On the Metamorphosis of the Bailey diagram for RR Lyrae stars

Abstract

We collected over 6000 high-resolution spectra of four dozen field RR Lyrae (RRL) variables pulsating either in the fundamental (39 RRab) or in the first overtone (9 RRc) mode. We measured radial velocities (RVs) of four strong metallic and four Balmer lines along the entire pulsational cycle and derived RV amplitudes with accuracies better than 1$-$2~\kmsec. The new amplitudes were combined with literature data for 23~RRab and 3~RRc stars (total sample 74 RRLs) which allowed us to investigate the variation of the Bailey diagram (photometric amplitude versus period) when moving from optical to mid-infrared bands and to re-cast the Bailey diagram in terms of RV amplitudes. We found that RV amplitudes for RRab are minimally affected by nonlinear phenomena (shocks) and multi-periodicity (Blazhko effect). The RV slope ($\log P$--A(V${}_r$)) when compared with the visual slope ($\log P$--A($V$)) is shallower and the dispersion, at fixed period, decreases by a factor of two. We constructed homogeneous sets of Horizontal Branch evolutionary models and nonlinear, convective pulsation models of RRLs to constrain the impact of evolutionary effects on their pulsation properties. Evolution causes, on the Bailey diagram based on RV amplitudes, a modest variation in pulsation period and a large dispersion in amplitude. The broad dispersion in period of the Bailey diagram is mainly caused by variation in RRL intrinsic parameters (stellar mass, chemical composition). Empirical evidence indicates that RV amplitudes are an optimal diagnostic for tracing the mean effective temperature across the RRab instability strip.

14 pages, 4 figures, 1 table, Accepted on ApJ Letter

References in corpus (8)

• Discovery of $\sim$ 9,000 new RR Lyrae in the Southern Catalina Surveys
• Spectroscopic Comparison of Metal-Rich RRab Stars of the Galactic Field with Their Metal-Poor Counterparts
• On the RR Lyrae stars in globulars: IV. $\omega$ Centauri Optical UBVRI Photometry
• Weak Galactic Halo--Fornax dSph Connection from RR Lyrae Stars
• Blazhko effect in the Galactic bulge fundamental mode RR~Lyrae stars I: Incidence rate and differences between modulated and non-modulated stars
• Blazhko modulation in the infrared
• Blazhko Effect in the first overtone RR Lyrae stars of the OGLE Galactic bulge collection
• The Axial Rotation and Variable Macroturbulence of RR Lyrae and Red Horizontal Branch Stars

Cited by in corpus (10)

• On the Use of Field RR Lyrae as Galactic Probes. II. A new $\Delta$S calibration to estimate their metallicity
• On the Use of Field RR Lyrae as Galactic Probes. III. The $\alpha$-element abundances
• On the use of field RR Lyrae as Galactic probes: IV. New insights into and around the Oosterhoff dichotomy
• On the Use of Field RR Lyrae as Galactic Probes. V. Optical and radial velocity curve templates
• On the Use of Field RR Lyrae as Galactic Probes. VI. Mixed mode RR Lyrae variables in Fornax and in nearby dwarf galaxies
• Probing the Galactic halo with RR Lyrae stars -- IV. On the Oosterhoff dichotomy of RR Lyrae stars
• MOCKA -- A PLATO mock asteroseismic catalogue: Simulations for gravity-mode oscillators
• On the Use of Field RR Lyrae as Galactic Probes -- VIII. Early Formation of the Galactic Spheroid
• RRab variables with identical light-curve shapes at different pulsation periods
• Reconsidering The Bailey Diagrams of ab-type RR Lyrae Stars, Metallicity-Mediated Evolution as the Direct Cause of the Oosterhoff Phenomenon