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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: refined analysis of the EP-WXT and autonomous EP-FXT observations
  2. EP260128a: Liverpool Telescope optical observations and possible counterpart
  3. EP260128a: LCO optical upper limits
  4. EP260126a: SVOM/VT optical upperlimit
  5. EP260128a: Global MASTER-Net observations report
  6. EP260128a: Einstein Probe detection of an X-ray transient
  7. Fermi GRB 260127A: Global MASTER-Net observations report
  8. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  9. GRB 260127A: Fermi GBM Observation
  10. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  11. GRB 260127A: COLIBRÍ optical observations
  12. GRB 260127A: NOT optical observations
  13. GRB 260127B: Swift ToO observations
  14. EP260126a: Seimei/TriCCS optical upper limit
  15. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  16. GRB 260127A: Swift-XRT refined Analysis
  17. GRB 260127B: GOTO candidate optical counterpart
  18. GRB 260127A: SVOM/C-GFT optical observations
  19. The EP-WXT trigger 01709253145 is likely a flaring star
  20. GRB 260127A: Enhanced Swift-XRT position
  21. Fermi GRB 260127B: Global MASTER-Net observations report
  22. GRB 260127B: Fermi GBM Final Real-time Localization
  23. GRB 260127A: Prompt enhanced Swift-XRT position
  24. Swift GRB 260127A: Global MASTER-Net observations report
  25. GRB 260127A: LCO optical afterglow discovery
  26. GRB 260127A: Swift detection of a burst
  27. GRB 260127A: Fermi GBM Final Real-time Localization
  28. GRB 260125A: Swift-XRT observations
  29. EP260126a: EP-FXT follow-up observation
  30. EP260126a: Optical upper limit with Kinder observations
  31. EP260126a: Liverpool Telescope optical upper limits
  32. EP260126a: Further NOT optical upper limits
  33. EP260126a: COLIBRÍ optical upper limits
  34. EP260126a: NOT optical observations
  35. EP260126a: Einstein Probe detection of a fast X-ray transient
  36. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  37. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  38. Konus-Wind detection of GRB 260120B
  39. GRB 251222A: SVOM/ECLAIRs refined analysis
  40. GRB 260125A: Swift ToO observations
  41. GRB 260125A: GOTO candidate optical counterpart
  42. Fermi GRB 260125B: Global MASTER-Net observations report
  43. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  44. GRB 260125B: Fermi GBM Final Real-time Localization
  45. GRB 260125A: Fermi GBM Final Real-time Localization
  46. GRB 260114A: SVOM/VT optical upper limits
  47. GRB 260120A: AstroSat CZTI detection
  48. GRB 260122B: Swift-BAT refined analysis
  49. GRB 260120B: SVOM/GRM observation
  50. GRB 260120A: GECAM-B observation
  51. GRB 260120B: AstroSat CZTI detection
  52. GRB 260114A: Insight-HXMT/HE detection
  53. GRB 260122B: Swift detection of a burst
  54. Swift GRB260122.97: Global MASTER-Net observations report
  55. EP260119a: Assy AZT-20 optical observations
  56. EP260119a: Mondy and SAO RAS optical upper limits
  57. GRB 260122A: Fermi GBM Final Real-time Localization
  58. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  59. EP260119a: Xinglong optical upper limit
  60. The EP-WXT trigger 01709251871 is likely a flaring star
  61. Fermi GRB 260120C: Global MASTER-Net observations report
  62. GRB 260120B: Swift-BAT refined analysis
  63. GRB 260120B: Swift-XRT refined Analysis
  64. EP260116a: COLIBRÍ further observations
  65. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  66. GRB 260120B: Fermi GBM Observation
  67. EP260105a: GTC/HiPERCAM optical observations
  68. GRB 260120B: Swift/UVOT Detection
  69. GRB 260120B: COLIBRÍ optical upper limits
  70. SVOM GRB260121.06: Global MASTER-Net observations report
  71. GRB 260120B: Enhanced Swift-XRT position
  72. GRB 260120B: SVOM/C-GFT optical counterpart detection
  73. GRB 260120C: Fermi GBM Final Real-time Localization
  74. GRB 260101A: 239Alferov CubeSat detection
  75. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  76. GRB 260120B: Swift detection of a burst
  77. Swift GRB260120B: Global MASTER-Net observations report
  78. GRB 260120B: Fermi GBM Final Real-time Localization
  79. EP260119A: Mondy I-Band Observations
  80. Fermi trigger No 790601190: Global MASTER-Net observations report
  81. Fermi trigger No 790570272: Global MASTER-Net observations report
  82. GRB 260114A: Swift/UVOT Upper Limits
  83. EP260119a: Liverpool Telescope optical follow-up observations
  84. GRB 251202A: further radio observations with the VLA
  85. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  86. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  87. EP260119a: KAIT optical observations
  88. GRB 260120A: Fermi GBM Final Real-time Localization
  89. EP260119a: SVOM/VT optical observation
  90. EP260119a: update of EP-FXT follow-up observation
  91. EP260119a: NOT optical observations
  92. EP260119a: SAO RAS optical observations
  93. SVOM GRB260119.92: Global MASTER-Net observations report
  94. SVOM GRB260119.92: Global MASTER-Net observations report
  95. SVOM GRB260119.90: Global MASTER-Net observations report
  96. EP260116a: COLIBRÍ detection of a fading optical source
  97. GRB 251208D: SVOM/ECLAIRs refined analysis
  98. GRB 251208D: SVOM/ECLAIRs refined analysis
  99. GRB 260117A: Swift-XRT afterglow detection
  100. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6

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