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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"

28047 results found.

  1. GRB 250427A: Swift-XRT refined Analysis
  2. EP250427a / GRB 250427A: LCO optical counterpart detection
  3. EP250427a: REM optical/NIR afterglow detection
  4. GRB 250424A: LCO optical observation
  5. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  6. EP250427A: COLIBRÍ Optical Detection
  7. EP250427a: TRT optical counterpart detection
  8. EP250427a: Einstein Probe detection of a fast X-ray transient
  9. GRB 250424A: Swift-BAT refined analysis
  10. GRB 250424A: SVOM/GRM observation of a long burst
  11. GRB 250424A: PRIME near-infrared detection
  12. GRB 250424A: WINTER J-band detection
  13. GRB 250424A: EIRSAT-1 GMOD Detection
  14. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  15. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  16. GRB 250419A: Mondy Optical Observations
  17. GRB 250424A: Swift/UVOT Detection
  18. Fermi-LAT gamma-ray observations of IceCube-250421A
  19. GRB 250424A: Skynet Optical Observations
  20. GRB 250424A: Kilonova-Catcher optical afterglow detection
  21. GRB 250330B: GRBAlpha detection
  22. GRB 250424A: Swift-XRT refined Analysis
  23. GRB 250424A: Enhanced Swift-XRT position
  24. GRB 250424A: AstroSat CZTI detection of a bright long burst
  25. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  26. GRB 250424A: BlackGEM optical afterglow detection
  27. GRB 250424A: DDOTI Afterglow Detection
  28. GRB 250424A: REM optical/NIR afterglow detection
  29. GRB 250424A: Swift detection of a burst with an optical counterpart
  30. Swift GRB 250424A: Global MASTER-Net OT detection
  31. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  32. EP250421a: Nickel optical upper limit
  33. EP250421a: Upper limits from Fermi-GBM Observations
  34. SVOM/sb25042207: SVOM detection of an X-ray transient
  35. IceCube-250421A: DDOTI Detection of the LAST Candidate
  36. GRB 250419A: Mephisto Multi-band Optical Detection
  37. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  38. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  39. EP250421a: NOT optical observations
  40. GRB 250419A: Optical Observations via Virtual Telescope Project
  41. EP250421a: REM optical upper limit
  42. EP250421A: COLIBRÍ Optical Upper Limit
  43. GRB 250419A: Mondy Continued Optical Observations
  44. GRB 250421B: AstroSat CZTI detection of a bright long burst
  45. EP250421a: Einstein Probe detection of an X-ray transient
  46. EP250421a: Mephisto optical counterpart confirmation
  47. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  48. EP250421a: JinShan likely optical counterpart
  49. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  50. GRB 250419A: LCO optical observation
  51. GRB 250419A: JinShan optical observations
  52. GRB 250419A: SVOM/C-GFT optical observations
  53. GRB 250419A: Swift/UVOT Follow up
  54. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  55. GRB 250419A: LCO optical afterglow multi-band observations
  56. GRB 250419A: Mondy and AbAO Optical Observations
  57. GRB 250419A: AKO Optical Afterglow Detection
  58. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  59. GRB 250419A: Swift-XRT refined Analysis
  60. GRB 250419A: KAIT optical afterglow observations
  61. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  62. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  63. GRB 250419A: SVOM detection of a soft burst
  64. EP250416a: Swift/XRT counterpart fading
  65. EP20250416a: Swift/XRT counterpart detection
  66. IceCube-250416A: DDOTI Optical Observations
  67. EP250416a: Gemini South-GMOS optical counterpart
  68. SVOM/sb25041603 is not a GRB
  69. EP250416a: GSP optical upper limit
  70. EP250416a: Einstein Probe detection of an X-ray transient
  71. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  72. SVOM/sb25041603: SVOM detection of an X-ray transient
  73. IceCube 250414.324: DDOTI Optical Observations
  74. GRB 250413A: AstroSat CZTI detection
  75. EP250304a: ATCA radio observations
  76. EP250404a: Nanshan 0.43m Telescope optical observatios
  77. GRB 250411A: DDOTI Optical Observations
  78. Fermi GRB 250411A: Global MASTER-Net observations report
  79. GRB 250407A: Continued KAIT/Nickel optical observations
  80. GRB 250314A: e-MERLIN observations
  81. GRB 250407A: Mondy and AbAO Optical Observations
  82. EP250227a: Further NOT optical observations
  83. GRB 250320B: cubesat Avion detection
  84. IceCube-250406A: Swift-XRT observations
  85. GRB 250407A: LCO detection of a fading optical counterpart
  86. Fermi-LAT gamma-ray observations of IceCube-250406A
  87. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  88. GRB 250407A: SVOM/GRM observation of a bright long burst
  89. GRB 250407A: EP-WXT afterglow detection
  90. EP250407a: EP-WXT detection of a fast X-ray transient
  91. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  92. GRB 250407A: KAIT Optical Afterglow Candidate
  93. IceCube-250406A: No candidates from the Zwicky Transient Facility
  94. GRB 250407A: Fermi GBM Detection
  95. GRB 250407A: Swift-XRT afterglow detection
  96. GRB 250407A: SRG/ART-XC afterglow detection
  97. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  98. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  99. IPN triangulation of GRB 250406B (short/hard)
  100. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)

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