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

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