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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"

8275 results found.

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

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