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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"

18694 results found.

  1. GRB 250217C: Tiled Swift observations
  2. IPN triangulation of GRB 250217C (short)
  3. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  4. SVOM/sb25021804: SVOM detection of a long X-ray transient
  5. GRB 250213A: Swift-XRT observations
  6. GRB 250215A / EP250215a: LCO detection of the afterglow
  7. GRB 250215A: Swift/UVOT Upper Limits
  8. GRB 250215A: Fermi GBM Observation
  9. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  10. GRB 250215A: Swift-XRT refined Analysis
  11. GRB 250213A: Swift ToO observations
  12. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  13. GRB 250211A: Swift ToO observations
  14. GRB 250207A: Fermi GBM Observation
  15. Konus-Wind detection of GRB 250207A
  16. GRB 250207A: Skynet optical afterglow observations
  17. GRB 250207A: 1.3m DFOT Optical observations
  18. GRB 250206A: Swift-XRT observations
  19. GRB 250129A: GRANDMA Continued Afterglow Detection
  20. GRB 250207A: Swift-BAT refined analysis
  21. GRB 250205A: 1.3m DFOT optical upper limit
  22. GRB 250206A: Tiled Swift observations
  23. GRB 250206A: Fermi-LAT detection
  24. GRB 250207B: Swift-XRT observations
  25. EP250207a: EP-WXT detection and XRT follow-up observation
  26. GRB 250207A: Swift-XRT refined Analysis
  27. GRB 250207A: Enhanced Swift-XRT position
  28. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  29. GRB 250207A: REM IR afterglow detection
  30. GRB 250207A: FRAM-Auger optical detection
  31. GRB 250207B: Tiled Swift observations
  32. GRB 250207A: REM optical afterglow detection
  33. GRB 250207A: Swift/UVOT Detection
  34. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  35. GRB 250207A: Swift detection of a burst with optical counterpart
  36. GRB 250205A: Fermi GBM Observation
  37. GRB 250205A: Swift/UVOT Upper Limits
  38. GRB 250205A: Swift/XRT detection
  39. IPN triangulation of GRB 250201A
  40. GRB 250129A: Swift-BAT refined analysis
  41. IPN triangulation of GRB 250204B (short/hard)
  42. IPN triangulation of GRB 250202B
  43. GRB 250129A: LCO late afterglow detection
  44. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  45. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  46. GRB 250129A: SVOM/C-GFT optical observations
  47. Swift GRB250129A: MASTER 4 days observations report
  48. Konus-Wind detection of GRB 250129A
  49. GRB 250129A: 1.3m DFOT Optical observations
  50. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  51. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  52. GRB 250129A: COLIBRÍ Optical Observations
  53. GRB 250129A: TNG NIR afterglow detection
  54. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  55. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  56. GRB 250128B: VLA radio upper limit
  57. Ep250125A: 1.3m DFOT optical upper limit
  58. GRB 250129A: Skynet optical observations
  59. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  60. GRB 250129A: Swift-XRT refined Analysis
  61. GRB 250128B: TNG optical upper limit
  62. GRB 250129A: Swift/UVOT Detection
  63. GRB 250127A: CrAO and Terskol optical upper limits
  64. GRB 250129A: Enhanced Swift-XRT position
  65. GRB 250128B: NOT optical upper limit
  66. GRB 250129A: REM optical/NIR afterglow detection
  67. GRB 250129A: Early afterglow detection by LCO.
  68. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  69. GRB 250129A: LCO optical observations
  70. GRB 250129A: GOTO optical observations show brightening afterglow
  71. Swift GRB 250129A: Global MASTER-Net observations report
  72. GRB 250128B: Enhanced Swift-XRT position
  73. GRB 250129A: Swift detection of a burst with an optical counterpart
  74. Swift GRB 250129A: Global MASTER-Net OT detection
  75. GRB 250128B: Swift-XRT refined Analysis
  76. GRB 250128B: Fermi GBM Observation
  77. GRB 250128B: GOTO optical upper limit
  78. Swift GRB 250128B: Global MASTER-Net observations report
  79. EP250125a: Upper limits from Swift/BAT-GUANO
  80. GRB 250128B: LCO optical observations
  81. GRB 250128B: Swift detection of a short burst
  82. GRB 250127A: Swift-XRT observations
  83. GRB 250127A: EP-FXT afterglow detection
  84. GRB 250117A: Fermi GBM Observation
  85. GRB 250127A: SVOM/VT upper limit
  86. IPN triangulation of GRB 250119C
  87. GRB 250127A: Swift ToO observations
  88. GECAM-A detection of a bright burst from SGR 1E1841-045
  89. GRB 250118A: Fermi GBM Observation
  90. EP250125a: REM optical counterpart detection
  91. GRB 250119C: Fermi GBM Observation
  92. EP250125a: Swift/XRT detection of a fading counterpart
  93. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  94. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  95. IPN triangulation of a bright burst from SGR 1E1841-045
  96. IPN triangulation of GRB 250118B
  97. Konus-Wind detection of GRB 250119B
  98. IPN triangulation of GRB 250119B
  99. Improved IPN triangulation of GRB 250107C
  100. GRB 250114A: Swift-BAT refined analysis

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