The Abundances of Vega from the Ultraviolet Spectrum

Abstract

AbstractWe derived preliminary abundances from the ultraviolet spectrum of Vega by comparing high-resolution Copernicus spectra with spectra computed with the ATLAS9 code and with updated line lists. The Teff=9400 K, log g=3.90 model, which fits the visual flux and the Balmer profiles is able to fit the ultraviolet flux either with [M/H]=−l and microturbulent velocity ξ= 2 km s−1 or with [M/H]=−0.5 and ξ=0 km s−1. The line spectrum is fitted by ξ=2 ± 0.5 km s−1 and by an iron abundance log (N(Fe)/Ntot)=−5.2 ±0.1 dex. All the observed elements indicate underabundances ranging from about −0.35 dex (C ) up to about −1 dex (Ni, Zn). The origin of the underabundances is an open question.