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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"
  1. GRID detection of GRB 260401A
  2. EP260321a: uGMRT observations
  3. GRB 260407A: Fermi GBM Final Real-time Localization
  4. EP260405a: GMOS-N optical upper limits
  5. EP260405a: SVOM/VT optical upper limits
  6. EP260405a: Global MASTER-Net observations report
  7. EP260405a: Einstein Probe detection of a fast X-ray transient
  8. The EP-WXT trigger 01709259621 is likely a flaring star
  9. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  10. The EP-WXT trigger 01709259615 is likely a flaring star
  11. Fermi trigger No 797039833: Global MASTER-Net observations report
  12. GRB 260403A: GECAM-B observation of a long burst
  13. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  14. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  15. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  16. The EP-WXT trigger 01709259586 is likely a flaring star
  17. GRB 260330B: SVOM/VT further optical observation
  18. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  19. GRB 260330B: SVOM/ECLAIRs refined analysis
  20. EP260403a: LCO optical observations of the counterpart
  21. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  22. EP260403a: LCO optical counterpart detection
  23. EP260403a: COLIBRÍ optical counterpart candidate
  24. GRB 260330B: SVOM/VT optical candidate
  25. EP260403a: Einstein Probe detection of an X-ray transient
  26. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  27. GRB 260403A: AstroSat CZTI detection
  28. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  29. GRB 260402B: GECAM-B observation
  30. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  31. GRB 260402C: NuSTAR detection of prompt emission
  32. GRB 260402C: AstroSat CZTI detection of a long burst
  33. EP260324A / AT 2026hir: COLIBRÍ optical observations
  34. GRB 260403A: Fermi GBM Final Real-time Localization
  35. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  36. GRB 260402B: Fermi GBM Final Real-time Localization
  37. GRB 260402A: WINTER J-band upper limit
  38. GRB260402A: GROWTH-India Telescope optical upper limit
  39. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  40. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  41. GRB 260401A: SVOM/GRM observation
  42. GRB 260401A: GECAM-B observation
  43. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  44. GRB 260402A: Kilonova-Catcher optical upper limit
  45. GRB 260402A: MASTER optical observations
  46. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  47. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  48. GRB 260402A: SVOM detection of a burst
  49. Fermi GRB 260401A: Global MASTER-Net observations report
  50. GRB 260401A: Fermi GBM Observation
  51. GRB 260401A: NuSTAR detection of prompt emission
  52. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  53. GRB 260401A: MAXI/GSC detection
  54. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  55. GRB 260401A: Fermi GBM Final Real-time Localization
  56. EP260329b: Mondy and Assy-Turgen optical upper limits
  57. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  58. EP260321a :Xinglong optical observations
  59. EP260327a: Xinglong optical upper limit
  60. EP260329b: GOTO detection of optical counterpart
  61. GRB 260330B: SVOM/VT optical upper limits
  62. Konus-Wind detection of GRB 260320A
  63. Konus-Wind detection of GRB 260316B (duplicate submission)
  64. Konus-Wind detection of GRB 260316B
  65. GRB 260321A: SVOM/ECLAIRs refined analysis
  66. EP260329b: J-band upper limits with WINTER
  67. EP260329a: J-band upper limit with WINTER
  68. GRB 260330A: Glowbug gamma-ray detection
  69. GRB 260310A: VLA Multi-frequency Radio Observations
  70. Fermi GBM Sub-Threshold Detection of GRB 260330B
  71. GRB 260330B: LCO optical upper limits
  72. GRB 260330B: SVOM detection of a burst
  73. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  74. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  75. EP260329a: COLIBRÍ optical upper limit
  76. EP260329a: EP-FXT follow up observation
  77. EP260329a: NOT optical counterpart candidate
  78. GRB 260330A: Fermi GBM Final Real-time Localization
  79. EP260329b: Global MASTER-Net observations report
  80. Fermi trigger No 796485221: Global MASTER-Net observations report
  81. GRB 260327A: Insight-HXMT/HE detection
  82. EP260329b: Optical follow-up with Kinder observations
  83. EP 260329b: COLIBRÍ optical observations
  84. EP260329a: Optical upper limit with Kinder observations
  85. EP260329b: LCO optical observations of the counterpart
  86. GRB 260326A: Insight-HXMT/HE detection
  87. EP260329b: Einstein Probe detection of an X-ray transient
  88. EP260329a: Einstein Probe detection of an X-ray transient
  89. EP-WXT trigger 01709259209: TRT optical counterpart detection
  90. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  91. GRID detection of GRB 260326A
  92. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  93. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  94. EP260327a: SVOM/VT optical upper limits
  95. SMA Detection of GRB 260310A / AT 2026fgk
  96. GRB 260307B: ATCA Radio Upper Limits
  97. EP260327a: WINTER J-band upper limit
  98. EP260327a: COLIBRÍ optical upper limits
  99. GRB 260327A: AstroSat CZTI detection of a long burst
  100. EP260327a: Gemini-North optical upper limits

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