A Spectroscopic Survey of Field Red Horizontal-branch Stars
Makaleler > Tam Makale · 2018
Yazarlar: Melike AFŞAR, Zeynep BOZKURT, Gamze Bocek TOPCU, Dana CASETTI-DINESCU, Christopher Sneden, Gizem SEHITOGLU
The Astronomical Journal, SCI Expanded İndekslerine Giren Dergi, Uluslararası, Wos, 2018, cilt 155, ss 240-240
Özet
Abstract A metallicity, chemical composition, and kinematic survey has been conducted for a sample of 340 candidate field red horizontal-branch (RHB) stars. Spectra with high resolution and high signal-to-noise ratio were gathered with the McDonald Observatory 2.7 m Tull and the Hobby–Eberly Telescope echelle spectrographs, and were used to determine effective temperatures, surface gravities, microturbulent velocities, [Fe/H] metallicities, and abundance ratios [X/Fe] for seven α and Fe-group species. The derived temperatures and gravities confirm that at least half of the candidates are true RHB stars, with (average) parameters T eff ∼ 5000 K and log g ∼ 2.5. From the α abundances alone, the thin and thick Galactic populations are apparent in our sample. Space motions for 90% of the program stars were computed from Hipparcos and Gaia parallaxes and proper motions. Correlations between chemical compositions and Galactic kinematics clearly indicate the existence of both thin-disk and thick-disk RHB stars.