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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.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

45449 results found.

  1. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  2. GRB 260131B: MAXI/GSC detection
  3. GRB 260131A: Fermi GBM Final Real-time Localization
  4. EP260131a: COLIBRÍ optical observations of the counterpart
  5. EP260131a: Las Cumbres detection of an optical counterpart
  6. GRB 260127B: AstroSat CZTI detection
  7. GRB 260130A: Fermi GBM Detection
  8. EP260131a: Einstein Probe detection of an X-ray transient
  9. GRB 260127B: Fermi GBM Detection
  10. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  11. Fermi GRB 260130A: Global MASTER-Net observations report
  12. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  13. GRB 260130A: Fermi GBM Final Real-time Localization
  14. Fermi GRB 260129A: Global MASTER-Net observations report
  15. GRB 260128B: LCO optical upper limits
  16. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  17. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  18. IPN triangulation of GRB 260121A
  19. GRB 260127A: Swift-BAT refined analysis
  20. GRB 260129B: Fermi GBM Final Localization
  21. GRB 260128B: SVOM detection of a burst through offline search
  22. GRB 260129A: Fermi GBM Final Localization
  23. IPN triangulation of GRB 260127B (short)
  24. GRB 260127B: Swift-XRT observations
  25. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  26. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  27. EP260128a: NOT optical counterpart candidate
  28. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  29. EP260128a: Liverpool Telescope optical observations and possible counterpart
  30. EP260128a: LCO optical upper limits
  31. EP260126a: SVOM/VT optical upperlimit
  32. EP260128a: Global MASTER-Net observations report
  33. EP260128a: Einstein Probe detection of an X-ray transient
  34. Fermi GRB 260127A: Global MASTER-Net observations report
  35. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  36. GRB 260127A: Fermi GBM Observation
  37. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  38. GRB 260127A: COLIBRÍ optical observations
  39. GRB 260127A: NOT optical observations
  40. GRB 260127B: Swift ToO observations
  41. EP260126a: Seimei/TriCCS optical upper limit
  42. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  43. GRB 260127A: Swift-XRT refined Analysis
  44. GRB 260127B: GOTO candidate optical counterpart
  45. GRB 260127A: SVOM/C-GFT optical observations
  46. The EP-WXT trigger 01709253145 is likely a flaring star
  47. GRB 260127A: Enhanced Swift-XRT position
  48. Fermi GRB 260127B: Global MASTER-Net observations report
  49. GRB 260127B: Fermi GBM Final Real-time Localization
  50. GRB 260127A: Prompt enhanced Swift-XRT position
  51. Swift GRB 260127A: Global MASTER-Net observations report
  52. GRB 260127A: LCO optical afterglow discovery
  53. GRB 260127A: Swift detection of a burst
  54. GRB 260127A: Fermi GBM Final Real-time Localization
  55. GRB 260125A: Swift-XRT observations
  56. EP260126a: EP-FXT follow-up observation
  57. EP260126a: Optical upper limit with Kinder observations
  58. EP260126a: Liverpool Telescope optical upper limits
  59. EP260126a: Further NOT optical upper limits
  60. EP260126a: COLIBRÍ optical upper limits
  61. EP260126a: NOT optical observations
  62. EP260126a: Einstein Probe detection of a fast X-ray transient
  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 260125B: Fermi GBM Final Real-time Localization
  72. GRB 260125A: Fermi GBM Final Real-time Localization
  73. GRB 260114A: SVOM/VT optical upper limits
  74. GRB 260120A: AstroSat CZTI detection
  75. GRB 260122B: Swift-BAT refined analysis
  76. GRB 260120B: SVOM/GRM observation
  77. GRB 260120A: GECAM-B observation
  78. GRB 260120B: AstroSat CZTI detection
  79. GRB 260114A: Insight-HXMT/HE detection
  80. GRB 260122B: Swift detection of a burst
  81. Swift GRB260122.97: Global MASTER-Net observations report
  82. EP260119a: Assy AZT-20 optical observations
  83. EP260119a: Mondy and SAO RAS optical upper limits
  84. GRB 260122A: Fermi GBM Final Real-time Localization
  85. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  86. EP260119a: Xinglong optical upper limit
  87. The EP-WXT trigger 01709251871 is likely a flaring star
  88. Fermi GRB 260120C: Global MASTER-Net observations report
  89. GRB 260120B: Swift-BAT refined analysis
  90. GRB 260120B: Swift-XRT refined Analysis
  91. EP260116a: COLIBRÍ further observations
  92. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  93. GRB 260120B: Fermi GBM Observation
  94. EP260105a: GTC/HiPERCAM optical observations
  95. GRB 260120B: Swift/UVOT Detection
  96. GRB 260120B: COLIBRÍ optical upper limits
  97. SVOM GRB260121.06: Global MASTER-Net observations report
  98. GRB 260120B: Enhanced Swift-XRT position
  99. GRB 260120B: SVOM/C-GFT optical counterpart detection
  100. GRB 260120C: Fermi GBM Final Real-time Localization

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