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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"

37107 results found.

  1. GRB 260511A: BALROG localization (Fermi Trigger 800172815 / GRB 260511259)
  2. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  3. GRB 260511A: Fermi GBM Final Real-time Localization
  4. GRB 260510B: SVOM/VT optical upper limits
  5. GRB 260510C: SVOM/VT optical upper limits
  6. GRB 260510C: MAXI/GSC detection
  7. Fermi GBM Sub-Threshold Detection of GRB 260510B
  8. GRB 260510D: Fermi GBM Final Real-time Localization
  9. GRB 260510B: GOTO early upper limit
  10. GRB 260510C: SVOM detection of a burst
  11. GRB 260510C: Fermi GBM Final Real-time Localization
  12. GRB 260510A: GECAM-B observation
  13. GRB 260510B: LCO optical upper limits
  14. GRB 260509A: Liverpool Telescope optical observations
  15. GRB 260510B: SVOM detection of a burst
  16. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  17. GRB 260509A: LCO optical observations
  18. SVOM GRB 260509A: MASTER-OAFA optical observation
  19. Fermi GRB 260510A: Global MASTER-Net observations report
  20. GRB 260509A: KAIT optical observations
  21. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  22. GRB 260510A: Fermi GBM Final Real-time Localization
  23. GRB 260509A: SVOM/VT optical candidate with VHF data
  24. GRB 260509A: LCO optical counterpart detection
  25. GRB 260509A: GOTO optical counterpart candidate
  26. GRB 260509A: SVOM detection of a burst
  27. GRB 260506B: AstroSat CZTI detection
  28. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  29. GRB 260507A: Fermi GBM Final Real-time Localization
  30. EP260507a: Kinder optical counterpart candidate
  31. GRB 260504B: AstroSat CZTI detection
  32. GRB 260504B: SVOM/ECLAIRs refined analysis
  33. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  34. GRB 260506B: Fermi GBM Final Real-time Localization
  35. Fermi GRB 260506A: Global MASTER-Net observations report
  36. GRB 260506A: Fermi GBM Final Real-time Localization
  37. GRB 260503A: GECAM-B observation of a burst
  38. GRB 260430B: Glowbug gamma-ray detection
  39. GRB 260504B: SVOM/VT optical upper limits
  40. GRB 260421B: radio observation with the VLA
  41. Konus-Wind detection of GRB 260504B (short/hard)
  42. GRB 260504B: GECAM-B detection
  43. GRB 260504C: SVOM/GRM observation of short GRB
  44. GRB 260504B: SVOM/GRM spectral analysis
  45. GRB 260430B: AstroSat CZTI detection of a long burst
  46. GRB 260504B: SVOM/MXT refined analysis and potential detection
  47. GRB 260504B: EP-FXT upper limit
  48. GRB 260502A: SVOM/GRM observation of a short GRB
  49. GRB 260503A: SVOM/GRM observation of a GRB
  50. Konus-Wind detection of GRB 260415C
  51. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  52. Konus-Wind detection of GRB 260411C
  53. GRB 260504B: REM optical/NIR observations
  54. IPN triangulation of GRB 260429A
  55. IPN triangulation of GRB 260428A
  56. GRB 260504B: AST3-2 i-band upper limit
  57. GRB 260504B: LCO z-band upper limit
  58. SVOM GRB 260504B: MASTER-OAFA optical observations
  59. GRB 260504B: SVOM detection of a short burst
  60. Fermi GRB 260504A: Global MASTER-Net observations report
  61. GRB 260504A: Fermi GBM Final Real-time Localization
  62. GRB 260503A: Fermi GBM Final Real-time Localization
  63. GRB 260502A: GECAM-B observation of a short burst
  64. GRB 260502A: Fermi GBM Final Localization
  65. GRB 260429B / EP260429a: EP-FXT follow-up observation
  66. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  67. GRB 260429B / EP260429a: AstroSat CZTI detection
  68. EP260502a: BOOTES-7: early optical upper limit
  69. GRB 260429A: SVOM/GRM observation of a short burst
  70. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  71. GRB 260424B: AstroSat CZTI detection
  72. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  73. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  74. GRB 260429A: Fermi GBM Detection
  75. Fermi GRB 260429A: Global MASTER-Net observations report
  76. GRB 260429A: Fermi GBM Final Real-time Localization
  77. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  78. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  79. GRB 260428A: AstroSat CZTI detection
  80. Fermi GRB 260428A: Global MASTER-Net observations report
  81. EP260416a: Mondy and Terskol optical upper limits
  82. GRB 260424B: Glowbug gamma-ray detection of a short burst
  83. GRB 260424B: COLIBRÍ optical upper limit
  84. Konus-Wind detection of GRB 260424B
  85. GRB 260428A: Fermi GBM Final Real-time Localization
  86. GRB 260424C: Fermi GBM Final Localization
  87. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  88. IPN triangulation of GRB 260424B (short)
  89. GRB 260424B: SVOM/GRM detection of a short burst
  90. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  91. GRB 260401A: cubesat Avion detection
  92. GRB 260424A: AstroSat CZTI detection of a long burst
  93. GRB 260421B: Kilonova-Catcher optical afterglow detection
  94. GRB 260421B: Insight-HXMT/HE detection
  95. The EP-WXT trigger 01709258652: Mondy optical observations
  96. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  97. EP260416a: Mondy optical observations
  98. GRB 260421B: SVOM/ECLAIRs refined analysis
  99. GRB 260421B: 3.6m DOT optical observation
  100. EP260416a: ZTSh R band observations

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