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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"

11525 results found.

  1. IPN triangulation of GRB 260121A
  2. GRB 260129B: Fermi GBM Final Localization
  3. GRB 260129A: Fermi GBM Final Localization
  4. IPN triangulation of GRB 260127B (short)
  5. GRB 260127B: Swift-XRT observations
  6. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  7. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  8. Fermi GRB 260127A: Global MASTER-Net observations report
  9. GRB 260127A: Fermi GBM Observation
  10. GRB 260127A: COLIBRÍ optical observations
  11. GRB 260127A: NOT optical observations
  12. GRB 260127B: Swift ToO observations
  13. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  14. GRB 260127B: GOTO candidate optical counterpart
  15. GRB 260127A: SVOM/C-GFT optical observations
  16. Fermi GRB 260127B: Global MASTER-Net observations report
  17. GRB 260127B: Fermi GBM Final Real-time Localization
  18. GRB 260127A: LCO optical afterglow discovery
  19. GRB 260127A: Fermi GBM Final Real-time Localization
  20. GRB 260125A: Swift-XRT observations
  21. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  22. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  23. Konus-Wind detection of GRB 260120B
  24. GRB 260125A: Swift ToO observations
  25. GRB 260125A: GOTO candidate optical counterpart
  26. Fermi GRB 260125B: Global MASTER-Net observations report
  27. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  28. GRB 260125B: Fermi GBM Final Real-time Localization
  29. GRB 260125A: Fermi GBM Final Real-time Localization
  30. GRB 260114A: SVOM/VT optical upper limits
  31. GRB 260120A: AstroSat CZTI detection
  32. GRB 260120B: SVOM/GRM observation
  33. GRB 260120A: GECAM-B observation
  34. GRB 260120B: AstroSat CZTI detection
  35. GRB 260114A: Insight-HXMT/HE detection
  36. GRB 260122A: Fermi GBM Final Real-time Localization
  37. Fermi GRB 260120C: Global MASTER-Net observations report
  38. GRB 260120B: Fermi GBM Observation
  39. GRB 260120B: COLIBRÍ optical upper limits
  40. GRB 260120B: SVOM/C-GFT optical counterpart detection
  41. GRB 260120C: Fermi GBM Final Real-time Localization
  42. GRB 260101A: 239Alferov CubeSat detection
  43. GRB 260120B: Fermi GBM Final Real-time Localization
  44. Fermi trigger No 790601190: Global MASTER-Net observations report
  45. Fermi trigger No 790570272: Global MASTER-Net observations report
  46. GRB 251202A: further radio observations with the VLA
  47. GRB 260120A: Fermi GBM Final Real-time Localization
  48. GRB 260115A: AstroSat CZTI detection
  49. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  50. GRB 260115A: GECAM-B observation
  51. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  52. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  53. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  54. Fermi GRB 260115A: Global MASTER-Net observations report
  55. GRB 260115A: Fermi GBM Final Real-time Localization
  56. GRB260114A: STEP/T80S optical limits
  57. GRB 251222A: radio detection with the VLA
  58. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  59. Konus-Wind detection of GRB 260114A
  60. GRB 260114A: 6 GHz VLA observations
  61. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  62. GRB 260114A : MITSuME Akeno optical upper limits
  63. GRB 260114A: COLIBRÍ optical upper limits
  64. GRB 260114A: TNG NIR upper limit
  65. GRB 260114A: NOT optical observations
  66. GRB 260114A: SVOM/GRM observation of a short burst
  67. GRB 260114A: GECAM-B observation of a short burst
  68. GRB 260114A: Mondy optical observations
  69. GRB 260114A: Fermi GBM observation
  70. GRB 260112B: GECAM-B observation
  71. GRB 260114A: GMG Optical Observation
  72. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  73. GRB 260114A: Fermi GBM Final Real-time Localization
  74. Konus-Wind detection of GRB 260101A
  75. GRB 260111A: Swift-XRT observations
  76. GRB 260111A: COLIBRÍ optical afterglow candidate
  77. GRB 260111A: GECAM-B observation of a burst
  78. GRB 260111A: Fermi GBM Observation
  79. GRB 260111A: GOTO optical upper limits
  80. GRB 260112B: Fermi GBM Final Real-time Localization
  81. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  82. GRB 260112A: Fermi GBM Final Real-time Localization
  83. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  84. Fermi GRB 260111A: Global MASTER-Net observations report
  85. GRB 260111A: Fermi GBM Final Real-time Localization
  86. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  87. GRB 260109B: Fermi GBM Final Real-time Localization
  88. GRB 260109A: Fermi GBM Final Real-time Localization
  89. Fermi GRB 260107A: Global MASTER-Net observations report
  90. GRB 260107A: Fermi GBM Final Real-time Localization
  91. Fermi GRB 260105A: Global MASTER-Net observations report
  92. GRB 260105B: Fermi GBM Detection
  93. GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
  94. GRB 260105A: SVOM/GRM observation
  95. GRB 260105B: SVOM/GRM observation
  96. Fermi GRB 260105B: Global MASTER-Net observations report
  97. GRB 260105B: Fermi GBM Final Real-time Localization
  98. GRB 260105A: Fermi GBM Final Real-time Localization
  99. GRB 260101A: COLIBRÍ optical upper limits
  100. GRB 260104C: Fermi GBM Final Real-time Localization

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