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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"

27776 results found.

  1. GRB 260208A: Fermi GBM Observation
  2. GRB 260208B: Swift-XRT observations
  3. GRB 260204A: Swift/UVOT Upper Limits
  4. GRB 260208A: 1.3m DFOT optical detection
  5. GRB 260208B: EP-FXT observation
  6. GRB 260208A: NOT spectroscopic redshift z = 2.36
  7. GRB 260208A: Liverpool Telescope optical detection
  8. GRB 260208B: SVOM/VT optical candidate
  9. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  10. GRB 260209A: Fermi GBM Final Real-time Localization
  11. GRB 260208A: SVOM/VT optical observation
  12. GRB 260208D: Fermi GBM Final Real-time Localization
  13. GRB 260208A: Swift-XRT observations
  14. GRB 260208B: Swift ToO observations
  15. GRB 260208B: Fermi GBM Detection
  16. GRB 260208B: Fermi-LAT detection
  17. GRB 260208C: Fermi GBM Final Real-time Localization
  18. GRB 260208A: Fermi-LAT detection
  19. GRB 260208A: Swift ToO observations
  20. GRB 260208A: Fermi GBM Classification Correction
  21. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  22. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  23. GRB 260208B: Fermi GBM Final Real-time Localization
  24. GRB 260208A: Fermi GBM Final Real-time Localization
  25. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  26. GRB 260207A : MASTER optical counterpart discovery
  27. GRB 260206A: Swift-XRT observations
  28. GRB 260207B: Fermi GBM Final Real-time Localization
  29. GRB 260207A: Fermi GBM Final Localization
  30. EP260131a: VLA detection
  31. GRB 260206A: Tiled Swift observations
  32. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  33. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  34. GRB 260204A: Swift-XRT observations
  35. GRB 260204A: LCO optical afterglow detection
  36. GRB 260204A: SVOM/VT optical candidate
  37. Fermi GBM Sub-Threshold Detection of GRB 260204A
  38. GRB 260204B: Fermi GBM Final Real-time Localization
  39. GRB 260204A: SVOM detection of a burst
  40. GRB 260121A: 239Alferov CubeSat detection
  41. Konus-Wind detection of GRB 260121A
  42. GRB 251230A: MeerLICHT afterglow detection
  43. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  44. GRID detection of GRB 260131A/B
  45. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  46. GRB 260130A: Insight-HXMT/HE detection
  47. GRB 260131A/B: EP/FXT X-ray afterglow detection
  48. GRB 260127B: Insight-HXMT/HE detection
  49. GRB 260127A: GECAM-B observation
  50. GRB 260131A: NOT spectroscopic redshift z = 1.434
  51. Konus-Wind detection of GRB 260128A / EP260128a
  52. GRB 260131A: Insight-HXMT/HE detection
  53. Konus-Wind detection of GRB 260131A/B
  54. EP260131a: Xinglong optical upper limit
  55. EP260131a: COLIBRÍ observations of slow optical fading
  56. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  57. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  58. GRB 260131B: MAXI/GSC detection
  59. GRB 260131A: Fermi GBM Final Real-time Localization
  60. EP260131a: Las Cumbres detection of an optical counterpart
  61. GRB 260127B: AstroSat CZTI detection
  62. GRB 260130A: Fermi GBM Detection
  63. EP260131a: Einstein Probe detection of an X-ray transient
  64. GRB 260127B: Fermi GBM Detection
  65. GRB 260130A: Fermi GBM Final Real-time Localization
  66. IPN triangulation of GRB 260121A
  67. GRB 260127A: Swift-BAT refined analysis
  68. GRB 260129B: Fermi GBM Final Localization
  69. GRB 260128B: SVOM detection of a burst through offline search
  70. GRB 260129A: Fermi GBM Final Localization
  71. IPN triangulation of GRB 260127B (short)
  72. GRB 260127B: Swift-XRT observations
  73. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  74. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  75. EP260128a: NOT optical counterpart candidate
  76. EP260128a: Liverpool Telescope optical observations and possible counterpart
  77. EP260126a: SVOM/VT optical upperlimit
  78. EP260128a: Einstein Probe detection of an X-ray transient
  79. GRB 260127A: Fermi GBM Observation
  80. GRB 260127A: COLIBRÍ optical observations
  81. GRB 260127B: Swift ToO observations
  82. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  83. GRB 260127A: Swift-XRT refined Analysis
  84. GRB 260127A: SVOM/C-GFT optical observations
  85. GRB 260127A: Enhanced Swift-XRT position
  86. GRB 260127B: Fermi GBM Final Real-time Localization
  87. GRB 260127A: Prompt enhanced Swift-XRT position
  88. Swift GRB 260127A: Global MASTER-Net observations report
  89. GRB 260127A: Swift detection of a burst
  90. GRB 260127A: Fermi GBM Final Real-time Localization
  91. GRB 260125A: Swift-XRT observations
  92. EP260126a: EP-FXT follow-up observation
  93. EP260126a: Liverpool Telescope optical upper limits
  94. EP260126a: Further NOT optical upper limits
  95. EP260126a: Einstein Probe detection of a fast X-ray transient
  96. Konus-Wind detection of GRB 260120B
  97. GRB 260125A: Swift ToO observations
  98. GRB 260125A: GOTO candidate optical counterpart
  99. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  100. GRB 260125B: Fermi GBM Final Real-time Localization

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