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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"

27227 results found.

  1. GRB 260330B: SVOM/VT further optical observation
  2. EP260403a: LCO optical counterpart detection
  3. GRB 260330B: SVOM/VT optical candidate
  4. EP260403a: Einstein Probe detection of an X-ray transient
  5. GRB 260403A: AstroSat CZTI detection
  6. GRB 260402C: NuSTAR detection of prompt emission
  7. GRB 260402C: AstroSat CZTI detection of a long burst
  8. GRB 260403A: Fermi GBM Final Real-time Localization
  9. GRB 260402B: Fermi GBM Final Real-time Localization
  10. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  11. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  12. GRB 260402A: SVOM detection of a burst
  13. GRB 260401A: NuSTAR detection of prompt emission
  14. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  15. GRB 260401A: MAXI/GSC detection
  16. GRB 260401A: Fermi GBM Final Real-time Localization
  17. EP260327a: Xinglong optical upper limit
  18. EP260329b: GOTO detection of optical counterpart
  19. GRB 260330B: SVOM/VT optical upper limits
  20. Konus-Wind detection of GRB 260320A
  21. Konus-Wind detection of GRB 260316B (duplicate submission)
  22. Konus-Wind detection of GRB 260316B
  23. GRB 260321A: SVOM/ECLAIRs refined analysis
  24. GRB 260330A: Glowbug gamma-ray detection
  25. Fermi GBM Sub-Threshold Detection of GRB 260330B
  26. GRB 260330B: SVOM detection of a burst
  27. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  28. EP260329a: COLIBRÍ optical upper limit
  29. GRB 260330A: Fermi GBM Final Real-time Localization
  30. GRB 260327A: Insight-HXMT/HE detection
  31. EP260329b: Optical follow-up with Kinder observations
  32. EP260329a: Optical upper limit with Kinder observations
  33. GRB 260326A: Insight-HXMT/HE detection
  34. EP260329b: Einstein Probe detection of an X-ray transient
  35. EP260329a: Einstein Probe detection of an X-ray transient
  36. EP-WXT trigger 01709259209: TRT optical counterpart detection
  37. GRID detection of GRB 260326A
  38. EP260327a: SVOM/VT optical upper limits
  39. SMA Detection of GRB 260310A / AT 2026fgk
  40. GRB 260327A: AstroSat CZTI detection of a long burst
  41. EP260327a: Einstein Probe detection of an X-ray transient
  42. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  43. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  44. IPN triangulation of GRB 260320A
  45. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  46. GRB 260326A: Fermi GBM Detection
  47. GRB 260325A: Fermi GBM Final Localization
  48. GRB 260326A: Fermi GBM Final Real-time Localization
  49. EP260321a: Upper limits from a neutrino search with IceCube
  50. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  51. IPN triangulation of GRB 260316B
  52. GRID detection of GRB 260320A
  53. EP260321a: Gemini-South confirmation of a supernova
  54. GRB 260310A: LBT optical observations
  55. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  56. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  57. GRB 260323A: Fermi GBM Final Real-time Localization
  58. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  59. GRB 260322A: Fermi GBM Final Localization
  60. GRB 260320A: Glowbug gamma-ray detection
  61. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  62. EP260321a: COLIBRÍ further optical observations and brightening
  63. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  64. EP260214b: ATCA 6 GHz detection
  65. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  66. EP260321a: GOTO detection of blue variable source
  67. EP260321a: further Kinder optical observations
  68. GRB 260320A: Insight-HXMT/HE detection
  69. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  70. Fermi GBM Sub-Threshold Detection of GRB 260321A
  71. GRB 260321A: SVOM detection of a burst
  72. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  73. EP260321a: Einstein Probe detection of an X-ray transient
  74. GRB 260318A: Glowbug gamma-ray detection
  75. GRB 260320A: NuSTAR detection of prompt emission
  76. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  77. GRB 260310A/AT2026fgk: LBT near-infrared observations
  78. NOEMA Detection of GRB 260310A / AT 2026fgk
  79. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  80. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  81. GRB 260318A: Fermi GBM Final Real-time Localization
  82. GRB 260310A / AT 2026fgk: radio detection with the VLA
  83. GRB 260317A: Fermi GBM Final Localization
  84. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  85. GRB 260316B: AstroSat CZTI detection
  86. EP260316a: Xinglong optical upper limit
  87. GRB 260316B: Fermi GBM Final Real-time Localization
  88. EP260316a: optical upper limit with Kinder observations
  89. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  90. GRB 260314A: Glowbug gamma-ray detection
  91. EP260314a: Xinglong optical upper limit
  92. EP260314a: optical upper limit with Kinder observations
  93. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  94. GRID detection of GRB 260312B
  95. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  96. EP260314a: BOOTES-6/DPR optical upper limits at early times
  97. EP260314a: Einstein Probe detection of an X-ray transient
  98. GRB 260310A/AT2026fgk: radio detection at 15GHz
  99. GRB 260310A / AT2026fgk: TNG NIR detection
  100. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations

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