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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"

40525 results found.

  1. GRB 260510D: Fermi GBM Final Real-time Localization
  2. GRB 260510B: GOTO early upper limit
  3. GRB 260510C: SVOM detection of a burst
  4. GRB 260510C: Fermi GBM Final Real-time Localization
  5. GRB 260510A: GECAM-B observation
  6. GRB 260510B: LCO optical upper limits
  7. EP260509a: Einstein Probe detection of an X-ray transient
  8. GRB 260509A: Liverpool Telescope optical observations
  9. GRB 260510B: SVOM detection of a burst
  10. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  11. GRB 260509A: LCO optical observations
  12. SVOM GRB 260509A: MASTER-OAFA optical observation
  13. Fermi GRB 260510A: Global MASTER-Net observations report
  14. GRB 260509A: KAIT optical observations
  15. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  16. GRB 260510A: Fermi GBM Final Real-time Localization
  17. GRB 260509A: SVOM/VT optical candidate with VHF data
  18. GRB 260509A: LCO optical counterpart detection
  19. GRB 260509A: GOTO optical counterpart candidate
  20. GRB 260509A: SVOM detection of a burst
  21. GRB 260506B: AstroSat CZTI detection
  22. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  23. EP260507a: REM optical/NIR observations
  24. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  25. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  26. EP260507a: COLIBRÍ optical observations
  27. EP260507a: SVOM/VT optical observations
  28. EP260507a: NOT optical observations
  29. EP260507a: further Liverpool Telescope observations
  30. EP260507a: Liverpool Telescope optical upper limits
  31. GRB 260507A: Fermi GBM Final Real-time Localization
  32. EP260507a: GOTO optical counterpart detection
  33. EP260507a: TRT optical counterpart detection
  34. EP260507a: Kinder optical counterpart candidate
  35. EP260507a: LCO optical counterpart
  36. EP260507a: Einstein Probe detection of an X-ray transient
  37. GRB 260504B: AstroSat CZTI detection
  38. GRB 260504B: SVOM/ECLAIRs refined analysis
  39. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  40. GRB 260506B: Fermi GBM Final Real-time Localization
  41. EP260502a is likely a flaring star
  42. Fermi GRB 260506A: Global MASTER-Net observations report
  43. GRB 260506A: Fermi GBM Final Real-time Localization
  44. GRB 260503A: GECAM-B observation of a burst
  45. IceCube Alert 260505A: Global MASTER-Net observations report
  46. GRB 260430B: Glowbug gamma-ray detection
  47. GRB 260504B: SVOM/VT optical upper limits
  48. GRB 260421B: radio observation with the VLA
  49. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  50. Konus-Wind detection of GRB 260504B (short/hard)
  51. GRB 260504B: GECAM-B detection
  52. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  53. GRB 260504C: SVOM/GRM observation of short GRB
  54. GRB 260504B: SVOM/GRM spectral analysis
  55. GRB 260430B: AstroSat CZTI detection of a long burst
  56. GRB 260504B: SVOM/MXT refined analysis and potential detection
  57. GRB 260504B: EP-FXT upper limit
  58. GRB 260502A: SVOM/GRM observation of a short GRB
  59. GRB 260503A: SVOM/GRM observation of a GRB
  60. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  61. Konus-Wind detection of GRB 260415C
  62. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  63. Konus-Wind detection of GRB 260411C
  64. GRB 260504B: REM optical/NIR observations
  65. GRB 260504B: AST3-2 i-band upper limit
  66. GRB 260504B: LCO z-band upper limit
  67. SVOM GRB 260504B: MASTER-OAFA optical observations
  68. GRB 260504B: SVOM detection of a short burst
  69. Fermi GRB 260504A: Global MASTER-Net observations report
  70. GRB 260504A: Fermi GBM Final Real-time Localization
  71. GRB 260503A: Fermi GBM Final Real-time Localization
  72. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  73. GRB 260502A: GECAM-B observation of a short burst
  74. IPN triangulation of a bright burst from SGR 1E1841-045
  75. GRB 260502A: Fermi GBM Final Localization
  76. The EP-WXT trigger 01709261576 is likely a flaring star
  77. GRB 260429B / EP260429a: EP-FXT follow-up observation
  78. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  79. GRB 260429B / EP260429a: AstroSat CZTI detection
  80. EP260502a: BOOTES-7: early optical upper limit
  81. EP260502a: Las Cumbres upper limit
  82. EP260502a: Einstein Probe detection of an X-ray transient
  83. GRB 260429A: SVOM/GRM observation of a short burst
  84. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  85. EP260429a: Global MASTER-Net observations report
  86. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  87. GRB 260424B: AstroSat CZTI detection
  88. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  89. EP260429a: LCO optical upper limits
  90. EP260430a: LCO optical upper limits
  91. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  92. GRB 260429A: Fermi GBM Detection
  93. Fermi GRB 260429A: Global MASTER-Net observations report
  94. EP260430a: Global MASTER-Net observations report
  95. EP260430a: Einstein Probe detection of an X-ray transient
  96. EP260429a: EP-WXT detection of a fast X-ray transient
  97. GRB 260429A: Fermi GBM Final Real-time Localization
  98. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  99. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  100. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube

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