We report the discovery of an extremely metal-poor（EMP） giant,LAMOST J110901.22＋075441.8, which exhibits a large excess of r-process elements with [Eu/Fe] ～ ＋1.16. The star is one of the newly discovered EMP star...We report the discovery of an extremely metal-poor（EMP） giant,LAMOST J110901.22＋075441.8, which exhibits a large excess of r-process elements with [Eu/Fe] ～ ＋1.16. The star is one of the newly discovered EMP stars identified from the LAMOST low-resolution spectroscopic survey and a highresolution follow-up observation with the Subaru Telescope. Stellar parameters and elemental abundances have been determined from the Subaru spectrum. Accurate abundances for a total of 23 elements including 11 neutron-capture elements from Sr through Dy have been derived for LAMOST J110901.22＋075441.8. The abundance pattern of LAMOST J110901.22＋075441.8 in the range of C through Zn is in line with the ＂normal＂ population of EMP halo stars, except that it shows a notable underabundance in carbon. The heavy element abundance pattern of LAMOST J110901.22＋075441.8 is in agreement with other well studied cool r-II metal-poor giants such as CS 22892-052 and CS 31082-001. The abundances of elements in the range from Ba through Dy match the scaled solar r-process pattern well.LAMOST J110901.22＋075441.8 provides the first detailed measurements of neutroncapture elements among r-II stars at such low metallicity with [Fe/H]-3.4, and exhibits similar behavior as other r-II stars in the abundance ratio of Zr/Eu as well as Sr/Eu and Ba/Eu.展开更多
Lithium is an ancient element that was first produced by the Big Bang Nucleosynthesis(BBN)a few minutes after the birth of the Universe.Lithium is a sensitive tracer for a number of processes in a variety of astrophys...Lithium is an ancient element that was first produced by the Big Bang Nucleosynthesis(BBN)a few minutes after the birth of the Universe.Lithium is a sensitive tracer for a number of processes in a variety of astrophysical environments due to its multi-channels of production and fragility.These features also make lithium a complex element at the center of many unsolved problems.The behavior of lithium in the low-mass evolved stars is one such issue.It is known that such stars not only destroy but also produce lithium,while neither the destruction details nor the production mechanisms over different evolutionary phases are clear.In this paper,we summarize the recent results obtained from the studies combining large-scale spectroscopic surveys,asteroseismology,and traditional high-resolution spectroscopy.We present the detailed evolution behaviors from the red giant branch(RGB)to the red clump(RC)phase characterized by the core helium-burning in the stellar interior.We show the new signatures discovered from the recent studies for the lithium-enhanced giants and also discuss various observational and theoretical constraints on lithium production in red clump stars.展开更多
基金the paper.H.N.L.and G.Z.acknowledge supports by the National Natural Science Foundation of China (Grant Nos.11103030, 11233004 and 11390371)W.A.and T.S.are supported by the JSPS Grant-in-Aid for Scientific Research (S: 23224004)+1 种基金S.H.is supported by the JSPS Grant-in-Aid for Scientific Research (c:26400231)N.C.acknowledges support from Sonderforschungsbereich 881 "The Milky Way System" (subproject A4) of the German Research Foundation (DFG)
文摘We report the discovery of an extremely metal-poor（EMP） giant,LAMOST J110901.22＋075441.8, which exhibits a large excess of r-process elements with [Eu/Fe] ～ ＋1.16. The star is one of the newly discovered EMP stars identified from the LAMOST low-resolution spectroscopic survey and a highresolution follow-up observation with the Subaru Telescope. Stellar parameters and elemental abundances have been determined from the Subaru spectrum. Accurate abundances for a total of 23 elements including 11 neutron-capture elements from Sr through Dy have been derived for LAMOST J110901.22＋075441.8. The abundance pattern of LAMOST J110901.22＋075441.8 in the range of C through Zn is in line with the ＂normal＂ population of EMP halo stars, except that it shows a notable underabundance in carbon. The heavy element abundance pattern of LAMOST J110901.22＋075441.8 is in agreement with other well studied cool r-II metal-poor giants such as CS 22892-052 and CS 31082-001. The abundances of elements in the range from Ba through Dy match the scaled solar r-process pattern well.LAMOST J110901.22＋075441.8 provides the first detailed measurements of neutroncapture elements among r-II stars at such low metallicity with [Fe/H]-3.4, and exhibits similar behavior as other r-II stars in the abundance ratio of Zr/Eu as well as Sr/Eu and Ba/Eu.
基金This work is supported by the National Natural Science Foundation of China(11988101,12090040,12090044,12022304,11833006,11973052,11973049,11890694,and U2031203)the National Key R&D Program of China(2019YFA0405502)+6 种基金support of the JSPS-CAS Joint Research Program.H.-L.Y.and H.L.acknowledge support from the Youth Innovation Promotion Association of the CAS(id.2019060 and Y202017,respectively)NAOC Nebula Talents Program.J.-H.Z.acknowledges support from NSFC(12103063)from China Postdoctoral Science Foundation funded project(2020M680672)Y.B.K acknowledges the support of the NSFC(11850410437)H.L.acknowledges support from the Strategic Priority Research Program of Chinese Academy of Sciences,(XDB34020205)Guoshoujing Telescope(the Large Sky Area Multi-Object Fiber Spectroscopic Telescope,LAMOST)is a National Major Scientific Project built by the Chinese Academy of Sciences.Funding for the project has been provided by the National Development and Reform CommissionLAMOST is operated and managed by the National Astronomical Observatories,Chinese Academy of Sciences.
文摘Lithium is an ancient element that was first produced by the Big Bang Nucleosynthesis(BBN)a few minutes after the birth of the Universe.Lithium is a sensitive tracer for a number of processes in a variety of astrophysical environments due to its multi-channels of production and fragility.These features also make lithium a complex element at the center of many unsolved problems.The behavior of lithium in the low-mass evolved stars is one such issue.It is known that such stars not only destroy but also produce lithium,while neither the destruction details nor the production mechanisms over different evolutionary phases are clear.In this paper,we summarize the recent results obtained from the studies combining large-scale spectroscopic surveys,asteroseismology,and traditional high-resolution spectroscopy.We present the detailed evolution behaviors from the red giant branch(RGB)to the red clump(RC)phase characterized by the core helium-burning in the stellar interior.We show the new signatures discovered from the recent studies for the lithium-enhanced giants and also discuss various observational and theoretical constraints on lithium production in red clump stars.
