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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

45945 results found.

  1. EP250427a / GRB 250427A: LCO optical counterpart detection
  2. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  3. EP250427A/GRB250427A: Keck/LRIS redshift
  4. EP250427a: REM optical/NIR afterglow detection
  5. GRB 250424A: LCO optical observation
  6. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  7. EP250427A: COLIBRÍ Optical Detection
  8. EP250427a: TRT optical counterpart detection
  9. EP 250427a: BOOTES-7 optical afterglow candidate
  10. EP250427a: Global MASTER-Net observations report
  11. EP250427a: Einstein Probe detection of a fast X-ray transient
  12. IceCube Alert 250426.74: Global MASTER-Net observations report
  13. GRB 250424A: Swift-BAT refined analysis
  14. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  15. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  16. GRB 250424A: SVOM/GRM observation of a long burst
  17. GRB 250424A: PRIME near-infrared detection
  18. GRB 250424A: WINTER J-band detection
  19. GRB 250424A: EIRSAT-1 GMOD Detection
  20. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  21. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  22. GRB 250424A: SVOM/VT optical observation
  23. GRB 250419A: Mondy Optical Observations
  24. GRB 250424A: Swift/UVOT Detection
  25. Konus-Wind detection of GRB 250424A
  26. Fermi-LAT gamma-ray observations of IceCube-250421A
  27. GRB 250424A: Skynet Optical Observations
  28. GRB 250424A: Kilonova-Catcher optical afterglow detection
  29. GRB 250419a: Continued Liverpool Telescope observations
  30. GRB 250419A: Liverpool Telescope optical upper limit
  31. GRB 250407A: GRBAlpha detection
  32. GRB 250404A / EP250404a: GRBAlpha detection
  33. GRB 250330B: GRBAlpha detection
  34. GRB 250419A: SVOM/ECLAIRs refined analysis
  35. GRB 250424A: Swift-XRT refined Analysis
  36. GRB 250424A: Enhanced Swift-XRT position
  37. GRB 250424A: AstroSat CZTI detection of a bright long burst
  38. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  39. GRB 250424A: BlackGEM optical afterglow detection
  40. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  41. GRB 250424A: likely host galaxy
  42. GRB 250424A: DDOTI Afterglow Detection
  43. GRB 250424A: REM optical/NIR afterglow detection
  44. GRB 250424A: Swift detection of a burst with an optical counterpart
  45. Swift GRB 250424A: Global MASTER-Net observations report
  46. Swift GRB 250424A: Global MASTER-Net OT detection
  47. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  48. EP250421a: Nickel optical upper limit
  49. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  50. EP250421a: Upper limits from Fermi-GBM Observations
  51. SVOM/sb25042207: XRT observations
  52. SVOM/sb25042207: BOOTES-2 early optical upper limit
  53. SVOM/sb25042207: GOTO optical upper limits
  54. GRB 250421A: AstroSat CZTI detection
  55. SVOM/sb25042207: SVOM detection of an X-ray transient
  56. GRB250419A: VLA radio detection
  57. IceCube-250421A: DDOTI Detection of the LAST Candidate
  58. GRB 250419A: Mephisto Multi-band Optical Detection
  59. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  60. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  61. EP250421a: NOT optical observations
  62. GRB 250419A: Optical Observations via Virtual Telescope Project
  63. EP250421a: REM optical upper limit
  64. EP250421a: Swift/XRT counterpart detection
  65. EP250421A: COLIBRÍ Optical Upper Limit
  66. GRB 250419A: Mondy Continued Optical Observations
  67. Fermi GRB 250421A: Global MASTER-Net observations report
  68. EP250421a: Global MASTER-Net observations report
  69. GRB 250421B: AstroSat CZTI detection of a bright long burst
  70. EP250421a: Einstein Probe detection of an X-ray transient
  71. EP250421a: Mephisto optical counterpart confirmation
  72. IceCube Alert 250421.71: Global MASTER-Net observations report
  73. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  74. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  75. EP250421a: JinShan likely optical counterpart
  76. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  77. GRB 250421A: Fermi GBM Final Real-time Localization
  78. GRB 250419A: Liverpool Telescope observations
  79. GRB 250419A: LCO optical observation
  80. GRB 250419A: JinShan optical observations
  81. GRB 250419A: SVOM/VT optical continuous observations
  82. GRB 250419A: SVOM/C-GFT optical observations
  83. GRB 250419A: Swift/UVOT Follow up
  84. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  85. GRB 250419A: LCO optical afterglow multi-band observations
  86. GRB 250419A: Mondy and AbAO Optical Observations
  87. GRB 250419A: Liverpool Telescope observations
  88. GRB 250419A: AKO Optical Afterglow Detection
  89. GRB 250419A: MASTER optical afterglow observation
  90. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  91. GRB 250407A: rest-frame energetics from Konus-Wind observation
  92. GRB 250419A: Swift-XRT localisation
  93. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  94. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  95. GRB 250419A: Swift-XRT refined Analysis
  96. GRB 250419A: GOTO optical counterpart detection
  97. GRB 250419A: KAIT optical afterglow observations
  98. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  99. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  100. GRB 250419A: SVOM detection of a soft burst

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