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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: Glowbug gamma-ray detection
  2. GRB 260402A: SVOM/ECLAIRs refined analysis
  3. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  4. GRB 260310A / AT2026fgk: X-ray rebrightening
  5. EP260402a / GRB 260402A: Mephisto optical upper limits
  6. EP-WXT01709259586: Xinglong optical upper limit
  7. EP260403a: Mephisto optical upper limits
  8. EP260402a/GRB 260402A: Xinglong optical upper limit
  9. EP260321a: Upper limits from VLA radio observations
  10. GRID detection of GRB 260401A
  11. EP260321a: uGMRT observations
  12. GRB 260407A: Fermi GBM Final Real-time Localization
  13. EP260405a: GMOS-N optical upper limits
  14. EP260405a: SVOM/VT optical upper limits
  15. EP260405a: Global MASTER-Net observations report
  16. EP260405a: Einstein Probe detection of a fast X-ray transient
  17. The EP-WXT trigger 01709259621 is likely a flaring star
  18. EP260405.149 / EP-WXT 11900672904: COLIBRÍ optical upper limits
  19. The EP-WXT trigger 01709259615 is likely a flaring star
  20. Fermi trigger No 797039833: Global MASTER-Net observations report
  21. GRB 260403A: GECAM-B observation of a long burst
  22. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  23. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  24. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  25. The EP-WXT trigger 01709259586 is likely a flaring star
  26. GRB 260330B: SVOM/VT further optical observation
  27. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  28. GRB 260330B: SVOM/ECLAIRs refined analysis
  29. EP260403a: LCO optical observations of the counterpart
  30. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  31. EP260403a: LCO optical counterpart detection
  32. EP260403a: COLIBRÍ optical counterpart candidate
  33. GRB 260330B: SVOM/VT optical candidate
  34. EP260403a: Einstein Probe detection of an X-ray transient
  35. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  36. GRB 260403A: AstroSat CZTI detection
  37. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  38. GRB 260402B: GECAM-B observation
  39. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  40. GRB 260402C: NuSTAR detection of prompt emission
  41. GRB 260402C: AstroSat CZTI detection of a long burst
  42. EP260324A / AT 2026hir: COLIBRÍ optical observations
  43. GRB 260403A: Fermi GBM Final Real-time Localization
  44. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  45. GRB 260402B: Fermi GBM Final Real-time Localization
  46. GRB 260402A: WINTER J-band upper limit
  47. GRB260402A: GROWTH-India Telescope optical upper limit
  48. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  49. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  50. GRB 260401A: SVOM/GRM observation
  51. GRB 260401A: GECAM-B observation
  52. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  53. GRB 260402A: Kilonova-Catcher optical upper limit
  54. GRB 260402A: MASTER optical observations
  55. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  56. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  57. GRB 260402A: SVOM detection of a burst
  58. Fermi GRB 260401A: Global MASTER-Net observations report
  59. GRB 260401A: Fermi GBM Observation
  60. GRB 260401A: NuSTAR detection of prompt emission
  61. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  62. GRB 260401A: MAXI/GSC detection
  63. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  64. GRB 260401A: Fermi GBM Final Real-time Localization
  65. EP260329b: Mondy and Assy-Turgen optical upper limits
  66. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  67. EP260321a :Xinglong optical observations
  68. EP260327a: Xinglong optical upper limit
  69. EP260329b: GOTO detection of optical counterpart
  70. GRB 260330B: SVOM/VT optical upper limits
  71. Konus-Wind detection of GRB 260320A
  72. Konus-Wind detection of GRB 260316B (duplicate submission)
  73. Konus-Wind detection of GRB 260316B
  74. GRB 260321A: SVOM/ECLAIRs refined analysis
  75. EP260329b: J-band upper limits with WINTER
  76. EP260329a: J-band upper limit with WINTER
  77. GRB 260330A: Glowbug gamma-ray detection
  78. GRB 260310A: VLA Multi-frequency Radio Observations
  79. Fermi GBM Sub-Threshold Detection of GRB 260330B
  80. GRB 260330B: LCO optical upper limits
  81. GRB 260330B: SVOM detection of a burst
  82. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  83. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  84. EP260329a: COLIBRÍ optical upper limit
  85. EP260329a: EP-FXT follow up observation
  86. EP260329a: NOT optical counterpart candidate
  87. GRB 260330A: Fermi GBM Final Real-time Localization
  88. EP260329b: Global MASTER-Net observations report
  89. Fermi trigger No 796485221: Global MASTER-Net observations report
  90. GRB 260327A: Insight-HXMT/HE detection
  91. EP260329b: Optical follow-up with Kinder observations
  92. EP 260329b: COLIBRÍ optical observations
  93. EP260329a: Optical upper limit with Kinder observations
  94. EP260329b: LCO optical observations of the counterpart
  95. GRB 260326A: Insight-HXMT/HE detection
  96. EP260329b: Einstein Probe detection of an X-ray transient
  97. EP260329a: Einstein Probe detection of an X-ray transient
  98. EP-WXT trigger 01709259209: TRT optical counterpart detection
  99. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  100. GRID detection of GRB 260326A

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