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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"

43105 results found.

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

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