Long-period variations in the radial velocity of spectroscopic binary m giant mu ursae majoris

TL;DR

This study investigates long-period radial velocity variations in the spectroscopic binary mu Ursae Majoris, attributing them to stellar pulsations and chromospheric activity rather than additional companions.

Contribution

It identifies and analyzes long-period RV variations in mu UMa, linking them to stellar activity and pulsations, expanding understanding of variability in giant binaries.

Findings

Detected a 471-day RV variation linked to stellar activity.

Identified a 230-day orbital period with a 1.6 M_Sun companion.

Attributed observed variations to stellar pulsations and chromospheric activity.

Abstract

We report that the spectroscopic binary ? Ursae Majoris (?mu UMa) has secondary RV variations of 471.2 days in addition to those of 230.0 days already known. Keplerian orbit analysis yields stellar mass companions of 1.6 M_Sun for the 230-d period and 0.14 M_Sun for the 471-d period. However, the HIPPARCOS photometries show a period similar to the stellar rotational period, which is one-quarter of the RV period. Variations in the bisector velocity curvature show a period of 463.6 days. We also find ~?473-day variations in the equivalent width (EW) measurements of the H_alpha and H_beta lines, whose origin is probably stellar activity. We note that the nature of 471-day variations is similar to one observed in "Sequence D" of symptotic Giant Branch (AGB) pulsating stars. We therefore conclude that the RV and the EW variations in the spectroscopic binary M giant mu UMa A originate from the complex pulsations and the chromospheric activity.