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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. GRB 260407A: Insight-HXMT/HE detection
  2. EP260409a: SVOM/VT optical upper limits
  3. EP260409a: COLIBRÍ optical upper limits
  4. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  5. EP260409a: Global MASTER-Net observations report
  6. EP260409a: Einstein Probe detection of an X-ray transient
  7. EP260321a: VLA radio detection
  8. GRB 260404A: Fermi GBM Final Localization
  9. GRB 260407A: Glowbug gamma-ray detection
  10. GRB 260402A: SVOM/ECLAIRs refined analysis
  11. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  12. GRB 260310A / AT2026fgk: X-ray rebrightening
  13. EP260402a / GRB 260402A: Mephisto optical upper limits
  14. EP-WXT01709259586: Xinglong optical upper limit
  15. EP260403a: Mephisto optical upper limits
  16. EP260402a/GRB 260402A: Xinglong optical upper limit
  17. EP260321a: Upper limits from VLA radio observations
  18. GRID detection of GRB 260401A
  19. EP260321a: uGMRT observations
  20. GRB 260407A: Fermi GBM Final Real-time Localization
  21. EP260405a: GMOS-N optical upper limits
  22. EP260405a: SVOM/VT optical upper limits
  23. EP260405a: Global MASTER-Net observations report
  24. EP260405a: Einstein Probe detection of a fast X-ray transient
  25. The EP-WXT trigger 01709259621 is likely a flaring star
  26. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  27. The EP-WXT trigger 01709259615 is likely a flaring star
  28. Fermi trigger No 797039833: Global MASTER-Net observations report
  29. GRB 260403A: GECAM-B observation of a long burst
  30. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  31. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  32. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  33. The EP-WXT trigger 01709259586 is likely a flaring star
  34. GRB 260330B: SVOM/VT further optical observation
  35. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  36. GRB 260330B: SVOM/ECLAIRs refined analysis
  37. EP260403a: LCO optical observations of the counterpart
  38. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  39. EP260403a: LCO optical counterpart detection
  40. EP260403a: COLIBRÍ optical counterpart candidate
  41. GRB 260330B: SVOM/VT optical candidate
  42. EP260403a: Einstein Probe detection of an X-ray transient
  43. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  44. GRB 260403A: AstroSat CZTI detection
  45. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  46. GRB 260402B: GECAM-B observation
  47. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  48. GRB 260402C: NuSTAR detection of prompt emission
  49. GRB 260402C: AstroSat CZTI detection of a long burst
  50. EP260324A / AT 2026hir: COLIBRÍ optical observations
  51. GRB 260403A: Fermi GBM Final Real-time Localization
  52. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  53. GRB 260402B: Fermi GBM Final Real-time Localization
  54. GRB 260402A: WINTER J-band upper limit
  55. GRB260402A: GROWTH-India Telescope optical upper limit
  56. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  57. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  58. GRB 260401A: SVOM/GRM observation
  59. GRB 260401A: GECAM-B observation
  60. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  61. GRB 260402A: Kilonova-Catcher optical upper limit
  62. GRB 260402A: MASTER optical observations
  63. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  64. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  65. GRB 260402A: SVOM detection of a burst
  66. Fermi GRB 260401A: Global MASTER-Net observations report
  67. GRB 260401A: Fermi GBM Observation
  68. GRB 260401A: NuSTAR detection of prompt emission
  69. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  70. GRB 260401A: MAXI/GSC detection
  71. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  72. GRB 260401A: Fermi GBM Final Real-time Localization
  73. EP260329b: Mondy and Assy-Turgen optical upper limits
  74. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  75. EP260321a :Xinglong optical observations
  76. EP260327a: Xinglong optical upper limit
  77. EP260329b: GOTO detection of optical counterpart
  78. GRB 260330B: SVOM/VT optical upper limits
  79. Konus-Wind detection of GRB 260320A
  80. Konus-Wind detection of GRB 260316B (duplicate submission)
  81. Konus-Wind detection of GRB 260316B
  82. GRB 260321A: SVOM/ECLAIRs refined analysis
  83. EP260329b: J-band upper limits with WINTER
  84. EP260329a: J-band upper limit with WINTER
  85. GRB 260330A: Glowbug gamma-ray detection
  86. GRB 260310A: VLA Multi-frequency Radio Observations
  87. Fermi GBM Sub-Threshold Detection of GRB 260330B
  88. GRB 260330B: LCO optical upper limits
  89. GRB 260330B: SVOM detection of a burst
  90. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  91. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  92. EP260329a: COLIBRÍ optical upper limit
  93. EP260329a: EP-FXT follow up observation
  94. EP260329a: NOT optical counterpart candidate
  95. GRB 260330A: Fermi GBM Final Real-time Localization
  96. EP260329b: Global MASTER-Net observations report
  97. Fermi trigger No 796485221: Global MASTER-Net observations report
  98. GRB 260327A: Insight-HXMT/HE detection
  99. EP260329b: Optical follow-up with Kinder observations
  100. EP 260329b: COLIBRÍ optical observations

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