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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"

19809 results found.

  1. EP260324A / AT 2026hir: COLIBRÍ optical observations
  2. GRB 260402A: WINTER J-band upper limit
  3. GRB260402A: GROWTH-India Telescope optical upper limit
  4. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  5. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  6. GRB 260401A: SVOM/GRM observation
  7. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  8. GRB 260402A: Kilonova-Catcher optical upper limit
  9. GRB 260402A: MASTER optical observations
  10. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  11. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  12. GRB 260402A: SVOM detection of a burst
  13. EP260329b: Mondy and Assy-Turgen optical upper limits
  14. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  15. EP260321a :Xinglong optical observations
  16. EP260327a: Xinglong optical upper limit
  17. GRB 260330B: SVOM/VT optical upper limits
  18. GRB 260321A: SVOM/ECLAIRs refined analysis
  19. EP260329b: J-band upper limits with WINTER
  20. EP260329a: J-band upper limit with WINTER
  21. GRB 260310A: VLA Multi-frequency Radio Observations
  22. GRB 260330B: LCO optical upper limits
  23. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  24. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  25. EP260329a: COLIBRÍ optical upper limit
  26. EP260329a: EP-FXT follow up observation
  27. EP260329a: NOT optical counterpart candidate
  28. EP260329b: Optical follow-up with Kinder observations
  29. EP 260329b: COLIBRÍ optical observations
  30. EP260329a: Optical upper limit with Kinder observations
  31. EP260329b: LCO optical observations of the counterpart
  32. EP260329b: Einstein Probe detection of an X-ray transient
  33. EP260329a: Einstein Probe detection of an X-ray transient
  34. EP-WXT trigger 01709259209: TRT optical counterpart detection
  35. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  36. GRID detection of GRB 260326A
  37. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  38. EP260327a: SVOM/VT optical upper limits
  39. EP260327a: WINTER J-band upper limit
  40. EP260327a: COLIBRÍ optical upper limits
  41. GRB 260327A: AstroSat CZTI detection of a long burst
  42. EP260327a: Gemini-North optical upper limits
  43. EP260324a: GROWTH-India Telescope optical observation
  44. EP260327a: Einstein Probe detection of an X-ray transient
  45. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  46. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  47. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  48. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  49. EP260321a: JinShan near-infrared observations
  50. EP260321a: Upper limits from a neutrino search with IceCube
  51. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  52. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  53. GRID detection of GRB 260320A
  54. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  55. EP260321a: COLIBRÍ further optical observations and brightening
  56. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  57. EP260214b: ATCA 6 GHz detection
  58. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  59. The EP-WXT trigger 01709259045 is likely a flaring star
  60. EP260321a: GOTO detection of blue variable source
  61. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  62. EP260321a: further Kinder optical observations
  63. GRB 260321A: SVOM/VT optical upper limits
  64. EP260321a: Las Cumbres upper limit
  65. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  66. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  67. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  68. EP260321a: SVOM/VT optical upper limit
  69. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  70. EP260321a: Einstein Probe detection of an X-ray transient
  71. GRB 260310A / AT 2026fgk: KAIT optical observations
  72. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  73. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  74. GRB 260318A: SVOM/GRM observation
  75. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  76. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  77. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  78. GRB 260310A / AT 2026fgk: radio detection with the VLA
  79. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  80. GRB 260310A / AT2026fgk: LCO optical observations
  81. GRB 260316B: SVOM/GRM observation
  82. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  83. EP260316a: COLIBRÍ faint optical counterpart candidate
  84. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  85. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  86. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  87. EP260316a: Xinglong optical upper limit
  88. EP260316a: optical upper limit with Kinder observations
  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. EP260314a: optical upper limit with Kinder observations
  94. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  95. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  96. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  97. GRB 260310A / AT 2026fgk: iTelescope optical observations
  98. EP260314a: COLIBRÍ optical upper limit
  99. GRID detection of GRB 260312B
  100. EP260314a: refined analysis of the EP-WXT and EP-FXT observations

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