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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"
  1. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  2. EP250427a / GRB 250427A: OHP/T193 photometric observations
  3. EP250427a: EP-FXT follow-up observations
  4. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  5. EP250427a: Lesedi optical counterpart detection
  6. EP250427A: COLIBRÍ Continuing Optical Observations
  7. GRB250427A/EP250427a GIT optical afterglow detection:
  8. EP250427a: LT optical counterpart detection
  9. GRB 250427A: Swift-XRT refined Analysis
  10. EP250427a / GRB 250427A: LCO optical counterpart detection
  11. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  12. EP250427A/GRB250427A: Keck/LRIS redshift
  13. EP250427a: REM optical/NIR afterglow detection
  14. GRB 250424A: LCO optical observation
  15. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  16. EP250427A: COLIBRÍ Optical Detection
  17. EP250427a: TRT optical counterpart detection
  18. EP 250427a: BOOTES-7 optical afterglow candidate
  19. EP250427a: Global MASTER-Net observations report
  20. EP250427a: Einstein Probe detection of a fast X-ray transient
  21. IceCube Alert 250426.74: Global MASTER-Net observations report
  22. GRB 250424A: Swift-BAT refined analysis
  23. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  24. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  25. GRB 250424A: SVOM/GRM observation of a long burst
  26. GRB 250424A: PRIME near-infrared detection
  27. GRB 250424A: WINTER J-band detection
  28. GRB 250424A: EIRSAT-1 GMOD Detection
  29. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  30. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  31. GRB 250424A: SVOM/VT optical observation
  32. GRB 250419A: Mondy Optical Observations
  33. GRB 250424A: Swift/UVOT Detection
  34. Konus-Wind detection of GRB 250424A
  35. Fermi-LAT gamma-ray observations of IceCube-250421A
  36. GRB 250424A: Skynet Optical Observations
  37. GRB 250424A: Kilonova-Catcher optical afterglow detection
  38. GRB 250419a: Continued Liverpool Telescope observations
  39. GRB 250419A: Liverpool Telescope optical upper limit
  40. GRB 250407A: GRBAlpha detection
  41. GRB 250404A / EP250404a: GRBAlpha detection
  42. GRB 250330B: GRBAlpha detection
  43. GRB 250419A: SVOM/ECLAIRs refined analysis
  44. GRB 250424A: Swift-XRT refined Analysis
  45. GRB 250424A: Enhanced Swift-XRT position
  46. GRB 250424A: AstroSat CZTI detection of a bright long burst
  47. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  48. GRB 250424A: BlackGEM optical afterglow detection
  49. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  50. GRB 250424A: likely host galaxy
  51. GRB 250424A: DDOTI Afterglow Detection
  52. GRB 250424A: REM optical/NIR afterglow detection
  53. GRB 250424A: Swift detection of a burst with an optical counterpart
  54. Swift GRB 250424A: Global MASTER-Net observations report
  55. Swift GRB 250424A: Global MASTER-Net OT detection
  56. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  57. EP250421a: Nickel optical upper limit
  58. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  59. EP250421a: Upper limits from Fermi-GBM Observations
  60. SVOM/sb25042207: XRT observations
  61. SVOM/sb25042207: BOOTES-2 early optical upper limit
  62. SVOM/sb25042207: GOTO optical upper limits
  63. GRB 250421A: AstroSat CZTI detection
  64. SVOM/sb25042207: SVOM detection of an X-ray transient
  65. GRB250419A: VLA radio detection
  66. IceCube-250421A: DDOTI Detection of the LAST Candidate
  67. GRB 250419A: Mephisto Multi-band Optical Detection
  68. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  69. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  70. EP250421a: NOT optical observations
  71. GRB 250419A: Optical Observations via Virtual Telescope Project
  72. EP250421a: REM optical upper limit
  73. EP250421a: Swift/XRT counterpart detection
  74. EP250421A: COLIBRÍ Optical Upper Limit
  75. GRB 250419A: Mondy Continued Optical Observations
  76. Fermi GRB 250421A: Global MASTER-Net observations report
  77. EP250421a: Global MASTER-Net observations report
  78. GRB 250421B: AstroSat CZTI detection of a bright long burst
  79. EP250421a: Einstein Probe detection of an X-ray transient
  80. EP250421a: Mephisto optical counterpart confirmation
  81. IceCube Alert 250421.71: Global MASTER-Net observations report
  82. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  83. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  84. EP250421a: JinShan likely optical counterpart
  85. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  86. GRB 250421A: Fermi GBM Final Real-time Localization
  87. GRB 250419A: Liverpool Telescope observations
  88. GRB 250419A: LCO optical observation
  89. GRB 250419A: JinShan optical observations
  90. GRB 250419A: SVOM/VT optical continuous observations
  91. GRB 250419A: SVOM/C-GFT optical observations
  92. GRB 250419A: Swift/UVOT Follow up
  93. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  94. GRB 250419A: LCO optical afterglow multi-band observations
  95. GRB 250419A: Mondy and AbAO Optical Observations
  96. GRB 250419A: Liverpool Telescope observations
  97. GRB 250419A: AKO Optical Afterglow Detection
  98. GRB 250419A: MASTER optical afterglow observation
  99. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  100. GRB 250407A: rest-frame energetics from Konus-Wind observation

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