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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"

27022 results found.

  1. EP260329b: Einstein Probe detection of an X-ray transient
  2. EP260329a: Einstein Probe detection of an X-ray transient
  3. EP-WXT trigger 01709259209: TRT optical counterpart detection
  4. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  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. EP260327a: Global MASTER-Net observations report
  12. EP260327a: Einstein Probe detection of an X-ray transient
  13. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  14. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  15. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  16. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  17. GRB 260326A: Fermi GBM Detection
  18. EP260321a: JinShan near-infrared observations
  19. EP260321a: Upper limits from a neutrino search with IceCube
  20. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  21. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  22. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  23. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  24. Fermi GRB 260323A: Global MASTER-Net observations report
  25. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  26. GRB 260320A: Glowbug gamma-ray detection
  27. EP260321a: COLIBRÍ further optical observations and brightening
  28. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  29. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  30. GRB 260321A: EP-FXT follow-up observation
  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. Fermi GBM Sub-Threshold Detection of GRB 260321A
  41. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  42. EP260321a: Global MASTER-Net observations report
  43. EP260321a: Einstein Probe detection of an X-ray transient
  44. GRB 260318A: Glowbug gamma-ray detection
  45. GRB 260310A / AT 2026fgk: KAIT optical observations
  46. GRB 260320A: NuSTAR detection of prompt emission
  47. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  48. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  49. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  50. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  51. GRB 260318A: SVOM/GRM observation
  52. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  53. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  54. Fermi GRB 260318A: Global MASTER-Net observations report
  55. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  56. GRB 260310A / AT 2026fgk: radio detection with the VLA
  57. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  58. GRB 260310A / AT2026fgk: LCO optical observations
  59. GRB 260316B: SVOM/GRM observation
  60. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  61. EP260316a: COLIBRÍ faint optical counterpart candidate
  62. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  63. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  64. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  65. EP260316a: Xinglong optical upper limit
  66. EP260316a: optical upper limit with Kinder observations
  67. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  68. GRB 260314A: Glowbug gamma-ray detection
  69. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  70. IceCube-260315A: COLIBRÍ optical observations
  71. EP260314a: Xinglong optical upper limit
  72. EP260314a: optical upper limit with Kinder observations
  73. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  74. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  75. GRB 260310A / AT 2026fgk: iTelescope optical observations
  76. EP260314a: COLIBRÍ optical upper limit
  77. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  78. EP260314a: Global MASTER-Net observations report
  79. EP260314a: SVOM/VT optical candidate
  80. Fermi trigger No 795185313: Global MASTER-Net observations report
  81. IceCube Alert 260315A: Global MASTER-Net observations report
  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. Fermi GRB 260314A: Global MASTER-Net observations report
  87. Fermi GRB 260313A: Global MASTER-Net observations report
  88. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  89. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  90. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  91. GRB 260312B: AstroSat CZTI detection
  92. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  93. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  94. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  95. GRB 260312B: Glowbug gamma-ray detection
  96. GRB 260310A: Fermi GBM Observation
  97. GRB 260310A: potential optical counterpart
  98. Fermi GRB 260312B: Global MASTER-Net observations report
  99. Fermi GRB 260311B: Global MASTER-Net observations report
  100. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)

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