Rotation periods of exoplanet host stars

TL;DR

This study determines rotation periods for ten exoplanet host stars using Ca II H & K flux and photometry, providing new data to infer stellar inclinations and exoplanet masses, including a candidate brown dwarf.

Contribution

It reports five new stellar rotation periods, updates existing ones, and estimates exoplanet masses assuming aligned stellar and orbital axes, highlighting a potential brown dwarf.

Findings

Five new stellar rotation periods identified

Estimated exoplanet masses suggest a brown dwarf candidate

Derived stellar inclinations can inform planet formation theories

Abstract

The stellar rotation periods of ten exoplanet host stars have been determined using newly analysed Ca II H & K flux records from Mount Wilson Observatory and Stromgren b, y photometric measurements from Tennessee State University's automatic photometric telescopes (APTs) at Fairborn Observatory. Five of the rotation periods have not previously been reported, with that of HD 130322 very strongly detected at Prot = 26.1 \pm 3.5 d. The rotation periods of five other stars have been updated using new data. We use the rotation periods to derive the line-of-sight inclinations of the stellar rotation axes, which may be used to probe theories of planet formation and evolution when combined with the planetary orbital inclination found from other methods. Finally, we estimate the masses of fourteen exoplanets under the assumption that the stellar rotation axis is aligned with the orbital axis. We calculate the mass of HD 92788 b (28 MJ) to be within the low-mass brown dwarf regime and suggest that this object warrants further investigation to confirm its true nature.