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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"

19934 results found.

  1. The EP-WXT trigger 01709198251 is likely a flaring star
  2. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  3. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  4. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  5. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
  6. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  7. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  8. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  9. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  10. GRB 250725A: AstroSat CZTI detection
  11. GRB 250727A: EP-FXT follow-up observation
  12. GRB 250725A: PRIME near-infrared observations
  13. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  14. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  15. GRB 250728A: Swift-XRT observations
  16. GRB 250728A: COLIBRÍ optical upper limit
  17. GRB 250728A: Fermi GBM Observation
  18. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  19. GRB 250728A: Swift ToO observations
  20. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  21. GRB 250727A: EP-FXT counterpart detection
  22. GRB250727A: SVOM/VT optical upper limit
  23. GRB 250727A: Swift-XRT observations
  24. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  25. GRB 250725A: Swift-XRT refined Analysis
  26. GRB 250725A: Fermi GBM Observation
  27. GRB 250725A: Swift-BAT refined analysis
  28. Konus-Wind detection of GRB 250725A
  29. GRB 250725A: SVOM/GRM observation
  30. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  31. GRB 250725A: Swift/UVOT Upper Limits
  32. GRB 250725A: Fermi-LAT detection
  33. GRB 250725A: BOOTES-7 early optical detection
  34. GRB 250725A: SVOM/VT optical candidate
  35. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  36. GRB 250725A: Enhanced Swift-XRT position
  37. GRB 250725A: Swift detection of a burst
  38. Swift GRB 250725A: Global MASTER-Net OT detection
  39. Swift GRB 250725A: Global MASTER-Net observations report
  40. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  41. Swift-BAT trigger 1334535 is not a GRB
  42. GRB 250721A: Swift-XRT observations
  43. GRB 250717B: SVOM/GRM observation
  44. GRB 250721A: Tiled Swift observations
  45. GRB 250717B: COLIBRÍ optical upper limit
  46. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  47. GRB 250717B: Swift-XRT observations
  48. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  49. Swift Trigger 1334535: a possible GRB 250718A
  50. Swift GRB250718.01: Global MASTER-Net observations report
  51. GRB 250717B: Swift ToO observations
  52. GRB 270713A: Kitab and AbAO Optical Observations
  53. GRB 250717B: Fermi GBM Observation
  54. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  55. GRB 250716A: Swift-XRT afterglow detection
  56. GRB 250716A: Swift ToO observations
  57. GRB 250713A: SVOM/C-GFT upper limit
  58. GRB 250713A: Swift-XRT observations
  59. GRB 250706A: Swift-BAT refined analysis
  60. GRB 250702F: Swift-BAT refined analysis
  61. GRB 250628A: Swift-BAT refined analysis
  62. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  63. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  64. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  65. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  66. GRB 250706B/C: Fermi-LAT detection
  67. GRB 250706B: Swift/UVOT Detection
  68. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  69. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  70. GRB 250702F: GRANDMA observations
  71. GRB 250706A: Swift-XRT refined Analysis
  72. GRB 250706A: Swift/UVOT Upper Limits
  73. GRB 250706A: REM optical/NIR observations
  74. Swift GRB 250706A: Global MASTER-Net observations report
  75. GRB 250706A: JinShan optical upper limits
  76. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  77. GRB250706B: Swift-XRT counterpart detection
  78. GRB 250706A: GROWTH-India Telescope optical upper limit
  79. GRB 250706A: Swift detection of a burst
  80. GRB 250704B: Swift-XRT refined Analysis
  81. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  82. GRB 250704B: Swift/UVOT Upper Limits
  83. GRB 250704A: Swift/UVOT Detection
  84. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  85. GRB 250702F: Kilonova-Catcher optical afterglow detection
  86. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  87. GRB 250704A: SVOM/VT optical observation
  88. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  89. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  90. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  91. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  92. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  93. EP250704a / GRB250704B: Swift-XRT counterpart detection
  94. GRB 250704A: Swift-XRT afterglow detection
  95. GRB 250702B / EP2050702a: FTW optical and NIR observations
  96. Konus-Wind detection of GRB 250702F
  97. GRB 250702F: GROWTH-India Telescope optical observations
  98. EP250702a: WFST optical observations
  99. GRB 250702F: SVOM/VT optical observation
  100. GRB 250702F: Swift/UVOT Detection

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