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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"

26499 results found.

  1. EP260329a: NOT optical counterpart candidate
  2. EP260329b: Optical follow-up with Kinder observations
  3. EP 260329b: COLIBRÍ optical observations
  4. EP260329a: Optical upper limit with Kinder 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. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  11. EP260327a: SVOM/VT optical upper limits
  12. EP260327a: WINTER J-band upper limit
  13. EP260327a: COLIBRÍ optical upper limits
  14. EP260327a: Gemini-North optical upper limits
  15. EP260324a: GROWTH-India Telescope optical observation
  16. EP260327a: Einstein Probe detection of an X-ray transient
  17. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  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. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  21. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  22. GRB 260326A: Fermi GBM Detection
  23. EP260321a: JinShan near-infrared observations
  24. EP260321a: Upper limits from a neutrino search with IceCube
  25. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  26. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  27. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  28. The EP-WXT trigger 01709259112 is likely a flaring star
  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 260320A: Glowbug gamma-ray detection
  32. EP260321a: COLIBRÍ further optical observations and brightening
  33. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  34. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  35. The EP-WXT trigger 01709259045 is likely a flaring star
  36. EP260321a: GOTO detection of blue variable source
  37. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  38. EP260321a: further Kinder optical observations
  39. GRB 260321A: SVOM/VT optical upper limits
  40. EP260321a: Las Cumbres upper limit
  41. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  42. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  43. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  44. EP260321a: SVOM/VT optical upper limit
  45. GRB 260321A: SVOM detection of a burst
  46. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  47. EP260321a: Einstein Probe detection of an X-ray transient
  48. GRB 260318A: Glowbug gamma-ray detection
  49. GRB 260310A / AT 2026fgk: KAIT optical observations
  50. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  51. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  52. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  53. NOEMA Detection of GRB 260310A / AT 2026fgk
  54. GRB 260318A: SVOM/GRM observation
  55. The EP-WXT trigger 01709258989 is likely a flaring star
  56. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  57. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  58. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  59. GRB 260310A / AT 2026fgk: radio detection with the VLA
  60. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  61. GRB 260310A / AT2026fgk: LCO optical observations
  62. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  63. GRB 260316B: SVOM/GRM observation
  64. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  65. EP260316a: COLIBRÍ faint optical counterpart candidate
  66. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  67. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  68. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  69. EP260316a: Xinglong optical upper limit
  70. EP260316a: optical upper limit with Kinder observations
  71. GRB 260314A: Glowbug gamma-ray detection
  72. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  73. IceCube-260315A: COLIBRÍ optical observations
  74. EP260314a: Xinglong optical upper limit
  75. EP260314a: optical upper limit with Kinder observations
  76. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  77. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  78. GRB 260310A / AT 2026fgk: iTelescope optical observations
  79. EP260314a: COLIBRÍ optical upper limit
  80. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  81. EP260314a: SVOM/VT optical candidate
  82. EP260314a: Einstein Probe detection of an X-ray transient
  83. GRB 260310A / AT2026fgk: SAO RAS optical observations
  84. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  85. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  86. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  87. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  88. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  89. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  90. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  91. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  92. GRB260310A / AT2026fgk: P200 Spectroscopy
  93. GRB 260312B: Glowbug gamma-ray detection
  94. GRB 260310A: Fermi GBM Observation
  95. GRB 260310A: potential optical counterpart
  96. GRB 260131A/B: radio detection with the VLA
  97. EP260302a: MeerKAT radio counterpart
  98. GRB 260308A: SVOM/GRM observation of a short GRB
  99. EP260306a: Mondy optical upper limit
  100. GRB 260310A: AstroSat CZTI detection of a long burst

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