Tadafumi Matsuno, SOKENDAI 3rd year (D1)(Supervisor: Wako Aoki,Takuji Tsujimoto,Yutaka Komiyama)
Chemically-old stars with young age estimates
The combination of a large spectroscopic survey and asteroseismology has discovered a peculiar stellar population in the Galactic disk: they are estimated to be young from their masses but has similar alpha-elements abundances to old stars. Since their existence is not predicted in simple galactic chemical evolution models, the origin is yet to be explained. We obtained high-quality high-resolution optical spectra for 14 of such stars. In addition to the confirmation of their alpha-enhancements, we show that they follow the typical abundance pattern of old stars in almost all the measured elements. Together with the high frequency of radial velocity variation, we suggest they are results of stellar merger or mass transfer from red giants.
Takafumi Tsukui, SOKENDAI 1st year (M1)(Supervisor: 井口聖,永井洋,松田有一)
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