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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. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  2. GRB 260127B: Insight-HXMT/HE detection
  3. GRB 260127B: GECAM-B observation of a short burst
  4. GRB 260127A: GECAM-B observation
  5. GRB 260131A: NOT spectroscopic redshift z = 1.434
  6. EP260131a: Liverpool Telescope optical upper limits
  7. EP260131a: COLIBRÍ further observations
  8. Konus-Wind detection of GRB 260128A / EP260128a
  9. GRB 260131A: Insight-HXMT/HE detection
  10. Konus-Wind detection of GRB 260131A/B
  11. EP260131a: SVOM/VT optical observation
  12. EP260131a: Xinglong optical upper limit
  13. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  14. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  15. GRB 260131A/B: Fermi GBM Observation
  16. EP260131a: COLIBRÍ observations of slow optical fading
  17. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  18. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  19. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  20. GRB 260131B: MAXI/GSC detection
  21. GRB 260131A: Fermi GBM Final Real-time Localization
  22. EP260131a: COLIBRÍ optical observations of the counterpart
  23. EP260131a: Las Cumbres detection of an optical counterpart
  24. GRB 260127B: AstroSat CZTI detection
  25. GRB 260130A: Fermi GBM Detection
  26. EP260131a: Einstein Probe detection of an X-ray transient
  27. GRB 260127B: Fermi GBM Detection
  28. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  29. Fermi GRB 260130A: Global MASTER-Net observations report
  30. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  31. GRB 260130A: Fermi GBM Final Real-time Localization
  32. Fermi GRB 260129A: Global MASTER-Net observations report
  33. GRB 260128B: LCO optical upper limits
  34. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  35. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  36. IPN triangulation of GRB 260121A
  37. GRB 260127A: Swift-BAT refined analysis
  38. GRB 260129B: Fermi GBM Final Localization
  39. GRB 260128B: SVOM detection of a burst through offline search
  40. GRB 260129A: Fermi GBM Final Localization
  41. IPN triangulation of GRB 260127B (short)
  42. GRB 260127B: Swift-XRT observations
  43. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  44. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  45. EP260128a: NOT optical counterpart candidate
  46. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  47. EP260128a: Liverpool Telescope optical observations and possible counterpart
  48. EP260128a: LCO optical upper limits
  49. EP260126a: SVOM/VT optical upperlimit
  50. EP260128a: Global MASTER-Net observations report
  51. EP260128a: Einstein Probe detection of an X-ray transient
  52. Fermi GRB 260127A: Global MASTER-Net observations report
  53. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  54. GRB 260127A: Fermi GBM Observation
  55. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  56. GRB 260127A: COLIBRÍ optical observations
  57. GRB 260127A: NOT optical observations
  58. GRB 260127B: Swift ToO observations
  59. EP260126a: Seimei/TriCCS optical upper limit
  60. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  61. GRB 260127A: Swift-XRT refined Analysis
  62. GRB 260127B: GOTO candidate optical counterpart
  63. GRB 260127A: SVOM/C-GFT optical observations
  64. The EP-WXT trigger 01709253145 is likely a flaring star
  65. GRB 260127A: Enhanced Swift-XRT position
  66. Fermi GRB 260127B: Global MASTER-Net observations report
  67. GRB 260127B: Fermi GBM Final Real-time Localization
  68. GRB 260127A: Prompt enhanced Swift-XRT position
  69. Swift GRB 260127A: Global MASTER-Net observations report
  70. GRB 260127A: LCO optical afterglow discovery
  71. GRB 260127A: Swift detection of a burst
  72. GRB 260127A: Fermi GBM Final Real-time Localization
  73. GRB 260125A: Swift-XRT observations
  74. EP260126a: EP-FXT follow-up observation
  75. EP260126a: Optical upper limit with Kinder observations
  76. EP260126a: Liverpool Telescope optical upper limits
  77. EP260126a: Further NOT optical upper limits
  78. EP260126a: COLIBRÍ optical upper limits
  79. EP260126a: NOT optical observations
  80. EP260126a: Einstein Probe detection of a fast X-ray transient
  81. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  82. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  83. Konus-Wind detection of GRB 260120B
  84. GRB 251222A: SVOM/ECLAIRs refined analysis
  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. EP260119a: Assy AZT-20 optical observations

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