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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').
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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"

36143 results found.

  1. GRB 260204A: LCO optical upper limits
  2. GRB 260204B: Fermi GBM Final Real-time Localization
  3. GRB 260204A: SVOM detection of a burst
  4. GRB 260121A: 239Alferov CubeSat detection
  5. Konus-Wind detection of GRB 260121A
  6. GRB 260131A/B: OHP/T193 optical observations
  7. GRB 260131A: KAIT optical observations
  8. GRB 251230A: MeerLICHT afterglow detection
  9. GRB 260131A: FTW optical and NIR observations
  10. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  11. GRID detection of GRB 260131A/B
  12. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  13. GRB 260130A: Insight-HXMT/HE detection
  14. GRB 260130A: GECAM-B observation of a short burst
  15. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  16. GRB 260131A/B: EP/FXT X-ray afterglow detection
  17. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  18. GRB 260127B: Insight-HXMT/HE detection
  19. GRB 260127B: GECAM-B observation of a short burst
  20. GRB 260127A: GECAM-B observation
  21. GRB 260131A: NOT spectroscopic redshift z = 1.434
  22. Konus-Wind detection of GRB 260128A / EP260128a
  23. GRB 260131A: Insight-HXMT/HE detection
  24. Konus-Wind detection of GRB 260131A/B
  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: VLT/X-shooter spectroscopic redshift z = 0.937
  29. GRB 260131B: MAXI/GSC detection
  30. GRB 260131A: Fermi GBM Final Real-time Localization
  31. GRB 260127B: AstroSat CZTI detection
  32. GRB 260130A: Fermi GBM Detection
  33. GRB 260127B: Fermi GBM Detection
  34. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  35. Fermi GRB 260130A: Global MASTER-Net observations report
  36. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  37. GRB 260130A: Fermi GBM Final Real-time Localization
  38. Fermi GRB 260129A: Global MASTER-Net observations report
  39. GRB 260128B: LCO optical upper limits
  40. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  41. IPN triangulation of GRB 260121A
  42. GRB 260127A: Swift-BAT refined analysis
  43. GRB 260129B: Fermi GBM Final Localization
  44. GRB 260128B: SVOM detection of a burst through offline search
  45. GRB 260129A: Fermi GBM Final Localization
  46. IPN triangulation of GRB 260127B (short)
  47. GRB 260127B: Swift-XRT observations
  48. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  49. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  50. Fermi GRB 260127A: Global MASTER-Net observations report
  51. GRB 260127A: Fermi GBM Observation
  52. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  53. GRB 260127A: COLIBRÍ optical observations
  54. GRB 260127A: NOT optical observations
  55. GRB 260127B: Swift ToO observations
  56. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  57. GRB 260127A: Swift-XRT refined Analysis
  58. GRB 260127B: GOTO candidate optical counterpart
  59. GRB 260127A: SVOM/C-GFT optical observations
  60. GRB 260127A: Enhanced Swift-XRT position
  61. Fermi GRB 260127B: Global MASTER-Net observations report
  62. GRB 260127B: Fermi GBM Final Real-time Localization
  63. GRB 260127A: Prompt enhanced Swift-XRT position
  64. Swift GRB 260127A: Global MASTER-Net observations report
  65. GRB 260127A: LCO optical afterglow discovery
  66. GRB 260127A: Swift detection of a burst
  67. GRB 260127A: Fermi GBM Final Real-time Localization
  68. GRB 260125A: Swift-XRT observations
  69. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  70. Konus-Wind detection of GRB 260120B
  71. GRB 251222A: SVOM/ECLAIRs refined analysis
  72. GRB 260125A: Swift ToO observations
  73. GRB 260125A: GOTO candidate optical counterpart
  74. Fermi GRB 260125B: Global MASTER-Net observations report
  75. GRB 260125B: Fermi GBM Final Real-time Localization
  76. GRB 260125A: Fermi GBM Final Real-time Localization
  77. GRB 260114A: SVOM/VT optical upper limits
  78. GRB 260120A: AstroSat CZTI detection
  79. GRB 260122B: Swift-BAT refined analysis
  80. GRB 260120B: SVOM/GRM observation
  81. GRB 260120A: GECAM-B observation
  82. GRB 260120B: AstroSat CZTI detection
  83. GRB 260114A: Insight-HXMT/HE detection
  84. GRB 260122B: Swift detection of a burst
  85. EP260119a: Assy AZT-20 optical observations
  86. EP260119a: Mondy and SAO RAS optical upper limits
  87. GRB 260122A: Fermi GBM Final Real-time Localization
  88. Fermi GRB 260120C: Global MASTER-Net observations report
  89. GRB 260120B: Swift-BAT refined analysis
  90. GRB 260120B: Swift-XRT refined Analysis
  91. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  92. GRB 260120B: Fermi GBM Observation
  93. GRB 260120B: Swift/UVOT Detection
  94. GRB 260120B: COLIBRÍ optical upper limits
  95. GRB 260120B: Enhanced Swift-XRT position
  96. GRB 260120B: SVOM/C-GFT optical counterpart detection
  97. GRB 260120C: Fermi GBM Final Real-time Localization
  98. GRB 260101A: 239Alferov CubeSat detection
  99. GRB 260120B: Swift detection of a burst
  100. GRB 260120B: Fermi GBM Final Real-time Localization

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