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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"

28096 results found.

  1. GRB 260411B: Fermi-LAT detection
  2. GRB 260412A: SVOM detection of a long burst
  3. GRB 260412A: Fermi GBM Final Real-time Localization
  4. GRB 260411B: COLIBRÍ optical observations
  5. GRB 260411B: Ondrejov D50 optical afterglow detection
  6. GRB260411B: 3.6m DOT optical observation
  7. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  8. GRB 260411B: SVOM/GRM observation of a long burst
  9. GRB 260409A: Insight-HXMT/HE detection
  10. GRB 260411B: Fermi GBM Detection
  11. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  12. GRB 260411B: Fermi GBM Final Real-time Localization
  13. GRB 260411A: Fermi GBM Final Real-time Localization
  14. EP-WXT01709259790: Optical Upper limits with kinder observations
  15. GRB 260410B: SVOM/GRM detection of a short faint burst
  16. GRB 260410B: Fermi GBM Final Real-time Localization
  17. EP-WXT01709259790: Xinglong optical upper limit
  18. GRB 260410A: Fermi-LAT detection
  19. GRB 260410A: Fermi GBM Final Real-time Localization
  20. EP260321a: Chandra X-ray Non-detection
  21. GRB 260409A: Fermi GBM Final Real-time Localization
  22. GRB 260407A: GECAM-A detection
  23. GRB 260407A: Insight-HXMT/HE detection
  24. EP260409a: SVOM/VT optical upper limits
  25. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  26. EP260409a: Einstein Probe detection of an X-ray transient
  27. EP260321a: VLA radio detection
  28. GRB 260404A: Fermi GBM Final Localization
  29. GRB 260407A: Glowbug gamma-ray detection
  30. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  31. GRB 260310A / AT2026fgk: X-ray rebrightening
  32. EP260402a / GRB 260402A: Mephisto optical upper limits
  33. EP-WXT01709259586: Xinglong optical upper limit
  34. EP260403a: Mephisto optical upper limits
  35. EP260402a/GRB 260402A: Xinglong optical upper limit
  36. EP260321a: Upper limits from VLA radio observations
  37. GRID detection of GRB 260401A
  38. GRB 260407A: Fermi GBM Final Real-time Localization
  39. EP260405a: Einstein Probe detection of a fast X-ray transient
  40. GRB 260330B: SVOM/VT further optical observation
  41. EP260403a: LCO optical counterpart detection
  42. GRB 260330B: SVOM/VT optical candidate
  43. EP260403a: Einstein Probe detection of an X-ray transient
  44. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  45. GRB 260403A: AstroSat CZTI detection
  46. GRB 260402C: NuSTAR detection of prompt emission
  47. GRB 260402C: AstroSat CZTI detection of a long burst
  48. GRB 260403A: Fermi GBM Final Real-time Localization
  49. GRB 260402B: Fermi GBM Final Real-time Localization
  50. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  51. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  52. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  53. GRB 260402A: SVOM detection of a burst
  54. GRB 260401A: NuSTAR detection of prompt emission
  55. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  56. GRB 260401A: MAXI/GSC detection
  57. GRB 260401A: Fermi GBM Final Real-time Localization
  58. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  59. EP260327a: Xinglong optical upper limit
  60. EP260329b: GOTO detection of optical counterpart
  61. GRB 260330B: SVOM/VT optical upper limits
  62. Konus-Wind detection of GRB 260320A
  63. Konus-Wind detection of GRB 260316B (duplicate submission)
  64. Konus-Wind detection of GRB 260316B
  65. GRB 260321A: SVOM/ECLAIRs refined analysis
  66. GRB 260330A: Glowbug gamma-ray detection
  67. GRB 260310A: VLA Multi-frequency Radio Observations
  68. Fermi GBM Sub-Threshold Detection of GRB 260330B
  69. GRB 260330B: SVOM detection of a burst
  70. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  71. EP260329a: COLIBRÍ optical upper limit
  72. GRB 260330A: Fermi GBM Final Real-time Localization
  73. GRB 260327A: Insight-HXMT/HE detection
  74. EP260329b: Optical follow-up with Kinder observations
  75. EP260329a: Optical upper limit with Kinder observations
  76. GRB 260326A: Insight-HXMT/HE detection
  77. EP260329b: Einstein Probe detection of an X-ray transient
  78. EP260329a: Einstein Probe detection of an X-ray transient
  79. EP-WXT trigger 01709259209: TRT optical counterpart detection
  80. GRID detection of GRB 260326A
  81. EP260327a: SVOM/VT optical upper limits
  82. SMA Detection of GRB 260310A / AT 2026fgk
  83. GRB 260327A: AstroSat CZTI detection of a long burst
  84. EP260327a: Einstein Probe detection of an X-ray transient
  85. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  86. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  87. IPN triangulation of GRB 260320A
  88. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  89. GRB 260326A: Fermi GBM Detection
  90. GRB 260325A: Fermi GBM Final Localization
  91. GRB 260326A: Fermi GBM Final Real-time Localization
  92. EP260321a: Upper limits from a neutrino search with IceCube
  93. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  94. IPN triangulation of GRB 260316B
  95. GRID detection of GRB 260320A
  96. EP260321a: Gemini-South confirmation of a supernova
  97. GRB 260310A: LBT optical observations
  98. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  99. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  100. GRB 260323A: Fermi GBM Final Real-time Localization

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