On the evolutionary status of high-latitude variable V534 Lyr

TL;DR

This study uses high-resolution spectral monitoring to analyze V534 Lyr, revealing its pulsating nature, systemic velocity, distance, and unique spectral phenomena, positioning it as a thick disk pulsating star near the HB.

Contribution

It provides the first detailed spectral analysis of V534 Lyr, identifying its pulsating behavior, systemic velocity, and spectral profile splitting, advancing understanding of high-latitude variable stars.

Findings

V534 Lyr has a systemic velocity of approximately -125 km/s.

Spectral profile splitting was observed at certain times, indicating complex atmospheric dynamics.

The star is a pulsating, high-luminosity star belonging to the thick disk of the Galaxy.

Abstract

Based on the high resolution spectral monitoring conducted at the 6-m BTA telescope, we study the optical spectrum of the high-latitude variable V534 Lyr. Heliocentric radial velocities Vr corresponding to the positions of all metal absorption components, as well as the NaI D and H$\alpha$ lines were measured during all the observational dates. The analysis of the velocity field examining the lines of various nature revealed a low-amplitude variability of Vr based on the lines with a high excitation potential, which are formed in deep layers of the stellar atmosphere, and allowed to estimate the systemic velocity of Vsys$\approx-125$ km/s (V(lsr)$\approx-105$ km/s). The distance estimate of d$\approx$6 kpc for the star leads us to its absolute magnitude of Mv$\approx -5.3^{m}$, what corresponds to the MK spectral classification. The previously undetected for this star spectral phenomenon was revealed: at certain times a splitting of the profiles of low-excited absorptions is observed, reaching $\Delta$Vr=20$\div$50 km/s. A combination of the parameters: reduced metallicity [Met/H]$_{\odot}=-0.28$, increased nitrogen abundance [N/Fe]=+1.10, large spatial velocity, high luminosity, a strong variability of the emission-absorption profiles of HI lines, splitting of metal absorptions at different observation moments and the variability of the velocity field in the atmosphere allow us to consider V534 Lyr as a pulsating star in the instability band near the HB and belonging to the thick disk of our Galaxy.