Subaru/HDS Study of the Extremely Metal-Poor Star CS 29498-043: Abundance Analysis Details and Comparison with Other Carbon-Rich Objects

摘要

WereportonthedetailsofanabundancestudyusingtheSubaruTelescopeHighDispersionSpectrographfortheextremelymetal-poor($$[mathrm{Fe/H}]=-3.75$$)starCS29498-043,whoseoverabundancesofC,N,Mg,andSiwerereportedinourpreviouswork.TheeffectofthelargeoverabundanceofMgfoundinthisobjectonthestellaratmosphereisincludedintheabundanceanalysis.Wealsoperformedasimilaranalysisfortheothereightcarbon-rich,metal-poor($$-2.7[mathrm{Fe/H}]-1.9$$)starswithexcessesof$$s$$-processelements,andforthecarbon-richobjectCS22957-027whichshowsnoexcessofneutron-captureelements.Neutron-captureelementsinCS29498-043,aswellasCS22949-037whichisalsoknowntohavelargeexcessesofC,N,Mg,andSi,donotshowanyoverabundance.Thisfactclearlydistinguishesthesetwostarsfromothercarbon-richobjectswithexcessesof$$s$$-processelements.TheabundancesofMg,Al,andSiinCS29498-043andCS22949-037aresignificantlyhigherthanthoseinothercarbon-richobjectsandnon-carbon-richstarswithsimilarmetallicities.Theabundancenatureofthesetwostarssuggeststheexistenceofaclassofextremelymetal-poorstarswithlargeexcessesofC,N,Mg,Al,andSi,whichpresumablyoriginatefromsupernovaeinwhichrelativelylittlematerialescapedfromtheironcore.