GRB 250320B: cubesat Avion detection
  59. IceCube-250406A: Swift-XRT observations
  60. IPN triangulation of GRB 250407A
  61. GRB 250407A: LCO detection of a fading optical counterpart
  62. EP250407a: Swift-XRT observations
  63. Konus-Wind detection of GRB 250407A
  64. GRB 250407A: SVOM/GRM observation of a bright long burst
  65. GRB 250407A: EP-WXT afterglow detection
  66. EP250407a: EP-WXT detection of a fast X-ray transient
  67. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  68. GRB 250407A: KAIT Optical Afterglow Candidate
  69. GRB 250407A: Fermi GBM Detection
  70. GRB 250407A: Swift-XRT afterglow detection
  71. GRB 250407A: Swift ToO observations
  72. GRB 250407A: SRG/ART-XC afterglow detection
  73. Konus-Wind detection of GRB 250406B (short/hard)
  74. GRB 250407A: Fermi GBM Final Real-time Localization
  75. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  76. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  77. GRB 250406A: AstroSat CZTI detection
  78. GRB 250406A: Fermi GBM Final Real-time Localization
  79. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  80. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  81. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  82. Konus-Wind detection of GRB 250404A / EP250404a
  83. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  84. GRB 250331D: Swift-XRT afterglow detection
  85. GRB 250404B: AstroSat CZTI detection of a short burst
  86. GRB 250403A: AstroSat CZTI detection
  87. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  88. EP250404a: REM optical/NIR observations
  89. EP250404a: Seimei/TriCCS optical counterpart detection
  90. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  91. EP250404a: LCO optical counterpart detection
  92. GRB 250403A: Montarrenti Observatory optical detection
  93. GRB 250404A: Fermi GBM Detection
  94. GRB 250403A: KAIT optical observations
  95. EP250404a: AKO Optical Afterglow Detection
  96. EP250404a: LAST detection of optical counterpart
  97. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  98. EP250404a: Xinglong-2.16m spectroscopic redshift
  99. GRB 250327B: VIRT Optical Upper Limit
  100. EP250404a: Mephisto multi-band optical detection

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