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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"

44281 results found.

  1. GRB 260510C: MAXI/GSC detection
  2. EP260509a: Global MASTER-Net observations report
  3. Fermi GBM Sub-Threshold Detection of GRB 260510B
  4. GRB 260510D: Fermi GBM Final Real-time Localization
  5. GRB 260510B: GOTO early upper limit
  6. GRB 260510C: SVOM detection of a burst
  7. GRB 260510C: Fermi GBM Final Real-time Localization
  8. GRB 260510A: GECAM-B observation
  9. GRB 260510B: LCO optical upper limits
  10. EP260509a: Einstein Probe detection of an X-ray transient
  11. GRB 260509A: Liverpool Telescope optical observations
  12. GRB 260510B: SVOM detection of a burst
  13. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  14. GRB 260509A: LCO optical observations
  15. SVOM GRB 260509A: MASTER-OAFA optical observation
  16. Fermi GRB 260510A: Global MASTER-Net observations report
  17. GRB 260509A: KAIT optical observations
  18. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  19. GRB 260510A: Fermi GBM Final Real-time Localization
  20. GRB 260509A: SVOM/VT optical candidate with VHF data
  21. GRB 260509A: LCO optical counterpart detection
  22. GRB 260509A: GOTO optical counterpart candidate
  23. GRB 260509A: SVOM detection of a burst
  24. GRB 260506B: AstroSat CZTI detection
  25. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  26. EP260507a: REM optical/NIR observations
  27. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  28. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  29. EP260507a: COLIBRÍ optical observations
  30. EP260507a: SVOM/VT optical observations
  31. EP260507a: NOT optical observations
  32. EP260507a: further Liverpool Telescope observations
  33. EP260507a: Liverpool Telescope optical upper limits
  34. GRB 260507A: Fermi GBM Final Real-time Localization
  35. EP260507a: GOTO optical counterpart detection
  36. EP260507a: TRT optical counterpart detection
  37. EP260507a: Kinder optical counterpart candidate
  38. EP260507a: LCO optical counterpart
  39. EP260507a: Einstein Probe detection of an X-ray transient
  40. GRB 260504B: AstroSat CZTI detection
  41. GRB 260504B: SVOM/ECLAIRs refined analysis
  42. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  43. GRB 260506B: Fermi GBM Final Real-time Localization
  44. EP260502a is likely a flaring star
  45. Fermi GRB 260506A: Global MASTER-Net observations report
  46. GRB 260506A: Fermi GBM Final Real-time Localization
  47. GRB 260503A: GECAM-B observation of a burst
  48. IceCube Alert 260505A: Global MASTER-Net observations report
  49. GRB 260430B: Glowbug gamma-ray detection
  50. GRB 260504B: SVOM/VT optical upper limits
  51. GRB 260421B: radio observation with the VLA
  52. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  53. Konus-Wind detection of GRB 260504B (short/hard)
  54. GRB 260504B: GECAM-B detection
  55. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  56. GRB 260504C: SVOM/GRM observation of short GRB
  57. GRB 260504B: SVOM/GRM spectral analysis
  58. GRB 260430B: AstroSat CZTI detection of a long burst
  59. GRB 260504B: SVOM/MXT refined analysis and potential detection
  60. GRB 260504B: EP-FXT upper limit
  61. GRB 260502A: SVOM/GRM observation of a short GRB
  62. GRB 260503A: SVOM/GRM observation of a GRB
  63. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  64. Konus-Wind detection of GRB 260415C
  65. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  66. Konus-Wind detection of GRB 260411C
  67. GRB 260504B: REM optical/NIR observations
  68. IPN triangulation of GRB 260429A
  69. IPN triangulation of GRB 260428A
  70. GRB 260504B: AST3-2 i-band upper limit
  71. GRB 260504B: LCO z-band upper limit
  72. SVOM GRB 260504B: MASTER-OAFA optical observations
  73. GRB 260504B: SVOM detection of a short burst
  74. Fermi GRB 260504A: Global MASTER-Net observations report
  75. GRB 260504A: Fermi GBM Final Real-time Localization
  76. GRB 260503A: Fermi GBM Final Real-time Localization
  77. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  78. GRB 260502A: GECAM-B observation of a short burst
  79. IPN triangulation of a bright burst from SGR 1E1841-045
  80. GRB 260502A: Fermi GBM Final Localization
  81. The EP-WXT trigger 01709261576 is likely a flaring star
  82. GRB 260429B / EP260429a: EP-FXT follow-up observation
  83. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  84. GRB 260429B / EP260429a: AstroSat CZTI detection
  85. EP260502a: BOOTES-7: early optical upper limit
  86. EP260502a: Las Cumbres upper limit
  87. EP260502a: Einstein Probe detection of an X-ray transient
  88. GRB 260429A: SVOM/GRM observation of a short burst
  89. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  90. EP260429a: Global MASTER-Net observations report
  91. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  92. GRB 260424B: AstroSat CZTI detection
  93. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  94. EP260429a: LCO optical upper limits
  95. EP260430a: LCO optical upper limits
  96. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  97. GRB 260429A: Fermi GBM Detection
  98. Fermi GRB 260429A: Global MASTER-Net observations report
  99. EP260430a: Global MASTER-Net observations report
  100. EP260430a: Einstein Probe detection of an X-ray transient

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