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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 260413A: Fermi GBM Final Real-time Localization
  2. GRB 260410B: Insight-HXMT/HE detection
  3. GRB 260410A: Insight-HXMT/HE detection
  4. Konus-Wind detection of GRB 260410A (short/hard)
  5. GRB 260411B: GECAM-B observation of a long burst
  6. EP260321a: SVOM/VT optical observations and color changes around peak
  7. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  8. The EP-WXT trigger 01709260010 is likely a flaring star
  9. GRB 260412A: GECAM-B observation of a long burst
  10. Fermi GRB 260412A: Global MASTER-Net observations report
  11. GRB 260412A: Fermi GBM Observation
  12. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  13. GRB 260411B: Fermi-LAT detection
  14. GRB 260412A: SVOM detection of a long burst
  15. GRB 260412A: Fermi GBM Final Real-time Localization
  16. GRB 260411B: COLIBRÍ optical observations
  17. GRB 260410B: Fermi GBM Observation
  18. GRB 260411B: Ondrejov D50 optical afterglow detection
  19. GRB260411B: 3.6m DOT optical observation
  20. GRB 260411A: SVOM/GRM observation
  21. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  22. GRB 260411B: SVOM/GRM observation of a long burst
  23. GRB 260409A: Insight-HXMT/HE detection
  24. GRB 260411B: Fermi GBM Detection
  25. GRB 260411B: GOTO optical counterpart candidate
  26. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  27. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  28. GRB 260411B: Fermi GBM Final Real-time Localization
  29. GRB 260411A: Fermi GBM Final Real-time Localization
  30. GRB 260410A: COLIBRÍ optical upper limit
  31. EP-WXT01709259790: Optical Upper limits with kinder observations
  32. GRB 260410A: Fermi GBM Observation
  33. GRB 260410B: SVOM/GRM detection of a short faint burst
  34. The EP-WXT trigger 01709259790 is likely a flaring star
  35. GRB 260410B: Fermi GBM Final Real-time Localization
  36. EP-WXT01709259790: Xinglong optical upper limit
  37. GRB 260410A: Fermi-LAT detection
  38. GRB 260410A: Fermi GBM Final Real-time Localization
  39. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  40. EP260321a: Chandra X-ray Non-detection
  41. GRB 260409A: Fermi GBM Final Real-time Localization
  42. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  43. The EP-WXT trigger 01709259773 is likely a flaring star
  44. GRB 260407A: GECAM-A detection
  45. GRB 260407A: Insight-HXMT/HE detection
  46. EP260409a: SVOM/VT optical upper limits
  47. EP260409a: COLIBRÍ optical upper limits
  48. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  49. EP260409a: Global MASTER-Net observations report
  50. EP260409a: Einstein Probe detection of an X-ray transient
  51. EP260321a: VLA radio detection
  52. GRB 260404A: Fermi GBM Final Localization
  53. GRB 260407A: Glowbug gamma-ray detection
  54. GRB 260402A: SVOM/ECLAIRs refined analysis
  55. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  56. GRB 260310A / AT2026fgk: X-ray rebrightening
  57. EP260402a / GRB 260402A: Mephisto optical upper limits
  58. EP-WXT01709259586: Xinglong optical upper limit
  59. EP260403a: Mephisto optical upper limits
  60. EP260402a/GRB 260402A: Xinglong optical upper limit
  61. EP260321a: Upper limits from VLA radio observations
  62. GRID detection of GRB 260401A
  63. EP260321a: uGMRT observations
  64. GRB 260407A: Fermi GBM Final Real-time Localization
  65. EP260405a: GMOS-N optical upper limits
  66. EP260405a: SVOM/VT optical upper limits
  67. EP260405a: Global MASTER-Net observations report
  68. EP260405a: Einstein Probe detection of a fast X-ray transient
  69. The EP-WXT trigger 01709259621 is likely a flaring star
  70. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  71. The EP-WXT trigger 01709259615 is likely a flaring star
  72. Fermi trigger No 797039833: Global MASTER-Net observations report
  73. GRB 260403A: GECAM-B observation of a long burst
  74. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  75. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  76. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  77. The EP-WXT trigger 01709259586 is likely a flaring star
  78. GRB 260330B: SVOM/VT further optical observation
  79. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  80. GRB 260330B: SVOM/ECLAIRs refined analysis
  81. EP260403a: LCO optical observations of the counterpart
  82. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  83. EP260403a: LCO optical counterpart detection
  84. EP260403a: COLIBRÍ optical counterpart candidate
  85. GRB 260330B: SVOM/VT optical candidate
  86. EP260403a: Einstein Probe detection of an X-ray transient
  87. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  88. GRB 260403A: AstroSat CZTI detection
  89. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  90. GRB 260402B: GECAM-B observation
  91. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  92. GRB 260402C: NuSTAR detection of prompt emission
  93. GRB 260402C: AstroSat CZTI detection of a long burst
  94. EP260324A / AT 2026hir: COLIBRÍ optical observations
  95. GRB 260403A: Fermi GBM Final Real-time Localization
  96. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  97. GRB 260402B: Fermi GBM Final Real-time Localization
  98. GRB 260402A: WINTER J-band upper limit
  99. GRB260402A: GROWTH-India Telescope optical upper limit
  100. GRB 260402A / EP260402a: SVOM/VT optical upper limits

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