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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"

27777 results found.

  1. GRB 260415B: NuSTAR detection of long prompt emission
  2. GRB 260415B: Fermi GBM Final Localization
  3. GRB 260415A: Fermi GBM Final Real-time Localization
  4. GRB 260414A: Glowbug gamma-ray detection
  5. GRB 260412A: Insight-HXMT/HE detection
  6. GRB 260414A: Fermi GBM Final Real-time Localization
  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 260410A: CALET Gamma-Ray Burst Monitor detection
  13. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  14. GRB 260411B: Fermi-LAT detection
  15. GRB 260412A: SVOM detection of a long burst
  16. GRB 260412A: Fermi GBM Final Real-time Localization
  17. GRB 260411B: COLIBRÍ optical observations
  18. GRB 260411B: Ondrejov D50 optical afterglow detection
  19. GRB260411B: 3.6m DOT optical observation
  20. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  21. GRB 260409A: Insight-HXMT/HE detection
  22. GRB 260411B: Fermi GBM Detection
  23. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  24. GRB 260411B: Fermi GBM Final Real-time Localization
  25. GRB 260411A: Fermi GBM Final Real-time Localization
  26. EP-WXT01709259790: Optical Upper limits with kinder observations
  27. GRB 260410B: SVOM/GRM detection of a short faint burst
  28. GRB 260410B: Fermi GBM Final Real-time Localization
  29. EP-WXT01709259790: Xinglong optical upper limit
  30. GRB 260410A: Fermi-LAT detection
  31. GRB 260410A: Fermi GBM Final Real-time Localization
  32. EP260321a: Chandra X-ray Non-detection
  33. GRB 260409A: Fermi GBM Final Real-time Localization
  34. GRB 260407A: GECAM-A detection
  35. GRB 260407A: Insight-HXMT/HE detection
  36. EP260409a: SVOM/VT optical upper limits
  37. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  38. EP260409a: Einstein Probe detection of an X-ray transient
  39. EP260321a: VLA radio detection
  40. GRB 260404A: Fermi GBM Final Localization
  41. GRB 260407A: Glowbug gamma-ray detection
  42. GRB 260310A / AT2026fgk: X-ray rebrightening
  43. EP260402a / GRB 260402A: Mephisto optical upper limits
  44. EP-WXT01709259586: Xinglong optical upper limit
  45. EP260403a: Mephisto optical upper limits
  46. EP260402a/GRB 260402A: Xinglong optical upper limit
  47. EP260321a: Upper limits from VLA radio observations
  48. GRID detection of GRB 260401A
  49. GRB 260407A: Fermi GBM Final Real-time Localization
  50. EP260405a: Einstein Probe detection of a fast X-ray transient
  51. GRB 260330B: SVOM/VT further optical observation
  52. EP260403a: LCO optical counterpart detection
  53. GRB 260330B: SVOM/VT optical candidate
  54. EP260403a: Einstein Probe detection of an X-ray transient
  55. GRB 260403A: AstroSat CZTI detection
  56. GRB 260402C: NuSTAR detection of prompt emission
  57. GRB 260402C: AstroSat CZTI detection of a long burst
  58. GRB 260403A: Fermi GBM Final Real-time Localization
  59. GRB 260402B: Fermi GBM Final Real-time Localization
  60. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  61. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  62. GRB 260402A: SVOM detection of a burst
  63. GRB 260401A: NuSTAR detection of prompt emission
  64. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  65. GRB 260401A: MAXI/GSC detection
  66. GRB 260401A: Fermi GBM Final Real-time Localization
  67. EP260327a: Xinglong optical upper limit
  68. EP260329b: GOTO detection of optical counterpart
  69. GRB 260330B: SVOM/VT optical upper limits
  70. Konus-Wind detection of GRB 260320A
  71. Konus-Wind detection of GRB 260316B (duplicate submission)
  72. Konus-Wind detection of GRB 260316B
  73. GRB 260321A: SVOM/ECLAIRs refined analysis
  74. GRB 260330A: Glowbug gamma-ray detection
  75. Fermi GBM Sub-Threshold Detection of GRB 260330B
  76. GRB 260330B: SVOM detection of a burst
  77. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  78. EP260329a: COLIBRÍ optical upper limit
  79. GRB 260330A: Fermi GBM Final Real-time Localization
  80. GRB 260327A: Insight-HXMT/HE detection
  81. EP260329b: Optical follow-up with Kinder observations
  82. EP260329a: Optical upper limit with Kinder observations
  83. GRB 260326A: Insight-HXMT/HE detection
  84. EP260329b: Einstein Probe detection of an X-ray transient
  85. EP260329a: Einstein Probe detection of an X-ray transient
  86. EP-WXT trigger 01709259209: TRT optical counterpart detection
  87. GRID detection of GRB 260326A
  88. EP260327a: SVOM/VT optical upper limits
  89. SMA Detection of GRB 260310A / AT 2026fgk
  90. GRB 260327A: AstroSat CZTI detection of a long burst
  91. EP260327a: Einstein Probe detection of an X-ray transient
  92. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  93. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  94. IPN triangulation of GRB 260320A
  95. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  96. GRB 260326A: Fermi GBM Detection
  97. GRB 260325A: Fermi GBM Final Localization
  98. GRB 260326A: Fermi GBM Final Real-time Localization
  99. EP260321a: Upper limits from a neutrino search with IceCube
  100. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time

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