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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"

19857 results found.

  1. EP260321a: JinShan near-infrared observations
  2. EP260321a: Upper limits from a neutrino search with IceCube
  3. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  4. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  5. GRID detection of GRB 260320A
  6. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  7. EP260321a: COLIBRÍ further optical observations and brightening
  8. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  9. EP260214b: ATCA 6 GHz detection
  10. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  11. The EP-WXT trigger 01709259045 is likely a flaring star
  12. EP260321a: GOTO detection of blue variable source
  13. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  14. EP260321a: further Kinder optical observations
  15. GRB 260321A: SVOM/VT optical upper limits
  16. EP260321a: Las Cumbres upper limit
  17. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  18. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  19. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  20. EP260321a: SVOM/VT optical upper limit
  21. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  22. EP260321a: Einstein Probe detection of an X-ray transient
  23. GRB 260310A / AT 2026fgk: KAIT optical observations
  24. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  25. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  26. GRB 260318A: SVOM/GRM observation
  27. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  28. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  29. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  30. GRB 260310A / AT 2026fgk: radio detection with the VLA
  31. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  32. GRB 260310A / AT2026fgk: LCO optical observations
  33. GRB 260316B: SVOM/GRM observation
  34. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  35. EP260316a: COLIBRÍ faint optical counterpart candidate
  36. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  37. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  38. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  39. EP260316a: Xinglong optical upper limit
  40. EP260316a: optical upper limit with Kinder observations
  41. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  42. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  43. IceCube-260315A: COLIBRÍ optical observations
  44. EP260314a: Xinglong optical upper limit
  45. EP260314a: optical upper limit with Kinder observations
  46. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  47. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  48. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  49. GRB 260310A / AT 2026fgk: iTelescope optical observations
  50. EP260314a: COLIBRÍ optical upper limit
  51. GRID detection of GRB 260312B
  52. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  53. EP260314a: SVOM/VT optical candidate
  54. EP260314a: Einstein Probe detection of an X-ray transient
  55. GRB 260310A / AT2026fgk: SAO RAS optical observations
  56. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  57. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  58. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  59. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  60. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  61. GRB 260312B: AstroSat CZTI detection
  62. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  63. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  64. GRB 260310A: potential optical counterpart
  65. Fermi GRB 260311B: Global MASTER-Net observations report
  66. GRB 260131A/B: radio detection with the VLA
  67. EP260302a: MeerKAT radio counterpart
  68. GRB 260308A: SVOM/GRM observation of a short GRB
  69. EP260306a: Mondy optical upper limit
  70. GRB 260307B: SVOM/ECLAIRs refined analysis
  71. GRB 260208A: radio detection with the VLA
  72. GRB 260307B: Mephisto optical upper limits
  73. GRB 260307B: possible NOT optical counterpart
  74. GRB 260307B: SVOM/VT upper limit with X band data analysis
  75. GRB260307B: GROWTH-India Telescope optical upper limit
  76. GRB 260307B: SVOM/VT optical candidate
  77. GRB 260307B: SVOM/C-GFT upper limit
  78. GRB 260307B: SVOM detection of a burst
  79. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  80. GRB 260207A: TESS Detection and Possible VLA Counterpart
  81. EP260302a: SVOM/VT optical observation
  82. EP260306a: SVOM/VT optical observation
  83. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  84. EP260306a: Einstein Probe detection of an X-ray transient
  85. GRB 260303A: 1.3m DFOT optical upper limit
  86. EP260214b: ATCA 6 GHz observations
  87. GRB 260303A: SVOM/ECLAIRs refined analysis
  88. GRB 260304A: AstroSat CZTI detection of a long burst
  89. GRB 260303A: SVOM/VT optical observations
  90. GRB 260303A: J-band observations with WINTER
  91. GRB 260228A: SVOM/ECLAIRs refined analysis
  92. GRB 260225A: SVOM/ECLAIRs refined analysis
  93. EP260302a: analysis of the follow-up EP-FXT observation
  94. EP260302a: LCO observations
  95. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  96. GRB 260303A: SVOM detection of a burst
  97. EP260302a: Einstein Probe detection of an X-ray transient
  98. EP260227a: Mondy optical observations
  99. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  100. EP260227a: Mephisto optical detection

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