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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').
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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"

15985 results found.

  1. EP260329b: Einstein Probe detection of an X-ray transient
  2. EP-WXT trigger 01709259209: TRT optical counterpart detection
  3. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  4. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  5. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  6. EP260327a: SVOM/VT optical upper limits
  7. EP260327a: WINTER J-band upper limit
  8. EP260327a: COLIBRÍ optical upper limits
  9. EP260327a: Gemini-North optical upper limits
  10. EP260324a: GROWTH-India Telescope optical observation
  11. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  12. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  13. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  14. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  15. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  16. EP260321a: JinShan near-infrared observations
  17. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  18. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  19. EP260321a: Gemini-South confirmation of a supernova
  20. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  21. GRB 260310A: LBT optical observations
  22. EP260321A: Mondy optical observations
  23. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  24. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  25. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  26. EP260321a: COLIBRÍ further optical observations and brightening
  27. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  28. EP260214b: ATCA 6 GHz detection
  29. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  30. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  31. EP260321a: GOTO detection of blue variable source
  32. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  33. EP260321a: further Kinder optical observations
  34. GRB 260321A: SVOM/VT optical upper limits
  35. EP260321a: Las Cumbres upper limit
  36. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  37. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  38. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  39. EP260321a: SVOM/VT optical upper limit
  40. GRB 260310A: continued optical observation at Mondy
  41. GRB 260321A: SVOM detection of a burst
  42. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  43. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  44. GRB 260310A / AT 2026fgk: KAIT optical observations
  45. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  46. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  47. GRB 260318A: SVOM/GRM observation
  48. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  49. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  50. GRB 260310A / AT 2026fgk: radio detection with the VLA
  51. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  52. GRB 260310A / AT2026fgk: LCO optical observations
  53. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  54. GRB 260316B: SVOM/GRM observation
  55. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  56. EP260316a: COLIBRÍ faint optical counterpart candidate
  57. EP260316a: Xinglong optical upper limit
  58. EP260316a: optical upper limit with Kinder observations
  59. IceCube-260315A: COLIBRÍ optical observations
  60. EP260314a: Xinglong optical upper limit
  61. EP260314a: optical upper limit with Kinder observations
  62. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  63. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  64. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  65. GRB 260310A / AT 2026fgk: iTelescope optical observations
  66. EP260314a: COLIBRÍ optical upper limit
  67. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  68. EP260314a: BOOTES-6/DPR optical upper limits at early times
  69. EP260314a: SVOM/VT optical candidate
  70. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  71. GRB 260310A / AT2026fgk: SAO RAS optical observations
  72. GRB 260310A / AT2026fgk: TNG NIR detection
  73. GRB 260310A / AT2026fgk: OASDG optical observations
  74. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  75. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  76. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  77. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  78. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  79. GRB 260310A: NOT optical polarimetry
  80. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  81. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  82. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  83. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  84. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  85. GRB260310A / AT2026fgk: P200 Spectroscopy
  86. GRB 260310A: Fermi GBM Observation
  87. GRB 260310A: potential optical counterpart
  88. GRB 260131A/B: radio detection with the VLA
  89. GRB 260308A: SVOM/GRM observation of a short GRB
  90. EP260306a: Mondy optical upper limit
  91. GRB 260208A: radio detection with the VLA
  92. GRB 260307B: Mephisto optical upper limits
  93. GRB 260307B: possible NOT optical counterpart
  94. GRB260307B: GROWTH-India Telescope optical upper limit
  95. GRB 260307B: SVOM/VT optical candidate
  96. GRB 260307B: SVOM detection of a burst
  97. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  98. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  99. EP260302a: SVOM/VT optical observation
  100. EP260306a: Gemini-North redshift z = 4.773

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