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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"

5531 results found.

  1. EP260507a: Xinglong Schmidt optical counterpart detection
  2. Fermi GRB 260512A: Global MASTER-Net observations report
  3. EP260512a: COLIBRÍ optical upper limits
  4. MASS-Cube (GRID 2.0) detection of GRB 260507A
  5. GRB 260511B: SAO RAS optical observations
  6. GRB 260511B: GOTO optical counterpart detection
  7. GRB 260511B: SVOM/VT optical observations
  8. Fermi GRB 260511A: Global MASTER-Net observations report
  9. GRB 260509A: Liverpool Telescope optical observations
  10. GRB 260509A: SVOM/VT optical candidate with VHF data
  11. GRB 260509A: LCO optical counterpart detection
  12. GRB 260509A: GOTO optical counterpart candidate
  13. GRB 260509A: SVOM detection of a burst
  14. EP260507a: Liverpool Telescope optical upper limits
  15. GRB 260504B: AstroSat CZTI detection
  16. IceCube Alert 260505A: Global MASTER-Net observations report
  17. Konus-Wind detection of GRB 260504B (short/hard)
  18. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  19. GRB 260504B: REM optical/NIR observations
  20. IPN triangulation of GRB 260429A
  21. GRB 260504B: AST3-2 i-band upper limit
  22. GRB 260504B: LCO z-band upper limit
  23. SVOM GRB 260504B: MASTER-OAFA optical observations
  24. Fermi GRB 260504A: Global MASTER-Net observations report
  25. GRB 260504A: Fermi GBM Final Real-time Localization
  26. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  27. Fermi GRB 260429A: Global MASTER-Net observations report
  28. EP260430a: Global MASTER-Net observations report
  29. Fermi GRB 260428A: Global MASTER-Net observations report
  30. EP260416a: Mondy and Terskol optical upper limits
  31. Fermi trigger No 798737427: Global MASTER-Net observations report
  32. Fermi GRB 260421C: Global MASTER-Net observations report
  33. Fermi GRB 260421B: Global MASTER-Net observations report
  34. Fermi GRB 260421A: Global MASTER-Net observations report
  35. GRB 260419A: Fermi GBM Final Real-time Localization
  36. Fermi GRB 260417B: Global MASTER-Net observations report
  37. EP260416a: Ondrejov D50 optical detection
  38. EP260417a: Global MASTER-Net observations report
  39. Fermi GRB 260417A: Global MASTER-Net observations report
  40. EP260416a: LCO observations confirm end of flaring phase
  41. Fermi trigger No 797912738: Global MASTER-Net observations report
  42. The EP-WXT trigger 01709260122 is likely a flaring star
  43. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  44. EP260409a: SVOM/VT optical upper limits
  45. EP260409a: COLIBRÍ optical upper limits
  46. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  47. EP260409a: Global MASTER-Net observations report
  48. GRB 260407A: Glowbug gamma-ray detection
  49. GRB 260407A: Fermi GBM Final Real-time Localization
  50. EP260405a: Global MASTER-Net observations report
  51. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  52. Fermi trigger No 797039833: Global MASTER-Net observations report
  53. EP260324A / AT 2026hir: COLIBRÍ optical observations
  54. GRB 260401A: MAXI/GSC detection
  55. EP260329b: J-band upper limits with WINTER
  56. EP260327a: Global MASTER-Net observations report
  57. IPN triangulation of GRB 260320A
  58. EP260321a: Upper limits from a neutrino search with IceCube
  59. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  60. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  61. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  62. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  63. EP260321a: Global MASTER-Net observations report
  64. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  65. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  66. GRB 260310A / AT2026fgk: LCO optical observations
  67. IceCube-260315A: COLIBRÍ optical observations
  68. EP260314a: optical upper limit with Kinder observations
  69. GRB 260310A / AT 2026fgk: iTelescope optical observations
  70. EP260314a: COLIBRÍ optical upper limit
  71. GRID detection of GRB 260312B
  72. EP260314a: Global MASTER-Net observations report
  73. Fermi trigger No 795185313: Global MASTER-Net observations report
  74. GRB 260310A / AT2026fgk: SAO RAS optical observations
  75. Fermi GRB 260313A: Global MASTER-Net observations report
  76. GRB 260312B: AstroSat CZTI detection
  77. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  78. GRB 260312B: Glowbug gamma-ray detection
  79. Fermi GRB 260311B: Global MASTER-Net observations report
  80. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  81. GRB 260312B: Fermi GBM Final Real-time Localization
  82. EP260306a: Mondy optical upper limit
  83. Fermi GRB 260310B: Global MASTER-Net observations report
  84. GRB 260207A: TESS Detection and Possible VLA Counterpart
  85. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  86. GRID detection of GRB 260223A
  87. GRB 260225A: WINTER J-band upper limit
  88. LAT GRB260226.44: Global MASTER-Net observations report
  89. Fermi GRB 260226A: Global MASTER-Net observations report
  90. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  91. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  92. EP260223a: Xinglong optical upper limit
  93. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  94. Fermi GRB 260223A: Global MASTER-Net observations report
  95. GRB 260223A: Fermi GBM Final Real-time Localization
  96. GRB 260222A: Fermi GBM Final Real-time Localization
  97. EP260221a: Xinglong optical upper limit
  98. IceCube Alert 260217A: Global MASTER-Net observations report
  99. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  100. GRB 260217A: Fermi GBM Final Localization

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