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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

19605 results found.

  1. GRB 250806A: Swift-XRT counterpart detection
  2. GRB 250805A: SVOM/VT optical counterpart
  3. GRB 250805A: ESO/VLT observations
  4. GRB 250805A: Swift-XRT refined Analysis
  5. GRB 250804B: Swift-XRT observations
  6. GRB 250805A: Enhanced Swift-XRT position
  7. GRB 250805A: TRT optical upper limits
  8. GRB 250805A: Swift-XRT observations
  9. GRB 250805A: Swift detection of a burst
  10. Swift GRB250805.26: Global MASTER-Net observations report
  11. GRB 250804B: Tiled Swift observations
  12. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  13. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  14. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  15. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
  16. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  17. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  18. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  19. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  20. GRB 250725A: AstroSat CZTI detection
  21. GRB 250727A: EP-FXT follow-up observation
  22. GRB 250725A: PRIME near-infrared observations
  23. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  24. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  25. GRB 250728A: Swift-XRT observations
  26. GRB 250728A: COLIBRÍ optical upper limit
  27. GRB 250728A: Fermi GBM Observation
  28. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  29. GRB 250728A: Swift ToO observations
  30. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  31. GRB 250727A: EP-FXT counterpart detection
  32. GRB250727A: SVOM/VT optical upper limit
  33. GRB 250727A: Swift-XRT observations
  34. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  35. GRB 250725A: Swift-XRT refined Analysis
  36. GRB 250725A: Fermi GBM Observation
  37. GRB 250725A: Swift-BAT refined analysis
  38. Konus-Wind detection of GRB 250725A
  39. GRB 250725A: SVOM/GRM observation
  40. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  41. GRB 250725A: Swift/UVOT Upper Limits
  42. GRB 250725A: Fermi-LAT detection
  43. GRB 250725A: BOOTES-7 early optical detection
  44. GRB 250725A: SVOM/VT optical candidate
  45. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  46. GRB 250725A: Enhanced Swift-XRT position
  47. GRB 250725A: Swift detection of a burst
  48. Swift GRB 250725A: Global MASTER-Net OT detection
  49. Swift GRB 250725A: Global MASTER-Net observations report
  50. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  51. Swift-BAT trigger 1334535 is not a GRB
  52. GRB 250721A: Swift-XRT observations
  53. GRB 250717B: SVOM/GRM observation
  54. GRB 250721A: Tiled Swift observations
  55. GRB 250717B: COLIBRÍ optical upper limit
  56. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  57. GRB 250717B: Swift-XRT observations
  58. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  59. Swift Trigger 1334535: a possible GRB 250718A
  60. Swift GRB250718.01: Global MASTER-Net observations report
  61. GRB 250717B: Swift ToO observations
  62. GRB 270713A: Kitab and AbAO Optical Observations
  63. GRB 250717B: Fermi GBM Observation
  64. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  65. GRB 250716A: Swift-XRT afterglow detection
  66. GRB 250716A: Swift ToO observations
  67. GRB 250713A: SVOM/C-GFT upper limit
  68. GRB 250713A: Swift-XRT observations
  69. GRB 250706A: Swift-BAT refined analysis
  70. GRB 250702F: Swift-BAT refined analysis
  71. GRB 250628A: Swift-BAT refined analysis
  72. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  73. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  74. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  75. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  76. GRB 250706B/C: Fermi-LAT detection
  77. GRB 250706B: Swift/UVOT Detection
  78. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  79. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  80. GRB 250702F: GRANDMA observations
  81. GRB 250706A: Swift-XRT refined Analysis
  82. GRB 250706A: Swift/UVOT Upper Limits
  83. GRB 250706A: REM optical/NIR observations
  84. Swift GRB 250706A: Global MASTER-Net observations report
  85. GRB 250706A: JinShan optical upper limits
  86. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  87. GRB250706B: Swift-XRT counterpart detection
  88. GRB 250706A: GROWTH-India Telescope optical upper limit
  89. GRB 250706A: Swift detection of a burst
  90. GRB 250704B: Swift-XRT refined Analysis
  91. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  92. GRB 250704B: Swift/UVOT Upper Limits
  93. GRB 250704A: Swift/UVOT Detection
  94. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  95. GRB 250702F: Kilonova-Catcher optical afterglow detection
  96. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  97. GRB 250704A: SVOM/VT optical observation
  98. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  99. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  100. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations

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