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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"

19804 results found.

  1. EP260131a: SVOM/VT optical observation
  2. EP260131a: Xinglong optical upper limit
  3. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  4. EP260131a: COLIBRÍ observations of slow optical fading
  5. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  6. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  7. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  8. EP260131a: COLIBRÍ optical observations of the counterpart
  9. EP260131a: Einstein Probe detection of an X-ray transient
  10. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  11. GRB 260128B: LCO optical upper limits
  12. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  13. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  14. GRB 260128B: SVOM detection of a burst through offline search
  15. GRB 260127B: Swift-XRT observations
  16. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  17. EP260128a: NOT optical counterpart candidate
  18. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  19. EP260128a: Liverpool Telescope optical observations and possible counterpart
  20. EP260128a: LCO optical upper limits
  21. EP260128a: Einstein Probe detection of an X-ray transient
  22. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  23. GRB 260127A: COLIBRÍ optical observations
  24. EP260126a: Seimei/TriCCS optical upper limit
  25. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  26. GRB 260127A: SVOM/C-GFT optical observations
  27. GRB 260127A: Enhanced Swift-XRT position
  28. GRB 260127A: LCO optical afterglow discovery
  29. GRB 260127A: Swift detection of a burst
  30. GRB 260125A: Swift-XRT observations
  31. EP260126a: Optical upper limit with Kinder observations
  32. EP260126a: Liverpool Telescope optical upper limits
  33. EP260126a: Further NOT optical upper limits
  34. EP260126a: COLIBRÍ optical upper limits
  35. EP260126a: NOT optical observations
  36. EP260126a: Einstein Probe detection of a fast X-ray transient
  37. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  38. GRB 251222A: SVOM/ECLAIRs refined analysis
  39. GRB 260125A: GOTO candidate optical counterpart
  40. GRB 260114A: SVOM/VT optical upper limits
  41. GRB 260120B: SVOM/GRM observation
  42. GRB 260120B: AstroSat CZTI detection
  43. EP260119a: Assy AZT-20 optical observations
  44. EP260119a: Mondy and SAO RAS optical upper limits
  45. EP260119a: Xinglong optical upper limit
  46. EP260116a: COLIBRÍ further observations
  47. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  48. GRB 260120B: Fermi GBM Observation
  49. EP260105a: GTC/HiPERCAM optical observations
  50. GRB 260120B: Swift/UVOT Detection
  51. GRB 260120B: COLIBRÍ optical upper limits
  52. GRB 260120B: Enhanced Swift-XRT position
  53. GRB 260120B: SVOM/C-GFT optical counterpart detection
  54. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  55. GRB 260120B: Swift detection of a burst
  56. EP260119A: Mondy I-Band Observations
  57. GRB 260114A: Swift/UVOT Upper Limits
  58. EP260119a: Liverpool Telescope optical follow-up observations
  59. GRB 251202A: further radio observations with the VLA
  60. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  61. EP260119a: KAIT optical observations
  62. EP260119a: SVOM/VT optical observation
  63. EP260119a: NOT optical observations
  64. EP260119a: SAO RAS optical observations
  65. EP260116a: COLIBRÍ detection of a fading optical source
  66. GRB 251208D: SVOM/ECLAIRs refined analysis
  67. GRB 251208D: SVOM/ECLAIRs refined analysis
  68. GRB 260117A: Swift-XRT afterglow detection
  69. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  70. EP260119a: LCO optical observations
  71. GRB 260117A: ZTSh optical upper limit
  72. EP260119a: COLIBRÍ optical counterpart candidate
  73. GRB 260110A: SVOM detection of a burst through offline search
  74. EP260119a: EP-WXT detection of a fast X-ray transient
  75. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  76. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  77. Swift trigger on the HMXB 1A 1118-61
  78. GRB 260117A: SVOM/C-GFT upper limit
  79. GRB 260117A: SVOM detection of a long faint burst
  80. EP 260116a: COLIBRÍ optical upper limit
  81. Swift triggered on the HMXB 1A 1118-61
  82. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  83. EP260116a: Liverpool Telescope upper limits
  84. EP260116A: 1.3m DFOT optical upper limit
  85. GRB 260114A: VLT/MUSE spectroscopic observations
  86. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  87. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  88. EP260116a: Xinglong optical upper limit
  89. EP260116a: Einstein Probe detection of an X-ray transient
  90. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  91. GRB 251222A: radio detection with the VLA
  92. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  93. GRB 260114A: Swift-XRT refined Analysis
  94. GRB 260114A: 6 GHz VLA observations
  95. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  96. GRB 260114A : MITSuME Akeno optical upper limits
  97. GRB 260114A: COLIBRÍ optical upper limits
  98. GRB 260114A: TNG NIR upper limit
  99. GRB 260114A: NOT optical observations
  100. GRB 260114A: SVOM/GRM observation of a short burst

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