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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"

27779 results found.

  1. EP260416a: Einstein Probe detection of an X-ray transient
  2. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  3. GRB 260415B: NuSTAR detection of long prompt emission
  4. GRB 260415B: Fermi GBM Final Localization
  5. GRB 260415A: Fermi GBM Final Real-time Localization
  6. GRB 260414A: Glowbug gamma-ray detection
  7. GRB 260412A: Insight-HXMT/HE detection
  8. GRB 260414A: Fermi GBM Final Real-time Localization
  9. GRB 260410A: Glowbug gamma-ray detection of a short burst
  10. GRB 260413A: Fermi GBM Final Real-time Localization
  11. GRB 260410B: Insight-HXMT/HE detection
  12. GRB 260410A: Insight-HXMT/HE detection
  13. Konus-Wind detection of GRB 260410A (short/hard)
  14. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  15. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  16. GRB 260411B: Fermi-LAT detection
  17. GRB 260412A: SVOM detection of a long burst
  18. GRB 260412A: Fermi GBM Final Real-time Localization
  19. GRB 260411B: COLIBRÍ optical observations
  20. GRB 260411B: Ondrejov D50 optical afterglow detection
  21. GRB260411B: 3.6m DOT optical observation
  22. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  23. GRB 260409A: Insight-HXMT/HE detection
  24. GRB 260411B: Fermi GBM Detection
  25. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  26. GRB 260411B: Fermi GBM Final Real-time Localization
  27. GRB 260411A: Fermi GBM Final Real-time Localization
  28. EP-WXT01709259790: Optical Upper limits with kinder observations
  29. GRB 260410B: SVOM/GRM detection of a short faint burst
  30. GRB 260410B: Fermi GBM Final Real-time Localization
  31. EP-WXT01709259790: Xinglong optical upper limit
  32. GRB 260410A: Fermi-LAT detection
  33. GRB 260410A: Fermi GBM Final Real-time Localization
  34. EP260321a: Chandra X-ray Non-detection
  35. GRB 260409A: Fermi GBM Final Real-time Localization
  36. GRB 260407A: GECAM-A detection
  37. GRB 260407A: Insight-HXMT/HE detection
  38. EP260409a: SVOM/VT optical upper limits
  39. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  40. EP260409a: Einstein Probe detection of an X-ray transient
  41. EP260321a: VLA radio detection
  42. GRB 260404A: Fermi GBM Final Localization
  43. GRB 260407A: Glowbug gamma-ray detection
  44. GRB 260310A / AT2026fgk: X-ray rebrightening
  45. EP260402a / GRB 260402A: Mephisto optical upper limits
  46. EP-WXT01709259586: Xinglong optical upper limit
  47. EP260403a: Mephisto optical upper limits
  48. EP260402a/GRB 260402A: Xinglong optical upper limit
  49. EP260321a: Upper limits from VLA radio observations
  50. GRID detection of GRB 260401A
  51. GRB 260407A: Fermi GBM Final Real-time Localization
  52. EP260405a: Einstein Probe detection of a fast X-ray transient
  53. GRB 260330B: SVOM/VT further optical observation
  54. EP260403a: LCO optical counterpart detection
  55. GRB 260330B: SVOM/VT optical candidate
  56. EP260403a: Einstein Probe detection of an X-ray transient
  57. GRB 260403A: AstroSat CZTI detection
  58. GRB 260402C: NuSTAR detection of prompt emission
  59. GRB 260402C: AstroSat CZTI detection of a long burst
  60. GRB 260403A: Fermi GBM Final Real-time Localization
  61. GRB 260402B: Fermi GBM Final Real-time Localization
  62. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  63. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  64. GRB 260402A: SVOM detection of a burst
  65. GRB 260401A: NuSTAR detection of prompt emission
  66. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  67. GRB 260401A: MAXI/GSC detection
  68. GRB 260401A: Fermi GBM Final Real-time Localization
  69. EP260327a: Xinglong optical upper limit
  70. EP260329b: GOTO detection of optical counterpart
  71. GRB 260330B: SVOM/VT optical upper limits
  72. Konus-Wind detection of GRB 260320A
  73. Konus-Wind detection of GRB 260316B (duplicate submission)
  74. Konus-Wind detection of GRB 260316B
  75. GRB 260321A: SVOM/ECLAIRs refined analysis
  76. GRB 260330A: Glowbug gamma-ray detection
  77. Fermi GBM Sub-Threshold Detection of GRB 260330B
  78. GRB 260330B: SVOM detection of a burst
  79. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  80. EP260329a: COLIBRÍ optical upper limit
  81. GRB 260330A: Fermi GBM Final Real-time Localization
  82. GRB 260327A: Insight-HXMT/HE detection
  83. EP260329b: Optical follow-up with Kinder observations
  84. EP260329a: Optical upper limit with Kinder observations
  85. GRB 260326A: Insight-HXMT/HE detection
  86. EP260329b: Einstein Probe detection of an X-ray transient
  87. EP260329a: Einstein Probe detection of an X-ray transient
  88. EP-WXT trigger 01709259209: TRT optical counterpart detection
  89. GRID detection of GRB 260326A
  90. EP260327a: SVOM/VT optical upper limits
  91. SMA Detection of GRB 260310A / AT 2026fgk
  92. GRB 260327A: AstroSat CZTI detection of a long burst
  93. EP260327a: Einstein Probe detection of an X-ray transient
  94. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  95. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  96. IPN triangulation of GRB 260320A
  97. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  98. GRB 260326A: Fermi GBM Detection
  99. GRB 260325A: Fermi GBM Final Localization
  100. GRB 260326A: Fermi GBM Final Real-time Localization

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