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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"

41745 results found.

  1. EP260509a: Einstein Probe detection of an X-ray transient
  2. GRB 260509A: Liverpool Telescope optical observations
  3. GRB 260510B: SVOM detection of a burst
  4. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  5. GRB 260509A: LCO optical observations
  6. SVOM GRB 260509A: MASTER-OAFA optical observation
  7. Fermi GRB 260510A: Global MASTER-Net observations report
  8. GRB 260509A: KAIT optical observations
  9. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) 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. GRB 260506B: AstroSat CZTI detection
  15. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  16. EP260507a: REM optical/NIR observations
  17. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  18. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  19. EP260507a: COLIBRÍ optical observations
  20. EP260507a: SVOM/VT optical observations
  21. EP260507a: NOT optical observations
  22. EP260507a: further Liverpool Telescope observations
  23. EP260507a: Liverpool Telescope optical upper limits
  24. EP260507a: GOTO optical counterpart detection
  25. EP260507a: TRT optical counterpart detection
  26. EP260507a: Kinder optical counterpart candidate
  27. EP260507a: LCO optical counterpart
  28. EP260507a: Einstein Probe detection of an X-ray transient
  29. GRB 260504B: AstroSat CZTI detection
  30. GRB 260504B: SVOM/ECLAIRs refined analysis
  31. EP260502a is likely a flaring star
  32. Fermi GRB 260506A: Global MASTER-Net observations report
  33. GRB 260503A: GECAM-B observation of a burst
  34. IceCube Alert 260505A: Global MASTER-Net observations report
  35. GRB 260430B: Glowbug gamma-ray detection
  36. GRB 260504B: SVOM/VT optical upper limits
  37. GRB 260421B: radio observation with the VLA
  38. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  39. Konus-Wind detection of GRB 260504B (short/hard)
  40. GRB 260504B: GECAM-B detection
  41. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  42. GRB 260504C: SVOM/GRM observation of short GRB
  43. GRB 260504B: SVOM/GRM spectral analysis
  44. GRB 260430B: AstroSat CZTI detection of a long burst
  45. GRB 260504B: SVOM/MXT refined analysis and potential detection
  46. GRB 260504B: EP-FXT upper limit
  47. GRB 260502A: SVOM/GRM observation of a short GRB
  48. GRB 260503A: SVOM/GRM observation of a GRB
  49. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  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. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  62. GRB 260502A: GECAM-B observation of a short burst
  63. IPN triangulation of a bright burst from SGR 1E1841-045
  64. The EP-WXT trigger 01709261576 is likely a flaring star
  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. EP260502a: Las Cumbres upper limit
  70. EP260502a: Einstein Probe detection of an X-ray transient
  71. GRB 260429A: SVOM/GRM observation of a short burst
  72. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  73. EP260429a: Global MASTER-Net observations report
  74. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  75. GRB 260424B: AstroSat CZTI detection
  76. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  77. EP260429a: LCO optical upper limits
  78. EP260430a: LCO optical upper limits
  79. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  80. GRB 260429A: Fermi GBM Detection
  81. Fermi GRB 260429A: Global MASTER-Net observations report
  82. EP260430a: Global MASTER-Net observations report
  83. EP260430a: Einstein Probe detection of an X-ray transient
  84. EP260429a: EP-WXT detection of a fast X-ray transient
  85. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  86. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  87. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  88. GRB 260428A: AstroSat CZTI detection
  89. Fermi GRB 260428A: Global MASTER-Net observations report
  90. EP260416a: Mondy and Terskol optical upper limits
  91. GRB 260424B: Glowbug gamma-ray detection of a short burst
  92. GRB 260424B: COLIBRÍ optical upper limit
  93. Konus-Wind detection of GRB 260424B
  94. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  95. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  96. IPN triangulation of GRB 260424B (short)
  97. GRB 260424B: SVOM/GRM detection of a short burst
  98. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  99. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  100. IceCube Alert 260425A: Global MASTER-Net observations report

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