Radial velocity study of the CP star Epsilon Ursae Majoris

TL;DR

This study analyzes radial velocity data of the chemically peculiar star Epsilon Ursae Majoris, revealing low-amplitude variations indicative of a brown dwarf companion with an eccentric orbit, based on archival spectroscopic data.

Contribution

It provides the first evidence of a brown dwarf companion to Epsilon Ursae Majoris through detailed radial velocity analysis using archival data.

Findings

Detected 5.0887-day radial velocity period.

Identified eccentric orbit with e=0.503.

Estimated companion mass ~14.7 Jupiter masses.

Abstract

In this Letter, the radial velocity variability of the chemically peculiar star Epsilon Ursae Majoris ($\epsilon$ UMa) from the sharp cores of the hydrogen lines is investigated. This study is based on the ELODIE archival data obtained at different phases of the rotational cycle. The star exhibits low-amplitude radial velocity variations with a period of P=5.0887 d. The best Keplerian solution yields an eccentricity e=0.503 and a minimum mass ~14.7$M_{\rm Jup}$ on the hypothesis that the rotational axis of $\epsilon$ UMa is perpendicular to the orbital plane. This result indicate that the companion is the brown-dwarf with the projected semi-amplitude variation of the radial velocity $K_{\rm 2}$=135.9 km/sec and the sine of inclination times semi-major axis $a_{2}$sin(i)=0.055 au.