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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 260411A: Fermi GBM Final Real-time Localization
  2. GRB 260410A: COLIBRÍ optical upper limit
  3. EP-WXT01709259790: Optical Upper limits with kinder observations
  4. GRB 260410A: Fermi GBM Observation
  5. GRB 260410B: SVOM/GRM detection of a short faint burst
  6. The EP-WXT trigger 01709259790 is likely a flaring star
  7. GRB 260410B: Fermi GBM Final Real-time Localization
  8. EP-WXT01709259790: Xinglong optical upper limit
  9. GRB 260410A: Fermi-LAT detection
  10. GRB 260410A: Fermi GBM Final Real-time Localization
  11. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  12. EP260321a: Chandra X-ray Non-detection
  13. GRB 260409A: Fermi GBM Final Real-time Localization
  14. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  15. The EP-WXT trigger 01709259773 is likely a flaring star
  16. GRB 260407A: GECAM-A detection
  17. GRB 260407A: Insight-HXMT/HE detection
  18. EP260409a: SVOM/VT optical upper limits
  19. EP260409a: COLIBRÍ optical upper limits
  20. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  21. EP260409a: Global MASTER-Net observations report
  22. EP260409a: Einstein Probe detection of an X-ray transient
  23. EP260321a: VLA radio detection
  24. GRB 260404A: Fermi GBM Final Localization
  25. GRB 260407A: Glowbug gamma-ray detection
  26. GRB 260402A: SVOM/ECLAIRs refined analysis
  27. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  28. GRB 260310A / AT2026fgk: X-ray rebrightening
  29. EP260402a / GRB 260402A: Mephisto optical upper limits
  30. EP-WXT01709259586: Xinglong optical upper limit
  31. EP260403a: Mephisto optical upper limits
  32. EP260402a/GRB 260402A: Xinglong optical upper limit
  33. EP260321a: Upper limits from VLA radio observations
  34. GRID detection of GRB 260401A
  35. EP260321a: uGMRT observations
  36. GRB 260407A: Fermi GBM Final Real-time Localization
  37. EP260405a: GMOS-N optical upper limits
  38. EP260405a: SVOM/VT optical upper limits
  39. EP260405a: Global MASTER-Net observations report
  40. EP260405a: Einstein Probe detection of a fast X-ray transient
  41. The EP-WXT trigger 01709259621 is likely a flaring star
  42. EP260405.149 / EP-WXT 11900672904: COLIBRÍ optical upper limits
  43. The EP-WXT trigger 01709259615 is likely a flaring star
  44. Fermi trigger No 797039833: Global MASTER-Net observations report
  45. GRB 260403A: GECAM-B observation of a long burst
  46. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  47. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  48. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  49. The EP-WXT trigger 01709259586 is likely a flaring star
  50. GRB 260330B: SVOM/VT further optical observation
  51. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  52. GRB 260330B: SVOM/ECLAIRs refined analysis
  53. EP260403a: LCO optical observations of the counterpart
  54. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  55. EP260403a: LCO optical counterpart detection
  56. EP260403a: COLIBRÍ optical counterpart candidate
  57. GRB 260330B: SVOM/VT optical candidate
  58. EP260403a: Einstein Probe detection of an X-ray transient
  59. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  60. GRB 260403A: AstroSat CZTI detection
  61. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  62. GRB 260402B: GECAM-B observation
  63. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  64. GRB 260402C: NuSTAR detection of prompt emission
  65. GRB 260402C: AstroSat CZTI detection of a long burst
  66. EP260324A / AT 2026hir: COLIBRÍ optical observations
  67. GRB 260403A: Fermi GBM Final Real-time Localization
  68. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  69. GRB 260402B: Fermi GBM Final Real-time Localization
  70. GRB 260402A: WINTER J-band upper limit
  71. GRB260402A: GROWTH-India Telescope optical upper limit
  72. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  73. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  74. GRB 260401A: SVOM/GRM observation
  75. GRB 260401A: GECAM-B observation
  76. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  77. GRB 260402A: Kilonova-Catcher optical upper limit
  78. GRB 260402A: MASTER optical observations
  79. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  80. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  81. GRB 260402A: SVOM detection of a burst
  82. Fermi GRB 260401A: Global MASTER-Net observations report
  83. GRB 260401A: Fermi GBM Observation
  84. GRB 260401A: NuSTAR detection of prompt emission
  85. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  86. GRB 260401A: MAXI/GSC detection
  87. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  88. GRB 260401A: Fermi GBM Final Real-time Localization
  89. EP260329b: Mondy and Assy-Turgen optical upper limits
  90. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  91. EP260321a :Xinglong optical observations
  92. EP260327a: Xinglong optical upper limit
  93. EP260329b: GOTO detection of optical counterpart
  94. GRB 260330B: SVOM/VT optical upper limits
  95. Konus-Wind detection of GRB 260320A
  96. Konus-Wind detection of GRB 260316B (duplicate submission)
  97. Konus-Wind detection of GRB 260316B
  98. GRB 260321A: SVOM/ECLAIRs refined analysis
  99. EP260329b: J-band upper limits with WINTER
  100. EP260329a: J-band upper limit with WINTER

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