J/ApJ/798/110ivo://CDS.VizieR/J/ApJ/798/110doi:10.26093/cds/vizier.17980110CDSLi H.-N.Zhao G.Christlieb N.Wang L.Wang W.Zhang Y.Hou Y.,Yuan H.2017-07-06T06:26:07Z2015-06-18T13:12:30ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frchemical-abundancesline-intensitiesradial-velocitychemically-peculiar-starsWe report on early results from a pilot program searching for metal-poor stars with LAMOST and follow-up high-resolution observation acquired with the MIKE spectrograph attached to the Magellan II telescope. We performed detailed abundance analysis for eight objects with iron abundances [Fe/H]<-2.0, including five extremely metal-poor (EMP; [Fe/H]<-3.0) stars with two having [Fe/H]<-3.5. Among these objects, three are newly discovered EMP stars, one of which is confirmed for the first time with high-resolution spectral observations. Three program stars are regarded as carbon-enhanced metal-poor (CEMP) stars, including two stars with no enhancement in their neutron-capture elements, which thus possibly belong to the class of CEMP-no stars; one of these objects also exhibits significant enhancement in nitrogen, and is thus a potential carbon and nitrogen-enhanced metal-poor star. The [X/Fe] ratios of the sample stars generally agree with those reported in the literature for other metal-poor stars in the same [Fe/H] range. We also compared the abundance patterns of individual program stars with the average abundance pattern of metal-poor stars and find only one chemically peculiar object with abundances of at least two elements (other than C and N) showing deviations larger than 0.5 dex. The distribution of [Sr/Ba] versus [Ba/H] agrees that an additional nucleosynthesis mechanism is needed aside from a single r-process. Two program stars with extremely low abundances of Sr and Ba support the prospect that both main and weak r-processes may have operated during the early phase of Galactic chemical evolution. The distribution of [C/N] shows that there are two groups of carbon-normal giants with different degrees of mixing. However, it is difficult to explain the observed behavior of the [C/N] of the nitrogen-enhanced unevolved stars based on current data.2015ApJ...798..110Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/798/110CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/570/A107 : WDMS from LAMOST DR1 (Ren+, 2014)J/ApJ/769/57 : Equivalent widths of metal-poor stars (Frebel+, 2013)J/ApJ/762/27 : Most metal-poor stars. III. [Fe/H]<=-3.0 stars (Yong+, 2013)J/ApJ/762/26 : Most metal-poor stars. II. Galactic halo stars (Yong+, 2013)J/ApJ/762/25 : The most metal-poor stars in HES and SDSS. I. (Norris+, 2013)J/ApJ/742/54 : CASH project II. 14 extremely metal-poor stars (Hollek+, 2011)J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)J/ApJ/724/341 : Nucleosynthesis of massive metal-free stars (Heger+, 2010)J/A+A/501/519 : Extremely metal-poor star abundances (Bonifacio+, 2009)J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)J/ApJ/681/1524 : Detailed abundances for 28 metal-poor stars (Lai+, 2008)J/A+A/484/721 : HES survey. IV. Candidate metal-poor stars (Christlieb+, 2008)J/ApJ/658/1203 : Nitrogen-enhanced metal-poor stars (Johnson+, 2007)J/ApJ/655/492 : Equivalent widths of 26 metal-poor stars (Aoki+, 2007)J/ApJ/652/1585 : Bright metal-poor stars from HES survey (Frebel+, 2006)J/A+A/439/129 : HERES II. Spectroscopic analysis (Barklem+, 2005)J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)J/A+A/404/187 : Equivalent widths for metal-poor stars (Gratton+, 2003)J/AJ/117/981 : Estimation of stellar metal abundance. II. (Beers+, 1999)J/AJ/103/1987 : Stars of very low metal abundance (Beers+ 1992)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/798/110https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/798/110http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/798/110https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/798/110https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/798/110http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/798/110GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/798/110/stars (Log of the Magellan/MIKE observations and adopted stellar parameters of the program stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/798/110/stars?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/798/110/stars?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/798/110/stars?GETtext/xml+votable180.050000true1.571666710.96161110.0055555555555555566/17749 18132 18178 19652 23097 23220 31737 32312https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/798/110?format=asciiOpticaldefaultJ/ApJ/798/110/starsLog of the Magellan/MIKE observations and adopted stellar parameters of the program starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDIdentifier (JHHMM+DDMM; <LAMOST JHHMMSS.ss+DDMMSS.s> in Simbad)meta.id;meta.maincharRAJ2000Hour of right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of declination (J2000)pos.eq.dec;meta.mainrmag[10.8/15] r-band magnitudemagphot.mag;em.opt.RfloatDateMagellan/MIKE observation datetime.epoch;obsnullableExp[360/2700] Exposure timestime.duration;obs.exposureintS/N[43/106] Signal to noise ratio at {lambda}~4500{AA} (pixel^-1^)stat.snrintRV[-325/122] Radial velocitykm/sphys.veloc;pos.heliocentricfloatAbDisplay the abundancesmeta.ref.urlcharEWsDisplay the equivalent width measurements for this starmeta.ref.urlcharTeff1[4330/6330] MIKE effective temperatureKphys.temperature.effectiveintlogg1[0.1/4.2] MIKE surface gravitylog(cm.s**-2)phys.gravityfloat[Fe/H]1[-3.8/-2.2] MIKE metallicitylog(Sun)phys.abund.ZfloatVt[1.5/2.8] MIKE microturbulent velocitykm/sphys.velocfloatTeff2[4795/6260] LAMOST effective temperatureKphys.temperature.effectiveintlogg2[1.2/3.6] LAMOST surface gravitylog(cm.s**-2)phys.gravityfloat[Fe/H]2[-3.4/-2.5] LAMOST metallicitylog(Sun)phys.abund.ZfloatJ/ApJ/798/110/table2Equivalent width measurements and line-by-line abundancesIonIon identifierphys.atmol.ionStagecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambda[3566.3/7699] Wavelength in Angstroms0.1nmem.wlfloatExPot[0/4.5] Excitation potential {chi}eVphys.atmol.excitationfloatlog(gf)[-5/0.7]? Log of oscillator strengthphys.atmol.oscStrengthfloatnullableEW1? Equivalenth width in J0006+1057 (m{AA})1e-13mspect.line.eqWidthfloatnullablef_EW1[s] s=synthetic-derived abundance in EW1meta.codecharlogAb1[-3/5.1]? Log({epsilon}(X)) in J0006+1057phys.abundfloatnullabledev1? Deviation of J0006+1057 abundance (1)obs.param;arith.difffloatnullableEW2? Equivalenth width in J0102+0428 (m{AA})1e-13mspect.line.eqWidthfloatnullablef_EW2[s] s=synthetic-derived abundance in EW2meta.codecharlogAb2[-2.2/5.4]? Log({epsilon}(X)) in J0102+0428phys.abundfloatnullabledev2? Deviation of J0102+0428 abundance (1)obs.param;arith.difffloatnullableEW3? Equivalenth width in J0126+0135 (m{AA})1e-13mspect.line.eqWidthfloatnullablef_EW3[s] s=synthetic-derived abundance in EW3meta.codecharlogAb3[-2.7/4.6]? Log({epsilon}(X)) in J0126+0135phys.abundfloatnullabledev3? Deviation of J0126+0135 abundance (1)obs.param;arith.difffloatnullableEW4? Equivalenth width in J0257-0022 (m{AA})1e-13mspect.line.eqWidthfloatnullablef_EW4[s] s=synthetic-derived abundance in EW4meta.codecharlogAb4[-0.2/6]? Log({epsilon}(X)) in J0257-0022phys.abundfloatnullabledev4? Deviation of J0257-0022 abundance (1)obs.param;arith.difffloatnullableEW5? Equivalenth width in J0326+0202 (m{AA})1e-13mspect.line.eqWidthfloatnullablef_EW5[s] s=synthetic-derived abundance in EW5meta.codecharlogAb5[-2.6/5.3]? Log({epsilon}(X)) in J0326+0202phys.abundfloatnullabledev5? Deviation of J0326+0202 abundance (1)obs.param;arith.difffloatnullableEW6? Equivalenth width in J0343-0227 (m{AA})1e-13mspect.line.eqWidthfloatnullablef_EW6[s] s=synthetic-derived abundance in EW6meta.codecharlogAb6[-2.1/5.6]? Log({epsilon}(X)) in J0343-0227phys.abundfloatnullabledev6? Deviation of J0343-0227 abundance (1)obs.param;arith.difffloatnullableEW7? Equivalenth width in J1626+1721 (m{AA})1e-13mspect.line.eqWidthfloatnullablef_EW7[s] s=synthetic-derived abundance in EW7meta.codecharlogAb7[-0.9/5.1]? Log({epsilon}(X)) in J1626+1721phys.abundfloatnullabledev7? Deviation of J1626+1721 abundance (1)obs.param;arith.difffloatnullableEW8? Equivalenth width in J1709+1616 (m{AA})1e-13mspect.line.eqWidthfloatnullablef_EW8[s] s=synthetic-derived abundance in EW8meta.codecharlogAb8[-1.6/4.3]? Log({epsilon}(X)) in J1709+1616phys.abundfloatnullabledev8? Deviation of J1709+1616 abundance (1)obs.param;arith.difffloatnullableEW9? Equivalenth width in J2113-0212 (m{AA}) (2)1e-13mspect.line.eqWidthfloatnullablef_EW9[s] s=synthetic-derived abundance in EW9meta.codecharlogAb9[-0.4/5.7]? Log({epsilon}(X)) in J2113-0212 (2)phys.abundfloatnullabledev9? Deviation of J2113-0212 abundance (1)obs.param;arith.difffloatnullableJ/ApJ/798/110/table4Mean abundances for the studied starsN8? Number of lines used to derive [X/Fe]8meta.numberintnullableN5? Number of lines used to derive [X/Fe]5meta.numberintnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIonIon or molecule designationphys.atmol.ionStagecharlogAb0Abundance in the Sun log{epsilon}(X)_{sun}_phys.abundfloatlogAb1? Log({epsilon}(X)) in J0006+1057phys.abundfloatnullable[X/Fe]1? Abundance relative to Felog(Sun)phys.abundfloatnullablee_[X/Fe]1? Mean error on [X/Fe]log(Sun)stat.error;phys.abundfloatnullableN1? Number of lines used to derive [X/Fe]1meta.numberintnullablelogAb2? Log({epsilon}(X)) in J0102+0428phys.abundfloatnullable[X/Fe]2? Abundance relative to Felog(Sun)phys.abundfloatnullablee_[X/Fe]2? Mean error on [X/Fe]log(Sun)stat.error;phys.abundfloatnullableN2? Number of lines used to derive [X/Fe]2meta.numberintnullablelogAb3? Log({epsilon}(X)) in J0126+0135phys.abundfloatnullable[X/Fe]3? Abundance relative to Felog(Sun)phys.abundfloatnullablee_[X/Fe]3? Mean error on [X/Fe]log(Sun)stat.error;phys.abundfloatnullableN3? Number of lines used to derive [X/Fe]3meta.numberintnullablelogAb4? Log({epsilon}(X)) in J0257-0022phys.abundfloatnullable[X/Fe]4? Abundance relative to Felog(Sun)phys.abundfloatnullablee_[X/Fe]4? Mean error on [X/Fe]log(Sun)stat.error;phys.abundfloatnullableN4? Number of lines used to derive [X/Fe]4meta.numberintnullablelogAb5? Log({epsilon}(X)) in J0326+0202phys.abundfloatnullable[X/Fe]5? Abundance relative to Felog(Sun)phys.abundfloatnullablee_[X/Fe]5? Mean error on [X/Fe]log(Sun)stat.error;phys.abundfloatnullablelogAb6? Log({epsilon}(X)) in J0343-0227phys.abundfloatnullable[X/Fe]6? Abundance relative to Felog(Sun)phys.abundfloatnullablee_[X/Fe]6? Mean error on [X/Fe]log(Sun)stat.error;phys.abundfloatnullableN6? Number of lines used to derive [X/Fe]6meta.numberintnullablelogAb7? Log({epsilon}(X)) in J1626+1721phys.abundfloatnullable[X/Fe]7? Abundance relative to Felog(Sun)phys.abundfloatnullablee_[X/Fe]7? Mean error on [X/Fe]log(Sun)stat.error;phys.abundfloatnullableN7? Number of lines used to derive [X/Fe]7meta.numberintnullablelogAb8? Log({epsilon}(X)) in J1709+1616phys.abundfloatnullable[X/Fe]8? Abundance relative to Felog(Sun)phys.abundfloatnullablee_[X/Fe]8? Mean error on [X/Fe]log(Sun)stat.error;phys.abundfloatnullable