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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"

17618 results found.

  1. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  2. The EP-WXT trigger 01709259586 is likely a flaring star
  3. GRB 260330B: SVOM/VT further optical observation
  4. EP260403a: LCO optical observations of the counterpart
  5. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  6. EP260403a: LCO optical counterpart detection
  7. EP260403a: COLIBRÍ optical counterpart candidate
  8. GRB 260330B: SVOM/VT optical candidate
  9. EP260403a: Einstein Probe detection of an X-ray transient
  10. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  11. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  12. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  13. EP260324A / AT 2026hir: COLIBRÍ optical observations
  14. GRB 260402A: WINTER J-band upper limit
  15. GRB260402A: GROWTH-India Telescope optical upper limit
  16. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  17. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  18. GRB 260401A: SVOM/GRM observation
  19. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  20. GRB 260402A: Kilonova-Catcher optical upper limit
  21. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  22. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  23. GRB 260402A: SVOM detection of a burst
  24. EP260329b: Mondy and Assy-Turgen optical upper limits
  25. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  26. EP260321a :Xinglong optical observations
  27. EP260327a: Xinglong optical upper limit
  28. GRB 260330B: SVOM/VT optical upper limits
  29. GRB 260321A: SVOM/ECLAIRs refined analysis
  30. EP260329b: J-band upper limits with WINTER
  31. EP260329a: J-band upper limit with WINTER
  32. GRB 260330B: LCO optical upper limits
  33. GRB 260330B: SVOM detection of a burst
  34. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  35. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  36. EP260329a: COLIBRÍ optical upper limit
  37. EP260329a: EP-FXT follow up observation
  38. EP260329a: NOT optical counterpart candidate
  39. EP260329b: Optical follow-up with Kinder observations
  40. EP 260329b: COLIBRÍ optical observations
  41. EP260329a: Optical upper limit with Kinder observations
  42. EP260329b: LCO optical observations of the counterpart
  43. EP260329b: Einstein Probe detection of an X-ray transient
  44. EP260329a: Einstein Probe detection of an X-ray transient
  45. EP-WXT trigger 01709259209: TRT optical counterpart detection
  46. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  47. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  48. EP260327a: SVOM/VT optical upper limits
  49. EP260327a: WINTER J-band upper limit
  50. EP260327a: COLIBRÍ optical upper limits
  51. EP260327a: Gemini-North optical upper limits
  52. EP260324a: GROWTH-India Telescope optical observation
  53. EP260327a: Einstein Probe detection of an X-ray transient
  54. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  55. The EP-WXT trigger 01709259173 is likely a flaring star
  56. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  57. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  58. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  59. EP260321a: JinShan near-infrared observations
  60. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  61. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  62. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  63. The EP-WXT trigger 01709259112 is likely a flaring star
  64. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  65. EP260321a: COLIBRÍ further optical observations and brightening
  66. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  67. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  68. GRB 260321A: EP-FXT follow-up observation
  69. The EP-WXT trigger 01709259045 is likely a flaring star
  70. EP260321a: GOTO detection of blue variable source
  71. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  72. EP260321a: further Kinder optical observations
  73. GRB 260321A: SVOM/VT optical upper limits
  74. EP260321a: Las Cumbres upper limit
  75. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  76. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  77. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  78. EP260321a: SVOM/VT optical upper limit
  79. GRB 260310A: continued optical observation at Mondy
  80. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  81. EP260321a: Einstein Probe detection of an X-ray transient
  82. GRB 260310A / AT 2026fgk: KAIT optical observations
  83. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  84. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  85. GRB 260318A: SVOM/GRM observation
  86. The EP-WXT trigger 01709258989 is likely a flaring star
  87. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  88. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  89. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  90. GRB 260310A / AT 2026fgk: radio detection with the VLA
  91. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  92. GRB 260310A / AT2026fgk: LCO optical observations
  93. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  94. GRB 260316B: SVOM/GRM observation
  95. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  96. EP260316a: COLIBRÍ faint optical counterpart candidate
  97. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  98. EP260316a: Xinglong optical upper limit
  99. EP260316a: optical upper limit with Kinder observations
  100. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up

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