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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 260127B: Insight-HXMT/HE detection
  2. GRB 260127B: GECAM-B observation of a short burst
  3. GRB 260127A: GECAM-B observation
  4. GRB 260131A: NOT spectroscopic redshift z = 1.434
  5. EP260131a: Liverpool Telescope optical upper limits
  6. EP260131a: COLIBRÍ further observations
  7. Konus-Wind detection of GRB 260128A / EP260128a
  8. GRB 260131A: Insight-HXMT/HE detection
  9. Konus-Wind detection of GRB 260131A/B
  10. EP260131a: SVOM/VT optical observation
  11. EP260131a: Xinglong optical upper limit
  12. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  13. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  14. GRB 260131A/B: Fermi GBM Observation
  15. EP260131a: COLIBRÍ observations of slow optical fading
  16. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  17. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  18. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  19. GRB 260131B: MAXI/GSC detection
  20. GRB 260131A: Fermi GBM Final Real-time Localization
  21. EP260131a: COLIBRÍ optical observations of the counterpart
  22. EP260131a: Las Cumbres detection of an optical counterpart
  23. GRB 260127B: AstroSat CZTI detection
  24. GRB 260130A: Fermi GBM Detection
  25. EP260131a: Einstein Probe detection of an X-ray transient
  26. GRB 260127B: Fermi GBM Detection
  27. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  28. Fermi GRB 260130A: Global MASTER-Net observations report
  29. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  30. GRB 260130A: Fermi GBM Final Real-time Localization
  31. Fermi GRB 260129A: Global MASTER-Net observations report
  32. GRB 260128B: LCO optical upper limits
  33. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  34. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  35. IPN triangulation of GRB 260121A
  36. GRB 260127A: Swift-BAT refined analysis
  37. GRB 260129B: Fermi GBM Final Localization
  38. GRB 260128B: SVOM detection of a burst through offline search
  39. GRB 260129A: Fermi GBM Final Localization
  40. IPN triangulation of GRB 260127B (short)
  41. GRB 260127B: Swift-XRT observations
  42. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  43. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  44. EP260128a: NOT optical counterpart candidate
  45. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  46. EP260128a: Liverpool Telescope optical observations and possible counterpart
  47. EP260128a: LCO optical upper limits
  48. EP260126a: SVOM/VT optical upperlimit
  49. EP260128a: Global MASTER-Net observations report
  50. EP260128a: Einstein Probe detection of an X-ray transient
  51. Fermi GRB 260127A: Global MASTER-Net observations report
  52. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  53. GRB 260127A: Fermi GBM Observation
  54. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  55. GRB 260127A: COLIBRÍ optical observations
  56. GRB 260127A: NOT optical observations
  57. GRB 260127B: Swift ToO observations
  58. EP260126a: Seimei/TriCCS optical upper limit
  59. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  60. GRB 260127A: Swift-XRT refined Analysis
  61. GRB 260127B: GOTO candidate optical counterpart
  62. GRB 260127A: SVOM/C-GFT optical observations
  63. The EP-WXT trigger 01709253145 is likely a flaring star
  64. GRB 260127A: Enhanced Swift-XRT position
  65. Fermi GRB 260127B: Global MASTER-Net observations report
  66. GRB 260127B: Fermi GBM Final Real-time Localization
  67. GRB 260127A: Prompt enhanced Swift-XRT position
  68. Swift GRB 260127A: Global MASTER-Net observations report
  69. GRB 260127A: LCO optical afterglow discovery
  70. GRB 260127A: Swift detection of a burst
  71. GRB 260127A: Fermi GBM Final Real-time Localization
  72. GRB 260125A: Swift-XRT observations
  73. EP260126a: EP-FXT follow-up observation
  74. EP260126a: Optical upper limit with Kinder observations
  75. EP260126a: Liverpool Telescope optical upper limits
  76. EP260126a: Further NOT optical upper limits
  77. EP260126a: COLIBRÍ optical upper limits
  78. EP260126a: NOT optical observations
  79. EP260126a: Einstein Probe detection of a fast X-ray transient
  80. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  81. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  82. Konus-Wind detection of GRB 260120B
  83. GRB 251222A: SVOM/ECLAIRs refined analysis
  84. GRB 260125A: Swift ToO observations
  85. GRB 260125A: GOTO candidate optical counterpart
  86. Fermi GRB 260125B: Global MASTER-Net observations report
  87. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  88. GRB 260125B: Fermi GBM Final Real-time Localization
  89. GRB 260125A: Fermi GBM Final Real-time Localization
  90. GRB 260114A: SVOM/VT optical upper limits
  91. GRB 260120A: AstroSat CZTI detection
  92. GRB 260122B: Swift-BAT refined analysis
  93. GRB 260120B: SVOM/GRM observation
  94. GRB 260120A: GECAM-B observation
  95. GRB 260120B: AstroSat CZTI detection
  96. GRB 260114A: Insight-HXMT/HE detection
  97. GRB 260122B: Swift detection of a burst
  98. Swift GRB260122.97: Global MASTER-Net observations report
  99. EP260119a: Assy AZT-20 optical observations
  100. EP260119a: Mondy and SAO RAS optical upper limits

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