As the Sun's, a localized region of the active solar-type star's surface and atmo sphere that display most or all of the following phenomena: sunspots, faculae, plages, filaments, prominences, flares and bright condensation in the corona. These phenom ena have been found in the surface and atmosphere of almost all solar-type stars. So that we call solar-type stars are active solar-type star. The recent study of the activity– rotation relation shows that the level of activity in the X-ray-to-bolometric luminosity ratio ( RX = LX/Lbol ) as a function of the rotation period of solar-type stars. So that the rapid rotators ( T Tauri stars, RS CVn and BY Dra system ) should have high level of activity. We selected a group of 9 stars ( four rotation stars, three double or Multi stars, one RS CVn and one BY Dra system ) for high-resolution spectroscopic observations. These stars, selected from the cross-correlation of the ROSAT X-ray catalog and the Tycho catalog, are strong X-ray sources that have been identified as bright ( mv ≤ 10 ) solar-type stars. To study the relationship between lithium and activity, we carry out a high-resolution spectrometry for 9 sample stars using the High Resolution Echlle Spec trograph ( HiRES ) attached to the 2.4 m telescope at the Lijiang station of the Yunnan Astronomical Observatories, Chinese Academy of Science ( YNAO ). Based on the high-resolution spectroscopic observations, we derived the lithium abundance of 9 ac tive solar-type stars by comparing the measured Li I λ = 670.8 nm equivalent width with the curve of growth calculations in non-LTE ( NLTE ) conditions. The study of the connection between the lithium abundance with X-ray luminosity finds that the ac tive solar-type stars with high X-ray luminosity also have higher lithium abundance. We also calculated the absolute flux of Ca II H and K line ( FBR ) for 9 sample stars, and search the connection between the lithium abundance with absolute flux of Ca II H and K line. We find that the lithium abundance increasing with the absolute flux of Ca II H and K lines increase. The result further confirms that the lithium abundance increasing with stellar activity. The result also indicates that as the active becomes stronger, the lithium abundance increases for these active solar-type stars. Considering the lithium abundance decrease with stellar age increasing, the results support that like lithium abundance, rotation velocity and activity level can also be an indicator of age for solar-type stars.
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