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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"

4237 results found.

  1. EP Alert 260914.53: Global MASTER-Net observations report
  2. GRB 260914A: SVOM/C-GFT optical observations
  3. GRB 260914A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  4. SVOM GRB260914.47: Global MASTER-Net observations report
  5. Fermi trigger No 810554827: Global MASTER-Net observations report
  6. The EP-WXT trigger 01709302592 is likely a flaring star
  7. NuSTAR Transient 260828: SOAR Optical Upper Limits
  8. GRB 260829A: AstroSat CZTI detection
  9. EP260830a: Global MASTER-Net observations report
  10. GRB 260829A: Fermi GBM Detection
  11. GRB 260829A: BALROG localization (Fermi Trigger 809676494 / GRB 260829256)
  12. GRB 260829A: Fermi GBM Final Real-time Localization
  13. Fermi GBM trigger 809666623/260829141 is not a GRB
  14. MAXI GRB260827.40: Global MASTER-Net observations report
  15. IceCube Alert 260825A: Global MASTER-Net observations report
  16. GRB 260818B: VLA radio observations
  17. GRB 260818B: SVOM/GRM observation
  18. EP260812a: AZT-22 optical upper limit
  19. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  20. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  21. GRB 260809A: NOT optical observations
  22. EP260809a: J-band upper limit with WINTER
  23. GRB 260808B: LCO optical observations
  24. Fermi GRB 260808A: Global MASTER-Net observations report
  25. SN 2026stf / GRB 260708A: ATLAS forced photometry
  26. Fermi GRB 260802B: Global MASTER-Net observations report
  27. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  28. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  29. EP260723a: SVOM/VT optical observation
  30. Fermi GRB 260718A: Global MASTER-Net observations report
  31. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  32. EP260711a: EP-FXT follow-up observation
  33. GRB 260629A: AstroSat CZTI detection
  34. GRB 260703A: Fermi GBM Final Localization
  35. Fermi trigger No 804552016: Global MASTER-Net observations report
  36. GRB 260629A: Fermi GBM Final Real-time Localization
  37. Fermi GRB 260628A: Global MASTER-Net observations report
  38. EP260623a: TNG NIR afterglow detection
  39. EP260623a: WINTER J-band observations
  40. GRB 260619A: SVOM possible detection of a faint burst
  41. GRB 260506B: cubesat Avion detection
  42. GRB 260429A: cubesat Avion detection
  43. GRB 260610B: further Liverpool Telescope optical observations
  44. GRB 260610B / AT2026owq: GRANDMA optical observations
  45. EP260605a: COLIBRÍ optical upper limits
  46. EP260610b: Liverpool Telescope optical upper limits
  47. GRB 260610B / AT2026owq: SVOM/VT optical observations
  48. GRB 260604C: SVOM/C-GFT upper limit
  49. EP260602a: COLIBRÍ optical observations
  50. SVOM GRB260603.23: Global MASTER-Net observations report
  51. Fermi GRB 260602B: Global MASTER-Net observations report
  52. Fermi GRB 260602B: Global MASTER-Net observations report
  53. GRB 260602A: Fermi GBM Final Real-time Localization
  54. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  55. AT2026nik: EP-FXT X-ray counterpart
  56. Fermi trigger No 801900520: Global MASTER-Net observations report
  57. EP260527a/GRB 260527A: further FTW optical and NIR observations
  58. GRB 260527A / EP260527a: VLA radio detection
  59. GRB 260529A: GOTO tentative optical afterglow candidate
  60. Fermi GRB 260529A: Global MASTER-Net observations report
  61. GRB 260529A: Fermi GBM Final Real-time Localization
  62. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  63. EP260527a: SVOM/VT optical observation
  64. Fermi trigger No 801580882: Global MASTER-Net observations report
  65. EP260526.405: COLIBRÍ optical upper limits
  66. EP-WXT 01709266106: NOT optical upper limits
  67. GRB 260515A: OHP/T193 optical observations
  68. SVOM GRB 260515A: Global MASTER-Net observations report
  69. GRB 260511B: Mephisto multi-band optical followup
  70. Fermi GRB 260514A: Global MASTER-Net observations report
  71. GRB 260511B SVOM/C-GFT optical counterpart detection
  72. Fermi GRB 260511A: Global MASTER-Net observations report
  73. GRB 260510C: MAXI/GSC detection
  74. EP260509a: Global MASTER-Net observations report
  75. SVOM GRB 260509A: MASTER-OAFA optical observation
  76. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  77. SVOM GRB 260504B: MASTER-OAFA optical observations
  78. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  79. IPN triangulation of a bright burst from SGR 1E1841-045
  80. GRB 260429B / EP260429a: AstroSat CZTI detection
  81. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  82. GRB 260429A: Fermi GBM Detection
  83. EP260429a: EP-WXT detection of a fast X-ray transient
  84. GRB 260429A: Fermi GBM Final Real-time Localization
  85. Fermi GRB 260428A: Global MASTER-Net observations report
  86. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  87. Fermi GRB 260421C: Global MASTER-Net observations report
  88. Fermi GRB 260421B: Global MASTER-Net observations report
  89. GRB 260421B: LCO optical afterglow confirmation
  90. Fermi GRB 260417B: Global MASTER-Net observations report
  91. EP260417a: Global MASTER-Net observations report
  92. EP260416a: GMG Optical Observation
  93. Fermi GRB 260417A: Global MASTER-Net observations report
  94. GRB 260417A: AstroSat CZTI detection
  95. IPN triangulation of GRB 260411B
  96. EP260416a: Einstein Probe detection of an X-ray transient
  97. Fermi trigger No 797912738: Global MASTER-Net observations report
  98. EP260321a: CMO SAI J,K observations
  99. Fermi GRB 260412A: Global MASTER-Net observations report
  100. GRB260411B: 3.6m DOT optical observation

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