摘要
We report on a pilot study on identifying metal-poor stars pre-enriched by Pair-Instability Supernovae（PISNe）.Very massive,first generation（Population Ⅲ） stars（140 M⊙≤M≤260 M⊙）end their lives as PISNe,which have been predicted by theories,but no relics of PISNe have been observed yet.Among the distinct characteristics of the yields of PISNe,as predicted by theoretical calculations,are a strong odd-even effect,and a strong overabundance of Ca with respect to iron and the solar ratio.We use the latter characteristic to identify metal-poor stars in the Galactic halo that have been pre-enriched by PISNe,by comparing metallicites derived from strong, co-added Fe lines detected in low-resolution（i.e.,R=λ/△λ～2000）spectra of the Sloan Digital Sky Survey（SDSS）,with metallicities determined by the SDSS Stellar Parameters Pipeline（SSPP）.The latter are based on the strength of the CaⅡ K line and assumptions on the Ca/Fe abundance ratio.Stars are selected as candidates if their metallicity derived from Fe lines is significantly lower than the SSPP metallicities.In a sample of 12 300 stars for which SDSS spectroscopy is available,we have identified 18 candidate stars.Higher resolution and signal-to-noise ratio spectra of these candidates are being obtained with the Very Large Telescope of the European Southern Observatory and the XSHOOTER spectrograph,to determine their abundance patterns,and to verify our selection method.We plan to apply our method to the database of several million stellar spectra to be acquired with the Guo Shou Jing Telescope （LAMOST）in the next five years.
We report on a pilot study on identifying metal-poor stars pre-enriched by Pair-Instability Supernovae（PISNe）.Very massive,first generation（Population Ⅲ） stars（140 M⊙≤M≤260 M⊙）end their lives as PISNe,which have been predicted by theories,but no relics of PISNe have been observed yet.Among the distinct characteristics of the yields of PISNe,as predicted by theoretical calculations,are a strong odd-even effect,and a strong overabundance of Ca with respect to iron and the solar ratio.We use the latter characteristic to identify metal-poor stars in the Galactic halo that have been pre-enriched by PISNe,by comparing metallicites derived from strong, co-added Fe lines detected in low-resolution（i.e.,R=λ/△λ～2000）spectra of the Sloan Digital Sky Survey（SDSS）,with metallicities determined by the SDSS Stellar Parameters Pipeline（SSPP）.The latter are based on the strength of the CaⅡ K line and assumptions on the Ca/Fe abundance ratio.Stars are selected as candidates if their metallicity derived from Fe lines is significantly lower than the SSPP metallicities.In a sample of 12 300 stars for which SDSS spectroscopy is available,we have identified 18 candidate stars.Higher resolution and signal-to-noise ratio spectra of these candidates are being obtained with the Very Large Telescope of the European Southern Observatory and the XSHOOTER spectrograph,to determine their abundance patterns,and to verify our selection method.We plan to apply our method to the database of several million stellar spectra to be acquired with the Guo Shou Jing Telescope （LAMOST）in the next five years.
基金
J.R.and N.C.acknowledge financial support by the Global Networks program of Universitt Heidelberg
by Deutsche Forschungsgemeinschaft through grant CH 214/5-1
Sonderforschungsbereich SFB 881"The Milky Way System"(subproject A4)
J.Ren and G.Zhao acknowledge the support by the National Natural Science Foundation of China(Grant Nos.11233004 and 11243004)
J.Ren acknowledges partial financial support from the Shandong University Fund for Graduate Study Abroad
Funding for the SDSS and SDSS-II has been provided by the Alfred P.Sloan Foundation,the Participating Institutions,the National Science Foundation,the U.S.Department of Energy,the National Aeronautics and Space Administration,the Japanese Monbukagakusho,the Max Planck Society,and the Higher Education Funding Council for England
