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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"

27778 results found.

  1. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  2. GRB 260415B: NuSTAR detection of long prompt emission
  3. GRB 260415B: Fermi GBM Final Localization
  4. GRB 260415A: Fermi GBM Final Real-time Localization
  5. GRB 260414A: Glowbug gamma-ray detection
  6. GRB 260412A: Insight-HXMT/HE detection
  7. GRB 260414A: Fermi GBM Final Real-time Localization
  8. GRB 260410A: Glowbug gamma-ray detection of a short burst
  9. GRB 260413A: Fermi GBM Final Real-time Localization
  10. GRB 260410B: Insight-HXMT/HE detection
  11. GRB 260410A: Insight-HXMT/HE detection
  12. Konus-Wind detection of GRB 260410A (short/hard)
  13. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  14. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  15. GRB 260411B: Fermi-LAT detection
  16. GRB 260412A: SVOM detection of a long burst
  17. GRB 260412A: Fermi GBM Final Real-time Localization
  18. GRB 260411B: COLIBRÍ optical observations
  19. GRB 260411B: Ondrejov D50 optical afterglow detection
  20. GRB260411B: 3.6m DOT optical observation
  21. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  22. GRB 260409A: Insight-HXMT/HE detection
  23. GRB 260411B: Fermi GBM Detection
  24. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  25. GRB 260411B: Fermi GBM Final Real-time Localization
  26. GRB 260411A: Fermi GBM Final Real-time Localization
  27. EP-WXT01709259790: Optical Upper limits with kinder observations
  28. GRB 260410B: SVOM/GRM detection of a short faint burst
  29. GRB 260410B: Fermi GBM Final Real-time Localization
  30. EP-WXT01709259790: Xinglong optical upper limit
  31. GRB 260410A: Fermi-LAT detection
  32. GRB 260410A: Fermi GBM Final Real-time Localization
  33. EP260321a: Chandra X-ray Non-detection
  34. GRB 260409A: Fermi GBM Final Real-time Localization
  35. GRB 260407A: GECAM-A detection
  36. GRB 260407A: Insight-HXMT/HE detection
  37. EP260409a: SVOM/VT optical upper limits
  38. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  39. EP260409a: Einstein Probe detection of an X-ray transient
  40. EP260321a: VLA radio detection
  41. GRB 260404A: Fermi GBM Final Localization
  42. GRB 260407A: Glowbug gamma-ray detection
  43. GRB 260310A / AT2026fgk: X-ray rebrightening
  44. EP260402a / GRB 260402A: Mephisto optical upper limits
  45. EP-WXT01709259586: Xinglong optical upper limit
  46. EP260403a: Mephisto optical upper limits
  47. EP260402a/GRB 260402A: Xinglong optical upper limit
  48. EP260321a: Upper limits from VLA radio observations
  49. GRID detection of GRB 260401A
  50. GRB 260407A: Fermi GBM Final Real-time Localization
  51. EP260405a: Einstein Probe detection of a fast X-ray transient
  52. GRB 260330B: SVOM/VT further optical observation
  53. EP260403a: LCO optical counterpart detection
  54. GRB 260330B: SVOM/VT optical candidate
  55. EP260403a: Einstein Probe detection of an X-ray transient
  56. GRB 260403A: AstroSat CZTI detection
  57. GRB 260402C: NuSTAR detection of prompt emission
  58. GRB 260402C: AstroSat CZTI detection of a long burst
  59. GRB 260403A: Fermi GBM Final Real-time Localization
  60. GRB 260402B: Fermi GBM Final Real-time Localization
  61. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  62. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  63. GRB 260402A: SVOM detection of a burst
  64. GRB 260401A: NuSTAR detection of prompt emission
  65. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  66. GRB 260401A: MAXI/GSC detection
  67. GRB 260401A: Fermi GBM Final Real-time Localization
  68. EP260327a: Xinglong optical upper limit
  69. EP260329b: GOTO detection of optical counterpart
  70. GRB 260330B: SVOM/VT optical upper limits
  71. Konus-Wind detection of GRB 260320A
  72. Konus-Wind detection of GRB 260316B (duplicate submission)
  73. Konus-Wind detection of GRB 260316B
  74. GRB 260321A: SVOM/ECLAIRs refined analysis
  75. GRB 260330A: Glowbug gamma-ray detection
  76. Fermi GBM Sub-Threshold Detection of GRB 260330B
  77. GRB 260330B: SVOM detection of a burst
  78. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  79. EP260329a: COLIBRÍ optical upper limit
  80. GRB 260330A: Fermi GBM Final Real-time Localization
  81. GRB 260327A: Insight-HXMT/HE detection
  82. EP260329b: Optical follow-up with Kinder observations
  83. EP260329a: Optical upper limit with Kinder observations
  84. GRB 260326A: Insight-HXMT/HE detection
  85. EP260329b: Einstein Probe detection of an X-ray transient
  86. EP260329a: Einstein Probe detection of an X-ray transient
  87. EP-WXT trigger 01709259209: TRT optical counterpart detection
  88. GRID detection of GRB 260326A
  89. EP260327a: SVOM/VT optical upper limits
  90. SMA Detection of GRB 260310A / AT 2026fgk
  91. GRB 260327A: AstroSat CZTI detection of a long burst
  92. EP260327a: Einstein Probe detection of an X-ray transient
  93. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  94. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  95. IPN triangulation of GRB 260320A
  96. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  97. GRB 260326A: Fermi GBM Detection
  98. GRB 260325A: Fermi GBM Final Localization
  99. GRB 260326A: Fermi GBM Final Real-time Localization
  100. EP260321a: Upper limits from a neutrino search with IceCube

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