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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: KAIT optical observations
  2. GRB 251230A: MeerLICHT afterglow detection
  3. GRB 260131A: FTW optical and NIR observations
  4. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  5. GRID detection of GRB 260131A/B
  6. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  7. GRB 260130A: Insight-HXMT/HE detection
  8. GRB 260130A: GECAM-B observation of a short burst
  9. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  10. GRB 260131A/B: EP/FXT X-ray afterglow detection
  11. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  12. GRB 260127B: Insight-HXMT/HE detection
  13. GRB 260127B: GECAM-B observation of a short burst
  14. GRB 260127A: GECAM-B observation
  15. GRB 260131A: NOT spectroscopic redshift z = 1.434
  16. EP260131a: Liverpool Telescope optical upper limits
  17. EP260131a: COLIBRÍ further observations
  18. Konus-Wind detection of GRB 260128A / EP260128a
  19. GRB 260131A: Insight-HXMT/HE detection
  20. Konus-Wind detection of GRB 260131A/B
  21. EP260131a: SVOM/VT optical observation
  22. EP260131a: Xinglong optical upper limit
  23. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  24. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  25. GRB 260131A/B: Fermi GBM Observation
  26. EP260131a: COLIBRÍ observations of slow optical fading
  27. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  28. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  29. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  30. GRB 260131B: MAXI/GSC detection
  31. GRB 260131A: Fermi GBM Final Real-time Localization
  32. EP260131a: COLIBRÍ optical observations of the counterpart
  33. EP260131a: Las Cumbres detection of an optical counterpart
  34. GRB 260127B: AstroSat CZTI detection
  35. GRB 260130A: Fermi GBM Detection
  36. EP260131a: Einstein Probe detection of an X-ray transient
  37. GRB 260127B: Fermi GBM Detection
  38. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  39. Fermi GRB 260130A: Global MASTER-Net observations report
  40. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  41. GRB 260130A: Fermi GBM Final Real-time Localization
  42. Fermi GRB 260129A: Global MASTER-Net observations report
  43. GRB 260128B: LCO optical upper limits
  44. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  45. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  46. IPN triangulation of GRB 260121A
  47. GRB 260127A: Swift-BAT refined analysis
  48. GRB 260129B: Fermi GBM Final Localization
  49. GRB 260128B: SVOM detection of a burst through offline search
  50. GRB 260129A: Fermi GBM Final Localization
  51. IPN triangulation of GRB 260127B (short)
  52. GRB 260127B: Swift-XRT observations
  53. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  54. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  55. EP260128a: NOT optical counterpart candidate
  56. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  57. EP260128a: Liverpool Telescope optical observations and possible counterpart
  58. EP260128a: LCO optical upper limits
  59. EP260126a: SVOM/VT optical upperlimit
  60. EP260128a: Global MASTER-Net observations report
  61. EP260128a: Einstein Probe detection of an X-ray transient
  62. Fermi GRB 260127A: Global MASTER-Net observations report
  63. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  64. GRB 260127A: Fermi GBM Observation
  65. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  66. GRB 260127A: COLIBRÍ optical observations
  67. GRB 260127A: NOT optical observations
  68. GRB 260127B: Swift ToO observations
  69. EP260126a: Seimei/TriCCS optical upper limit
  70. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  71. GRB 260127A: Swift-XRT refined Analysis
  72. GRB 260127B: GOTO candidate optical counterpart
  73. GRB 260127A: SVOM/C-GFT optical observations
  74. The EP-WXT trigger 01709253145 is likely a flaring star
  75. GRB 260127A: Enhanced Swift-XRT position
  76. Fermi GRB 260127B: Global MASTER-Net observations report
  77. GRB 260127B: Fermi GBM Final Real-time Localization
  78. GRB 260127A: Prompt enhanced Swift-XRT position
  79. Swift GRB 260127A: Global MASTER-Net observations report
  80. GRB 260127A: LCO optical afterglow discovery
  81. GRB 260127A: Swift detection of a burst
  82. GRB 260127A: Fermi GBM Final Real-time Localization
  83. GRB 260125A: Swift-XRT observations
  84. EP260126a: EP-FXT follow-up observation
  85. EP260126a: Optical upper limit with Kinder observations
  86. EP260126a: Liverpool Telescope optical upper limits
  87. EP260126a: Further NOT optical upper limits
  88. EP260126a: COLIBRÍ optical upper limits
  89. EP260126a: NOT optical observations
  90. EP260126a: Einstein Probe detection of a fast X-ray transient
  91. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  92. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  93. Konus-Wind detection of GRB 260120B
  94. GRB 251222A: SVOM/ECLAIRs refined analysis
  95. GRB 260125A: Swift ToO observations
  96. GRB 260125A: GOTO candidate optical counterpart
  97. Fermi GRB 260125B: Global MASTER-Net observations report
  98. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  99. GRB 260125B: Fermi GBM Final Real-time Localization
  100. GRB 260125A: Fermi GBM Final Real-time Localization

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