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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"

28071 results found.

  1. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  2. EP260327a: SVOM/VT optical upper limits
  3. EP260327a: WINTER J-band upper limit
  4. EP260327a: COLIBRÍ optical upper limits
  5. EP260327a: Gemini-North optical upper limits
  6. EP260324a: GROWTH-India Telescope optical observation
  7. EP260327a: Global MASTER-Net observations report
  8. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  9. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  10. The EP-WXT trigger 01709259173 is likely a flaring star
  11. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  12. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  13. GRB 260326A: Fermi GBM Detection
  14. GRB 260325A: Fermi GBM Final Localization
  15. GRB 260326A: Fermi GBM Final Real-time Localization
  16. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  17. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  18. IPN triangulation of GRB 260316B
  19. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  20. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  21. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  22. GRB 260310A: LBT optical observations
  23. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  24. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  25. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  26. The EP-WXT trigger 01709259112 is likely a flaring star
  27. Fermi GRB 260323A: Global MASTER-Net observations report
  28. GRB 260323A: Fermi GBM Final Real-time Localization
  29. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  30. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  31. GRB 260322A: Fermi GBM Final Localization
  32. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  33. EP260321a: COLIBRÍ further optical observations and brightening
  34. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  35. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  36. EP260214b: ATCA 6 GHz detection
  37. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  38. GRB 260321A: EP-FXT follow-up observation
  39. The EP-WXT trigger 01709259045 is likely a flaring star
  40. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  41. EP260321a: GOTO detection of blue variable source
  42. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  43. EP260321a: further Kinder optical observations
  44. GRB 260321A: SVOM/VT optical upper limits
  45. EP260321a: Las Cumbres upper limit
  46. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  47. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  48. EP260321a: SVOM/VT optical upper limit
  49. GRB 260310A: continued optical observation at Mondy
  50. Fermi GBM Sub-Threshold Detection of GRB 260321A
  51. GRB 260321A: SVOM detection of a burst
  52. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  53. EP260321a: Global MASTER-Net observations report
  54. GRB 260318A: Glowbug gamma-ray detection
  55. GRB 260310A / AT 2026fgk: KAIT optical observations
  56. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  57. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  58. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  59. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  60. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  61. GRB 260310A/AT2026fgk: LBT near-infrared observations
  62. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  63. GRB 260318A: SVOM/GRM observation
  64. The EP-WXT trigger 01709258989 is likely a flaring star
  65. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  66. GRB 260318A: GECAM-B observation
  67. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  68. Fermi GRB 260318A: Global MASTER-Net observations report
  69. GRB 260318A: Fermi GBM Final Real-time Localization
  70. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  71. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  72. GRB 260310A / AT 2026fgk: radio detection with the VLA
  73. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  74. GRB 260310A / AT2026fgk: LCO optical observations
  75. GRB 260317A: Fermi GBM Final Localization
  76. GRB 260316B: GECAM-B observation
  77. GRB 260316B: SVOM/GRM observation
  78. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  79. EP260316a: COLIBRÍ faint optical counterpart candidate
  80. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  81. GRB 260316B: AstroSat CZTI detection
  82. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  83. EP260316a: Xinglong optical upper limit
  84. GRB 260316B: Fermi GBM Final Real-time Localization
  85. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  86. GRB 260314A: Glowbug gamma-ray detection
  87. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  88. IceCube-260315A: COLIBRÍ optical observations
  89. EP260314a: Xinglong optical upper limit
  90. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  91. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  92. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  93. GRB 260310A / AT 2026fgk: iTelescope optical observations
  94. EP260314a: COLIBRÍ optical upper limit
  95. GRID detection of GRB 260312B
  96. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  97. EP260314a: BOOTES-6/DPR optical upper limits at early times
  98. EP260314a: Global MASTER-Net observations report
  99. EP260314a: SVOM/VT optical candidate
  100. Fermi trigger No 795185313: Global MASTER-Net observations report

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