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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"

24844 results found.

  1. EP250427a / GRB 250427A: LCO optical counterpart detection
  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. EP250427a: Einstein Probe detection of a fast X-ray transient
  8. GRB 250424A: Swift-BAT refined analysis
  9. GRB 250424A: SVOM/GRM observation of a long burst
  10. GRB 250424A: PRIME near-infrared detection
  11. GRB 250424A: WINTER J-band detection
  12. GRB 250424A: EIRSAT-1 GMOD Detection
  13. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  14. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  15. GRB 250419A: Mondy Optical Observations
  16. GRB 250424A: Swift/UVOT Detection
  17. Fermi-LAT gamma-ray observations of IceCube-250421A
  18. GRB 250424A: Skynet Optical Observations
  19. GRB 250424A: Kilonova-Catcher optical afterglow detection
  20. GRB 250330B: GRBAlpha detection
  21. GRB 250424A: Swift-XRT refined Analysis
  22. GRB 250424A: Enhanced Swift-XRT position
  23. GRB 250424A: AstroSat CZTI detection of a bright long burst
  24. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  25. GRB 250424A: BlackGEM optical afterglow detection
  26. GRB 250424A: DDOTI Afterglow Detection
  27. GRB 250424A: REM optical/NIR afterglow detection
  28. GRB 250424A: Swift detection of a burst with an optical counterpart
  29. Swift GRB 250424A: Global MASTER-Net OT detection
  30. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  31. EP250421a: Nickel optical upper limit
  32. EP250421a: Upper limits from Fermi-GBM Observations
  33. SVOM/sb25042207: SVOM detection of an X-ray transient
  34. IceCube-250421A: DDOTI Detection of the LAST Candidate
  35. GRB 250419A: Mephisto Multi-band Optical Detection
  36. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  37. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  38. EP250421a: NOT optical observations
  39. GRB 250419A: Optical Observations via Virtual Telescope Project
  40. EP250421a: REM optical upper limit
  41. EP250421A: COLIBRÍ Optical Upper Limit
  42. GRB 250419A: Mondy Continued Optical Observations
  43. GRB 250421B: AstroSat CZTI detection of a bright long burst
  44. EP250421a: Einstein Probe detection of an X-ray transient
  45. EP250421a: Mephisto optical counterpart confirmation
  46. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  47. EP250421a: JinShan likely optical counterpart
  48. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  49. GRB 250419A: LCO optical observation
  50. GRB 250419A: JinShan optical observations
  51. GRB 250419A: SVOM/C-GFT optical observations
  52. GRB 250419A: Swift/UVOT Follow up
  53. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  54. GRB 250419A: LCO optical afterglow multi-band observations
  55. GRB 250419A: Mondy and AbAO Optical Observations
  56. GRB 250419A: AKO Optical Afterglow Detection
  57. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  58. GRB 250419A: Swift-XRT refined Analysis
  59. GRB 250419A: KAIT optical afterglow observations
  60. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  61. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  62. GRB 250419A: SVOM detection of a soft burst
  63. EP250416a: Swift/XRT counterpart fading
  64. EP20250416a: Swift/XRT counterpart detection
  65. IceCube-250416A: DDOTI Optical Observations
  66. EP250416a: Gemini South-GMOS optical counterpart
  67. SVOM/sb25041603 is not a GRB
  68. EP250416a: GSP optical upper limit
  69. EP250416a: Einstein Probe detection of an X-ray transient
  70. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  71. SVOM/sb25041603: SVOM detection of an X-ray transient
  72. IceCube 250414.324: DDOTI Optical Observations
  73. GRB 250413A: AstroSat CZTI detection
  74. EP250304a: ATCA radio observations
  75. EP250404a: Nanshan 0.43m Telescope optical observatios
  76. GRB 250411A: DDOTI Optical Observations
  77. Fermi GRB 250411A: Global MASTER-Net observations report
  78. GRB 250407A: Continued KAIT/Nickel optical observations
  79. GRB 250314A: e-MERLIN observations
  80. GRB 250407A: Mondy and AbAO Optical Observations
  81. EP250227a: Further NOT optical observations
  82. GRB 250320B: cubesat Avion detection
  83. IceCube-250406A: Swift-XRT observations
  84. GRB 250407A: LCO detection of a fading optical counterpart
  85. Fermi-LAT gamma-ray observations of IceCube-250406A
  86. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  87. GRB 250407A: SVOM/GRM observation of a bright long burst
  88. GRB 250407A: EP-WXT afterglow detection
  89. EP250407a: EP-WXT detection of a fast X-ray transient
  90. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  91. GRB 250407A: KAIT Optical Afterglow Candidate
  92. IceCube-250406A: No candidates from the Zwicky Transient Facility
  93. GRB 250407A: Fermi GBM Detection
  94. GRB 250407A: Swift-XRT afterglow detection
  95. GRB 250407A: SRG/ART-XC afterglow detection
  96. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  97. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  98. IPN triangulation of GRB 250406B (short/hard)
  99. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  100. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit

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