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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"

44412 results found.

  1. GRB 260127A: COLIBRÍ optical observations
  2. GRB 260127A: NOT optical observations
  3. GRB 260127B: Swift ToO observations
  4. EP260126a: Seimei/TriCCS optical upper limit
  5. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  6. GRB 260127A: Swift-XRT refined Analysis
  7. GRB 260127B: GOTO candidate optical counterpart
  8. GRB 260127A: SVOM/C-GFT optical observations
  9. The EP-WXT trigger 01709253145 is likely a flaring star
  10. GRB 260127A: Enhanced Swift-XRT position
  11. Fermi GRB 260127B: Global MASTER-Net observations report
  12. GRB 260127B: Fermi GBM Final Real-time Localization
  13. GRB 260127A: Prompt enhanced Swift-XRT position
  14. Swift GRB 260127A: Global MASTER-Net observations report
  15. GRB 260127A: LCO optical afterglow discovery
  16. GRB 260127A: Swift detection of a burst
  17. GRB 260127A: Fermi GBM Final Real-time Localization
  18. GRB 260125A: Swift-XRT observations
  19. EP260126a: EP-FXT follow-up observation
  20. EP260126a: Optical upper limit with Kinder observations
  21. EP260126a: Liverpool Telescope optical upper limits
  22. EP260126a: Further NOT optical upper limits
  23. EP260126a: COLIBRÍ optical upper limits
  24. EP260126a: NOT optical observations
  25. EP260126a: Einstein Probe detection of a fast X-ray transient
  26. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  27. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  28. Konus-Wind detection of GRB 260120B
  29. GRB 251222A: SVOM/ECLAIRs refined analysis
  30. GRB 260125A: Swift ToO observations
  31. GRB 260125A: GOTO candidate optical counterpart
  32. Fermi GRB 260125B: Global MASTER-Net observations report
  33. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  34. GRB 260125B: Fermi GBM Final Real-time Localization
  35. GRB 260125A: Fermi GBM Final Real-time Localization
  36. GRB 260114A: SVOM/VT optical upper limits
  37. GRB 260120A: AstroSat CZTI detection
  38. GRB 260122B: Swift-BAT refined analysis
  39. GRB 260120B: SVOM/GRM observation
  40. GRB 260120A: GECAM-B observation
  41. GRB 260120B: AstroSat CZTI detection
  42. GRB 260114A: Insight-HXMT/HE detection
  43. GRB 260122B: Swift detection of a burst
  44. Swift GRB260122.97: Global MASTER-Net observations report
  45. EP260119a: Assy AZT-20 optical observations
  46. EP260119a: Mondy and SAO RAS optical upper limits
  47. GRB 260122A: Fermi GBM Final Real-time Localization
  48. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  49. EP260119a: Xinglong optical upper limit
  50. The EP-WXT trigger 01709251871 is likely a flaring star
  51. Fermi GRB 260120C: Global MASTER-Net observations report
  52. GRB 260120B: Swift-BAT refined analysis
  53. GRB 260120B: Swift-XRT refined Analysis
  54. EP260116a: COLIBRÍ further observations
  55. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  56. GRB 260120B: Fermi GBM Observation
  57. EP260105a: GTC/HiPERCAM optical observations
  58. GRB 260120B: Swift/UVOT Detection
  59. GRB 260120B: COLIBRÍ optical upper limits
  60. SVOM GRB260121.06: Global MASTER-Net observations report
  61. GRB 260120B: Enhanced Swift-XRT position
  62. GRB 260120B: SVOM/C-GFT optical counterpart detection
  63. GRB 260120C: Fermi GBM Final Real-time Localization
  64. GRB 260101A: 239Alferov CubeSat detection
  65. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  66. GRB 260120B: Swift detection of a burst
  67. Swift GRB260120B: Global MASTER-Net observations report
  68. GRB 260120B: Fermi GBM Final Real-time Localization
  69. EP260119A: Mondy I-Band Observations
  70. Fermi trigger No 790601190: Global MASTER-Net observations report
  71. Fermi trigger No 790570272: Global MASTER-Net observations report
  72. GRB 260114A: Swift/UVOT Upper Limits
  73. EP260119a: Liverpool Telescope optical follow-up observations
  74. GRB 251202A: further radio observations with the VLA
  75. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  76. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  77. EP260119a: KAIT optical observations
  78. GRB 260120A: Fermi GBM Final Real-time Localization
  79. EP260119a: SVOM/VT optical observation
  80. EP260119a: update of EP-FXT follow-up observation
  81. EP260119a: NOT optical observations
  82. EP260119a: SAO RAS optical observations
  83. SVOM GRB260119.92: Global MASTER-Net observations report
  84. SVOM GRB260119.92: Global MASTER-Net observations report
  85. SVOM GRB260119.90: Global MASTER-Net observations report
  86. EP260116a: COLIBRÍ detection of a fading optical source
  87. GRB 251208D: SVOM/ECLAIRs refined analysis
  88. GRB 251208D: SVOM/ECLAIRs refined analysis
  89. GRB 260117A: Swift-XRT afterglow detection
  90. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  91. EP260119a: Global MASTER-Net observations report
  92. GRB 260115A: AstroSat CZTI detection
  93. EP260119a: LCO optical observations
  94. GRB 260117A: ZTSh optical upper limit
  95. EP260119a: COLIBRÍ optical counterpart candidate
  96. EP260119a: preliminary result from the EP-FXT observation
  97. GRB 260110A: SVOM detection of a burst through offline search
  98. EP260119a: EP-WXT detection of a fast X-ray transient
  99. Swift GRB260118.48: Global MASTER-Net observations report
  100. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations

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