High-resolution spectroscopy and abundance analysis of Delta Scuti stars near the Gamma Doradus instability strip

Abstract

$\hat{I}´$ Scuti stars are remarkable objects for asteroseismology. In spite of decades of investigations, there are still important questions about these pulsating stars to be answered, such as their positions in $\log$$T_{\mathrm{eff}}$ $-$ $\log g$ diagram, or the dependence of the pulsation modes on atmospheric parameters and rotation. Therefore, we performed a detailed spectroscopic study of $41$ $\hat{I}´$ Scuti stars. The selected objects are located near the ${\hat{I}}^3$ Doradus instability strip to make a reliable comparison between both types of variables. Spectral classification, stellar atmospheric parameters ($T_{\mathrm{eff}}$, $\log g$, $\hat{I}¾$) and $v\sin i$ values were determined. The spectral types and luminosity classes of stars were found to be A1$-$F5 and III$-$V, respectively. The $T_{\mathrm{eff}}$ ranges from $6600$ to $9400$ K, whereas the obtained $\log g$ values are from $3.4$ to $4.3$. The $v\sin i$ values were found between $10$ and $222$ km s${}^{-1}$. The derived chemical abundances of $\hat{I}´$ Scuti stars were compared to those of the non-pulsating stars and ${\hat{I}}^3$ Doradus variables. It turned out that both $\hat{I}´$ Scuti and ${\hat{I}}^3$ Doradus variables have similar abundance patterns, which are slightly different from the non-pulsating stars. These chemical differences can help us to understand why there are non-pulsating stars in classical instability strip. Effects of the obtained parameters on pulsation period and amplitude were examined. It appears that the pulsation period decreases with increasing $T_{\mathrm{eff}}$. No significant correlations were found between pulsation period, amplitude and $v\sin i$.

14 pages, 13 figures, 5 tables