Polaris B, an optical companion of the Polaris (α UMi) system: atmospheric parameters, chemical composition, distance and mass

Abstract We present an analysis of high-resolution spectroscopic observations of Polaris B, the optical companion of the Polaris Ab system. The star has a radial velocity of −16.6 to −18.9 km s−1, and a projected rotational velocity v sin i= 110 km s−1. The derived atmospheric parameters are: Teff= 6900 K; log g= 4.3; Vt= 2.5 km s−1. Polaris B has elemental abundances generally similar to those of the Cepheid Polaris A, although carbon, sodium and magnesium are close to the solar values. At a spectral type of F3 V Polaris B has a luminosity of 3.868 L⊙, an absolute magnitude of +3.30 mag, and a distance of 109.5 pc. The mass of the star is estimated to be 1.39 M⊙, close to a mass of 1.38 ± 0.61 M⊙ for the recently resolved orbital period companion Polaris Ab observed by Evans et al.