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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"

12288 results found.

  1. GRB 260207A : MASTER optical counterpart discovery
  2. GRB 260131A/B: Mondy and Terskol optical observations
  3. Fermi GRB 260207B: Global MASTER-Net observations report
  4. GRB 260207B: Fermi GBM Final Real-time Localization
  5. GRB 260207A: Fermi GBM Final Localization
  6. Fermi trigger No 792135758: Global MASTER-Net observations report
  7. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  8. GRB 260204A : MASTER Global robotic net optical observations
  9. Fermi GBM Sub-Threshold Detection of GRB 260204A
  10. GRB 260204B: Fermi GBM Final Real-time Localization
  11. GRB 260131A/B: OHP/T193 optical observations
  12. GRB 260131A: KAIT optical observations
  13. GRB 260131A: FTW optical and NIR observations
  14. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  15. GRID detection of GRB 260131A/B
  16. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  17. GRB 260130A: Insight-HXMT/HE detection
  18. GRB 260130A: GECAM-B observation of a short burst
  19. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  20. GRB 260131A/B: EP/FXT X-ray afterglow detection
  21. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  22. GRB 260127B: Insight-HXMT/HE detection
  23. GRB 260127B: GECAM-B observation of a short burst
  24. GRB 260127A: GECAM-B observation
  25. GRB 260131A: NOT spectroscopic redshift z = 1.434
  26. Konus-Wind detection of GRB 260128A / EP260128a
  27. GRB 260131A: Insight-HXMT/HE detection
  28. Konus-Wind detection of GRB 260131A/B
  29. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  30. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  31. GRB 260131A/B: Fermi GBM Observation
  32. GRB 260131A: Fermi GBM Final Real-time Localization
  33. GRB 260127B: AstroSat CZTI detection
  34. GRB 260130A: Fermi GBM Detection
  35. GRB 260127B: Fermi GBM Detection
  36. Fermi GRB 260130A: Global MASTER-Net observations report
  37. GRB 260130A: Fermi GBM Final Real-time Localization
  38. Fermi GRB 260129A: Global MASTER-Net observations report
  39. IPN triangulation of GRB 260121A
  40. GRB 260129B: Fermi GBM Final Localization
  41. GRB 260129A: Fermi GBM Final Localization
  42. IPN triangulation of GRB 260127B (short)
  43. GRB 260127B: Swift-XRT observations
  44. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  45. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  46. Fermi GRB 260127A: Global MASTER-Net observations report
  47. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  48. GRB 260127A: Fermi GBM Observation
  49. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  50. GRB 260127A: COLIBRÍ optical observations
  51. GRB 260127A: NOT optical observations
  52. GRB 260127B: Swift ToO observations
  53. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  54. GRB 260127B: GOTO candidate optical counterpart
  55. GRB 260127A: SVOM/C-GFT optical observations
  56. Fermi GRB 260127B: Global MASTER-Net observations report
  57. GRB 260127B: Fermi GBM Final Real-time Localization
  58. GRB 260127A: LCO optical afterglow discovery
  59. GRB 260127A: Fermi GBM Final Real-time Localization
  60. GRB 260125A: Swift-XRT observations
  61. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  62. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  63. Konus-Wind detection of GRB 260120B
  64. GRB 260125A: Swift ToO observations
  65. GRB 260125A: GOTO candidate optical counterpart
  66. Fermi GRB 260125B: Global MASTER-Net observations report
  67. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  68. GRB 260125B: Fermi GBM Final Real-time Localization
  69. GRB 260125A: Fermi GBM Final Real-time Localization
  70. GRB 260114A: SVOM/VT optical upper limits
  71. GRB 260120A: AstroSat CZTI detection
  72. GRB 260120B: SVOM/GRM observation
  73. GRB 260120A: GECAM-B observation
  74. GRB 260120B: AstroSat CZTI detection
  75. GRB 260114A: Insight-HXMT/HE detection
  76. GRB 260122A: Fermi GBM Final Real-time Localization
  77. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  78. Fermi GRB 260120C: Global MASTER-Net observations report
  79. GRB 260120B: Fermi GBM Observation
  80. GRB 260120B: COLIBRÍ optical upper limits
  81. GRB 260120B: SVOM/C-GFT optical counterpart detection
  82. GRB 260120C: Fermi GBM Final Real-time Localization
  83. GRB 260101A: 239Alferov CubeSat detection
  84. GRB 260120B: Fermi GBM Final Real-time Localization
  85. Fermi trigger No 790601190: Global MASTER-Net observations report
  86. Fermi trigger No 790570272: Global MASTER-Net observations report
  87. GRB 251202A: further radio observations with the VLA
  88. GRB 260120A: Fermi GBM Final Real-time Localization
  89. GRB 260115A: AstroSat CZTI detection
  90. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  91. GRB 260115A: GECAM-B observation
  92. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  93. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  94. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  95. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  96. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  97. Fermi GRB 260115A: Global MASTER-Net observations report
  98. GRB 260115A: Fermi GBM Final Real-time Localization
  99. GRB260114A: STEP/T80S optical limits
  100. GRB 251222A: radio detection with the VLA

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