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

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