514 citations · 1.1k across the 23 of their papers we have counts for
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Chromospheric Mg I Emission Lines of Pre-Main-Sequence Stars
Mai Yamashita, Yoichi Itoh, Yuhei Takagi
To reveal details of the internal structure, the relationship between chromospheric activity and the Rossby number has been extensively examined for main-sequence stars. For active…
Rotation-Activity Relation of Ca II and Mg I Infrared Emission Lines of Young Stars
Mai Yamashita, Yoichi Itoh, Yuhei Takagi
To reveal the detail of the internal structure, the relationship between chromospheric activity and the Rossby number, N_R (= rotational period P / convective turnover time tau_c),…
Revealing the spectroscopic variations of FU Orionis object V960 Mon with high-resolution spectroscopy
Yuhei Takagi, Satoshi Honda, Akira Arai +3
We present the results of the high-resolution spectroscopy of the FU Orionis-type star V960 Mon. The brightness of V960 Mon decreased continuously after the outburst was detected i…
Measurements of the Ca II infrared triplet emission lines of pre-main-sequence stars
Mai Yamashita, Yoichi Itoh, Yuhei Takagi
We investigated the chromospheric activity of 60 pre-main-sequence (PMS) stars in four molecular clouds and five moving groups. It is considered that strong chromospheric activity…
The Spectroscopic Variations of the FU Orionis Object V960 Mon
Yuhei Takagi, Satoshi Honda, Akira Arai +4
We present the results of the spectroscopic monitoring of the FU Orionis type star V960 Mon. Spectroscopic variations of a FU Orionis type star will provide valuable information of…
Rapid Dissipation of Protoplanetary Disks in Ophiuchus
Yuhei Takagi, Yoichi Itoh, Akira Arai +2
We present the results of an age determination study for pre-main sequence stars in the Ophiuchus molecular cloud. The ages of eight pre-main sequence stars were estimated from sur…
Disk Dissipation Timescale of Pre-main Sequence Stars in Taurus
Yuhei Takagi, Yoichi Itoh, Yumiko Oasa
We present the results of an age determination study of pre-main sequence stars in the Taurus star-forming region. The ages of 10 single stars with masses of 0.5-1.1 Msun were deri…
Age Determination Method of Pre-Main Sequence Stars with High-Resolution I-Band Spectroscopy
Yuhei Takagi, Yoichi Itoh, Yumiko Oasa
We present a new method for determining the age of late-K type pre-main sequence (PMS) stars by deriving their surface gravity from high-resolution I-band spectroscopy. Since PMS s…