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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"
  1. GRB 260130A: Fermi GBM Detection
  2. EP260131a: Einstein Probe detection of an X-ray transient
  3. GRB 260127B: Fermi GBM Detection
  4. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  5. Fermi GRB 260130A: Global MASTER-Net observations report
  6. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  7. GRB 260130A: Fermi GBM Final Real-time Localization
  8. Fermi GRB 260129A: Global MASTER-Net observations report
  9. GRB 260128B: LCO optical upper limits
  10. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  11. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  12. IPN triangulation of GRB 260121A
  13. GRB 260127A: Swift-BAT refined analysis
  14. GRB 260129B: Fermi GBM Final Localization
  15. GRB 260128B: SVOM detection of a burst through offline search
  16. GRB 260129A: Fermi GBM Final Localization
  17. IPN triangulation of GRB 260127B (short)
  18. GRB 260127B: Swift-XRT observations
  19. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  20. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  21. EP260128a: NOT optical counterpart candidate
  22. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  23. EP260128a: Liverpool Telescope optical observations and possible counterpart
  24. EP260128a: LCO optical upper limits
  25. EP260126a: SVOM/VT optical upperlimit
  26. EP260128a: Global MASTER-Net observations report
  27. EP260128a: Einstein Probe detection of an X-ray transient
  28. Fermi GRB 260127A: Global MASTER-Net observations report
  29. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  30. GRB 260127A: Fermi GBM Observation
  31. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  32. GRB 260127A: COLIBRÍ optical observations
  33. GRB 260127A: NOT optical observations
  34. GRB 260127B: Swift ToO observations
  35. EP260126a: Seimei/TriCCS optical upper limit
  36. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  37. GRB 260127A: Swift-XRT refined Analysis
  38. GRB 260127B: GOTO candidate optical counterpart
  39. GRB 260127A: SVOM/C-GFT optical observations
  40. The EP-WXT trigger 01709253145 is likely a flaring star
  41. GRB 260127A: Enhanced Swift-XRT position
  42. Fermi GRB 260127B: Global MASTER-Net observations report
  43. GRB 260127B: Fermi GBM Final Real-time Localization
  44. GRB 260127A: Prompt enhanced Swift-XRT position
  45. Swift GRB 260127A: Global MASTER-Net observations report
  46. GRB 260127A: LCO optical afterglow discovery
  47. GRB 260127A: Swift detection of a burst
  48. GRB 260127A: Fermi GBM Final Real-time Localization
  49. GRB 260125A: Swift-XRT observations
  50. EP260126a: EP-FXT follow-up observation
  51. EP260126a: Optical upper limit with Kinder observations
  52. EP260126a: Liverpool Telescope optical upper limits
  53. EP260126a: Further NOT optical upper limits
  54. EP260126a: COLIBRÍ optical upper limits
  55. EP260126a: NOT optical observations
  56. EP260126a: Einstein Probe detection of a fast X-ray transient
  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 260125B: Fermi GBM Final Real-time Localization
  66. GRB 260125A: Fermi GBM Final Real-time Localization
  67. GRB 260114A: SVOM/VT optical upper limits
  68. GRB 260120A: AstroSat CZTI detection
  69. GRB 260122B: Swift-BAT refined analysis
  70. GRB 260120B: SVOM/GRM observation
  71. GRB 260120A: GECAM-B observation
  72. GRB 260120B: AstroSat CZTI detection
  73. GRB 260114A: Insight-HXMT/HE detection
  74. GRB 260122B: Swift detection of a burst
  75. Swift GRB260122.97: Global MASTER-Net observations report
  76. EP260119a: Assy AZT-20 optical observations
  77. EP260119a: Mondy and SAO RAS optical upper limits
  78. GRB 260122A: Fermi GBM Final Real-time Localization
  79. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  80. EP260119a: Xinglong optical upper limit
  81. The EP-WXT trigger 01709251871 is likely a flaring star
  82. Fermi GRB 260120C: Global MASTER-Net observations report
  83. GRB 260120B: Swift-BAT refined analysis
  84. GRB 260120B: Swift-XRT refined Analysis
  85. EP260116a: COLIBRÍ further observations
  86. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  87. GRB 260120B: Fermi GBM Observation
  88. EP260105a: GTC/HiPERCAM optical observations
  89. GRB 260120B: Swift/UVOT Detection
  90. GRB 260120B: COLIBRÍ optical upper limits
  91. SVOM GRB260121.06: Global MASTER-Net observations report
  92. GRB 260120B: Enhanced Swift-XRT position
  93. GRB 260120B: SVOM/C-GFT optical counterpart detection
  94. GRB 260120C: Fermi GBM Final Real-time Localization
  95. GRB 260101A: 239Alferov CubeSat detection
  96. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  97. GRB 260120B: Swift detection of a burst
  98. Swift GRB260120B: Global MASTER-Net observations report
  99. GRB 260120B: Fermi GBM Final Real-time Localization
  100. EP260119A: Mondy I-Band Observations

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