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

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