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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: GECAM-B observation of a long burst
  2. EP260321a: SVOM/VT optical observations and color changes around peak
  3. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  4. The EP-WXT trigger 01709260010 is likely a flaring star
  5. GRB 260412A: GECAM-B observation of a long burst
  6. Fermi GRB 260412A: Global MASTER-Net observations report
  7. GRB 260412A: Fermi GBM Observation
  8. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  9. GRB 260411B: Fermi-LAT detection
  10. GRB 260412A: SVOM detection of a long burst
  11. GRB 260412A: Fermi GBM Final Real-time Localization
  12. GRB 260411B: COLIBRÍ optical observations
  13. GRB 260410B: Fermi GBM Observation
  14. GRB 260411B: Ondrejov D50 optical afterglow detection
  15. GRB260411B: 3.6m DOT optical observation
  16. GRB 260411A: SVOM/GRM observation
  17. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  18. GRB 260411B: SVOM/GRM observation of a long burst
  19. GRB 260409A: Insight-HXMT/HE detection
  20. GRB 260411B: Fermi GBM Detection
  21. GRB 260411B: GOTO optical counterpart candidate
  22. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  23. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  24. GRB 260411B: Fermi GBM Final Real-time Localization
  25. GRB 260411A: Fermi GBM Final Real-time Localization
  26. GRB 260410A: COLIBRÍ optical upper limit
  27. EP-WXT01709259790: Optical Upper limits with kinder observations
  28. GRB 260410A: Fermi GBM Observation
  29. GRB 260410B: SVOM/GRM detection of a short faint burst
  30. The EP-WXT trigger 01709259790 is likely a flaring star
  31. GRB 260410B: Fermi GBM Final Real-time Localization
  32. EP-WXT01709259790: Xinglong optical upper limit
  33. GRB 260410A: Fermi-LAT detection
  34. GRB 260410A: Fermi GBM Final Real-time Localization
  35. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  36. EP260321a: Chandra X-ray Non-detection
  37. GRB 260409A: Fermi GBM Final Real-time Localization
  38. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  39. The EP-WXT trigger 01709259773 is likely a flaring star
  40. GRB 260407A: GECAM-A detection
  41. GRB 260407A: Insight-HXMT/HE detection
  42. EP260409a: SVOM/VT optical upper limits
  43. EP260409a: COLIBRÍ optical upper limits
  44. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  45. EP260409a: Global MASTER-Net observations report
  46. EP260409a: Einstein Probe detection of an X-ray transient
  47. EP260321a: VLA radio detection
  48. GRB 260404A: Fermi GBM Final Localization
  49. GRB 260407A: Glowbug gamma-ray detection
  50. GRB 260402A: SVOM/ECLAIRs refined analysis
  51. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  52. GRB 260310A / AT2026fgk: X-ray rebrightening
  53. EP260402a / GRB 260402A: Mephisto optical upper limits
  54. EP-WXT01709259586: Xinglong optical upper limit
  55. EP260403a: Mephisto optical upper limits
  56. EP260402a/GRB 260402A: Xinglong optical upper limit
  57. EP260321a: Upper limits from VLA radio observations
  58. GRID detection of GRB 260401A
  59. EP260321a: uGMRT observations
  60. GRB 260407A: Fermi GBM Final Real-time Localization
  61. EP260405a: GMOS-N optical upper limits
  62. EP260405a: SVOM/VT optical upper limits
  63. EP260405a: Global MASTER-Net observations report
  64. EP260405a: Einstein Probe detection of a fast X-ray transient
  65. The EP-WXT trigger 01709259621 is likely a flaring star
  66. EP260405.149 / EP-WXT 11900672904: COLIBRÍ optical upper limits
  67. The EP-WXT trigger 01709259615 is likely a flaring star
  68. Fermi trigger No 797039833: Global MASTER-Net observations report
  69. GRB 260403A: GECAM-B observation of a long burst
  70. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  71. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  72. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  73. The EP-WXT trigger 01709259586 is likely a flaring star
  74. GRB 260330B: SVOM/VT further optical observation
  75. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  76. GRB 260330B: SVOM/ECLAIRs refined analysis
  77. EP260403a: LCO optical observations of the counterpart
  78. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  79. EP260403a: LCO optical counterpart detection
  80. EP260403a: COLIBRÍ optical counterpart candidate
  81. GRB 260330B: SVOM/VT optical candidate
  82. EP260403a: Einstein Probe detection of an X-ray transient
  83. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  84. GRB 260403A: AstroSat CZTI detection
  85. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  86. GRB 260402B: GECAM-B observation
  87. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  88. GRB 260402C: NuSTAR detection of prompt emission
  89. GRB 260402C: AstroSat CZTI detection of a long burst
  90. EP260324A / AT 2026hir: COLIBRÍ optical observations
  91. GRB 260403A: Fermi GBM Final Real-time Localization
  92. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  93. GRB 260402B: Fermi GBM Final Real-time Localization
  94. GRB 260402A: WINTER J-band upper limit
  95. GRB260402A: GROWTH-India Telescope optical upper limit
  96. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  97. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  98. GRB 260401A: SVOM/GRM observation
  99. GRB 260401A: GECAM-B observation
  100. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient

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