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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"

27777 results found.

  1. IPN triangulation of GRB 260316B
  2. GRID detection of GRB 260320A
  3. EP260321a: Gemini-South confirmation of a supernova
  4. GRB 260310A: LBT optical observations
  5. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  6. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  7. GRB 260323A: Fermi GBM Final Real-time Localization
  8. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  9. GRB 260322A: Fermi GBM Final Localization
  10. GRB 260320A: Glowbug gamma-ray detection
  11. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  12. EP260321a: COLIBRÍ further optical observations and brightening
  13. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  14. EP260214b: ATCA 6 GHz detection
  15. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  16. EP260321a: GOTO detection of blue variable source
  17. EP260321a: further Kinder optical observations
  18. GRB 260320A: Insight-HXMT/HE detection
  19. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  20. Fermi GBM Sub-Threshold Detection of GRB 260321A
  21. GRB 260321A: SVOM detection of a burst
  22. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  23. EP260321a: Einstein Probe detection of an X-ray transient
  24. GRB 260318A: Glowbug gamma-ray detection
  25. GRB 260320A: NuSTAR detection of prompt emission
  26. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  27. GRB 260310A/AT2026fgk: LBT near-infrared observations
  28. NOEMA Detection of GRB 260310A / AT 2026fgk
  29. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  30. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  31. GRB 260318A: Fermi GBM Final Real-time Localization
  32. GRB 260310A / AT 2026fgk: radio detection with the VLA
  33. GRB 260317A: Fermi GBM Final Localization
  34. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  35. GRB 260316B: AstroSat CZTI detection
  36. EP260316a: Xinglong optical upper limit
  37. GRB 260316B: Fermi GBM Final Real-time Localization
  38. EP260316a: optical upper limit with Kinder observations
  39. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  40. GRB 260314A: Glowbug gamma-ray detection
  41. EP260314a: Xinglong optical upper limit
  42. EP260314a: optical upper limit with Kinder observations
  43. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  44. GRID detection of GRB 260312B
  45. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  46. EP260314a: BOOTES-6/DPR optical upper limits at early times
  47. EP260314a: Einstein Probe detection of an X-ray transient
  48. GRB 260310A/AT2026fgk: radio detection at 15GHz
  49. GRB 260310A / AT2026fgk: TNG NIR detection
  50. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  51. GRB 260314A: Fermi GBM Final Real-time Localization
  52. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  53. GRB 260310B: Insight-HXMT/HE detection
  54. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  55. GRB 260312B: AstroSat CZTI detection
  56. Swift BAT trigger 1500295: A solar flare
  57. GRB 260313A: Fermi GBM Final Real-time Localization
  58. Swift BAT trigger 1500287: A solar flare
  59. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  60. GRB 260308A: Insight-HXMT/HE detection
  61. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  62. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  63. GRB 260312B: Glowbug gamma-ray detection
  64. GRB 260310A: potential optical counterpart
  65. Swift BAT trigger 1500148: A solar flare
  66. GRB 260312B: Fermi GBM Final Real-time Localization
  67. Retraction of GCN 43965: GRB is actually solar flare
  68. GRB 260312A: Swift detection of a burst
  69. GRB 260311B: Fermi GBM Final Real-time Localization
  70. GRB 260131A/B: radio detection with the VLA
  71. GRB 260310A: AstroSat CZTI detection of a long burst
  72. GRB 260311A: Fermi GBM Final Real-time Localization
  73. GRB 260310B: Fermi GBM Final Real-time Localization
  74. GRB 260208A: radio detection with the VLA
  75. GRB 260310A: Fermi GBM Final Real-time Localization
  76. GRB 260307A: Glowbug gamma-ray detection
  77. GRB 260308A: Fermi GBM Final Real-time Localization
  78. Fermi GBM Sub-Threshold Detection of GRB 260307B
  79. GRB 260307B: Mephisto optical upper limits
  80. GRB 260307B: possible NOT optical counterpart
  81. GRB 260307B: SVOM/VT upper limit with X band data analysis
  82. GRB 260307B: SVOM/VT optical candidate
  83. GRB 260307B: SVOM detection of a burst
  84. GRB 260307A: Fermi GBM Final Localization
  85. GRB 260207A: TESS Detection and Possible VLA Counterpart
  86. EP260306a: Gemini-North redshift z = 4.773
  87. EP260306a: Einstein Probe detection of an X-ray transient
  88. GRB 260303A: 1.3m DFOT optical upper limit
  89. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  90. GRB 260305A: Fermi GBM Final Real-time Localization
  91. GRB 260303B: AstroSat CZTI detection
  92. GRB 260304A: AstroSat CZTI detection of a long burst
  93. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  94. GRB 260303B: NuSTAR detection of prompt emission
  95. GRB 260303B: Fermi GBM Final Real-time Localization
  96. EP260302a: BOOTES-7 optical counterpart detection at early times
  97. GRB 260303A: SVOM detection of a burst
  98. EP260302a: Einstein Probe detection of an X-ray transient
  99. GRB 251130B: TERI Gamma-ray detection
  100. GRB 260208A: TERI Gamma-ray detection

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