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

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