On the Use of Field RR Lyrae as Galactic Probes. II. A New Δ<i>S</i> Calibration to Estimate Their Metallicity*

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dc.contributor.authorCrestani, J.
dc.contributor.authorFabrizio, M.
dc.contributor.authorBraga, V. F.
dc.contributor.authorSneden, C.
dc.contributor.authorPreston, G.
dc.contributor.authorFerraro, I.
dc.contributor.authorIannicola, G.
dc.contributor.authorBono, G.
dc.contributor.authorAlves-Brito, A.
dc.contributor.authorNonino, M.
dc.contributor.authorD'Orazi, V.
dc.contributor.authorInno, L.
dc.contributor.authorMonelli, M.
dc.contributor.authorStorm, J.
dc.contributor.authorAltavilla, G.
dc.contributor.authorChaboyer, B.
dc.contributor.authorDall'Ora, M.
dc.contributor.authorFiorentino, G.
dc.contributor.authorGilligan, C.
dc.contributor.authorGrebel, E. K.
dc.contributor.authorLala, H.
dc.contributor.authorLemasle, B.
dc.contributor.authorMarengo, M.
dc.contributor.authorMarinoni, S.
dc.contributor.authorMarrese, P. M.
dc.contributor.authorMartinez-Vazquez, C. E.
dc.contributor.authorMatsunaga, N.
dc.contributor.authorMullen, J. P.
dc.contributor.authorNeeley, J.
dc.contributor.authorPrudil, Z.
dc.contributor.authorda Silva, R.
dc.contributor.authorStetson, P. B.
dc.contributor.authorThevenin, F.
dc.contributor.authorValenti, E.
dc.contributor.authorWalker, A.
dc.contributor.authorZoccali, M.
dc.date.accessioned2025-01-20T23:55:01Z
dc.date.available2025-01-20T23:55:01Z
dc.date.issued2021
dc.description.abstractWe performed the largest and most homogeneous spectroscopic survey of field RR Lyraes (RRLs). We secured 6300 high-resolution (HR, R similar to 35,000) spectra for 143 RRLs (111 fundamental, RRab; 32 first-overtone, RRc). The atmospheric parameters were estimated by using the traditional approach and the iron abundances were measured by using an LTE line analysis. The resulting iron distribution shows a well-defined metal-rich tail approaching solar iron abundance. This suggests that field RRLs experienced a complex chemical enrichment in the early halo formation. We used these data to develop a new calibration of the Delta S method. This diagnostic, based on the equivalent widths of Ca ii K and three Balmer (H-delta,H-gamma,H-beta) lines, traces the metallicity of RRLs. For the first time, the new empirical calibration: (i) includes spectra collected over the entire pulsation cycle; (ii) includes RRc variables; (iii) relies on spectroscopic calibrators covering more than three dex in iron abundance; and (iv) provides independent calibrations based on one/two/three Balmer lines. The new calibrations were applied to a data set of both SEGUE-SDSS and degraded HR spectra totalling 6451 low-resolution (R similar to 2000) spectra for 5001 RRLs (3439 RRab, 1562 RRc). This resulted in an iron distribution with a median eta = -1.55 0.01 and sigma = 0.51 dex, in good agreement with literature values. We also found that RRc are 0.10 dex more metal-poor than RRab variables, and have a distribution with a smoother metal-poor tail. This finding supports theoretical prescriptions suggesting a steady decrease in the RRc number when moving from metal-poor to metal-rich stellar environments.
dc.fuente.origenWOS
dc.identifier.doi10.3847/1538-4357/abd183
dc.identifier.eissn1538-4357
dc.identifier.issn0004-637X
dc.identifier.urihttps://doi.org/10.3847/1538-4357/abd183
dc.identifier.urihttps://repositorio.uc.cl/handle/11534/95066
dc.identifier.wosidWOS:000616533700001
dc.issue.numero1
dc.language.isoen
dc.revistaAstrophysical journal
dc.rightsacceso restringido
dc.subjectRR Lyrae variable stars
dc.subjectMilky Way stellar halo
dc.subjectHigh resolution spectroscopy
dc.subjectMetallicity
dc.titleOn the Use of Field RR Lyrae as Galactic Probes. II. A New Δ<i>S</i> Calibration to Estimate Their Metallicity*
dc.typeartículo
dc.volumen908
sipa.indexWOS
sipa.trazabilidadWOS;2025-01-12
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