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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"

45550 results found.

  1. EP250428b: LAST optical upper limit
  2. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  3. GRB 250427A: Swift/UVOT Detection
  4. EP250428b: Global MASTER-Net observations report
  5. EP250428b: Einstein Probe detection of a fast X-ray transient
  6. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  7. EP250427a / GRB 250427A: OHP/T193 photometric observations
  8. EP250427a: EP-FXT follow-up observations
  9. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  10. EP250427a: Lesedi optical counterpart detection
  11. EP250427A: COLIBRÍ Continuing Optical Observations
  12. GRB250427A/EP250427a GIT optical afterglow detection:
  13. EP250427a: LT optical counterpart detection
  14. GRB 250427A: Swift-XRT refined Analysis
  15. EP250427a / GRB 250427A: LCO optical counterpart detection
  16. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  17. EP250427A/GRB250427A: Keck/LRIS redshift
  18. EP250427a: REM optical/NIR afterglow detection
  19. GRB 250424A: LCO optical observation
  20. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  21. EP250427A: COLIBRÍ Optical Detection
  22. EP250427a: TRT optical counterpart detection
  23. EP 250427a: BOOTES-7 optical afterglow candidate
  24. EP250427a: Global MASTER-Net observations report
  25. EP250427a: Einstein Probe detection of a fast X-ray transient
  26. IceCube Alert 250426.74: Global MASTER-Net observations report
  27. GRB 250424A: Swift-BAT refined analysis
  28. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  29. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  30. GRB 250424A: SVOM/GRM observation of a long burst
  31. GRB 250424A: PRIME near-infrared detection
  32. GRB 250424A: WINTER J-band detection
  33. GRB 250424A: EIRSAT-1 GMOD Detection
  34. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  35. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  36. GRB 250424A: SVOM/VT optical observation
  37. GRB 250419A: Mondy Optical Observations
  38. GRB 250424A: Swift/UVOT Detection
  39. Konus-Wind detection of GRB 250424A
  40. Fermi-LAT gamma-ray observations of IceCube-250421A
  41. GRB 250424A: Skynet Optical Observations
  42. GRB 250424A: Kilonova-Catcher optical afterglow detection
  43. GRB 250419a: Continued Liverpool Telescope observations
  44. GRB 250419A: Liverpool Telescope optical upper limit
  45. GRB 250407A: GRBAlpha detection
  46. GRB 250404A / EP250404a: GRBAlpha detection
  47. GRB 250330B: GRBAlpha detection
  48. GRB 250419A: SVOM/ECLAIRs refined analysis
  49. GRB 250424A: Swift-XRT refined Analysis
  50. GRB 250424A: Enhanced Swift-XRT position
  51. GRB 250424A: AstroSat CZTI detection of a bright long burst
  52. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  53. GRB 250424A: BlackGEM optical afterglow detection
  54. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  55. GRB 250424A: likely host galaxy
  56. GRB 250424A: DDOTI Afterglow Detection
  57. GRB 250424A: REM optical/NIR afterglow detection
  58. GRB 250424A: Swift detection of a burst with an optical counterpart
  59. Swift GRB 250424A: Global MASTER-Net observations report
  60. Swift GRB 250424A: Global MASTER-Net OT detection
  61. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  62. EP250421a: Nickel optical upper limit
  63. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  64. EP250421a: Upper limits from Fermi-GBM Observations
  65. SVOM/sb25042207: XRT observations
  66. SVOM/sb25042207: BOOTES-2 early optical upper limit
  67. SVOM/sb25042207: GOTO optical upper limits
  68. GRB 250421A: AstroSat CZTI detection
  69. SVOM/sb25042207: SVOM detection of an X-ray transient
  70. GRB250419A: VLA radio detection
  71. IceCube-250421A: DDOTI Detection of the LAST Candidate
  72. GRB 250419A: Mephisto Multi-band Optical Detection
  73. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  74. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  75. EP250421a: NOT optical observations
  76. GRB 250419A: Optical Observations via Virtual Telescope Project
  77. EP250421a: REM optical upper limit
  78. EP250421a: Swift/XRT counterpart detection
  79. EP250421A: COLIBRÍ Optical Upper Limit
  80. GRB 250419A: Mondy Continued Optical Observations
  81. Fermi GRB 250421A: Global MASTER-Net observations report
  82. EP250421a: Global MASTER-Net observations report
  83. GRB 250421B: AstroSat CZTI detection of a bright long burst
  84. EP250421a: Einstein Probe detection of an X-ray transient
  85. EP250421a: Mephisto optical counterpart confirmation
  86. IceCube Alert 250421.71: Global MASTER-Net observations report
  87. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  88. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  89. EP250421a: JinShan likely optical counterpart
  90. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  91. GRB 250421A: Fermi GBM Final Real-time Localization
  92. GRB 250419A: Liverpool Telescope observations
  93. GRB 250419A: LCO optical observation
  94. GRB 250419A: JinShan optical observations
  95. GRB 250419A: SVOM/VT optical continuous observations
  96. GRB 250419A: SVOM/C-GFT optical observations
  97. GRB 250419A: Swift/UVOT Follow up
  98. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  99. GRB 250419A: LCO optical afterglow multi-band observations
  100. GRB 250419A: Mondy and AbAO Optical Observations

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