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We present an analysis of the relative abundance features of a number of chemical elements in the atmospheres of metal-rich () Galactic-field RR Lyrae variable stars and the kinematic characteristics of these stars. We have previously shown that the relative abundances of some elements: magnesium, silicon, calcium, and to a greater extent of titanium, as well as yttrium and scandium in such stars are lower than in most other types of stars bearing similar metallicity. It is found here that some of these metal-rich RR Lyrae stars also have very low relative abundances of sodium, aluminum, and nickel. The orbital parameters of all the metal-rich RR Lyrae variables studied in this paper are typical of the Galactic thin or thick disk objects, however, the unusual chemical composition let us to suggest a possible extragalactic origin for some of them. [ABSTRACT FROM AUTHOR]

We use the data of our extended catalog of spectroscopic determinations of elemental abundances in the atmospheres of Galactic-field RR Lyrae type variables to show that metal-rich RR Lyraes ([Fe/H] > −1.0) have anomalous abundances of some elements. In particular, the relative abundances of scandium, titanium, and yttrium in metal-rich RR Lyrae type variables are lower than the corresponding abundances in field stars of similar metallicity beyond the errors. We discuss the errors of the determination of the abundances of the above elements and point out the fact that no europium, zirconium, and lanthanum abundance determinations are available for metal-rich RR Lyrae type variables. We also analyze various possible causes of the observed peculiarities of the chemical composition of metal-rich RR Lyrae type variables. [ABSTRACT FROM AUTHOR]

Abstract—Using modern published data on velocities and spectroscopic definitions of chemical elements in stellar objects of the Galaxy, we investigated the relationship of chemical composition with the kinematics of different populations. The paper shows that the old stellar populations of the Galaxy, belonging (by the kinematic criterion) to the thick disk subsystem—globular clusters, field variables of the type RR Lyrae (lyrids), as well as close F– G dwarfs and field giants, have different chemical composition. In particular, the dwarfs and giants of the field are on average more metallic than the globular clusters and lyrids of the field. Moreover, the relative abundances of α-elements in the range [Fe/H] > −1.0 are the highest for globular clusters, and are the lowest for field variables of the RR Lyrae type. Based on the analysis of the nature of the dependences of [α/Fe] on [Fe/H] for these objects it was suggested that the thick disk subsystem in the Galaxy is composite and at least three components exist independently within it. The oldest one includes metal-rich globular clusters that formed from a single proto-galactic cloud shortly after the start of type Ia supernovae outbursts. Then the subsystem of field stars of a thick disk was formed as a result of "heating" of stars of already formed thin disk of the Galaxy by a rather massive dwarf satellite galaxy that fell on it. And finally, subsystems of field stars with the kinematics of not only a thick, but even a thin disk that fell on the Galaxy from this captured satellite galaxy. [ABSTRACT FROM AUTHOR]

Based on published parameters of their atmospheres, the masses of 100 RR Lyrae variables (lyrids) in the field are determined using evolutionary tracks from the Dartmouth data base and the properties of lyrids with different metallicities are compared. It was found that the masses of the metal-rich ([Fe/H] > –0.5) lyrids with thin-disk kinematics lie within an interval of (0.51-0.60) Mʘ. According to modern concepts, the initial masses of these stars should be no more than (0.7-0.8) Mʘ. The long evolution time of these low-mass stars conflicts with the significantly lower age of even the oldest stars in the thin-disk subsystem of the Galaxy. A possible explanation is proposed for the nature of these comparatively young and metal-rich variables. [ABSTRACT FROM AUTHOR]

Published data from 25 papers published between 1995 and 2017 are used to find the effective temperatures and surface acceleration of gravity for 100 RR Lyrae variables in the galactic field with known chemical composition. The atmospheric parameters of almost half the stars in our list were determined in two or more papers. The mean-weighted values of the parameters are calculated for these stars. The values of Teff and logg for almost all the stars studied here lie within the theoretically calculated range where highly evolved stars turn out to be variable. The convergence of the various determinations of the corresponding parameters is analyzed. It is concluded that the values of the effective temperatures and acceleration of gravity for these RR Lyrae variables are highly reliable. [ABSTRACT FROM AUTHOR]

The surface gravities and effective temperatures have been added to a compilative catalog published earlier, which includes the relative abundances of several chemical elements for 100 field RR Lyrae stars. These atmoshperic parameters and evolutionary tracks from the Dartmouth database are used to determine the masses of the stars and perform a comparative analysis of the properties of RR Lyrae stars with different chemical compositions. The masses of metal-rich ([Fe/H] > −0.5) RR Lyrae stars with thin disk kinematics are in the range (0.51−0.60)M⊙. Only stars with initial masses exceeding 1M⊙ can reach the horizontal branch during the lifetime of this subsystem. To become an RR Lyrae variable, a star must have lost approximately half of its mass during the red-giant phase. The appearance of such young, metal-rich RR Lyrae stars is possibly due to high initial helium abundances of their progenitors. According to the Dartmouth evolutionary tracks for Y = 0.4, a star with an initial mass as low as 0.8 M⊙ could evolve to become an RR Lyrae variable during this time. Such stars should have lost (0.2−0.3)M⊙ in the red-giant phase, which seems quite realistic. Populations of red giants and RR Lyrae stars with such high helium abundances have already been discovered in the bulge; some of these could easily be transported to the solar neighborhood as a consequence of perturbations due to inhomogeneities of the Galaxy's gravitational potential. [ABSTRACT FROM AUTHOR]

Several errors concerning the single star V455 Oph have been discovered in the study [1], which, however, do not affect the main conclusions of that study. V455 Oph was mistakenly ascribed the elemental composition of a different star. The spectroscopic elemental abundances of the RR Lyrae star V455 Oph were not determined, making it necessary to use the photometric abundance [Fe/H] = −1.42, and not +0.19, as was indicated in the published paper and in the on-line catalog; any reference to the star should be removed from the abstract and text of the paper. The authors apologize for these errors. In particular, the following text should be removed from Section 3 (p. 56): “However, RR Lyrae stars with the kinematics of the accreted halo also include some very metals-rich objects. For example, V455 Oph”… to the end of that paragraph. The second-to-last paragraph of Section 5, beginning “We also consider the chemical composition of V455 Oph to be unique”… should be removed in its entirety. Finally, the points ascribed to V455 Oph in Figs. 1e, 1f, Figs. 2a-2d, and Figs. 3a-3d should be considered erroneous. [ABSTRACT FROM AUTHOR]