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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"

14824 results found.

  1. GRB 260330B: SVOM/VT optical candidate
  2. EP260403a: Einstein Probe detection of an X-ray transient
  3. GRB 260403A: AstroSat CZTI detection
  4. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  5. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  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. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  10. GRB 260402B: Fermi GBM Final Real-time Localization
  11. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  12. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  13. GRB 260402A: SVOM detection of a burst
  14. GRB 260401A: NuSTAR detection of prompt emission
  15. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  16. GRB 260401A: MAXI/GSC detection
  17. GRB 260401A: Fermi GBM Final Real-time Localization
  18. EP260327a: Xinglong optical upper limit
  19. EP260329b: GOTO detection of optical counterpart
  20. GRB 260330B: SVOM/VT optical upper limits
  21. Konus-Wind detection of GRB 260320A
  22. Konus-Wind detection of GRB 260316B (duplicate submission)
  23. Konus-Wind detection of GRB 260316B
  24. GRB 260321A: SVOM/ECLAIRs refined analysis
  25. EP260329a: J-band upper limit with WINTER
  26. GRB 260330A: Glowbug gamma-ray detection
  27. Fermi GBM Sub-Threshold Detection of GRB 260330B
  28. GRB 260330B: SVOM detection of a burst
  29. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  30. EP260329a: COLIBRÍ optical upper limit
  31. EP260329a: EP-FXT follow up observation
  32. EP260329a: NOT optical counterpart candidate
  33. GRB 260330A: Fermi GBM Final Real-time Localization
  34. GRB 260327A: Insight-HXMT/HE detection
  35. EP260329b: Optical follow-up with Kinder observations
  36. EP260329a: Optical upper limit with Kinder observations
  37. GRB 260326A: Insight-HXMT/HE detection
  38. EP260329b: Einstein Probe detection of an X-ray transient
  39. EP260329a: Einstein Probe detection of an X-ray transient
  40. EP-WXT trigger 01709259209: TRT optical counterpart detection
  41. GRID detection of GRB 260326A
  42. EP260327a: SVOM/VT optical upper limits
  43. SMA Detection of GRB 260310A / AT 2026fgk
  44. GRB 260327A: AstroSat CZTI detection of a long burst
  45. EP260327a: Einstein Probe detection of an X-ray transient
  46. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  47. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  48. IPN triangulation of GRB 260320A
  49. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  50. GRB 260326A: Fermi GBM Detection
  51. EP260321a: JinShan near-infrared observations
  52. GRB 260325A: Fermi GBM Final Localization
  53. GRB 260326A: Fermi GBM Final Real-time Localization
  54. EP260321a: Upper limits from a neutrino search with IceCube
  55. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  56. IPN triangulation of GRB 260316B
  57. GRID detection of GRB 260320A
  58. EP260321a: Gemini-South confirmation of a supernova
  59. GRB 260310A: LBT optical observations
  60. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  61. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  62. GRB 260323A: Fermi GBM Final Real-time Localization
  63. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  64. GRB 260322A: Fermi GBM Final Localization
  65. GRB 260320A: Glowbug gamma-ray detection
  66. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  67. EP260321a: COLIBRÍ further optical observations and brightening
  68. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  69. EP260214b: ATCA 6 GHz detection
  70. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  71. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  72. EP260321a: GOTO detection of blue variable source
  73. EP260321a: further Kinder optical observations
  74. GRB 260320A: Insight-HXMT/HE detection
  75. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  76. Fermi GBM Sub-Threshold Detection of GRB 260321A
  77. GRB 260321A: SVOM detection of a burst
  78. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  79. EP260321a: Einstein Probe detection of an X-ray transient
  80. GRB 260318A: Glowbug gamma-ray detection
  81. GRB 260320A: NuSTAR detection of prompt emission
  82. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  83. GRB 260310A/AT2026fgk: LBT near-infrared observations
  84. NOEMA Detection of GRB 260310A / AT 2026fgk
  85. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  86. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  87. GRB 260318A: Fermi GBM Final Real-time Localization
  88. GRB 260310A / AT 2026fgk: radio detection with the VLA
  89. GRB 260317A: Fermi GBM Final Localization
  90. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  91. GRB 260316B: AstroSat CZTI detection
  92. EP260316a: Xinglong optical upper limit
  93. GRB 260316B: Fermi GBM Final Real-time Localization
  94. EP260316a: optical upper limit with Kinder observations
  95. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  96. GRB 260314A: Glowbug gamma-ray detection
  97. EP260314a: Xinglong optical upper limit
  98. EP260314a: optical upper limit with Kinder observations
  99. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  100. GRID detection of GRB 260312B

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