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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"

3136 results found.

  1. GRB 260514A: Fermi GBM Final Real-time Localization
  2. Fermi GRB 260512A: Global MASTER-Net observations report
  3. Konus-Wind detection of GRB 260511B
  4. GRB 260511B: AstroSat CZTI detection
  5. GRB 260510C: AstroSat CZTI detection
  6. GRB 260511A: SVOM/VT optical observation with VHF data
  7. Fermi GRB 260511A: Global MASTER-Net observations report
  8. GRB 260510C: MAXI/GSC detection
  9. SVOM GRB 260509A: MASTER-OAFA optical observation
  10. GRB 260504B: AstroSat CZTI detection
  11. EP260502a is likely a flaring star
  12. IceCube Alert 260505A: Global MASTER-Net observations report
  13. GRB 260430B: AstroSat CZTI detection of a long burst
  14. SVOM GRB 260504B: MASTER-OAFA optical observations
  15. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  16. GRB 260429B / EP260429a: AstroSat CZTI detection
  17. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  18. GRB 260424B: AstroSat CZTI detection
  19. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  20. GRB 260428A: AstroSat CZTI detection
  21. Fermi GRB 260428A: Global MASTER-Net observations report
  22. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  23. IceCube Alert 260425A: Global MASTER-Net observations report
  24. GRB 260424A: AstroSat CZTI detection of a long burst
  25. EP260416a: ZTSh R band observations
  26. GRB 260419A: AstroSat CZTI detection
  27. GRB 260421A: AstroSat CZTI detection
  28. GRB 260310A: Late-time Chandra X-ray Detection
  29. Fermi GRB 260421C: Global MASTER-Net observations report
  30. Fermi GRB 260421B: Global MASTER-Net observations report
  31. Fermi trigger No 798275385: Global MASTER-Net observations report
  32. EP260417a: Global MASTER-Net observations report
  33. Fermi GRB 260417A: Global MASTER-Net observations report
  34. GRB 260417A: AstroSat CZTI detection
  35. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  36. EP260416a: Global MASTER-Net observations report
  37. GRB 260411B: GOTO optical counterpart candidate
  38. EP-WXT01709259790: Optical Upper limits with kinder observations
  39. GRB 260410B: Fermi GBM Final Real-time Localization
  40. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  41. EP260321a: Upper limits from VLA radio observations
  42. EP260405a: Global MASTER-Net observations report
  43. Fermi trigger No 797039833: Global MASTER-Net observations report
  44. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  45. GRB 260403A: AstroSat CZTI detection
  46. GRB 260402C: AstroSat CZTI detection of a long burst
  47. GRB 260401A: NuSTAR detection of prompt emission
  48. EP260321a :Xinglong optical observations
  49. GRB 260327A: AstroSat CZTI detection of a long burst
  50. EP260327a: Global MASTER-Net observations report
  51. IPN triangulation of GRB 260320A
  52. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  53. GRB 260321A: SVOM/VT optical upper limits
  54. EP260321a: Global MASTER-Net observations report
  55. NOEMA Detection of GRB 260310A / AT 2026fgk
  56. GRB 260316B: AstroSat CZTI detection
  57. EP260314a: Global MASTER-Net observations report
  58. Fermi trigger No 795185313: Global MASTER-Net observations report
  59. GRB 260310A / AT2026fgk: SAO RAS optical observations
  60. Fermi GRB 260313A: Global MASTER-Net observations report
  61. GRB 260312B: AstroSat CZTI detection
  62. GRB260310A / AT2026fgk: P200 Spectroscopy
  63. EP260306a: Mondy optical upper limit
  64. GRB 260310A: AstroSat CZTI detection of a long burst
  65. Fermi GRB 260310B: Global MASTER-Net observations report
  66. GRB 260310A: Fermi GBM Final Real-time Localization
  67. GRB 260303B: AstroSat CZTI detection
  68. GRB 260304A: AstroSat CZTI detection of a long burst
  69. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  70. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  71. EP260227a: Global MASTER-Net observations report
  72. LAT GRB260226.44: Global MASTER-Net observations report
  73. Fermi GRB 260226A: Global MASTER-Net observations report
  74. GRB 260226A: AstroSat CZTI detection of bright long burst
  75. EP260126a: VLA 6 GHz detection
  76. EP260224a: Einstein Probe detection of an X-ray transient
  77. EP 260225.148: COLIBRÍ Confirmation of flaring star
  78. EP260221a: Optical upper limit with Kinder observations
  79. GRB 260222A: Fermi GBM Final Real-time Localization
  80. GRB 260219A: AstroSat CZTI detection
  81. GRB 260212A: AstroSat CZTI detection
  82. Konus-Wind detection of GRB 260207B
  83. Fermi trigger No 792537871: Global MASTER-Net observations report
  84. Fermi GRB 260210C: Global MASTER-Net observations report
  85. EP260210a: Global MASTER-Net observations report
  86. GRB 260210C: Fermi GBM Final Real-time Localization
  87. EP260210a: SVOM/VT optical upper limit
  88. GRB 260210A: AstroSat CZTI detection
  89. GRB 260208C: AstroSat CZTI detection
  90. GRB 260207B: AstroSat CZTI detection
  91. GRB 260208B: AstroSat CZTI detection of a bright long burst
  92. Fermi GRB 260209A: Global MASTER-Net observations report
  93. Fermi GRB 260208C: Global MASTER-Net observations report
  94. GRB 260208D: Fermi GBM Final Real-time Localization
  95. Fermi GRB 260208A: Global MASTER-Net observations report
  96. GRB 260207A: Fermi GBM Final Localization
  97. GRB 260204A: LCO optical upper limits
  98. GRB 260127B: AstroSat CZTI detection
  99. Fermi GRB 260129A: Global MASTER-Net observations report
  100. Fermi GRB 260127A: Global MASTER-Net observations report

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