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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"

36210 results found.

  1. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  2. GRB 260511A: TRT optical counterpart detection
  3. GRB 260511A: SVOM detection of a bright burst
  4. GRB 260511A: BALROG localization (Fermi Trigger 800172815 / GRB 260511259)
  5. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  6. GRB 260511A: Fermi GBM Final Real-time Localization
  7. GRB 260510B: SVOM/VT optical upper limits
  8. GRB 260510C: SVOM/VT optical upper limits
  9. GRB 260510C: MAXI/GSC detection
  10. Fermi GBM Sub-Threshold Detection of GRB 260510B
  11. GRB 260510D: Fermi GBM Final Real-time Localization
  12. GRB 260510B: GOTO early upper limit
  13. GRB 260510C: SVOM detection of a burst
  14. GRB 260510C: Fermi GBM Final Real-time Localization
  15. GRB 260510A: GECAM-B observation
  16. GRB 260510B: LCO optical upper limits
  17. GRB 260509A: Liverpool Telescope optical observations
  18. GRB 260510B: SVOM detection of a burst
  19. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  20. GRB 260509A: LCO optical observations
  21. SVOM GRB 260509A: MASTER-OAFA optical observation
  22. Fermi GRB 260510A: Global MASTER-Net observations report
  23. GRB 260509A: KAIT optical observations
  24. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  25. GRB 260510A: Fermi GBM Final Real-time Localization
  26. GRB 260509A: SVOM/VT optical candidate with VHF data
  27. GRB 260509A: LCO optical counterpart detection
  28. GRB 260509A: GOTO optical counterpart candidate
  29. GRB 260509A: SVOM detection of a burst
  30. GRB 260506B: AstroSat CZTI detection
  31. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  32. GRB 260507A: Fermi GBM Final Real-time Localization
  33. EP260507a: Kinder optical counterpart candidate
  34. GRB 260504B: AstroSat CZTI detection
  35. GRB 260504B: SVOM/ECLAIRs refined analysis
  36. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  37. GRB 260506B: Fermi GBM Final Real-time Localization
  38. Fermi GRB 260506A: Global MASTER-Net observations report
  39. GRB 260506A: Fermi GBM Final Real-time Localization
  40. GRB 260503A: GECAM-B observation of a burst
  41. GRB 260430B: Glowbug gamma-ray detection
  42. GRB 260504B: SVOM/VT optical upper limits
  43. GRB 260421B: radio observation with the VLA
  44. Konus-Wind detection of GRB 260504B (short/hard)
  45. GRB 260504B: GECAM-B detection
  46. GRB 260504C: SVOM/GRM observation of short GRB
  47. GRB 260504B: SVOM/GRM spectral analysis
  48. GRB 260430B: AstroSat CZTI detection of a long burst
  49. GRB 260504B: SVOM/MXT refined analysis and potential detection
  50. GRB 260504B: EP-FXT upper limit
  51. GRB 260502A: SVOM/GRM observation of a short GRB
  52. GRB 260503A: SVOM/GRM observation of a GRB
  53. Konus-Wind detection of GRB 260415C
  54. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  55. Konus-Wind detection of GRB 260411C
  56. GRB 260504B: REM optical/NIR observations
  57. IPN triangulation of GRB 260429A
  58. IPN triangulation of GRB 260428A
  59. GRB 260504B: AST3-2 i-band upper limit
  60. GRB 260504B: LCO z-band upper limit
  61. SVOM GRB 260504B: MASTER-OAFA optical observations
  62. GRB 260504B: SVOM detection of a short burst
  63. Fermi GRB 260504A: Global MASTER-Net observations report
  64. GRB 260504A: Fermi GBM Final Real-time Localization
  65. GRB 260503A: Fermi GBM Final Real-time Localization
  66. GRB 260502A: GECAM-B observation of a short burst
  67. GRB 260502A: Fermi GBM Final Localization
  68. GRB 260429B / EP260429a: EP-FXT follow-up observation
  69. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  70. GRB 260429B / EP260429a: AstroSat CZTI detection
  71. EP260502a: BOOTES-7: early optical upper limit
  72. GRB 260429A: SVOM/GRM observation of a short burst
  73. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  74. GRB 260424B: AstroSat CZTI detection
  75. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  76. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  77. GRB 260429A: Fermi GBM Detection
  78. Fermi GRB 260429A: Global MASTER-Net observations report
  79. GRB 260429A: Fermi GBM Final Real-time Localization
  80. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  81. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  82. GRB 260428A: AstroSat CZTI detection
  83. Fermi GRB 260428A: Global MASTER-Net observations report
  84. EP260416a: Mondy and Terskol optical upper limits
  85. GRB 260424B: Glowbug gamma-ray detection of a short burst
  86. GRB 260424B: COLIBRÍ optical upper limit
  87. Konus-Wind detection of GRB 260424B
  88. GRB 260428A: Fermi GBM Final Real-time Localization
  89. GRB 260424C: Fermi GBM Final Localization
  90. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  91. IPN triangulation of GRB 260424B (short)
  92. GRB 260424B: SVOM/GRM detection of a short burst
  93. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  94. GRB 260401A: cubesat Avion detection
  95. GRB 260424A: AstroSat CZTI detection of a long burst
  96. GRB 260421B: Kilonova-Catcher optical afterglow detection
  97. GRB 260421B: Insight-HXMT/HE detection
  98. The EP-WXT trigger 01709258652: Mondy optical observations
  99. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  100. EP260416a: Mondy optical observations

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