Non-LTE abundance analysis of the early-type high galactic latitude star HD 100340.

Abstract

Stellar equivalent widths and line profiles, measured from high resolution AAT and IUE spectra, are used in conjunction with non-LTE and LTE model atmosphere calculations to estimate the atmospheric parameters and chemical composition of the early-type high galactic latitude star HD 100340. The effective temperature (T_eff= 25000K), surface gravity (log g = 3.8) and abundances of He, C, O, Al, Si, and Fe are similar to those of Population I OB stars, from which it is concluded that HD 100340 is a normal star at a distance from the galactic plane of z = 4.6±0.8 kpc. Several possible explanations for the existence of this star at such a large z-distance are discussed, including ejection from the galactic plane and formation in the halo.