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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. Konus-Wind detection of GRB 260121A
  2. GRB 260131A/B: OHP/T193 optical observations
  3. GRB 260131A: KAIT optical observations
  4. GRB 251230A: MeerLICHT afterglow detection
  5. GRB 260131A: FTW optical and NIR observations
  6. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  7. GRID detection of GRB 260131A/B
  8. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  9. GRB 260130A: Insight-HXMT/HE detection
  10. GRB 260130A: GECAM-B observation of a short burst
  11. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  12. GRB 260131A/B: EP/FXT X-ray afterglow detection
  13. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  14. GRB 260127B: Insight-HXMT/HE detection
  15. GRB 260127B: GECAM-B observation of a short burst
  16. GRB 260127A: GECAM-B observation
  17. GRB 260131A: NOT spectroscopic redshift z = 1.434
  18. EP260131a: Liverpool Telescope optical upper limits
  19. EP260131a: COLIBRÍ further observations
  20. Konus-Wind detection of GRB 260128A / EP260128a
  21. GRB 260131A: Insight-HXMT/HE detection
  22. Konus-Wind detection of GRB 260131A/B
  23. EP260131a: SVOM/VT optical observation
  24. EP260131a: Xinglong optical upper limit
  25. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  26. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  27. GRB 260131A/B: Fermi GBM Observation
  28. EP260131a: COLIBRÍ observations of slow optical fading
  29. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  30. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  31. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  32. GRB 260131B: MAXI/GSC detection
  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. EP260131a: Einstein Probe detection of an X-ray transient
  39. GRB 260127B: Fermi GBM Detection
  40. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  41. Fermi GRB 260130A: Global MASTER-Net observations report
  42. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  43. GRB 260130A: Fermi GBM Final Real-time Localization
  44. Fermi GRB 260129A: Global MASTER-Net observations report
  45. GRB 260128B: LCO optical upper limits
  46. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  47. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  48. IPN triangulation of GRB 260121A
  49. GRB 260127A: Swift-BAT refined analysis
  50. GRB 260129B: Fermi GBM Final Localization
  51. GRB 260128B: SVOM detection of a burst through offline search
  52. GRB 260129A: Fermi GBM Final Localization
  53. IPN triangulation of GRB 260127B (short)
  54. GRB 260127B: Swift-XRT observations
  55. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  56. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  57. EP260128a: NOT optical counterpart candidate
  58. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  59. EP260128a: Liverpool Telescope optical observations and possible counterpart
  60. EP260128a: LCO optical upper limits
  61. EP260126a: SVOM/VT optical upperlimit
  62. EP260128a: Global MASTER-Net observations report
  63. EP260128a: Einstein Probe detection of an X-ray transient
  64. Fermi GRB 260127A: Global MASTER-Net observations report
  65. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  66. GRB 260127A: Fermi GBM Observation
  67. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  68. GRB 260127A: COLIBRÍ optical observations
  69. GRB 260127A: NOT optical observations
  70. GRB 260127B: Swift ToO observations
  71. EP260126a: Seimei/TriCCS optical upper limit
  72. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  73. GRB 260127A: Swift-XRT refined Analysis
  74. GRB 260127B: GOTO candidate optical counterpart
  75. GRB 260127A: SVOM/C-GFT optical observations
  76. The EP-WXT trigger 01709253145 is likely a flaring star
  77. GRB 260127A: Enhanced Swift-XRT position
  78. Fermi GRB 260127B: Global MASTER-Net observations report
  79. GRB 260127B: Fermi GBM Final Real-time Localization
  80. GRB 260127A: Prompt enhanced Swift-XRT position
  81. Swift GRB 260127A: Global MASTER-Net observations report
  82. GRB 260127A: LCO optical afterglow discovery
  83. GRB 260127A: Swift detection of a burst
  84. GRB 260127A: Fermi GBM Final Real-time Localization
  85. GRB 260125A: Swift-XRT observations
  86. EP260126a: EP-FXT follow-up observation
  87. EP260126a: Optical upper limit with Kinder observations
  88. EP260126a: Liverpool Telescope optical upper limits
  89. EP260126a: Further NOT optical upper limits
  90. EP260126a: COLIBRÍ optical upper limits
  91. EP260126a: NOT optical observations
  92. EP260126a: Einstein Probe detection of a fast X-ray transient
  93. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  94. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  95. Konus-Wind detection of GRB 260120B
  96. GRB 251222A: SVOM/ECLAIRs refined analysis
  97. GRB 260125A: Swift ToO observations
  98. GRB 260125A: GOTO candidate optical counterpart
  99. Fermi GRB 260125B: Global MASTER-Net observations report
  100. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event

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