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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 260415B: Fermi GBM Final Localization
  2. GRB 260415A: Fermi GBM Final Real-time Localization
  3. Fermi trigger No 797912738: Global MASTER-Net observations report
  4. GRB 260414A: Glowbug gamma-ray detection
  5. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  6. EP260321a: CMO SAI J,K observations
  7. GRB 260412A: Insight-HXMT/HE detection
  8. GRB 260414A: Fermi GBM Final Real-time Localization
  9. The EP-WXT trigger 01709260122 is likely a flaring star
  10. Fermi GRB 260413A: Global MASTER-Net observations report
  11. GRB 260410A: Glowbug gamma-ray detection of a short burst
  12. GRB 260413A: Fermi GBM Final Real-time Localization
  13. GRB 260410B: Insight-HXMT/HE detection
  14. GRB 260410A: Insight-HXMT/HE detection
  15. Konus-Wind detection of GRB 260410A (short/hard)
  16. GRB 260411B: GECAM-B observation of a long burst
  17. EP260321a: SVOM/VT optical observations and color changes around peak
  18. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  19. The EP-WXT trigger 01709260010 is likely a flaring star
  20. GRB 260412A: GECAM-B observation of a long burst
  21. Fermi GRB 260412A: Global MASTER-Net observations report
  22. GRB 260412A: Fermi GBM Observation
  23. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  24. GRB 260411B: Fermi-LAT detection
  25. GRB 260412A: SVOM detection of a long burst
  26. GRB 260412A: Fermi GBM Final Real-time Localization
  27. GRB 260411B: COLIBRÍ optical observations
  28. GRB 260410B: Fermi GBM Observation
  29. GRB 260411B: Ondrejov D50 optical afterglow detection
  30. GRB260411B: 3.6m DOT optical observation
  31. GRB 260411A: SVOM/GRM observation
  32. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  33. GRB 260411B: SVOM/GRM observation of a long burst
  34. GRB 260409A: Insight-HXMT/HE detection
  35. GRB 260411B: Fermi GBM Detection
  36. GRB 260411B: GOTO optical counterpart candidate
  37. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  38. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  39. GRB 260411B: Fermi GBM Final Real-time Localization
  40. GRB 260411A: Fermi GBM Final Real-time Localization
  41. GRB 260410A: COLIBRÍ optical upper limit
  42. EP-WXT01709259790: Optical Upper limits with kinder observations
  43. GRB 260410A: Fermi GBM Observation
  44. GRB 260410B: SVOM/GRM detection of a short faint burst
  45. The EP-WXT trigger 01709259790 is likely a flaring star
  46. GRB 260410B: Fermi GBM Final Real-time Localization
  47. EP-WXT01709259790: Xinglong optical upper limit
  48. GRB 260410A: Fermi-LAT detection
  49. GRB 260410A: Fermi GBM Final Real-time Localization
  50. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  51. EP260321a: Chandra X-ray Non-detection
  52. GRB 260409A: Fermi GBM Final Real-time Localization
  53. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  54. The EP-WXT trigger 01709259773 is likely a flaring star
  55. GRB 260407A: GECAM-A detection
  56. GRB 260407A: Insight-HXMT/HE detection
  57. EP260409a: SVOM/VT optical upper limits
  58. EP260409a: COLIBRÍ optical upper limits
  59. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  60. EP260409a: Global MASTER-Net observations report
  61. EP260409a: Einstein Probe detection of an X-ray transient
  62. EP260321a: VLA radio detection
  63. GRB 260404A: Fermi GBM Final Localization
  64. GRB 260407A: Glowbug gamma-ray detection
  65. GRB 260402A: SVOM/ECLAIRs refined analysis
  66. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  67. GRB 260310A / AT2026fgk: X-ray rebrightening
  68. EP260402a / GRB 260402A: Mephisto optical upper limits
  69. EP-WXT01709259586: Xinglong optical upper limit
  70. EP260403a: Mephisto optical upper limits
  71. EP260402a/GRB 260402A: Xinglong optical upper limit
  72. EP260321a: Upper limits from VLA radio observations
  73. GRID detection of GRB 260401A
  74. EP260321a: uGMRT observations
  75. GRB 260407A: Fermi GBM Final Real-time Localization
  76. EP260405a: GMOS-N optical upper limits
  77. EP260405a: SVOM/VT optical upper limits
  78. EP260405a: Global MASTER-Net observations report
  79. EP260405a: Einstein Probe detection of a fast X-ray transient
  80. The EP-WXT trigger 01709259621 is likely a flaring star
  81. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  82. The EP-WXT trigger 01709259615 is likely a flaring star
  83. Fermi trigger No 797039833: Global MASTER-Net observations report
  84. GRB 260403A: GECAM-B observation of a long burst
  85. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  86. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  87. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  88. The EP-WXT trigger 01709259586 is likely a flaring star
  89. GRB 260330B: SVOM/VT further optical observation
  90. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  91. GRB 260330B: SVOM/ECLAIRs refined analysis
  92. EP260403a: LCO optical observations of the counterpart
  93. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  94. EP260403a: LCO optical counterpart detection
  95. EP260403a: COLIBRÍ optical counterpart candidate
  96. GRB 260330B: SVOM/VT optical candidate
  97. EP260403a: Einstein Probe detection of an X-ray transient
  98. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  99. GRB 260403A: AstroSat CZTI detection
  100. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations

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