Masses of RR Lyrae Stars with Different Chemical Abundances in the Galactic Field

Abstract

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 $(0.51-0.60)M_{\odot }$. Only stars with initial masses exceeding $1M_{\odot }$ can reach the horizontal branch during the life time 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 $0.8M_{\odot }$ could evolve to become an RR~Lyrae variable during this time. Such stars should have lost $(0.2-0.3)M_{\odot }$ in the red-giant phase, which seems quite realistic.

12 pages, 2 figures

References in corpus (5)

• The Dartmouth Stellar Evolution Database
• Spectroscopic Comparison of Metal-Rich RRab Stars of the Galactic Field with Their Metal-Poor Counterparts
• Photospheric diagnostics of core helium burning in giant stars
• Common Origin of Two RR Lyrae Populations and the Double Red Clump in the Milky Way Bulge
• Formation of Galactic Systems in Light of the Magnesium Abundance in Field Stars: The Thin Disk

Cited by in corpus (10)

• Chemo-kinematics of the $Gaia$ RR Lyrae: the halo and the disc
• Evidence for Galactic disc RR~Lyrae stars in the Solar neighbourhood
• RR Lyrae From Binary Evolution: Abundant, Young and Metal-Rich
• Asteroseismology of RR Lyrae stars with non-radial modes
• The GALAH survey: Tracing the Milky Way's formation and evolution through RR Lyrae stars
• An old, metal-rich accreted stellar component in the Milky Way stellar disk
• The Milky Way Revealed by Variable Stars I: Sample Selection of RR Lyrae stars, and Evidence for the Merger History
• Globular Clusters of the Galaxy: Chemical Composition vs Kinematics
• Inconsistency of Chemical Properties of Stellar Populations in the Thick Disk Subsystem of Our Galaxy
• Peculiarities of Abundances of Selected Elements in Metal-Rich Field RR Lyrae Stars