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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 260414A: Fermi GBM Final Real-time Localization
  2. The EP-WXT trigger 01709260122 is likely a flaring star
  3. Fermi GRB 260413A: Global MASTER-Net observations report
  4. GRB 260410A: Glowbug gamma-ray detection of a short burst
  5. GRB 260413A: Fermi GBM Final Real-time Localization
  6. GRB 260410B: Insight-HXMT/HE detection
  7. GRB 260410A: Insight-HXMT/HE detection
  8. Konus-Wind detection of GRB 260410A (short/hard)
  9. GRB 260411B: GECAM-B observation of a long burst
  10. EP260321a: SVOM/VT optical observations and color changes around peak
  11. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  12. The EP-WXT trigger 01709260010 is likely a flaring star
  13. GRB 260412A: GECAM-B observation of a long burst
  14. Fermi GRB 260412A: Global MASTER-Net observations report
  15. GRB 260412A: Fermi GBM Observation
  16. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  17. GRB 260411B: Fermi-LAT detection
  18. GRB 260412A: SVOM detection of a long burst
  19. GRB 260412A: Fermi GBM Final Real-time Localization
  20. GRB 260411B: COLIBRÍ optical observations
  21. GRB 260410B: Fermi GBM Observation
  22. GRB 260411B: Ondrejov D50 optical afterglow detection
  23. GRB260411B: 3.6m DOT optical observation
  24. GRB 260411A: SVOM/GRM observation
  25. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  26. GRB 260411B: SVOM/GRM observation of a long burst
  27. GRB 260409A: Insight-HXMT/HE detection
  28. GRB 260411B: Fermi GBM Detection
  29. GRB 260411B: GOTO optical counterpart candidate
  30. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  31. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  32. GRB 260411B: Fermi GBM Final Real-time Localization
  33. GRB 260411A: Fermi GBM Final Real-time Localization
  34. GRB 260410A: COLIBRÍ optical upper limit
  35. EP-WXT01709259790: Optical Upper limits with kinder observations
  36. GRB 260410A: Fermi GBM Observation
  37. GRB 260410B: SVOM/GRM detection of a short faint burst
  38. The EP-WXT trigger 01709259790 is likely a flaring star
  39. GRB 260410B: Fermi GBM Final Real-time Localization
  40. EP-WXT01709259790: Xinglong optical upper limit
  41. GRB 260410A: Fermi-LAT detection
  42. GRB 260410A: Fermi GBM Final Real-time Localization
  43. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  44. EP260321a: Chandra X-ray Non-detection
  45. GRB 260409A: Fermi GBM Final Real-time Localization
  46. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  47. The EP-WXT trigger 01709259773 is likely a flaring star
  48. GRB 260407A: GECAM-A detection
  49. GRB 260407A: Insight-HXMT/HE detection
  50. EP260409a: SVOM/VT optical upper limits
  51. EP260409a: COLIBRÍ optical upper limits
  52. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  53. EP260409a: Global MASTER-Net observations report
  54. EP260409a: Einstein Probe detection of an X-ray transient
  55. EP260321a: VLA radio detection
  56. GRB 260404A: Fermi GBM Final Localization
  57. GRB 260407A: Glowbug gamma-ray detection
  58. GRB 260402A: SVOM/ECLAIRs refined analysis
  59. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  60. GRB 260310A / AT2026fgk: X-ray rebrightening
  61. EP260402a / GRB 260402A: Mephisto optical upper limits
  62. EP-WXT01709259586: Xinglong optical upper limit
  63. EP260403a: Mephisto optical upper limits
  64. EP260402a/GRB 260402A: Xinglong optical upper limit
  65. EP260321a: Upper limits from VLA radio observations
  66. GRID detection of GRB 260401A
  67. EP260321a: uGMRT observations
  68. GRB 260407A: Fermi GBM Final Real-time Localization
  69. EP260405a: GMOS-N optical upper limits
  70. EP260405a: SVOM/VT optical upper limits
  71. EP260405a: Global MASTER-Net observations report
  72. EP260405a: Einstein Probe detection of a fast X-ray transient
  73. The EP-WXT trigger 01709259621 is likely a flaring star
  74. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  75. The EP-WXT trigger 01709259615 is likely a flaring star
  76. Fermi trigger No 797039833: Global MASTER-Net observations report
  77. GRB 260403A: GECAM-B observation of a long burst
  78. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  79. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  80. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  81. The EP-WXT trigger 01709259586 is likely a flaring star
  82. GRB 260330B: SVOM/VT further optical observation
  83. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  84. GRB 260330B: SVOM/ECLAIRs refined analysis
  85. EP260403a: LCO optical observations of the counterpart
  86. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  87. EP260403a: LCO optical counterpart detection
  88. EP260403a: COLIBRÍ optical counterpart candidate
  89. GRB 260330B: SVOM/VT optical candidate
  90. EP260403a: Einstein Probe detection of an X-ray transient
  91. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  92. GRB 260403A: AstroSat CZTI detection
  93. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  94. GRB 260402B: GECAM-B observation
  95. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  96. GRB 260402C: NuSTAR detection of prompt emission
  97. GRB 260402C: AstroSat CZTI detection of a long burst
  98. EP260324A / AT 2026hir: COLIBRÍ optical observations
  99. GRB 260403A: Fermi GBM Final Real-time Localization
  100. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph

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