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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

17576 results found.

  1. EP260329b: Einstein Probe detection of an X-ray transient
  2. EP260329a: Einstein Probe detection of an X-ray transient
  3. EP-WXT trigger 01709259209: TRT optical counterpart detection
  4. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  5. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  6. EP260327a: SVOM/VT optical upper limits
  7. EP260327a: WINTER J-band upper limit
  8. EP260327a: COLIBRÍ optical upper limits
  9. EP260327a: Gemini-North optical upper limits
  10. EP260324a: GROWTH-India Telescope optical observation
  11. EP260327a: Einstein Probe detection of an X-ray transient
  12. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  13. The EP-WXT trigger 01709259173 is likely a flaring star
  14. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  15. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  16. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  17. EP260321a: JinShan near-infrared observations
  18. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  19. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  20. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  21. The EP-WXT trigger 01709259112 is likely a flaring star
  22. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  23. EP260321a: COLIBRÍ further optical observations and brightening
  24. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  25. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  26. GRB 260321A: EP-FXT follow-up observation
  27. The EP-WXT trigger 01709259045 is likely a flaring star
  28. EP260321a: GOTO detection of blue variable source
  29. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  30. EP260321a: further Kinder optical observations
  31. GRB 260321A: SVOM/VT optical upper limits
  32. EP260321a: Las Cumbres upper limit
  33. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  34. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  35. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  36. EP260321a: SVOM/VT optical upper limit
  37. GRB 260310A: continued optical observation at Mondy
  38. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  39. EP260321a: Einstein Probe detection of an X-ray transient
  40. GRB 260310A / AT 2026fgk: KAIT optical observations
  41. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  42. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  43. GRB 260318A: SVOM/GRM observation
  44. The EP-WXT trigger 01709258989 is likely a flaring star
  45. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  46. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  47. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  48. GRB 260310A / AT 2026fgk: radio detection with the VLA
  49. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  50. GRB 260310A / AT2026fgk: LCO optical observations
  51. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  52. GRB 260316B: SVOM/GRM observation
  53. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  54. EP260316a: COLIBRÍ faint optical counterpart candidate
  55. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  56. EP260316a: Xinglong optical upper limit
  57. EP260316a: optical upper limit with Kinder observations
  58. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  59. IceCube-260315A: COLIBRÍ optical observations
  60. EP260314a: Xinglong optical upper limit
  61. EP260314a: optical upper limit with Kinder observations
  62. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  63. GRB 260310A / AT 2026fgk: iTelescope optical observations
  64. EP260314a: COLIBRÍ optical upper limit
  65. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  66. EP260314a: SVOM/VT optical candidate
  67. EP260314a: Einstein Probe detection of an X-ray transient
  68. GRB 260310A / AT2026fgk: SAO RAS optical observations
  69. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  70. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  71. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  72. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  73. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  74. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  75. GRB 260310A: potential optical counterpart
  76. GRB 260131A/B: radio detection with the VLA
  77. EP260302a: MeerKAT radio counterpart
  78. GRB 260308A: SVOM/GRM observation of a short GRB
  79. EP260306a: Mondy optical upper limit
  80. GRB 260208A: radio detection with the VLA
  81. GRB 260307B: Mephisto optical upper limits
  82. GRB 260307B: possible NOT optical counterpart
  83. GRB 260307B: SVOM/VT upper limit with X band data analysis
  84. GRB260307B: GROWTH-India Telescope optical upper limit
  85. GRB 260307B: SVOM/VT optical candidate
  86. GRB 260307B: SVOM/C-GFT upper limit
  87. GRB 260307B: SVOM detection of a burst
  88. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  89. GRB 260207A: TESS Detection and Possible VLA Counterpart
  90. EP260302a: SVOM/VT optical observation
  91. EP260306a: SVOM/VT optical observation
  92. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  93. EP260306a: Einstein Probe detection of an X-ray transient
  94. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  95. GRB 260303A: 1.3m DFOT optical upper limit
  96. GRB 260304A: AstroSat CZTI detection of a long burst
  97. GRB 260303A: SVOM/VT optical observations
  98. GRB 260303A: J-band observations with WINTER
  99. EP260302a: analysis of the follow-up EP-FXT observation
  100. EP260302a: LCO observations

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