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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"

38156 results found.

  1. GRB 260506B: AstroSat CZTI detection
  2. EP260507a: REM optical/NIR observations
  3. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  4. EP260507a: COLIBRÍ optical observations
  5. GRB 260507A: Fermi GBM Final Real-time Localization
  6. EP260507a: TRT optical counterpart detection
  7. EP260507a: LCO optical counterpart
  8. GRB 260504B: AstroSat CZTI detection
  9. GRB 260504B: SVOM/ECLAIRs refined analysis
  10. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  11. GRB 260506B: Fermi GBM Final Real-time Localization
  12. Fermi GRB 260506A: Global MASTER-Net observations report
  13. GRB 260506A: Fermi GBM Final Real-time Localization
  14. GRB 260503A: GECAM-B observation of a burst
  15. IceCube Alert 260505A: Global MASTER-Net observations report
  16. GRB 260430B: Glowbug gamma-ray detection
  17. GRB 260504B: SVOM/VT optical upper limits
  18. GRB 260421B: radio observation with the VLA
  19. Konus-Wind detection of GRB 260504B (short/hard)
  20. GRB 260504B: GECAM-B detection
  21. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  22. GRB 260504C: SVOM/GRM observation of short GRB
  23. GRB 260504B: SVOM/GRM spectral analysis
  24. GRB 260430B: AstroSat CZTI detection of a long burst
  25. GRB 260504B: SVOM/MXT refined analysis and potential detection
  26. GRB 260504B: EP-FXT upper limit
  27. GRB 260502A: SVOM/GRM observation of a short GRB
  28. GRB 260503A: SVOM/GRM observation of a GRB
  29. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  30. Konus-Wind detection of GRB 260415C
  31. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  32. Konus-Wind detection of GRB 260411C
  33. GRB 260504B: REM optical/NIR observations
  34. IPN triangulation of GRB 260429A
  35. IPN triangulation of GRB 260428A
  36. GRB 260504B: AST3-2 i-band upper limit
  37. GRB 260504B: LCO z-band upper limit
  38. SVOM GRB 260504B: MASTER-OAFA optical observations
  39. GRB 260504B: SVOM detection of a short burst
  40. Fermi GRB 260504A: Global MASTER-Net observations report
  41. GRB 260504A: Fermi GBM Final Real-time Localization
  42. GRB 260503A: Fermi GBM Final Real-time Localization
  43. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  44. GRB 260502A: GECAM-B observation of a short burst
  45. GRB 260502A: Fermi GBM Final Localization
  46. GRB 260429B / EP260429a: EP-FXT follow-up observation
  47. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  48. GRB 260429B / EP260429a: AstroSat CZTI detection
  49. GRB 260429A: SVOM/GRM observation of a short burst
  50. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  51. EP260429a: Global MASTER-Net observations report
  52. GRB 260424B: AstroSat CZTI detection
  53. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  54. EP260429a: LCO optical upper limits
  55. EP260430a: LCO optical upper limits
  56. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  57. GRB 260429A: Fermi GBM Detection
  58. Fermi GRB 260429A: Global MASTER-Net observations report
  59. EP260430a: Global MASTER-Net observations report
  60. GRB 260429A: Fermi GBM Final Real-time Localization
  61. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  62. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  63. GRB 260428A: AstroSat CZTI detection
  64. Fermi GRB 260428A: Global MASTER-Net observations report
  65. EP260416a: Mondy and Terskol optical upper limits
  66. GRB 260424B: Glowbug gamma-ray detection of a short burst
  67. GRB 260424B: COLIBRÍ optical upper limit
  68. Konus-Wind detection of GRB 260424B
  69. GRB 260428A: Fermi GBM Final Real-time Localization
  70. GRB 260424C: Fermi GBM Final Localization
  71. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  72. IPN triangulation of GRB 260424B (short)
  73. GRB 260424B: SVOM/GRM detection of a short burst
  74. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  75. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  76. IceCube Alert 260425A: Global MASTER-Net observations report
  77. Fermi trigger No 798737427: Global MASTER-Net observations report
  78. GRB 260401A: cubesat Avion detection
  79. GRB 260424A: AstroSat CZTI detection of a long burst
  80. GRB 260421B: Kilonova-Catcher optical afterglow detection
  81. GRB 260421B: Insight-HXMT/HE detection
  82. The EP-WXT trigger 01709258652: Mondy optical observations
  83. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  84. EP260416a: Mondy optical observations
  85. GRB 260421B: SVOM/ECLAIRs refined analysis
  86. GRB 260421B: 3.6m DOT optical observation
  87. EP260416a: ZTSh R band observations
  88. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  89. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  90. GRB 260419A: AstroSat CZTI detection
  91. GRB 260421B: SVOM/GRM observation
  92. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  93. GRB 260421B: EP-FXT follow-up observation
  94. GRB 260421B: J-band upper limit with WINTER
  95. GRB 260421B: LCO optical counterpart detection
  96. GRB 260421B: Fermi GBM Observation
  97. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  98. GRB 260421A: AstroSat CZTI detection
  99. GRB 260412A: SVOM/ECLAIRs refined analysis
  100. GRB 260421B: SVOM/VT optical observations

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