On the Evolutionary State of High-Latitude Variable V534 Lyr

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 V r corresponding to the positions of all metal absorption components, as well as the Na I D and Hα 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 V r 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 V sys ≈ −125 km s −1 (V lsr ≈ −105 km s −1 ). The distance estimate of d ≈ 6 kpc for the star leads us to its absolute magnitude of M V ≈ −5. m 3, 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 ∆V r = 20-50 km s −1 . A combination of the parameters: reduced metallicity [Met/H] ⊙ = −0.28, increased nitrogen abundance [N/Fe] = +1.10, large spatial velocity, high luminosity, a strong variability of the emission-absorption profiles of H I lines, splitting of metal absorptions at different times of observations and the variability of the velocity field in the atmosphere allow us to classify V534 Lyr as a pulsating star near the HB and belonging to the thick disk of our Galaxy.

Spectroscopy of Supergiants with Infrared Excess: Results of 1998–2018

“…In the course of subse-quent evolution, it may approach the instability band, and then the AGB stage. The authors [101] eventually concluded on the discrepancy of the V534 Lyr belonging to the post-AGB stage.…”

“…Based on multiple observations at the 6-m telescope with the NES echelle spectrograph, we thoroughly studied the features of the optical spectrum of V534 Lyr and the temporal behavior of the heliocentric radial velocity corresponding to the position of all the metal absorption components as well as the Na I D-lines and the Hα line [101]. The analysis of the velocity field of spectral features of various nature revealed a low-amplitude variability of V r from the lines with a high excitation po- tential, which form in deep layers of the stellar atmosphere, and allowed to estimate the systemic velocity V lsr ≈ −105 km s −1 .…”

Gaia DR 2 data and the evolutionary status of eight high velocity hot post-AGB candidates

“…It is a small amplitude light and radial velocity variable. Recently, Klochkova et al (2018) made detailed analysis of the high resolution spectra of this star and derived its chemical composition. They find T eff = 10,000K, log g = 2.5.…”

“…They conclude that it is a population-II pulsating star near the horizontal branch. Klochkova et al (2018) derived a distance of 6 kpc, whereas Bonsack, & Greenstein (1956) estimated a distance of 5.7 kpc. The Gaia DR 2 data (Tables 1 and 2), however, clearly shows that their distance estimate is wrong.…”

“…We considered the hot post-AGB candidates given in the following papers: Mello et al (2012); Venn et al (1998); Kendall et al (1994); Przybylski (1969); Klochkova et al (2018); Sarkar et al (2005); Sarkar et al (2012). From the Gaia DR 2 data we found LS 3593 (SAO 243754), LSE 148 (HD 177566), LS 5107 (IRAS 18365-1353), HD 172324 (V 534 Lyr), HD 214539, and LS 3099 to be high velocity stars with accurate Gaia DR 2 parallaxes (see Tables 1 and 2).…”