J/ApJ/769/57ivo://CDS.VizieR/J/ApJ/769/57doi:10.26093/cds/vizier.17690057CDSFrebel A.Casey A.R.Jacobson H.R.Yu Q.2017-12-06T07:38:22Z2015-01-13T07:43:34ZCDS support team

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

cds-question@unistra.frline-intensitieseffective-temperaturechemical-abundanceschemically-peculiar-starsIt is well established that stellar effective temperatures determined from photometry and spectroscopy yield systematically different results. We describe a new, simple method to correct spectroscopically derived temperatures ("excitation temperatures") of metal-poor stars based on a literature sample with -3.3<[Fe/H]<-2.5. Excitation temperatures were determined from Fe I line abundances in high-resolution optical spectra in the wavelength range of ~3700-7000{AA}, although shorter wavelength ranges, up to 4750-6800{AA}, can also be employed, and compared with photometric literature temperatures. Our adjustment scheme increases the temperatures up to several hundred degrees for cool red giants, while leaving the near-main-sequence stars mostly unchanged. Hence, it brings the excitation temperatures in good agreement with photometrically derived values. The modified temperature also influences other stellar parameters, as the Fe I-Fe II ionization balance is simultaneously used to determine the surface gravity, while also forcing no abundance trend on the absorption line strengths to obtain the microturbulent velocity. As a result of increasing the temperature, the often too low gravities and too high microturbulent velocities in red giants become higher and lower, respectively. Our adjustment scheme thus continues to build on the advantage of deriving temperatures from spectroscopy alone, independent of reddening, while at the same time producing stellar chemical abundances that are more straightforwardly comparable to studies based on photometrically derived temperatures. Hence, our method may prove beneficial for comparing different studies in the literature as well as the many high-resolution stellar spectroscopic surveys that are or will be carried out in the next few years.2013ApJ...769...57Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/769/57CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/AJ/147/136 : Stars of very low metal abundance. VI. (Roederer+, 2014)J/ApJ/762/26 : Most metal-poor stars. II. Galactic halo stars (Yong+, 2013)J/ApJ/753/64 : Detailed abundances for 97 metal-poor stars (Ishigaki+, 2012)J/ApJ/742/54 : CASH project II. 14 extremely metal-poor stars (Hollek+, 2011)J/ApJ/711/573 : Detailed abundances in a halo stellar stream (Roederer+, 2010)J/ApJ/708/560 : Spectroscopy of UMa II and Coma Ber (Frebel+, 2010)J/A+A/512/A54 : Teff and Fbol from Infrared Flux Method (Casagrande+, 2010)J/A+A/493/601 : Lithium abundances of halo dwarfs (Hosford+, 2009)J/ApJ/681/1524 : Detailed abundances for 28 metal-poor stars (Lai+, 2008)J/ApJS/168/128 : UBVRcIc photometry of FHB and metal-poor stars (Beers+, 2007)J/AJ/132/137 : Abundances of extremely metal-poor carbon stars (Cohen+, 2006)J/A+A/440/321 : Chemical abundances in 43 metal-poor stars (Jonsell+, 2005)J/A+A/439/129 : HERES II. Spectroscopic analysis (Barklem+, 2005)J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)J/AJ/128/2402 : Extremely metal-poor star candidates abundances (Lai+, 2004)J/A+A/425/671 : Equivalent widths of 10 metal-poor halo stars (Bai+, 2004)J/A+A/404/187 : Equivalent widths for metal-poor stars (Gratton+, 2003)J/A+A/403/1105 : Extremely metal-poor giants EWs (Francois+, 2003)J/AJ/119/1448 : Improved properties for cool stars (Houdashelt+, 2000)J/A+AS/131/209 : JHK(L') photometry of giant stars (Alonso+ 1998)J/A+AS/97/951 : uvby-beta photometry of metal-poor stars (Schuster+ 1993)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/769/57https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/769/57http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/769/57https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/769/57https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/769/57http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/769/57GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/769/57/table3 (Stellar parameters of the sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/769/57/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/769/57/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/769/57/table3?GETtext/xml+votable180.050000true210.63268949.68609670.0055555555555555566/16935 26025 26457 44542 44890 48501 48798https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/769/57?format=asciiOpticaldefaultJ/ApJ/769/57/table3Stellar parameters of the sampleSimbadNameSimbad column added by the CDSmeta.idcharNameStar namemeta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTeff[4630/6420] Adopted effective temperatureKphys.temperature.effectiveintTeff2[4644/6276]? Effective temperature from V-KKphys.temperature.effectiveintnullableTeffi[4380/6430] Initial determination of TeffKphys.temperature.effectiveintloggi[0.05/4.4] Initial determination of log(g)log(cm.s**-2)phys.gravityfloat[Fe/H]i[-3.3/-2.7] Initial determination of [Fe/H]log(Sun)phys.abund.FefloatVti[1.3/2.9] Initial determination of microturbulent velocity (V_t_)km/sphys.veloc;phys.atmol.initialfloatTeffc[4612/6457] Teff after temperature correctionKphys.temperature.effectiveintloggc[0.8/4.4] log(g) after temperature correctionlog(cm.s**-2)phys.gravityfloat[Fe/H]c[-3.3/-2.6] [Fe/H] after temperature correctionlog(Sun)phys.abund.FefloatVtc[1.4/2.7] V_t_ after temperature correctionkm/sphys.veloc.microTurbfloatEWsDisplay the Equivalent Widths for this star (table1)meta.ref.urlchar_RAPositions from SIMBAD database (right ascension part)degpos.eq.ra;meta.main_DEPositions from SIMBAD database (declination part)degpos.eq.dec;meta.mainJ/ApJ/769/57/table1Equivalent widths and metal line abundances of stars in the calibration samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelength{lambda}; Angstroms0.1nmem.wldoubleIonSpecies identifierphys.atmol.ionStagecharExPotExcitation potentialeVphys.atmol.excitationfloatlog(gf)? Log of the oscillator strengthphys.atmol.oscStrengthfloatnullableW(HD122563)? Equivalent width in HD122563 (m{AA})1e-13mspect.line.eqWidthfloatnullablee(HD122563)? log{epsilon} abundance in HD122563phys.abundfloatnullableW(HE1523-0901)? Equivalent width in HE1523-0901 (m{AA})1e-13mspect.line.eqWidthfloatnullablee(HE1523-0901)? log{epsilon} abundance in HE1523-0901phys.abundfloatnullableW(BD-185550)? Equivalent width in BD-18 5550 (m{AA})1e-13mspect.line.eqWidthfloatnullablee(BD-185550)? log{epsilon} abundance in BD-18 5550phys.abundfloatnullableW(CS22892-052)? Equivalent width in CS22892-052 (m{AA})1e-13mspect.line.eqWidthfloatnullablee(CS22892-052)? log{epsilon} abundance in CS22892-052phys.abundfloatnullableW(HD140283)? Equivalent width in HD140283 (m{AA})1e-13mspect.line.eqWidthfloatnullablee(HD140283)? log{epsilon} abundance in HD140283phys.abundfloatnullableW(CD-2417504)? Equivalent width in CD-24 17504 (m{AA})1e-13mspect.line.eqWidthfloatnullablee(CD-2417504)? log{epsilon} abundance in CD-24 17504phys.abundfloatnullableW(G64-12)? Equivalent width in G64-12 (m{AA})1e-13mspect.line.eqWidthfloatnullablee(G64-12)? log{epsilon} abundance in G64-12phys.abundfloatnullable