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

TL;DR

This study analyzes high-resolution spectra of Polaris B, revealing its atmospheric parameters, chemical composition, and distance, and compares its properties with Polaris A and the Polaris Ab system.

Contribution

It provides detailed atmospheric and chemical analysis of Polaris B and estimates its mass and distance, enhancing understanding of the Polaris system's stellar components.

Findings

Polaris B has Teff=6900K and logg=4.3.

Its elemental abundances are similar to Polaris A, with some solar-like values.

The star's estimated mass is 1.39 solar masses, close to the orbital companion Polaris Ab.

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 V_r of -16.6km/s to -18.9km/s, and a projected rotational velocity vsini=110 km/s. The derived atmospheric parameters are: Teff=6900K; logg=4.3; V_t=2.5km/s. Polaris B has elemental abundances generally similar to those of the Cepheid Polaris A (Usenko et al. 2005a), although carbon, sodium and magnesium are close to the solar values. At a spectral type of F3V Polaris B has a luminosity of 3.868L_sun, an absolute magnitude of +3.30mag, and a distance of 109.5pc. The mass of the star is estimated to be 1.39M_sun, close to a mass of 1.38+/-0.61M_sun for the recently-resolved orbital periods companion Polaris Ab observed by Evans et al. (2007).