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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"

27016 results found.

  1. GRB 260330A: Fermi GBM Final Real-time Localization
  2. EP260329b: Global MASTER-Net observations report
  3. Fermi trigger No 796485221: Global MASTER-Net observations report
  4. EP 260329b: COLIBRÍ optical observations
  5. EP260329b: LCO optical observations of the counterpart
  6. EP260329b: Einstein Probe detection of an X-ray transient
  7. EP260329a: Einstein Probe detection of an X-ray transient
  8. EP-WXT trigger 01709259209: TRT optical counterpart detection
  9. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  10. GRID detection of GRB 260326A
  11. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  12. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  13. EP260327a: SVOM/VT optical upper limits
  14. EP260327a: WINTER J-band upper limit
  15. EP260327a: COLIBRÍ optical upper limits
  16. EP260327a: Gemini-North optical upper limits
  17. EP260324a: GROWTH-India Telescope optical observation
  18. EP260327a: Global MASTER-Net observations report
  19. EP260327a: Einstein Probe detection of an X-ray transient
  20. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  21. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  22. The EP-WXT trigger 01709259173 is likely a flaring star
  23. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  24. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  25. GRB 260326A: Fermi GBM Detection
  26. GRB 260325A: Fermi GBM Final Localization
  27. GRB 260326A: Fermi GBM Final Real-time Localization
  28. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  29. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  30. IPN triangulation of GRB 260316B
  31. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  32. GRID detection of GRB 260320A
  33. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  34. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  35. GRB 260310A: LBT optical observations
  36. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  37. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  38. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  39. The EP-WXT trigger 01709259112 is likely a flaring star
  40. Fermi GRB 260323A: Global MASTER-Net observations report
  41. GRB 260323A: Fermi GBM Final Real-time Localization
  42. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  43. GRB 260322A: Fermi GBM Final Localization
  44. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  45. EP260321a: COLIBRÍ further optical observations and brightening
  46. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  47. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  48. EP260214b: ATCA 6 GHz detection
  49. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  50. GRB 260321A: EP-FXT follow-up observation
  51. The EP-WXT trigger 01709259045 is likely a flaring star
  52. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  53. EP260321a: GOTO detection of blue variable source
  54. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  55. EP260321a: further Kinder optical observations
  56. GRB 260321A: SVOM/VT optical upper limits
  57. EP260321a: Las Cumbres upper limit
  58. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  59. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  60. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  61. EP260321a: SVOM/VT optical upper limit
  62. Fermi GBM Sub-Threshold Detection of GRB 260321A
  63. GRB 260321A: SVOM detection of a burst
  64. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  65. EP260321a: Global MASTER-Net observations report
  66. EP260321a: Einstein Probe detection of an X-ray transient
  67. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  68. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  69. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  70. GRB 260310A/AT2026fgk: LBT near-infrared observations
  71. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  72. GRB 260318A: SVOM/GRM observation
  73. The EP-WXT trigger 01709258989 is likely a flaring star
  74. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  75. GRB 260318A: GECAM-B observation
  76. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  77. Fermi GRB 260318A: Global MASTER-Net observations report
  78. GRB 260318A: Fermi GBM Final Real-time Localization
  79. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  80. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  81. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  82. GRB 260310A / AT2026fgk: LCO optical observations
  83. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  84. GRB 260317A: Fermi GBM Final Localization
  85. GRB 260316B: GECAM-B observation
  86. GRB 260316B: SVOM/GRM observation
  87. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  88. EP260316a: COLIBRÍ faint optical counterpart candidate
  89. GRB 260316B: AstroSat CZTI detection
  90. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  91. EP260316a: Xinglong optical upper limit
  92. GRB 260316B: Fermi GBM Final Real-time Localization
  93. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  94. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  95. IceCube-260315A: COLIBRÍ optical observations
  96. EP260314a: Xinglong optical upper limit
  97. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  98. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  99. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  100. GRB 260310A / AT 2026fgk: iTelescope optical observations

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