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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"

27320 results found.

  1. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  2. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  3. EP260327a: SVOM/VT optical upper limits
  4. EP260327a: WINTER J-band upper limit
  5. EP260327a: COLIBRÍ optical upper limits
  6. EP260327a: Gemini-North optical upper limits
  7. EP260324a: GROWTH-India Telescope optical observation
  8. EP260327a: Global MASTER-Net observations report
  9. EP260327a: Einstein Probe detection of an X-ray transient
  10. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  11. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  12. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  13. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  14. GRB 260326A: Fermi GBM Detection
  15. EP260321a: JinShan near-infrared observations
  16. EP260321a: Upper limits from a neutrino search with IceCube
  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. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  20. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  21. Fermi GRB 260323A: Global MASTER-Net observations report
  22. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  23. GRB 260320A: Glowbug gamma-ray detection
  24. EP260321a: COLIBRÍ further optical observations and brightening
  25. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  26. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  27. GRB 260321A: EP-FXT follow-up observation
  28. EP260321a: GOTO detection of blue variable source
  29. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  30. EP260321a: further Kinder optical observations
  31. GRB 260321A: SVOM/VT optical upper limits
  32. EP260321a: Las Cumbres upper limit
  33. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  34. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  35. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  36. EP260321a: SVOM/VT optical upper limit
  37. Fermi GBM Sub-Threshold Detection of GRB 260321A
  38. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  39. EP260321a: Global MASTER-Net observations report
  40. EP260321a: Einstein Probe detection of an X-ray transient
  41. GRB 260318A: Glowbug gamma-ray detection
  42. GRB 260310A / AT 2026fgk: KAIT optical observations
  43. GRB 260320A: NuSTAR detection of prompt emission
  44. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  45. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  46. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  47. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  48. GRB 260318A: SVOM/GRM observation
  49. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  50. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  51. Fermi GRB 260318A: Global MASTER-Net observations report
  52. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  53. GRB 260310A / AT 2026fgk: radio detection with the VLA
  54. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  55. GRB 260310A / AT2026fgk: LCO optical observations
  56. GRB 260316B: SVOM/GRM observation
  57. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  58. EP260316a: COLIBRÍ faint optical counterpart candidate
  59. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  60. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  61. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  62. EP260316a: Xinglong optical upper limit
  63. EP260316a: optical upper limit with Kinder observations
  64. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  65. GRB 260314A: Glowbug gamma-ray detection
  66. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  67. IceCube-260315A: COLIBRÍ optical observations
  68. EP260314a: Xinglong optical upper limit
  69. EP260314a: optical upper limit with Kinder observations
  70. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  71. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  72. GRB 260310A / AT 2026fgk: iTelescope optical observations
  73. EP260314a: COLIBRÍ optical upper limit
  74. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  75. EP260314a: Global MASTER-Net observations report
  76. EP260314a: SVOM/VT optical candidate
  77. Fermi trigger No 795185313: Global MASTER-Net observations report
  78. IceCube Alert 260315A: Global MASTER-Net observations report
  79. EP260314a: Einstein Probe detection of an X-ray transient
  80. GRB 260310A / AT2026fgk: SAO RAS optical observations
  81. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  82. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  83. Fermi GRB 260314A: Global MASTER-Net observations report
  84. Fermi GRB 260313A: Global MASTER-Net observations report
  85. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  86. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  87. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  88. GRB 260312B: AstroSat CZTI detection
  89. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  90. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  91. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  92. GRB 260312B: Glowbug gamma-ray detection
  93. GRB 260310A: Fermi GBM Observation
  94. GRB 260310A: potential optical counterpart
  95. Fermi GRB 260312B: Global MASTER-Net observations report
  96. Fermi GRB 260311B: Global MASTER-Net observations report
  97. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  98. GRB 260131A/B: radio detection with the VLA
  99. EP260302a: MeerKAT radio counterpart
  100. GRB 260308A: SVOM/GRM observation of a short GRB

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