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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"

21392 results found.

  1. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  2. GRB 250221A: continued Mondy optical observations, brightening afterglow
  3. GRB 250221A: Optical counterpart detection by LCO.
  4. GRB 250221A: Mondy optical observations
  5. Konus-Wind detection of GRB 250221A
  6. GRB 250221A: Assy optical observations
  7. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  8. GRB 250221A: GRANDMA/TAROT Detection
  9. GRB 250221A: Swift-XRT refined Analysis
  10. GRB 250221A: NOT optical observations
  11. GRB 250221A: 1.6m Mephisto optical detection
  12. GRB 250221A: AKO Optical Upper Limit
  13. GRB 250221A: Swift/UVOT Detection
  14. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  15. GRB 250221A: REM optical/NIR afterglow detection
  16. GRB 250221A: Enhanced Swift-XRT position
  17. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  18. GRB 250221A: Swift detection of a burst with an optical counterpart
  19. Swift GRB250221.15: Global MASTER-Net OT detection
  20. Swift GRB250221.15: Global MASTER-Net observations report
  21. GRB 250219A: Swift/UVOT Upper Limits
  22. GRB 250219A: OHP/T193 optical upper limit
  23. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  24. GRB 250219A: 1.6m Mephisto optical upper limits
  25. GRB 250219A: SVOM/VT optical counterpart
  26. GRB 250219A: Swift-XRT observations
  27. GRB 250219A: Swift ToO observations
  28. GRB 250217C: Swift-XRT observations
  29. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  30. GRB 250217C: Tiled Swift observations
  31. IPN triangulation of GRB 250217C (short)
  32. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  33. SVOM/sb25021804: SVOM detection of a long X-ray transient
  34. GRB 250213A: Swift-XRT observations
  35. GRB 250215A / EP250215a: LCO detection of the afterglow
  36. GRB 250215A: Swift/UVOT Upper Limits
  37. GRB 250215A: Fermi GBM Observation
  38. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  39. GRB 250215A: Swift-XRT refined Analysis
  40. GRB 250213A: Swift ToO observations
  41. GRB 250205A: VIRT Optical Upper Limit
  42. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  43. GRB 250211A: Swift ToO observations
  44. GRB 250207A: Fermi GBM Observation
  45. Konus-Wind detection of GRB 250207A
  46. GRB 250207A: Skynet optical afterglow observations
  47. GRB 241128A: VIRT Optical Upper Limit
  48. GRB 250207A: 1.3m DFOT Optical observations
  49. GRB 250206A: Swift-XRT observations
  50. GRB 250129A: GRANDMA Continued Afterglow Detection
  51. GRB 250207A: Swift-BAT refined analysis
  52. GRB 250205A: 1.3m DFOT optical upper limit
  53. GRB 250206A: Tiled Swift observations
  54. GRB 250206A: Fermi-LAT detection
  55. GRB 250207B: Swift-XRT observations
  56. EP250207a: EP-WXT detection and XRT follow-up observation
  57. GRB 250207A: Swift-XRT refined Analysis
  58. GRB 250207A: Enhanced Swift-XRT position
  59. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  60. GRB 250207A: REM IR afterglow detection
  61. GRB 250207A: FRAM-Auger optical detection
  62. GRB 250207B: Tiled Swift observations
  63. GRB 250207A: REM optical afterglow detection
  64. GRB 250207A: Swift/UVOT Detection
  65. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  66. GRB 250207A: Swift detection of a burst with optical counterpart
  67. GRB 250205A: Fermi GBM Observation
  68. GRB 250205A: Swift/UVOT Upper Limits
  69. GRB 250205A: Swift/XRT detection
  70. IPN triangulation of GRB 250201A
  71. GRB 250129A: Swift-BAT refined analysis
  72. IPN triangulation of GRB 250204B (short/hard)
  73. IPN triangulation of GRB 250202B
  74. GRB 250129A: LCO late afterglow detection
  75. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  76. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  77. GRB 250129A: SVOM/C-GFT optical observations
  78. Swift GRB250129A: MASTER 4 days observations report
  79. Konus-Wind detection of GRB 250129A
  80. GRB 250129A: 1.3m DFOT Optical observations
  81. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  82. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  83. GRB 250129A: COLIBRÍ Optical Observations
  84. GRB 250128B: VLA possible radio detection
  85. GRB 250129A: TNG NIR afterglow detection
  86. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  87. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  88. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  89. GRB 250128B: VLA radio upper limit
  90. Ep250125A: 1.3m DFOT optical upper limit
  91. GRB 250129A: Skynet optical observations
  92. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  93. GRB 250129A: Swift-XRT refined Analysis
  94. GRB 250128B: Gemini-North optical extended source detection
  95. GRB 250128B: TNG optical upper limit
  96. GRB 250129A: Swift/UVOT Detection
  97. GRB 250128B: VLT/HAWKI near-infrared observations
  98. GRB 250127A: CrAO and Terskol optical upper limits
  99. GRB 250129A: Enhanced Swift-XRT position
  100. GRB 250128B: NOT optical upper limit

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