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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"

8474 results found.

  1. GRB 260515A: JinShan optical counterpart candidate
  2. IceCube-260504A: No Candidate Transients from the Zwicky Transient Facility
  3. GRB 260511B: AstroSat CZTI detection
  4. GRB 260511B: NuSTAR detection of prompt emission
  5. GRB 260511A: NuSTAR detection of prompt emission
  6. GRB 260511B: SVOM/VT optical observation with VHF data
  7. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  8. GRB 260511A: SVOM/VT optical observation with VHF data
  9. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  10. Fermi GBM Sub-Threshold Detection of GRB 260510B
  11. GRB 260509A: LCO optical observations
  12. GRB 260509A: SVOM/VT optical candidate with VHF data
  13. GRB 260509A: LCO optical counterpart detection
  14. GRB 260509A: GOTO optical counterpart candidate
  15. GRB 260506B: AstroSat CZTI detection
  16. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  17. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  18. EP260507a: COLIBRÍ optical observations
  19. EP260507a: Kinder optical counterpart candidate
  20. GRB 260421B: radio observation with the VLA
  21. GRB 260430B: AstroSat CZTI detection of a long burst
  22. GRB 260504B: SVOM/MXT refined analysis and potential detection
  23. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  24. GRB 260429B / EP260429a: AstroSat CZTI detection
  25. GRB 260424B: AstroSat CZTI detection
  26. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  27. GRB 260428A: AstroSat CZTI detection
  28. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  29. GRB 260424A: AstroSat CZTI detection of a long burst
  30. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  31. GRB 260421B: BOOTES-7 early optical afterglow detection
  32. GRB 260421B: LCO optical afterglow confirmation
  33. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  34. EP260416a: Optical follow-up observations with Kinder
  35. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  36. EP260416a: WFST optical observations and rebrightening
  37. EP260416a: SVOM/VT optical observation
  38. EP260416a: COLIBRÍ optical counterpart candidate
  39. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  40. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  41. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  42. GRB 260411B: Fermi-LAT detection
  43. GRB 260411B: GOTO optical counterpart candidate
  44. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  45. GRB 260330B: SVOM/VT further optical observation
  46. EP260403a: COLIBRÍ optical counterpart candidate
  47. GRB 260330B: SVOM/VT optical candidate
  48. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  49. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  50. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  51. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  52. EP260329b: GOTO detection of optical counterpart
  53. Fermi GBM Sub-Threshold Detection of GRB 260330B
  54. EP260329a: COLIBRÍ optical upper limit
  55. EP260329a: NOT optical counterpart candidate
  56. EP260329b: Optical follow-up with Kinder observations
  57. EP-WXT trigger 01709259209: TRT optical counterpart detection
  58. EP260327a: COLIBRÍ optical upper limits
  59. EP260321a: Upper limits from a neutrino search with IceCube
  60. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  61. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  62. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  63. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  64. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  65. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  66. EP260321a: further Kinder optical observations
  67. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  68. Fermi GBM Sub-Threshold Detection of GRB 260321A
  69. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  70. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  71. GRB 260310A / AT 2026fgk: radio detection with the VLA
  72. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  73. EP260316a: COLIBRÍ faint optical counterpart candidate
  74. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  75. EP260316a: Xinglong optical upper limit
  76. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  77. IceCube-260315A: COLIBRÍ optical observations
  78. EP260314a: optical upper limit with Kinder observations
  79. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  80. EP260314a: COLIBRÍ optical upper limit
  81. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  82. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  83. EP260314a: SVOM/VT optical candidate
  84. GRB 260310A / AT2026fgk: SAO RAS optical observations
  85. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  86. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  87. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  88. GRB260310A / AT2026fgk: P200 Spectroscopy
  89. GRB 260131A/B: radio detection with the VLA
  90. GRB 260208A: radio detection with the VLA
  91. Fermi GBM Sub-Threshold Detection of GRB 260307B
  92. GRB 260307B: Mephisto optical upper limits
  93. GRB 260307B: possible NOT optical counterpart
  94. GRB 260307B: SVOM/VT upper limit with X band data analysis
  95. GRB 260307B: SVOM/VT optical candidate
  96. GRB 260307B: SVOM/C-GFT upper limit
  97. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  98. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  99. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  100. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow

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