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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"

3029 results found.

  1. GRB 260510C: MAXI/GSC detection
  2. SVOM GRB 260509A: MASTER-OAFA optical observation
  3. GRB 260504B: AstroSat CZTI detection
  4. EP260502a is likely a flaring star
  5. IceCube Alert 260505A: Global MASTER-Net observations report
  6. GRB 260430B: AstroSat CZTI detection of a long burst
  7. SVOM GRB 260504B: MASTER-OAFA optical observations
  8. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  9. GRB 260429B / EP260429a: AstroSat CZTI detection
  10. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  11. GRB 260424B: AstroSat CZTI detection
  12. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  13. GRB 260428A: AstroSat CZTI detection
  14. Fermi GRB 260428A: Global MASTER-Net observations report
  15. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  16. IceCube Alert 260425A: Global MASTER-Net observations report
  17. GRB 260424A: AstroSat CZTI detection of a long burst
  18. EP260416a: ZTSh R band observations
  19. GRB 260419A: AstroSat CZTI detection
  20. GRB 260421A: AstroSat CZTI detection
  21. GRB 260310A: Late-time Chandra X-ray Detection
  22. Fermi GRB 260421C: Global MASTER-Net observations report
  23. Fermi GRB 260421B: Global MASTER-Net observations report
  24. Fermi trigger No 798275385: Global MASTER-Net observations report
  25. EP260417a: Global MASTER-Net observations report
  26. Fermi GRB 260417A: Global MASTER-Net observations report
  27. GRB 260417A: AstroSat CZTI detection
  28. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  29. EP260416a: Global MASTER-Net observations report
  30. GRB 260411B: GOTO optical counterpart candidate
  31. EP-WXT01709259790: Optical Upper limits with kinder observations
  32. GRB 260410B: Fermi GBM Final Real-time Localization
  33. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  34. EP260321a: Upper limits from VLA radio observations
  35. EP260405a: Global MASTER-Net observations report
  36. Fermi trigger No 797039833: Global MASTER-Net observations report
  37. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  38. GRB 260403A: AstroSat CZTI detection
  39. GRB 260402C: AstroSat CZTI detection of a long burst
  40. GRB 260401A: NuSTAR detection of prompt emission
  41. EP260321a :Xinglong optical observations
  42. GRB 260327A: AstroSat CZTI detection of a long burst
  43. EP260327a: Global MASTER-Net observations report
  44. IPN triangulation of GRB 260320A
  45. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  46. GRB 260321A: SVOM/VT optical upper limits
  47. EP260321a: Global MASTER-Net observations report
  48. NOEMA Detection of GRB 260310A / AT 2026fgk
  49. GRB 260316B: AstroSat CZTI detection
  50. EP260314a: Global MASTER-Net observations report
  51. Fermi trigger No 795185313: Global MASTER-Net observations report
  52. GRB 260310A / AT2026fgk: SAO RAS optical observations
  53. Fermi GRB 260313A: Global MASTER-Net observations report
  54. GRB 260312B: AstroSat CZTI detection
  55. GRB260310A / AT2026fgk: P200 Spectroscopy
  56. EP260306a: Mondy optical upper limit
  57. GRB 260310A: AstroSat CZTI detection of a long burst
  58. Fermi GRB 260310B: Global MASTER-Net observations report
  59. GRB 260310A: Fermi GBM Final Real-time Localization
  60. GRB 260303B: AstroSat CZTI detection
  61. GRB 260304A: AstroSat CZTI detection of a long burst
  62. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  63. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  64. EP260227a: Global MASTER-Net observations report
  65. LAT GRB260226.44: Global MASTER-Net observations report
  66. Fermi GRB 260226A: Global MASTER-Net observations report
  67. GRB 260226A: AstroSat CZTI detection of bright long burst
  68. EP260126a: VLA 6 GHz detection
  69. EP260224a: Einstein Probe detection of an X-ray transient
  70. EP 260225.148: COLIBRÍ Confirmation of flaring star
  71. EP260221a: Optical upper limit with Kinder observations
  72. GRB 260222A: Fermi GBM Final Real-time Localization
  73. GRB 260219A: AstroSat CZTI detection
  74. GRB 260212A: AstroSat CZTI detection
  75. Konus-Wind detection of GRB 260207B
  76. Fermi trigger No 792537871: Global MASTER-Net observations report
  77. Fermi GRB 260210C: Global MASTER-Net observations report
  78. EP260210a: Global MASTER-Net observations report
  79. GRB 260210C: Fermi GBM Final Real-time Localization
  80. EP260210a: SVOM/VT optical upper limit
  81. GRB 260210A: AstroSat CZTI detection
  82. GRB 260208C: AstroSat CZTI detection
  83. GRB 260207B: AstroSat CZTI detection
  84. GRB 260208B: AstroSat CZTI detection of a bright long burst
  85. Fermi GRB 260209A: Global MASTER-Net observations report
  86. Fermi GRB 260208C: Global MASTER-Net observations report
  87. GRB 260208D: Fermi GBM Final Real-time Localization
  88. Fermi GRB 260208A: Global MASTER-Net observations report
  89. GRB 260207A: Fermi GBM Final Localization
  90. GRB 260204A: LCO optical upper limits
  91. GRB 260127B: AstroSat CZTI detection
  92. Fermi GRB 260129A: Global MASTER-Net observations report
  93. Fermi GRB 260127A: Global MASTER-Net observations report
  94. GRB 260127B: GOTO candidate optical counterpart
  95. GRB 260127A: LCO optical afterglow discovery
  96. GRB 260120A: AstroSat CZTI detection
  97. GRB 260120B: AstroSat CZTI detection
  98. SVOM GRB260121.06: Global MASTER-Net observations report
  99. GRB 260120B: Swift detection of a burst
  100. EP260119A: Mondy I-Band Observations

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