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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. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  2. Fermi GRB 260130A: Global MASTER-Net observations report
  3. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  4. GRB 260130A: Fermi GBM Final Real-time Localization
  5. Fermi GRB 260129A: Global MASTER-Net observations report
  6. GRB 260128B: LCO optical upper limits
  7. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  8. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  9. IPN triangulation of GRB 260121A
  10. GRB 260127A: Swift-BAT refined analysis
  11. GRB 260129B: Fermi GBM Final Localization
  12. GRB 260128B: SVOM detection of a burst through offline search
  13. GRB 260129A: Fermi GBM Final Localization
  14. IPN triangulation of GRB 260127B (short)
  15. GRB 260127B: Swift-XRT observations
  16. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  17. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  18. EP260128a: NOT optical counterpart candidate
  19. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  20. EP260128a: Liverpool Telescope optical observations and possible counterpart
  21. EP260128a: LCO optical upper limits
  22. EP260126a: SVOM/VT optical upperlimit
  23. EP260128a: Global MASTER-Net observations report
  24. EP260128a: Einstein Probe detection of an X-ray transient
  25. Fermi GRB 260127A: Global MASTER-Net observations report
  26. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  27. GRB 260127A: Fermi GBM Observation
  28. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  29. GRB 260127A: COLIBRÍ optical observations
  30. GRB 260127A: NOT optical observations
  31. GRB 260127B: Swift ToO observations
  32. EP260126a: Seimei/TriCCS optical upper limit
  33. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  34. GRB 260127A: Swift-XRT refined Analysis
  35. GRB 260127B: GOTO candidate optical counterpart
  36. GRB 260127A: SVOM/C-GFT optical observations
  37. The EP-WXT trigger 01709253145 is likely a flaring star
  38. GRB 260127A: Enhanced Swift-XRT position
  39. Fermi GRB 260127B: Global MASTER-Net observations report
  40. GRB 260127B: Fermi GBM Final Real-time Localization
  41. GRB 260127A: Prompt enhanced Swift-XRT position
  42. Swift GRB 260127A: Global MASTER-Net observations report
  43. GRB 260127A: LCO optical afterglow discovery
  44. GRB 260127A: Swift detection of a burst
  45. GRB 260127A: Fermi GBM Final Real-time Localization
  46. GRB 260125A: Swift-XRT observations
  47. EP260126a: EP-FXT follow-up observation
  48. EP260126a: Optical upper limit with Kinder observations
  49. EP260126a: Liverpool Telescope optical upper limits
  50. EP260126a: Further NOT optical upper limits
  51. EP260126a: COLIBRÍ optical upper limits
  52. EP260126a: NOT optical observations
  53. EP260126a: Einstein Probe detection of a fast X-ray transient
  54. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  55. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  56. Konus-Wind detection of GRB 260120B
  57. GRB 251222A: SVOM/ECLAIRs refined analysis
  58. GRB 260125A: Swift ToO observations
  59. GRB 260125A: GOTO candidate optical counterpart
  60. Fermi GRB 260125B: Global MASTER-Net observations report
  61. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  62. GRB 260125B: Fermi GBM Final Real-time Localization
  63. GRB 260125A: Fermi GBM Final Real-time Localization
  64. GRB 260114A: SVOM/VT optical upper limits
  65. GRB 260120A: AstroSat CZTI detection
  66. GRB 260122B: Swift-BAT refined analysis
  67. GRB 260120B: SVOM/GRM observation
  68. GRB 260120A: GECAM-B observation
  69. GRB 260120B: AstroSat CZTI detection
  70. GRB 260114A: Insight-HXMT/HE detection
  71. GRB 260122B: Swift detection of a burst
  72. Swift GRB260122.97: Global MASTER-Net observations report
  73. EP260119a: Assy AZT-20 optical observations
  74. EP260119a: Mondy and SAO RAS optical upper limits
  75. GRB 260122A: Fermi GBM Final Real-time Localization
  76. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  77. EP260119a: Xinglong optical upper limit
  78. The EP-WXT trigger 01709251871 is likely a flaring star
  79. Fermi GRB 260120C: Global MASTER-Net observations report
  80. GRB 260120B: Swift-BAT refined analysis
  81. GRB 260120B: Swift-XRT refined Analysis
  82. EP260116a: COLIBRÍ further observations
  83. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  84. GRB 260120B: Fermi GBM Observation
  85. EP260105a: GTC/HiPERCAM optical observations
  86. GRB 260120B: Swift/UVOT Detection
  87. GRB 260120B: COLIBRÍ optical upper limits
  88. SVOM GRB260121.06: Global MASTER-Net observations report
  89. GRB 260120B: Enhanced Swift-XRT position
  90. GRB 260120B: SVOM/C-GFT optical counterpart detection
  91. GRB 260120C: Fermi GBM Final Real-time Localization
  92. GRB 260101A: 239Alferov CubeSat detection
  93. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  94. GRB 260120B: Swift detection of a burst
  95. Swift GRB260120B: Global MASTER-Net observations report
  96. GRB 260120B: Fermi GBM Final Real-time Localization
  97. EP260119A: Mondy I-Band Observations
  98. Fermi trigger No 790601190: Global MASTER-Net observations report
  99. Fermi trigger No 790570272: Global MASTER-Net observations report
  100. GRB 260114A: Swift/UVOT Upper Limits

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