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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 260411B: SVOM/GRM observation of a long burst
  2. GRB 260409A: Insight-HXMT/HE detection
  3. GRB 260411B: Fermi GBM Detection
  4. GRB 260411B: GOTO optical counterpart candidate
  5. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  6. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  7. GRB 260411B: Fermi GBM Final Real-time Localization
  8. GRB 260411A: Fermi GBM Final Real-time Localization
  9. GRB 260410A: COLIBRÍ optical upper limit
  10. EP-WXT01709259790: Optical Upper limits with kinder observations
  11. GRB 260410A: Fermi GBM Observation
  12. GRB 260410B: SVOM/GRM detection of a short faint burst
  13. The EP-WXT trigger 01709259790 is likely a flaring star
  14. GRB 260410B: Fermi GBM Final Real-time Localization
  15. EP-WXT01709259790: Xinglong optical upper limit
  16. GRB 260410A: Fermi-LAT detection
  17. GRB 260410A: Fermi GBM Final Real-time Localization
  18. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  19. EP260321a: Chandra X-ray Non-detection
  20. GRB 260409A: Fermi GBM Final Real-time Localization
  21. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  22. The EP-WXT trigger 01709259773 is likely a flaring star
  23. GRB 260407A: GECAM-A detection
  24. GRB 260407A: Insight-HXMT/HE detection
  25. EP260409a: SVOM/VT optical upper limits
  26. EP260409a: COLIBRÍ optical upper limits
  27. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  28. EP260409a: Global MASTER-Net observations report
  29. EP260409a: Einstein Probe detection of an X-ray transient
  30. EP260321a: VLA radio detection
  31. GRB 260404A: Fermi GBM Final Localization
  32. GRB 260407A: Glowbug gamma-ray detection
  33. GRB 260402A: SVOM/ECLAIRs refined analysis
  34. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  35. GRB 260310A / AT2026fgk: X-ray rebrightening
  36. EP260402a / GRB 260402A: Mephisto optical upper limits
  37. EP-WXT01709259586: Xinglong optical upper limit
  38. EP260403a: Mephisto optical upper limits
  39. EP260402a/GRB 260402A: Xinglong optical upper limit
  40. EP260321a: Upper limits from VLA radio observations
  41. GRID detection of GRB 260401A
  42. EP260321a: uGMRT observations
  43. GRB 260407A: Fermi GBM Final Real-time Localization
  44. EP260405a: GMOS-N optical upper limits
  45. EP260405a: SVOM/VT optical upper limits
  46. EP260405a: Global MASTER-Net observations report
  47. EP260405a: Einstein Probe detection of a fast X-ray transient
  48. The EP-WXT trigger 01709259621 is likely a flaring star
  49. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  50. The EP-WXT trigger 01709259615 is likely a flaring star
  51. Fermi trigger No 797039833: Global MASTER-Net observations report
  52. GRB 260403A: GECAM-B observation of a long burst
  53. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  54. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  55. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  56. The EP-WXT trigger 01709259586 is likely a flaring star
  57. GRB 260330B: SVOM/VT further optical observation
  58. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  59. GRB 260330B: SVOM/ECLAIRs refined analysis
  60. EP260403a: LCO optical observations of the counterpart
  61. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  62. EP260403a: LCO optical counterpart detection
  63. EP260403a: COLIBRÍ optical counterpart candidate
  64. GRB 260330B: SVOM/VT optical candidate
  65. EP260403a: Einstein Probe detection of an X-ray transient
  66. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  67. GRB 260403A: AstroSat CZTI detection
  68. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  69. GRB 260402B: GECAM-B observation
  70. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  71. GRB 260402C: NuSTAR detection of prompt emission
  72. GRB 260402C: AstroSat CZTI detection of a long burst
  73. EP260324A / AT 2026hir: COLIBRÍ optical observations
  74. GRB 260403A: Fermi GBM Final Real-time Localization
  75. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  76. GRB 260402B: Fermi GBM Final Real-time Localization
  77. GRB 260402A: WINTER J-band upper limit
  78. GRB260402A: GROWTH-India Telescope optical upper limit
  79. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  80. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  81. GRB 260401A: SVOM/GRM observation
  82. GRB 260401A: GECAM-B observation
  83. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  84. GRB 260402A: Kilonova-Catcher optical upper limit
  85. GRB 260402A: MASTER optical observations
  86. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  87. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  88. GRB 260402A: SVOM detection of a burst
  89. Fermi GRB 260401A: Global MASTER-Net observations report
  90. GRB 260401A: Fermi GBM Observation
  91. GRB 260401A: NuSTAR detection of prompt emission
  92. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  93. GRB 260401A: MAXI/GSC detection
  94. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  95. GRB 260401A: Fermi GBM Final Real-time Localization
  96. EP260329b: Mondy and Assy-Turgen optical upper limits
  97. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  98. EP260321a :Xinglong optical observations
  99. EP260327a: Xinglong optical upper limit
  100. EP260329b: GOTO detection of optical counterpart

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