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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').
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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"

27012 results found.

  1. EP260329b: LCO optical observations of the counterpart
  2. EP260329b: Einstein Probe detection of an X-ray transient
  3. EP260329a: Einstein Probe detection of an X-ray transient
  4. EP-WXT trigger 01709259209: TRT optical counterpart detection
  5. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  6. GRID detection of GRB 260326A
  7. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  8. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  9. EP260327a: SVOM/VT optical upper limits
  10. EP260327a: WINTER J-band upper limit
  11. EP260327a: COLIBRÍ optical upper limits
  12. EP260327a: Gemini-North optical upper limits
  13. EP260324a: GROWTH-India Telescope optical observation
  14. EP260327a: Global MASTER-Net observations report
  15. EP260327a: Einstein Probe detection of an X-ray transient
  16. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  17. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  18. The EP-WXT trigger 01709259173 is likely a flaring star
  19. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  20. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  21. GRB 260326A: Fermi GBM Detection
  22. GRB 260325A: Fermi GBM Final Localization
  23. GRB 260326A: Fermi GBM Final Real-time Localization
  24. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  25. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  26. IPN triangulation of GRB 260316B
  27. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  28. GRID detection of GRB 260320A
  29. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  30. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  31. GRB 260310A: LBT optical observations
  32. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  33. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  34. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  35. The EP-WXT trigger 01709259112 is likely a flaring star
  36. Fermi GRB 260323A: Global MASTER-Net observations report
  37. GRB 260323A: Fermi GBM Final Real-time Localization
  38. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  39. GRB 260322A: Fermi GBM Final Localization
  40. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  41. EP260321a: COLIBRÍ further optical observations and brightening
  42. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  43. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  44. EP260214b: ATCA 6 GHz detection
  45. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  46. GRB 260321A: EP-FXT follow-up observation
  47. The EP-WXT trigger 01709259045 is likely a flaring star
  48. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  49. EP260321a: GOTO detection of blue variable source
  50. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  51. EP260321a: further Kinder optical observations
  52. GRB 260321A: SVOM/VT optical upper limits
  53. EP260321a: Las Cumbres upper limit
  54. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  55. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  56. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  57. EP260321a: SVOM/VT optical upper limit
  58. Fermi GBM Sub-Threshold Detection of GRB 260321A
  59. GRB 260321A: SVOM detection of a burst
  60. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  61. EP260321a: Global MASTER-Net observations report
  62. EP260321a: Einstein Probe detection of an X-ray transient
  63. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  64. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  65. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  66. GRB 260310A/AT2026fgk: LBT near-infrared observations
  67. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  68. GRB 260318A: SVOM/GRM observation
  69. The EP-WXT trigger 01709258989 is likely a flaring star
  70. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  71. GRB 260318A: GECAM-B observation
  72. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  73. Fermi GRB 260318A: Global MASTER-Net observations report
  74. GRB 260318A: Fermi GBM Final Real-time Localization
  75. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  76. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  77. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  78. GRB 260310A / AT2026fgk: LCO optical observations
  79. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  80. GRB 260317A: Fermi GBM Final Localization
  81. GRB 260316B: GECAM-B observation
  82. GRB 260316B: SVOM/GRM observation
  83. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  84. EP260316a: COLIBRÍ faint optical counterpart candidate
  85. GRB 260316B: AstroSat CZTI detection
  86. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  87. EP260316a: Xinglong optical upper limit
  88. GRB 260316B: Fermi GBM Final Real-time Localization
  89. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  90. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  91. IceCube-260315A: COLIBRÍ optical observations
  92. EP260314a: Xinglong optical upper limit
  93. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  94. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  95. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  96. GRB 260310A / AT 2026fgk: iTelescope optical observations
  97. EP260314a: COLIBRÍ optical upper limit
  98. GRID detection of GRB 260312B
  99. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  100. EP260314a: BOOTES-6/DPR optical upper limits at early times

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