Spectral analysis of HD 49798, a bright, hydrogen-deficient sdO-type donor star in an accreting X-ray binary

Thomas Rauch, Paul Strauß

Context: HD 49798 is a bright ($m_{\mathrm{V}}=8.287$), hot (effective temperature $T_{\mathrm{eff}}=45000$ K) subdwarf star of the spectral type O (sdO). It is the only confirmed sdO-ty…