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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"

32537 results found.

  1. GRB 260131A/B: EP/FXT X-ray afterglow detection
  2. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  3. GRB 260127B: Insight-HXMT/HE detection
  4. GRB 260127B: GECAM-B observation of a short burst
  5. GRB 260127A: GECAM-B observation
  6. GRB 260131A: NOT spectroscopic redshift z = 1.434
  7. EP260131a: Liverpool Telescope optical upper limits
  8. EP260131a: COLIBRÍ further observations
  9. Konus-Wind detection of GRB 260128A / EP260128a
  10. GRB 260131A: Insight-HXMT/HE detection
  11. Konus-Wind detection of GRB 260131A/B
  12. EP260131a: SVOM/VT optical observation
  13. EP260131a: Xinglong optical upper limit
  14. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  15. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  16. GRB 260131A/B: Fermi GBM Observation
  17. EP260131a: COLIBRÍ observations of slow optical fading
  18. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  19. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  20. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  21. EP260131a: COLIBRÍ optical observations of the counterpart
  22. GRB 260127B: AstroSat CZTI detection
  23. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  24. Fermi GRB 260130A: Global MASTER-Net observations report
  25. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  26. Fermi GRB 260129A: Global MASTER-Net observations report
  27. GRB 260128B: LCO optical upper limits
  28. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  29. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  30. IPN triangulation of GRB 260121A
  31. GRB 260127A: Swift-BAT refined analysis
  32. IPN triangulation of GRB 260127B (short)
  33. GRB 260127B: Swift-XRT observations
  34. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  35. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  36. EP260128a: NOT optical counterpart candidate
  37. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  38. EP260128a: Liverpool Telescope optical observations and possible counterpart
  39. EP260128a: LCO optical upper limits
  40. EP260126a: SVOM/VT optical upperlimit
  41. EP260128a: Global MASTER-Net observations report
  42. Fermi GRB 260127A: Global MASTER-Net observations report
  43. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  44. GRB 260127A: Fermi GBM Observation
  45. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  46. GRB 260127A: COLIBRÍ optical observations
  47. GRB 260127A: NOT optical observations
  48. GRB 260127B: Swift ToO observations
  49. EP260126a: Seimei/TriCCS optical upper limit
  50. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  51. GRB 260127B: GOTO candidate optical counterpart
  52. GRB 260127A: SVOM/C-GFT optical observations
  53. Fermi GRB 260127B: Global MASTER-Net observations report
  54. Swift GRB 260127A: Global MASTER-Net observations report
  55. GRB 260127A: LCO optical afterglow discovery
  56. GRB 260125A: Swift-XRT observations
  57. EP260126a: EP-FXT follow-up observation
  58. EP260126a: Optical upper limit with Kinder observations
  59. EP260126a: Liverpool Telescope optical upper limits
  60. EP260126a: Further NOT optical upper limits
  61. EP260126a: COLIBRÍ optical upper limits
  62. EP260126a: NOT optical observations
  63. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  64. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  65. Konus-Wind detection of GRB 260120B
  66. GRB 251222A: SVOM/ECLAIRs refined analysis
  67. GRB 260125A: Swift ToO observations
  68. GRB 260125A: GOTO candidate optical counterpart
  69. Fermi GRB 260125B: Global MASTER-Net observations report
  70. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  71. GRB 260114A: SVOM/VT optical upper limits
  72. GRB 260120A: AstroSat CZTI detection
  73. GRB 260122B: Swift-BAT refined analysis
  74. GRB 260120B: SVOM/GRM observation
  75. GRB 260120A: GECAM-B observation
  76. GRB 260120B: AstroSat CZTI detection
  77. GRB 260114A: Insight-HXMT/HE detection
  78. EP260119a: Assy AZT-20 optical observations
  79. EP260119a: Mondy and SAO RAS optical upper limits
  80. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  81. EP260119a: Xinglong optical upper limit
  82. Fermi GRB 260120C: Global MASTER-Net observations report
  83. GRB 260120B: Swift-BAT refined analysis
  84. EP260116a: COLIBRÍ further observations
  85. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  86. GRB 260120B: Fermi GBM Observation
  87. EP260105a: GTC/HiPERCAM optical observations
  88. GRB 260120B: Swift/UVOT Detection
  89. GRB 260120B: COLIBRÍ optical upper limits
  90. GRB 260120B: SVOM/C-GFT optical counterpart detection
  91. GRB 260101A: 239Alferov CubeSat detection
  92. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  93. EP260119A: Mondy I-Band Observations
  94. GRB 260114A: Swift/UVOT Upper Limits
  95. EP260119a: Liverpool Telescope optical follow-up observations
  96. GRB 251202A: further radio observations with the VLA
  97. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  98. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  99. EP260119a: KAIT optical observations
  100. EP260119a: SVOM/VT optical observation

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