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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"

27475 results found.

  1. GRB 260407A: GECAM-A detection
  2. GRB 260407A: Insight-HXMT/HE detection
  3. EP260409a: SVOM/VT optical upper limits
  4. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  5. EP260409a: Einstein Probe detection of an X-ray transient
  6. EP260321a: VLA radio detection
  7. GRB 260404A: Fermi GBM Final Localization
  8. GRB 260407A: Glowbug gamma-ray detection
  9. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  10. GRB 260310A / AT2026fgk: X-ray rebrightening
  11. EP260402a / GRB 260402A: Mephisto optical upper limits
  12. EP-WXT01709259586: Xinglong optical upper limit
  13. EP260403a: Mephisto optical upper limits
  14. EP260402a/GRB 260402A: Xinglong optical upper limit
  15. EP260321a: Upper limits from VLA radio observations
  16. GRID detection of GRB 260401A
  17. GRB 260407A: Fermi GBM Final Real-time Localization
  18. EP260405a: Einstein Probe detection of a fast X-ray transient
  19. GRB 260330B: SVOM/VT further optical observation
  20. EP260403a: LCO optical counterpart detection
  21. GRB 260330B: SVOM/VT optical candidate
  22. EP260403a: Einstein Probe detection of an X-ray transient
  23. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  24. GRB 260403A: AstroSat CZTI detection
  25. GRB 260402C: NuSTAR detection of prompt emission
  26. GRB 260402C: AstroSat CZTI detection of a long burst
  27. GRB 260403A: Fermi GBM Final Real-time Localization
  28. GRB 260402B: Fermi GBM Final Real-time Localization
  29. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  30. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  31. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  32. GRB 260402A: SVOM detection of a burst
  33. GRB 260401A: NuSTAR detection of prompt emission
  34. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  35. GRB 260401A: MAXI/GSC detection
  36. GRB 260401A: Fermi GBM Final Real-time Localization
  37. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  38. EP260327a: Xinglong optical upper limit
  39. EP260329b: GOTO detection of optical counterpart
  40. GRB 260330B: SVOM/VT optical upper limits
  41. Konus-Wind detection of GRB 260320A
  42. Konus-Wind detection of GRB 260316B (duplicate submission)
  43. Konus-Wind detection of GRB 260316B
  44. GRB 260321A: SVOM/ECLAIRs refined analysis
  45. GRB 260330A: Glowbug gamma-ray detection
  46. GRB 260310A: VLA Multi-frequency Radio Observations
  47. Fermi GBM Sub-Threshold Detection of GRB 260330B
  48. GRB 260330B: SVOM detection of a burst
  49. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  50. EP260329a: COLIBRÍ optical upper limit
  51. GRB 260330A: Fermi GBM Final Real-time Localization
  52. GRB 260327A: Insight-HXMT/HE detection
  53. EP260329b: Optical follow-up with Kinder observations
  54. EP260329a: Optical upper limit with Kinder observations
  55. GRB 260326A: Insight-HXMT/HE detection
  56. EP260329b: Einstein Probe detection of an X-ray transient
  57. EP260329a: Einstein Probe detection of an X-ray transient
  58. EP-WXT trigger 01709259209: TRT optical counterpart detection
  59. GRID detection of GRB 260326A
  60. EP260327a: SVOM/VT optical upper limits
  61. SMA Detection of GRB 260310A / AT 2026fgk
  62. GRB 260327A: AstroSat CZTI detection of a long burst
  63. EP260327a: Einstein Probe detection of an X-ray transient
  64. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  65. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  66. IPN triangulation of GRB 260320A
  67. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  68. GRB 260326A: Fermi GBM Detection
  69. GRB 260325A: Fermi GBM Final Localization
  70. GRB 260326A: Fermi GBM Final Real-time Localization
  71. EP260321a: Upper limits from a neutrino search with IceCube
  72. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  73. IPN triangulation of GRB 260316B
  74. GRID detection of GRB 260320A
  75. EP260321a: Gemini-South confirmation of a supernova
  76. GRB 260310A: LBT optical observations
  77. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  78. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  79. GRB 260323A: Fermi GBM Final Real-time Localization
  80. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  81. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  82. GRB 260322A: Fermi GBM Final Localization
  83. GRB 260320A: Glowbug gamma-ray detection
  84. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  85. EP260321a: COLIBRÍ further optical observations and brightening
  86. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  87. EP260214b: ATCA 6 GHz detection
  88. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  89. EP260321a: GOTO detection of blue variable source
  90. EP260321a: further Kinder optical observations
  91. GRB 260320A: Insight-HXMT/HE detection
  92. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  93. Fermi GBM Sub-Threshold Detection of GRB 260321A
  94. GRB 260321A: SVOM detection of a burst
  95. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  96. EP260321a: Einstein Probe detection of an X-ray transient
  97. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  98. GRB 260318A: Glowbug gamma-ray detection
  99. GRB 260310A / AT 2026fgk: KAIT optical observations
  100. GRB 260320A: NuSTAR detection of prompt emission

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