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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"

45428 results found.

  1. GRB 260129A: Fermi GBM Final Localization
  2. IPN triangulation of GRB 260127B (short)
  3. GRB 260127B: Swift-XRT observations
  4. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  5. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  6. EP260128a: NOT optical counterpart candidate
  7. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  8. EP260128a: Liverpool Telescope optical observations and possible counterpart
  9. EP260128a: LCO optical upper limits
  10. EP260126a: SVOM/VT optical upperlimit
  11. EP260128a: Global MASTER-Net observations report
  12. EP260128a: Einstein Probe detection of an X-ray transient
  13. Fermi GRB 260127A: Global MASTER-Net observations report
  14. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  15. GRB 260127A: Fermi GBM Observation
  16. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  17. GRB 260127A: COLIBRÍ optical observations
  18. GRB 260127A: NOT optical observations
  19. GRB 260127B: Swift ToO observations
  20. EP260126a: Seimei/TriCCS optical upper limit
  21. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  22. GRB 260127A: Swift-XRT refined Analysis
  23. GRB 260127B: GOTO candidate optical counterpart
  24. GRB 260127A: SVOM/C-GFT optical observations
  25. The EP-WXT trigger 01709253145 is likely a flaring star
  26. GRB 260127A: Enhanced Swift-XRT position
  27. Fermi GRB 260127B: Global MASTER-Net observations report
  28. GRB 260127B: Fermi GBM Final Real-time Localization
  29. GRB 260127A: Prompt enhanced Swift-XRT position
  30. Swift GRB 260127A: Global MASTER-Net observations report
  31. GRB 260127A: LCO optical afterglow discovery
  32. GRB 260127A: Swift detection of a burst
  33. GRB 260127A: Fermi GBM Final Real-time Localization
  34. GRB 260125A: Swift-XRT observations
  35. EP260126a: EP-FXT follow-up observation
  36. EP260126a: Optical upper limit with Kinder observations
  37. EP260126a: Liverpool Telescope optical upper limits
  38. EP260126a: Further NOT optical upper limits
  39. EP260126a: COLIBRÍ optical upper limits
  40. EP260126a: NOT optical observations
  41. EP260126a: Einstein Probe detection of a fast X-ray transient
  42. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  43. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  44. Konus-Wind detection of GRB 260120B
  45. GRB 251222A: SVOM/ECLAIRs refined analysis
  46. GRB 260125A: Swift ToO observations
  47. GRB 260125A: GOTO candidate optical counterpart
  48. Fermi GRB 260125B: Global MASTER-Net observations report
  49. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  50. GRB 260125B: Fermi GBM Final Real-time Localization
  51. GRB 260125A: Fermi GBM Final Real-time Localization
  52. GRB 260114A: SVOM/VT optical upper limits
  53. GRB 260120A: AstroSat CZTI detection
  54. GRB 260122B: Swift-BAT refined analysis
  55. GRB 260120B: SVOM/GRM observation
  56. GRB 260120A: GECAM-B observation
  57. GRB 260120B: AstroSat CZTI detection
  58. GRB 260114A: Insight-HXMT/HE detection
  59. GRB 260122B: Swift detection of a burst
  60. Swift GRB260122.97: Global MASTER-Net observations report
  61. EP260119a: Assy AZT-20 optical observations
  62. EP260119a: Mondy and SAO RAS optical upper limits
  63. GRB 260122A: Fermi GBM Final Real-time Localization
  64. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  65. EP260119a: Xinglong optical upper limit
  66. The EP-WXT trigger 01709251871 is likely a flaring star
  67. Fermi GRB 260120C: Global MASTER-Net observations report
  68. GRB 260120B: Swift-BAT refined analysis
  69. GRB 260120B: Swift-XRT refined Analysis
  70. EP260116a: COLIBRÍ further observations
  71. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  72. GRB 260120B: Fermi GBM Observation
  73. EP260105a: GTC/HiPERCAM optical observations
  74. GRB 260120B: Swift/UVOT Detection
  75. GRB 260120B: COLIBRÍ optical upper limits
  76. SVOM GRB260121.06: Global MASTER-Net observations report
  77. GRB 260120B: Enhanced Swift-XRT position
  78. GRB 260120B: SVOM/C-GFT optical counterpart detection
  79. GRB 260120C: Fermi GBM Final Real-time Localization
  80. GRB 260101A: 239Alferov CubeSat detection
  81. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  82. GRB 260120B: Swift detection of a burst
  83. Swift GRB260120B: Global MASTER-Net observations report
  84. GRB 260120B: Fermi GBM Final Real-time Localization
  85. EP260119A: Mondy I-Band Observations
  86. Fermi trigger No 790601190: Global MASTER-Net observations report
  87. Fermi trigger No 790570272: Global MASTER-Net observations report
  88. GRB 260114A: Swift/UVOT Upper Limits
  89. EP260119a: Liverpool Telescope optical follow-up observations
  90. GRB 251202A: further radio observations with the VLA
  91. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  92. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  93. EP260119a: KAIT optical observations
  94. GRB 260120A: Fermi GBM Final Real-time Localization
  95. EP260119a: SVOM/VT optical observation
  96. EP260119a: update of EP-FXT follow-up observation
  97. EP260119a: NOT optical observations
  98. EP260119a: SAO RAS optical observations
  99. SVOM GRB260119.92: Global MASTER-Net observations report
  100. SVOM GRB260119.92: Global MASTER-Net observations report

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