The Relationship of Sodium and Oxygen in Galactic Field RR Lyrae Stars

Abstract

We analyzed 62 high-resolution spectra of 30 Galactic Field RR Lyrae-type stars with the aim of deriving their atmospheric parameters (T eff , g log , V t ), metallicity ([Fe/H]), radial velocities, and NLTE abundances of oxygen and sodium. We found that there is no clear anti-correlation between [O/Fe] and [Na/Fe] as is seen in globular clusters. On this basis, we conclude that the majority of field RR Lyrae-type stars should hardly be considered to be remnants of the dissolution of globular clusters.

NLTE CNO abundances in a sample of nine field RR Lyr type stars

“…The authors obtained an increased oxygen abundance in their program stars, [O/Fe] is in the range from about 0 to +1, as expected for metal-poor objects. A similar result was obtained by Andrievsky et al (2018), who derived NLTE oxygen abundances in a sample of 30 Galactic field RR Lyrae stars. [O/Fe] were distributed in the range from 0 to about 1 dex with a typical for the Population II stars dependence on [Fe/H] (metallicity is in the range from 0 to about −3 dex).…”

“…Note that for most of the stars of our program, the atmospheric parameters were first determined in our previous work by Andrievsky et al (2018) using the SME code (Piskunov & Valenti 2017). These parameters were used as a first approximation for the current standard abundance analysis.…”

Chemical Compositions of Field and Globular Cluster RR Lyrae Stars. I. NGC 3201∗

“…A comprehensive abundance analysis cannot leave possible NLTE corrections out of consideration. Several works are available in recent literature dealing with NLTE in RRL stars (Wallerstein & Huang 2010;Hansen et al 2011;Andrievsky et al 2018), but the analysis is far to be complete. Indeed, not all the elements we are dealing with have already been studied.…”

New distance estimates to RX Eri, an RR Lyrae star in Eridanis, using near infrared photometry

“…Observations of RX Eri demonstrate a reliable measurement of its period and class (RRab) across many authors (Carrillo et al, 1995;Kovacs, 2005;Neeley et al, 2017;Andrievsky et al, 2017;Siegel, 1982). A summary of RX Eri data is presented in table 1.…”

“…As Table 2 shows, there has been a large amount of variability in the measurement of metallicity which is difficult to critique without detailed analysis of the various methods used. In the absence of this information the calculations used for this paper, the value determined by (Neeley et al, 2017) was selected as (Gaia et al, 2018) Coordinates Dec -15 44 31.8 Period 0.587246d (Carrillo et al, 1995) 0.587247d (Kovacs, 2005) 0.587242d (Neeley et al, 2017) Teff 6178K (Andrievsky et al, 2017) 6300K (Siegel, 1982) Radial 80Km/s-1 (Andrievsky et al, 2017) Velocity Spectral Type F2D (Gaia et al, 2018) Mv 0.41 (Siegel, 1982) 0.66 (Fernley, Carney, Skillen, Cacciari, & Janes, 1998) 0.54 (Woolley & Dean, 1976) Vmag 9.72 (Kovacs, 2005) 9.70 (Carrillo et al, 1995) 9.69 (Muraveva et al, 2015) O/Fe 0.52 (Andrievsky et al, 2017) Na/Fe -0.37 (Andrievsky et al, 2017) it represented the measurement most related to the time the photometric measurements were made and is also a mode value of the data presented.…”