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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"

24656 results found.

  1. EP250428b: LAST optical upper limit
  2. GRB 250427A: Swift/UVOT Detection
  3. EP250428b: Global MASTER-Net observations report
  4. EP250428b: Einstein Probe detection of a fast X-ray transient
  5. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  6. EP250427a: Lesedi optical counterpart detection
  7. EP250427A: COLIBRÍ Continuing Optical Observations
  8. GRB250427A/EP250427a GIT optical afterglow detection:
  9. EP250427a: LT optical counterpart detection
  10. GRB 250427A: Swift-XRT refined Analysis
  11. EP250427a / GRB 250427A: LCO optical counterpart detection
  12. EP250427a: REM optical/NIR afterglow detection
  13. GRB 250424A: LCO optical observation
  14. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  15. EP250427A: COLIBRÍ Optical Detection
  16. EP250427a: TRT optical counterpart detection
  17. EP250427a: Einstein Probe detection of a fast X-ray transient
  18. GRB 250424A: Swift-BAT refined analysis
  19. GRB 250424A: SVOM/GRM observation of a long burst
  20. GRB 250424A: PRIME near-infrared detection
  21. GRB 250424A: WINTER J-band detection
  22. GRB 250424A: EIRSAT-1 GMOD Detection
  23. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  24. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  25. GRB 250419A: Mondy Optical Observations
  26. GRB 250424A: Swift/UVOT Detection
  27. Fermi-LAT gamma-ray observations of IceCube-250421A
  28. GRB 250424A: Skynet Optical Observations
  29. GRB 250424A: Kilonova-Catcher optical afterglow detection
  30. GRB 250330B: GRBAlpha detection
  31. GRB 250424A: Swift-XRT refined Analysis
  32. GRB 250424A: Enhanced Swift-XRT position
  33. GRB 250424A: AstroSat CZTI detection of a bright long burst
  34. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  35. GRB 250424A: BlackGEM optical afterglow detection
  36. GRB 250424A: DDOTI Afterglow Detection
  37. GRB 250424A: REM optical/NIR afterglow detection
  38. GRB 250424A: Swift detection of a burst with an optical counterpart
  39. Swift GRB250424A: Global MASTER-Net OT detection
  40. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  41. EP250421a: Nickel optical upper limit
  42. EP250421a: Upper limits from Fermi-GBM Observations
  43. SVOM/sb25042207: SVOM detection of an X-ray transient
  44. IceCube-250421A: DDOTI Detection of the LAST Candidate
  45. GRB 250419A: Mephisto Multi-band Optical Detection
  46. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  47. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  48. EP250421a: NOT optical observations
  49. GRB 250419A: Optical Observations via Virtual Telescope Project
  50. EP250421a: REM optical upper limit
  51. EP250421A: COLIBRÍ Optical Upper Limit
  52. GRB 250419A: Mondy Continued Optical Observations
  53. GRB 250421B: AstroSat CZTI detection of a bright long burst
  54. EP250421a: Einstein Probe detection of an X-ray transient
  55. EP250421a: Mephisto optical counterpart confirmation
  56. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  57. EP250421a: JinShan likely optical counterpart
  58. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  59. GRB 250419A: LCO optical observation
  60. GRB 250419A: JinShan optical observations
  61. GRB 250419A: SVOM/C-GFT optical observations
  62. GRB 250419A: Swift/UVOT Follow up
  63. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  64. GRB 250419A: LCO optical afterglow multi-band observations
  65. GRB 250419A: Mondy and AbAO Optical Observations
  66. GRB 250419A: AKO Optical Afterglow Detection
  67. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  68. GRB 250419A: Swift-XRT refined Analysis
  69. GRB 250419A: KAIT optical afterglow observations
  70. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  71. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  72. GRB 250419A: SVOM detection of a soft burst
  73. EP250416a: Swift/XRT counterpart fading
  74. EP20250416a: Swift/XRT counterpart detection
  75. IceCube-250416A: DDOTI Optical Observations
  76. EP250416a: Gemini South-GMOS optical counterpart
  77. SVOM/sb25041603 is not a GRB
  78. EP250416a: GSP optical upper limit
  79. EP250416a: Einstein Probe detection of an X-ray transient
  80. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  81. SVOM/sb25041603: SVOM detection of an X-ray transient
  82. IceCube 250414.324: DDOTI Optical Observations
  83. GRB 250413A: AstroSat CZTI detection
  84. EP250304a: ATCA radio observations
  85. EP250404a: Nanshan 0.43m Telescope optical observatios
  86. GRB 250411A: DDOTI Optical Observations
  87. Fermi GRB 250411A: Global MASTER-Net observations report
  88. GRB 250407A: Continued KAIT/Nickel optical observations
  89. GRB 250314A: e-MERLIN observations
  90. GRB 250407A: Mondy and AbAO Optical Observations
  91. EP250227a: Further NOT optical observations
  92. GRB 250320B: cubesat Avion detection
  93. IceCube-250406A: Swift-XRT observations
  94. GRB 250407A: LCO detection of a fading optical counterpart
  95. Fermi-LAT gamma-ray observations of IceCube-250406A
  96. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  97. GRB 250407A: SVOM/GRM observation of a bright long burst
  98. GRB 250407A: EP-WXT afterglow detection
  99. EP250407a: EP-WXT detection of a fast X-ray transient
  100. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart

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