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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"

21459 results found.

  1. GRB 250807A: Enhanced Swift-XRT position
  2. GRB 250807B: Swift detection of a burst with an optical counterpart.
  3. GRB 250805A: Kilonova-Catcher optical upper limits
  4. GRB 250805A: Swift/UVOT Upper Limits
  5. GRB 250806A: Swift/UVOT U-band detection
  6. GRB 250807A: Swift detection of a burst with an optical counterpart
  7. GRB 250806A: EP-FXT observation
  8. EP#01709198415/EP250806a: Swift-XRT observations
  9. GRB 250805A: Swift-BAT refined analysis
  10. GRB 250806A: KAIT optical upper limit
  11. GRB 250806A: SVOM/VT refined analysis
  12. GRB 250806A: Swift-XRT counterpart detection
  13. GRB 250805A: SVOM/VT optical counterpart
  14. GRB 250805A: ESO/VLT observations
  15. GRB 250805A: Swift-XRT refined Analysis
  16. GRB 250804B: Swift-XRT observations
  17. GRB 250805A: Enhanced Swift-XRT position
  18. GRB 250805A: TRT optical upper limits
  19. GRB 250805A: Swift-XRT observations
  20. GRB 250805A: Swift detection of a burst
  21. Swift GRB250805.26: Global MASTER-Net observations report
  22. GRB 250804B: Tiled Swift observations
  23. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  24. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  25. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  26. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
  27. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  28. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  29. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  30. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  31. GRB 250725A: AstroSat CZTI detection
  32. GRB 250727A: EP-FXT follow-up observation
  33. GRB 250725A: PRIME near-infrared observations
  34. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  35. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  36. GRB 250728A: Swift-XRT observations
  37. GRB 250728A: COLIBRÍ optical upper limit
  38. GRB 250728A: Fermi GBM Observation
  39. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  40. GRB 250728A: Swift ToO observations
  41. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  42. GRB 250727A: EP-FXT counterpart detection
  43. GRB250727A: SVOM/VT optical upper limit
  44. GRB 250727A: Swift-XRT observations
  45. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  46. GRB 250725A: Swift-XRT refined Analysis
  47. GRB 250725A: Fermi GBM Observation
  48. GRB 250725A: Swift-BAT refined analysis
  49. Konus-Wind detection of GRB 250725A
  50. GRB 250725A: SVOM/GRM observation
  51. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  52. GRB 250725A: Swift/UVOT Upper Limits
  53. GRB 250725A: Fermi-LAT detection
  54. GRB 250725A: BOOTES-7 early optical detection
  55. GRB 250725A: SVOM/VT optical candidate
  56. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  57. GRB 250725A: Enhanced Swift-XRT position
  58. GRB 250725A: Swift detection of a burst
  59. Swift GRB 250725A: Global MASTER-Net OT detection
  60. Swift GRB 250725A: Global MASTER-Net observations report
  61. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  62. Swift-BAT trigger 1334535 is not a GRB
  63. GRB 250721A: Swift-XRT observations
  64. GRB 250717B: SVOM/GRM observation
  65. GRB 250721A: Tiled Swift observations
  66. GRB 250717B: COLIBRÍ optical upper limit
  67. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  68. GRB 250717B: Swift-XRT observations
  69. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  70. Swift Trigger 1334535: a possible GRB 250718A
  71. Swift GRB250718.01: Global MASTER-Net observations report
  72. GRB 250717B: Swift ToO observations
  73. GRB 270713A: Kitab and AbAO Optical Observations
  74. GRB 250717B: Fermi GBM Observation
  75. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  76. GRB 250716A: Swift-XRT afterglow detection
  77. GRB 250716A: Swift ToO observations
  78. GRB 250713A: SVOM/VT optical upper limit
  79. GRB 250713A: SVOM/C-GFT upper limit
  80. GRB 250713A: Swift-XRT observations
  81. GRB 250706A: Swift-BAT refined analysis
  82. GRB 250702F: Swift-BAT refined analysis
  83. GRB 250628A: Swift-BAT refined analysis
  84. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  85. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  86. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  87. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  88. GRB 250706B/C: Fermi-LAT detection
  89. GRB 250706B: Swift/UVOT Detection
  90. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  91. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  92. GRB 250702F: GRANDMA observations
  93. GRB 250706A: Swift-XRT refined Analysis
  94. GRB 250706A: Swift/UVOT Upper Limits
  95. GRB 250706A: REM optical/NIR observations
  96. Swift GRB 250706A: Global MASTER-Net observations report
  97. GRB 250706A: JinShan optical upper limits
  98. GRB 250706A: SAO RAS optical observations
  99. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  100. GRB250706B: Swift-XRT counterpart detection

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