HERMES spectra of IP Eri

Previous spectroscopic analyses of the WD, based on a distance of 101pc inferred from its Hipparcos parallax, yielded a mass of only 0.43M_{sun}_, implying it to be a helium-core WD. The orbital properties of IP~Eri are similar to those of the newly discovered long-period subdwarf B star (sdB) binaries, which involve stars with He-burning cores surrounded by extremely thin H envelopes, and are therefore close relatives to He WDs.

We performed a spectroscopic analysis of high-resolution spectra from the HERMES/Mercator spectrograph and concluded that the atmospheric parameters of the K0 component are Teff=4960K, logg=3.3, [Fe/H]=0.09 and vt=1.5km/s. The detailed abundance analysis focuses on C, N, O abundances, carbon isotopic ratio, light (Na, Mg, Al, Si, Ca, Ti) and s-process (Sr, Y, Zr, Ba, La, Ce, Nd) elements. We conclude that IP~Eri abundances agree with those of normal field stars of the same metallicity.