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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"

41626 results found.

  1. GRB 260131A/B: Fermi GBM Observation
  2. EP260131a: COLIBRÍ observations of slow optical fading
  3. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  4. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  5. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  6. GRB 260131B: MAXI/GSC detection
  7. GRB 260131A: Fermi GBM Final Real-time Localization
  8. EP260131a: COLIBRÍ optical observations of the counterpart
  9. EP260131a: Las Cumbres detection of an optical counterpart
  10. GRB 260127B: AstroSat CZTI detection
  11. GRB 260130A: Fermi GBM Detection
  12. EP260131a: Einstein Probe detection of an X-ray transient
  13. GRB 260127B: Fermi GBM Detection
  14. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  15. Fermi GRB 260130A: Global MASTER-Net observations report
  16. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  17. GRB 260130A: Fermi GBM Final Real-time Localization
  18. Fermi GRB 260129A: Global MASTER-Net observations report
  19. GRB 260128B: LCO optical upper limits
  20. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  21. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  22. GRB 260127A: Swift-BAT refined analysis
  23. GRB 260129B: Fermi GBM Final Localization
  24. GRB 260128B: SVOM detection of a burst through offline search
  25. GRB 260129A: Fermi GBM Final Localization
  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. EP260128a: Einstein Probe detection of an X-ray transient
  37. Fermi GRB 260127A: Global MASTER-Net observations report
  38. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  39. GRB 260127A: Fermi GBM Observation
  40. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  41. GRB 260127A: COLIBRÍ optical observations
  42. GRB 260127A: NOT optical observations
  43. GRB 260127B: Swift ToO observations
  44. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  45. GRB 260127A: Swift-XRT refined Analysis
  46. GRB 260127B: GOTO candidate optical counterpart
  47. GRB 260127A: SVOM/C-GFT optical observations
  48. The EP-WXT trigger 01709253145 is likely a flaring star
  49. GRB 260127A: Enhanced Swift-XRT position
  50. Fermi GRB 260127B: Global MASTER-Net observations report
  51. GRB 260127B: Fermi GBM Final Real-time Localization
  52. GRB 260127A: Prompt enhanced Swift-XRT position
  53. Swift GRB 260127A: Global MASTER-Net observations report
  54. GRB 260127A: LCO optical afterglow discovery
  55. GRB 260127A: Swift detection of a burst
  56. GRB 260127A: Fermi GBM Final Real-time Localization
  57. GRB 260125A: Swift-XRT observations
  58. EP260126a: EP-FXT follow-up observation
  59. EP260126a: Optical upper limit with Kinder observations
  60. EP260126a: Liverpool Telescope optical upper limits
  61. EP260126a: Further NOT optical upper limits
  62. EP260126a: COLIBRÍ optical upper limits
  63. EP260126a: NOT optical observations
  64. EP260126a: Einstein Probe detection of a fast X-ray transient
  65. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  66. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  67. Konus-Wind detection of GRB 260120B
  68. GRB 251222A: SVOM/ECLAIRs refined analysis
  69. GRB 260125A: Swift ToO observations
  70. GRB 260125A: GOTO candidate optical counterpart
  71. Fermi GRB 260125B: Global MASTER-Net observations report
  72. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  73. GRB 260125B: Fermi GBM Final Real-time Localization
  74. GRB 260125A: Fermi GBM Final Real-time Localization
  75. GRB 260114A: SVOM/VT optical upper limits
  76. GRB 260120A: AstroSat CZTI detection
  77. GRB 260122B: Swift-BAT refined analysis
  78. GRB 260120B: SVOM/GRM observation
  79. GRB 260120A: GECAM-B observation
  80. GRB 260120B: AstroSat CZTI detection
  81. GRB 260114A: Insight-HXMT/HE detection
  82. GRB 260122B: Swift detection of a burst
  83. Swift GRB260122.97: Global MASTER-Net observations report
  84. EP260119a: Assy AZT-20 optical observations
  85. GRB 260122A: Fermi GBM Final Real-time Localization
  86. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  87. EP260119a: Xinglong optical upper limit
  88. The EP-WXT trigger 01709251871 is likely a flaring star
  89. Fermi GRB 260120C: Global MASTER-Net observations report
  90. GRB 260120B: Swift-BAT refined analysis
  91. GRB 260120B: Swift-XRT refined Analysis
  92. EP260116a: COLIBRÍ further observations
  93. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  94. GRB 260120B: Fermi GBM Observation
  95. EP260105a: GTC/HiPERCAM optical observations
  96. GRB 260120B: Swift/UVOT Detection
  97. GRB 260120B: COLIBRÍ optical upper limits
  98. SVOM GRB260121.06: Global MASTER-Net observations report
  99. GRB 260120B: Enhanced Swift-XRT position
  100. GRB 260120B: SVOM/C-GFT optical counterpart detection

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