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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"

32532 results found.

  1. EP260131a: Liverpool Telescope optical upper limits
  2. EP260131a: COLIBRÍ further observations
  3. Konus-Wind detection of GRB 260128A / EP260128a
  4. GRB 260131A: Insight-HXMT/HE detection
  5. Konus-Wind detection of GRB 260131A/B
  6. EP260131a: SVOM/VT optical observation
  7. EP260131a: Xinglong optical upper limit
  8. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  9. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  10. GRB 260131A/B: Fermi GBM Observation
  11. EP260131a: COLIBRÍ observations of slow optical fading
  12. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  13. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  14. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  15. EP260131a: COLIBRÍ optical observations of the counterpart
  16. GRB 260127B: AstroSat CZTI detection
  17. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  18. Fermi GRB 260130A: Global MASTER-Net observations report
  19. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  20. Fermi GRB 260129A: Global MASTER-Net observations report
  21. GRB 260128B: LCO optical upper limits
  22. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  23. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  24. IPN triangulation of GRB 260121A
  25. GRB 260127A: Swift-BAT refined analysis
  26. IPN triangulation of GRB 260127B (short)
  27. GRB 260127B: Swift-XRT observations
  28. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  29. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  30. EP260128a: NOT optical counterpart candidate
  31. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  32. EP260128a: Liverpool Telescope optical observations and possible counterpart
  33. EP260128a: LCO optical upper limits
  34. EP260126a: SVOM/VT optical upperlimit
  35. EP260128a: Global MASTER-Net observations report
  36. Fermi GRB 260127A: Global MASTER-Net observations report
  37. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  38. GRB 260127A: Fermi GBM Observation
  39. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  40. GRB 260127A: COLIBRÍ optical observations
  41. GRB 260127A: NOT optical observations
  42. GRB 260127B: Swift ToO observations
  43. EP260126a: Seimei/TriCCS optical upper limit
  44. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  45. GRB 260127B: GOTO candidate optical counterpart
  46. GRB 260127A: SVOM/C-GFT optical observations
  47. Fermi GRB 260127B: Global MASTER-Net observations report
  48. Swift GRB 260127A: Global MASTER-Net observations report
  49. GRB 260127A: LCO optical afterglow discovery
  50. GRB 260125A: Swift-XRT observations
  51. EP260126a: EP-FXT follow-up observation
  52. EP260126a: Optical upper limit with Kinder observations
  53. EP260126a: Liverpool Telescope optical upper limits
  54. EP260126a: Further NOT optical upper limits
  55. EP260126a: COLIBRÍ optical upper limits
  56. EP260126a: NOT optical observations
  57. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  58. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  59. Konus-Wind detection of GRB 260120B
  60. GRB 251222A: SVOM/ECLAIRs refined analysis
  61. GRB 260125A: Swift ToO observations
  62. GRB 260125A: GOTO candidate optical counterpart
  63. Fermi GRB 260125B: Global MASTER-Net observations report
  64. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  65. GRB 260114A: SVOM/VT optical upper limits
  66. GRB 260120A: AstroSat CZTI detection
  67. GRB 260122B: Swift-BAT refined analysis
  68. GRB 260120B: SVOM/GRM observation
  69. GRB 260120A: GECAM-B observation
  70. GRB 260120B: AstroSat CZTI detection
  71. GRB 260114A: Insight-HXMT/HE detection
  72. EP260119a: Assy AZT-20 optical observations
  73. EP260119a: Mondy and SAO RAS optical upper limits
  74. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  75. EP260119a: Xinglong optical upper limit
  76. Fermi GRB 260120C: Global MASTER-Net observations report
  77. GRB 260120B: Swift-BAT refined analysis
  78. EP260116a: COLIBRÍ further observations
  79. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  80. GRB 260120B: Fermi GBM Observation
  81. EP260105a: GTC/HiPERCAM optical observations
  82. GRB 260120B: Swift/UVOT Detection
  83. GRB 260120B: COLIBRÍ optical upper limits
  84. GRB 260120B: SVOM/C-GFT optical counterpart detection
  85. GRB 260101A: 239Alferov CubeSat detection
  86. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  87. EP260119A: Mondy I-Band Observations
  88. GRB 260114A: Swift/UVOT Upper Limits
  89. EP260119a: Liverpool Telescope optical follow-up observations
  90. GRB 251202A: further radio observations with the VLA
  91. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  92. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  93. EP260119a: KAIT optical observations
  94. EP260119a: SVOM/VT optical observation
  95. EP260119a: update of EP-FXT follow-up observation
  96. EP260119a: NOT optical observations
  97. EP260119a: SAO RAS optical observations
  98. EP260116a: COLIBRÍ detection of a fading optical source
  99. GRB 251208D: SVOM/ECLAIRs refined analysis
  100. GRB 251208D: SVOM/ECLAIRs refined analysis

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