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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"

28932 results found.

  1. EP260110a: Late GTC/EMIR near-infrared observations
  2. GRB 260204B: Fermi GBM Final Real-time Localization
  3. GRB 260204A: SVOM detection of a burst
  4. GRB 260131A/B: OHP/T193 optical observations
  5. GRB 260131A: KAIT optical observations
  6. GRB 251230A: MeerLICHT afterglow detection
  7. GRB 260131A: FTW optical and NIR observations
  8. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  9. GRID detection of GRB 260131A/B
  10. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  11. GRB 260130A: Insight-HXMT/HE detection
  12. GRB 260130A: GECAM-B observation of a short burst
  13. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  14. GRB 260131A/B: EP/FXT X-ray afterglow detection
  15. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  16. GRB 260127B: Insight-HXMT/HE detection
  17. GRB 260127B: GECAM-B observation of a short burst
  18. GRB 260127A: GECAM-B observation
  19. GRB 260131A: NOT spectroscopic redshift z = 1.434
  20. EP260131a: Liverpool Telescope optical upper limits
  21. EP260131a: COLIBRÍ further observations
  22. Konus-Wind detection of GRB 260128A / EP260128a
  23. GRB 260131A: Insight-HXMT/HE detection
  24. Konus-Wind detection of GRB 260131A/B
  25. EP260131a: Xinglong optical upper limit
  26. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  27. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  28. GRB 260131A/B: Fermi GBM Observation
  29. EP260131a: COLIBRÍ observations of slow optical fading
  30. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  31. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  32. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  33. GRB 260131A: Fermi GBM Final Real-time Localization
  34. EP260131a: COLIBRÍ optical observations of the counterpart
  35. EP260131a: Las Cumbres detection of an optical counterpart
  36. GRB 260127B: AstroSat CZTI detection
  37. GRB 260130A: Fermi GBM Detection
  38. GRB 260127B: Fermi GBM Detection
  39. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  40. Fermi GRB 260130A: Global MASTER-Net observations report
  41. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  42. GRB 260130A: Fermi GBM Final Real-time Localization
  43. Fermi GRB 260129A: Global MASTER-Net observations report
  44. GRB 260128B: LCO optical upper limits
  45. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  46. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  47. IPN triangulation of GRB 260121A
  48. GRB 260127A: Swift-BAT refined analysis
  49. GRB 260129B: Fermi GBM Final Localization
  50. GRB 260128B: SVOM detection of a burst through offline search
  51. GRB 260129A: Fermi GBM Final Localization
  52. IPN triangulation of GRB 260127B (short)
  53. GRB 260127B: Swift-XRT observations
  54. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  55. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  56. EP260128a: NOT optical counterpart candidate
  57. EP260128a: LCO optical upper limits
  58. EP260126a: SVOM/VT optical upperlimit
  59. EP260128a: Global MASTER-Net observations report
  60. Fermi GRB 260127A: Global MASTER-Net observations report
  61. GRB 260127A: Fermi GBM Observation
  62. GRB 260127A: COLIBRÍ optical observations
  63. GRB 260127A: NOT optical observations
  64. GRB 260127B: Swift ToO observations
  65. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  66. GRB 260127A: Swift-XRT refined Analysis
  67. GRB 260127B: GOTO candidate optical counterpart
  68. GRB 260127A: SVOM/C-GFT optical observations
  69. The EP-WXT trigger 01709253145 is likely a flaring star
  70. Fermi GRB 260127B: Global MASTER-Net observations report
  71. GRB 260127B: Fermi GBM Final Real-time Localization
  72. Swift GRB 260127A: Global MASTER-Net observations report
  73. GRB 260127A: LCO optical afterglow discovery
  74. GRB 260127A: Swift detection of a burst
  75. GRB 260127A: Fermi GBM Final Real-time Localization
  76. GRB 260125A: Swift-XRT observations
  77. EP260126a: Optical upper limit with Kinder observations
  78. EP260126a: Further NOT optical upper limits
  79. EP260126a: COLIBRÍ optical upper limits
  80. EP260126a: NOT optical observations
  81. EP260126a: Einstein Probe detection of a fast X-ray transient
  82. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  83. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  84. Konus-Wind detection of GRB 260120B
  85. GRB 260125A: Swift ToO observations
  86. GRB 260125A: GOTO candidate optical counterpart
  87. Fermi GRB 260125B: Global MASTER-Net observations report
  88. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  89. GRB 260125B: Fermi GBM Final Real-time Localization
  90. GRB 260125A: Fermi GBM Final Real-time Localization
  91. GRB 260114A: SVOM/VT optical upper limits
  92. GRB 260120A: AstroSat CZTI detection
  93. GRB 260122B: Swift-BAT refined analysis
  94. GRB 260120B: SVOM/GRM observation
  95. GRB 260120A: GECAM-B observation
  96. GRB 260120B: AstroSat CZTI detection
  97. GRB 260114A: Insight-HXMT/HE detection
  98. GRB 260122B: Swift detection of a burst
  99. Swift GRB260122.97: Global MASTER-Net observations report
  100. GRB 260122A: Fermi GBM Final Real-time Localization

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